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+<html><head>
+ <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
+ <title>8. Field Mapping</title><base href="display"><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"><link rel="home" href="manual.html" title="Apache OpenJPA 2.4 User's Guide"><link rel="up" href="jpa_overview_mapping.html" title="Chapter 13. Mapping Metadata"><link rel="prev" href="jpa_overview_mapping_discrim.html" title="7. Discriminator"><link rel="next" href="jpa_overview_mapping_full.html" title="9. The Complete Mappings"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">8.
+ Field Mapping
+ </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="jpa_overview_mapping_discrim.html">Prev</a> </td><th width="60%" align="center">Chapter 13.
+ Mapping Metadata
+ </th><td width="20%" align="right"> <a accesskey="n" href="jpa_overview_mapping_full.html">Next</a></td></tr></table><hr></div><div class="section" title="8. Field Mapping"><div class="titlepage"><div><div><h2 class="title" style="clear: both" id="jpa_overview_mapping_field">8.
+ Field Mapping
+ </h2></div></div></div><div class="toc"><dl><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_basic">8.1.
+ Basic Mapping
+ </a></span></dt><dd><dl><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_lob">8.1.1.
+ LOBs
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_enum">8.1.2.
+ Enumerated
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_temporal">8.1.3.
+ Temporal Types
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_basic_example">8.1.4.
+ The Updated Mappings
+ </a></span></dt></dl></dd><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_secondary">8.2.
+ Secondary Tables
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_embed">8.3.
+ Embedded Mapping
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_rel">8.4.
+ Direct Relations
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_assoccoll">8.5.
+ Join Table
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_bidi">8.6.
+ Bidirectional Mapping
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_map">8.7.
+ Map Mapping
+ </a></span></dt></dl></div>
+
+ <a class="indexterm" name="d5e6214"></a>
+ <a class="indexterm" name="d5e6218"></a>
+ <p>
+The following sections enumerate the myriad of field mappings JPA
+supports. JPA augments the persistence metadata covered in
+<a class="xref" href="jpa_overview_meta.html" title="Chapter 5. Metadata">Chapter 5, <i>
+ Metadata
+ </i></a> with many new object-relational
+annotations. As we explore the library of standard mappings, we introduce each
+of these enhancements in context.
+ </p>
+ <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
+ <p>
+OpenJPA supports many additional field types, and allows you to create custom
+mappings for unsupported field types or database schemas. See the Reference
+Guide's <a class="xref" href="ref_guide_mapping.html" title="Chapter 7. Mapping">Chapter 7, <i>
+ Mapping
+ </i></a> for complete coverage of
+OpenJPA's mapping capabilities.
+ </p>
+ </div>
+ <div class="section" title="8.1. Basic Mapping"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_basic">8.1.
+ Basic Mapping
+ </h3></div></div></div><div class="toc"><dl><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_lob">8.1.1.
+ LOBs
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_enum">8.1.2.
+ Enumerated
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_temporal">8.1.3.
+ Temporal Types
+ </a></span></dt><dt><span class="section"><a href="jpa_overview_mapping_field.html#jpa_overview_mapping_basic_example">8.1.4.
+ The Updated Mappings
+ </a></span></dt></dl></div>
+
+ <a class="indexterm" name="d5e6228"></a>
+ <a class="indexterm" name="d5e6232"></a>
+ <p>
+A <span class="emphasis"><em>basic</em></span> field mapping stores the field value directly into
+a database column. The following field metadata types use basic mapping. These
+types were defined in <a class="xref" href="jpa_overview_meta_field.html" title="2. Field and Property Metadata">Section 2, “
+ Field and Property Metadata
+ ”</a>.
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_id" title="2.3. Id"><code class="classname">Id</code></a> fields.
+ </p>
+ </li><li class="listitem">
+ <p>
+<a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_version" title="2.6. Version"><code class="classname"> Version</code></a>
+fields.
+ </p>
+ </li><li class="listitem">
+ <p>
+<a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_basic" title="2.7. Basic"><code class="classname">Basic</code></a>
+fields.
+ </p>
+ </li></ul></div>
+ <p>
+In fact, you have already seen examples of basic field mappings in this chapter
+- the mapping of all identity fields in
+<a class="xref" href="jpa_overview_mapping_id.html#jpa_overview_mapping_identityex" title="Example 13.3. Identity Mapping">Example 13.3, “
+ Identity Mapping
+ ”</a>. As you saw in that
+section, to write a basic field mapping you use the <code class="classname">Column
+</code> annotation to describe the column the field value is stored in. We
+discussed the <code class="classname">Column</code> annotation in
+<a class="xref" href="jpa_overview_mapping_column.html" title="3. Column">Section 3, “
+ Column
+ ”</a>. Recall that the name of
+the column defaults to the field name, and the type of the column defaults to an
+appropriate type for the field type. These defaults allow you to sometimes omit
+the annotation altogether.
+ </p>
+ <div class="section" title="8.1.1. LOBs"><div class="titlepage"><div><div><h4 class="title" id="jpa_overview_mapping_lob">8.1.1.
+ LOBs
+ </h4></div></div></div>
+
+ <a class="indexterm" name="d5e6258"></a>
+ <a class="indexterm" name="d5e6260"></a>
+ <a class="indexterm" name="d5e6263"></a>
+ <p>
+Adding the <code class="classname">Lob</code> marker annotation to a basic field signals
+that the data is to be stored as a LOB (Large OBject). If the field holds string
+or character data, it will map to a <code class="literal">CLOB</code> (Character Large
+OBject) database column. If the field holds any other data type, it will be
+stored as binary data in a <code class="literal">BLOB</code> (Binary Large OBject) column.
+The implementation will serialize the Java value if needed.
+ </p>
+ <p>
+The equivalent XML element is <code class="literal">lob</code>, which has no children or
+attributes.
+ </p>
+ <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
+ <p>
+OpenJPA also supports LOB streaming. See <a class="xref" href="ref_guide_mapping_jpa.html#ref_guide_streamsupport" title="7.11. LOB Streaming">Section 7.11, “
+ LOB Streaming
+ ”</a> in
+the Reference Guide for details.
+ </p>
+ </div>
+ </div>
+ <div class="section" title="8.1.2. Enumerated"><div class="titlepage"><div><div><h4 class="title" id="jpa_overview_mapping_enum">8.1.2.
+ Enumerated
+ </h4></div></div></div>
+
+ <a class="indexterm" name="d5e6277"></a>
+ <a class="indexterm" name="d5e6279"></a>
+ <a class="indexterm" name="d5e6282"></a>
+ <p>
+You can apply the <code class="classname">Enumerated</code> annotation to your
+<code class="classname">Enum</code> fields to control how they map to the database. The
+<code class="classname">Enumerated</code> annotation's value one of the following
+constants from the <code class="classname">EnumType</code> enum:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">EnumType.ORDINAL</code>: The default. The persistence
+implementation places the ordinal value of the enum in a numeric column. This is
+an efficient mapping, but may break if you rearrange the Java enum declaration.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">EnumType.STRING</code>: Store the name of the enum value rather
+than the ordinal. This mapping uses a <code class="literal">VARCHAR</code> column rather
+than a numeric one.
+ </p>
+ </li></ul></div>
+ <p>
+The <code class="classname">Enumerated</code> annotation is optional. Any un-annotated
+enumeration field defaults to <code class="literal">ORDINAL</code> mapping.
+ </p>
+ <p>
+The corresponding XML element is <code class="literal">enumerated</code>. Its embedded
+text must be one of <code class="literal">STRING</code> or <code class="literal">ORIDINAL</code>.
+ </p>
+ </div>
+ <div class="section" title="8.1.3. Temporal Types"><div class="titlepage"><div><div><h4 class="title" id="jpa_overview_mapping_temporal">8.1.3.
+ Temporal Types
+ </h4></div></div></div>
+
+ <a class="indexterm" name="d5e6307"></a>
+ <a class="indexterm" name="d5e6310"></a>
+ <p>
+The <code class="classname">Temporal</code> annotation determines how the implementation
+handles your basic <code class="classname"> java.util.Date</code> and <code class="classname">
+java.util.Calendar</code> fields at the JDBC level. The <code class="classname">
+Temporal</code> annotation's value is a constant from the <code class="classname">
+TemporalType</code> enum. Available values are:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">TemporalType.TIMESTAMP</code>: The default. Use JDBC's timestamp
+APIs to manipulate the column data.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">TemporalType.DATE</code>: Use JDBC's SQL date APIs to manipulate
+the column data.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">TemporalType.TIME</code>: Use JDBC's time APIs to manipulate the
+column data.
+ </p>
+ </li></ul></div>
+ <p>
+If the <code class="classname">Temporal</code> annotation is omitted, the implementation
+will treat the data as a timestamp.
+ </p>
+ <p>
+The corresponding XML element is <code class="literal">temporal</code>, whose text value
+must be one of: <code class="literal">TIME</code>, <code class="literal">DATE</code>, or <code class="literal">
+TIMESTAMP</code>.
+ </p>
+ </div>
+ <div class="section" title="8.1.4. The Updated Mappings"><div class="titlepage"><div><div><h4 class="title" id="jpa_overview_mapping_basic_example">8.1.4.
+ The Updated Mappings
+ </h4></div></div></div>
+
+ <p>
+Below we present an updated diagram of our model and its associated database
+schema, followed by the corresponding mapping metadata. Note that the mapping
+metadata relies on defaults where possible. Also note that as a mapped
+superclass, <code class="classname">Document</code> can define mappings that will
+automatically transfer to its subclass' tables. In
+<a class="xref" href="jpa_overview_mapping_field.html#jpa_overview_mapping_embed" title="8.3. Embedded Mapping">Section 8.3, “
+ Embedded Mapping
+ ”</a>, you will see how a subclass
+can override its mapped superclass' mappings.
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="387"><tr><td><img src="img/jpa-basic-field.png"></td></tr></table></div>
+ <div class="example"><a name="jpa_overview_mapping_basicex"></a><p class="title"><b>Example 13.10.
+ Basic Field Mapping
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag;
+
+@Entity
+@IdClass(Magazine.MagazineId.class)
+@Table(name="MAG")
+@DiscriminatorValue("Mag")
+public class Magazine {
+
+ @Column(length=9)
+ @Id private String isbn;
+ @Id private String title;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ private String name;
+ private double price;
+
+ @Column(name="COPIES")
+ private int copiesSold;
+
+ ...
+
+ public static class MagazineId {
+ ...
+ }
+}
+
+@Entity
+@Table(name="ART", uniqueConstraints=@Unique(columnNames="TITLE"))
+@SequenceGenerator(name="ArticleSeq", sequenceName="ART_SEQ")
+public class Article {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="ArticleSeq")
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ private String title;
+ private byte[] content;
+
+ ...
+}
+
+
+package org.mag.pub;
+
+@Entity
+@Table(name="COMP")
+public class Company {
+
+ @Column(name="CID")
+ @Id private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ private String name;
+
+ @Column(name="REV")
+ private double revenue;
+
+ ...
+}
+
+@Entity
+@Table(name="AUTH")
+public class Author {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.TABLE, generator="AuthorGen")
+ @TableGenerator(name="AuthorGen", table="AUTH_GEN", pkColumnName="PK",
+ valueColumnName="AID")
+ @Column(name="AID", columnDefinition="INTEGER64")
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ @Column(name="FNAME")
+ private String firstName;
+
+ @Column(name="LNAME")
+ private String lastName;
+
+ ...
+}
+
+@Embeddable
+public class Address {
+ ...
+}
+
+package org.mag.subscribe;
+
+@MappedSuperclass
+public abstract class Document {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.IDENTITY)
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ ...
+}
+
+@Entity
+@Table(schema="CNTRCT")
+@Inheritance(strategy=InheritanceType.JOINED)
+@DiscriminatorColumn(name="CTYPE")
+public class Contract
+ extends Document {
+
+ @Lob
+ private String terms;
+
+ ...
+}
+
+@Entity
+@Table(name="SUB", schema="CNTRCT")
+@DiscriminatorColumn(name="KIND", discriminatorType=DiscriminatorType.INTEGER)
+@DiscriminatorValue("1")
+public class Subscription {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.IDENTITY)
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ @Column(name="START")
+ private Date startDate;
+
+ @Column(name="PAY")
+ private double payment;
+
+ ...
+
+ @Entity
+ @Table(name="LINE_ITEM", schema="CNTRCT")
+ public static class LineItem
+ extends Contract {
+
+ @Column(name="COMM")
+ private String comments;
+
+ private double price;
+ private long num;
+ ...
+ }
+}
+
+@Entity(name="Lifetime")
+@DiscriminatorValue("2")
+public class LifetimeSubscription
+ extends Subscription {
+
+ @Basic(fetch=FetchType.LAZY)
+ @Column(name="ELITE")
+ private boolean getEliteClub() { ... }
+ public void setEliteClub(boolean elite) { ... }
+
+ ...
+}
+
+@Entity(name="Trial")
+@DiscriminatorValue("3")
+public class TrialSubscription
+ extends Subscription {
+
+ @Column(name="END")
+ public Date getEndDate() { ... }
+ public void setEndDate(Date end) { ... }
+
+ ...
+}
+</pre>
+ <p>
+The same metadata expressed in XML:
+ </p>
+<pre class="programlisting">
+<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_1_0.xsd"
+ version="1.0">
+ <mapped-superclass class="org.mag.subscribe.Document">
+ <attributes>
+ <id name="id">
+ <generated-value strategy="IDENTITY"/>
+ </id>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ ...
+ </attributes>
+ </mapped-superclass>
+ <entity class="org.mag.Magazine">
+ <table name="MAG"/>
+ <id-class="org.mag.Magazine.MagazineId"/>
+ <discriminator-value>Mag</discriminator-value>
+ <attributes>
+ <id name="isbn">
+ <column length="9"/>
+ </id>
+ <id name="title"/>
+ <basic name="name"/>
+ <basic name="price"/>
+ <basic name="copiesSold">
+ <column name="COPIES"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.Article">
+ <table name="ART">
+ <unique-constraint>
+ <column-name>TITLE</column-name>
+ </unique-constraint>
+ </table>
+ <sequence-generator name="ArticleSeq", sequenceName="ART_SEQ"/>
+ <attributes>
+ <id name="id">
+ <generated-value strategy="SEQUENCE" generator="ArticleSeq"/>
+ </id>
+ <basic name="title"/>
+ <basic name="content"/>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.pub.Company">
+ <table name="COMP"/>
+ <attributes>
+ <id name="id">
+ <column name="CID"/>
+ </id>
+ <basic name="name"/>
+ <basic name="revenue">
+ <column name="REV"/>
+ </basic>
+ </attributes>
+ </entity>
+ <entity class="org.mag.pub.Author">
+ <table name="AUTH"/>
+ <attributes>
+ <id name="id">
+ <column name="AID" column-definition="INTEGER64"/>
+ <generated-value strategy="TABLE" generator="AuthorGen"/>
+ <table-generator name="AuthorGen" table="AUTH_GEN"
+ pk-column-name="PK" value-column-name="AID"/>
+ </id>
+ <basic name="firstName">
+ <column name="FNAME"/>
+ </basic>
+ <basic name="lastName">
+ <column name="LNAME"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.subcribe.Contract">
+ <table schema="CNTRCT"/>
+ <inheritance strategy="JOINED"/>
+ <discriminator-column name="CTYPE"/>
+ <attributes>
+ <basic name="terms">
+ <lob/>
+ </basic>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.subcribe.Subscription">
+ <table name="SUB" schema="CNTRCT"/>
+ <inheritance strategy="SINGLE_TABLE"/>
+ <discriminator-value>1</discriminator-value>
+ <discriminator-column name="KIND" discriminator-type="INTEGER"/>
+ <attributes>
+ <id name="id">
+ <generated-value strategy="IDENTITY"/>
+ </id>
+ <basic name="payment">
+ <column name="PAY"/>
+ </basic>
+ <basic name="startDate">
+ <column name="START"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.subscribe.Subscription.LineItem">
+ <table name="LINE_ITEM" schema="CNTRCT"/>
+ <primary-key-join-column name="ID" referenced-column-name="PK"/>
+ <attributes>
+ <basic name="comments">
+ <column name="COMM"/>
+ </basic>
+ <basic name="price"/>
+ <basic name="num"/>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.subscribe.LifetimeSubscription" name="Lifetime">
+ <discriminator-value>2</discriminator-value>
+ <attributes>
+ <basic name="eliteClub" fetch="LAZY">
+ <column name="ELITE"/>
+ </basic>
+ ...
+ </attributes>
+ </entity>
+ <entity class="org.mag.subscribe.TrialSubscription" name="Trial">
+ <discriminator-value>3</discriminator-value>
+ <attributes>
+ <basic name="endDate">
+ <column name="END"/>
+ </basic>
+ ...
+ </attributes>
+ </entity>
+</entity-mappings>
+</pre>
+ </div></div><br class="example-break">
+ </div>
+ </div>
+ <div class="section" title="8.2. Secondary Tables"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_secondary">8.2.
+ Secondary Tables
+ </h3></div></div></div>
+
+ <a class="indexterm" name="d5e6351"></a>
+ <a class="indexterm" name="d5e6355"></a>
+ <p>
+Sometimes a logical record is spread over multiple database tables. JPA
+calls a class' declared table the <span class="emphasis"><em>primary</em></span>
+table, and calls other tables that make up a logical record <span class="emphasis"><em>secondary
+</em></span> tables. You can map any persistent field to a secondary table. Just
+write the standard field mapping, then perform these two additional steps:
+ </p>
+ <div class="orderedlist"><ol class="orderedlist" type="1"><li class="listitem">
+ <p>
+Set the <code class="literal">table</code> attribute of each of the field's columns or
+join columns to the name of the secondary table.
+ </p>
+ </li><li class="listitem">
+ <p>
+Define the secondary table on the entity class declaration.
+ </p>
+ </li></ol></div>
+ <p>
+You define secondary tables with the <code class="classname">SecondaryTable</code>
+annotation. This annotation has all the properties of the <code class="classname">Table
+</code> annotation covered in <a class="xref" href="jpa_overview_mapping.html#jpa_overview_mapping_table" title="1. Table">Section 1, “
+ Table
+ ”</a>
+, plus a <code class="literal"> pkJoinColumns</code> property.
+ </p>
+ <p>
+The <code class="literal">pkJoinColumns</code> property is an array of <code class="classname">
+PrimaryKeyJoinColumn</code>s dictating how to join secondary table records
+to their owning primary table records. Each <code class="classname">PrimaryKeyJoinColumn
+</code> joins a secondary table column to a primary key column in the
+primary table. See <a class="xref" href="jpa_overview_mapping_inher.html#jpa_overview_mapping_inher_joined" title="6.2. Joined">Section 6.2, “
+ Joined
+ ”</a>
+above for coverage of <code class="classname">PrimaryKeyJoinColumn</code>'s properties.
+ </p>
+ <p>
+The corresponding XML element is <code class="literal">secondary-table</code>. This
+element has all the attributes of the <code class="literal">table</code> element, but also
+accepts nested <code class="literal">primary-key-join-column</code> elements.
+ </p>
+ <p>
+In the following example, we move the <code class="literal">Article.content</code> field
+we mapped in <a class="xref" href="jpa_overview_mapping_field.html#jpa_overview_mapping_basic" title="8.1. Basic Mapping">Section 8.1, “
+ Basic Mapping
+ ”</a> into a joined
+secondary table, like so:
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="189"><tr><td><img src="img/secondary-table.png"></td></tr></table></div>
+ <div class="example"><a name="jpa_overview_mapping_secondaryex"></a><p class="title"><b>Example 13.11.
+ Secondary Table Field Mapping
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag;
+
+@Entity
+@Table(name="ART")
+@SecondaryTable(name="ART_DATA",
+ pkJoinColumns=@PrimaryKeyJoinColumn(name="ART_ID", referencedColumnName="ID"))
+public class Article {
+
+ @Id private long id;
+
+ @Column(table="ART_DATA")
+ private byte[] content;
+
+ ...
+}
+</pre>
+ <p>
+And in XML:
+ </p>
+<pre class="programlisting">
+<entity class="org.mag.Article">
+ <table name="ART"/>
+ <secondary-table name="ART_DATA">
+ <primary-key-join-column name="ART_ID" referenced-column-name="ID"/>
+ </secondary-table>
+ <attributes>
+ <id name="id"/>
+ <basic name="content">
+ <column table="ART_DATA"/>
+ </basic>
+ ...
+ </attributes>
+</entity>
+</pre>
+ </div></div><br class="example-break">
+ </div>
+ <div class="section" title="8.3. Embedded Mapping"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_embed">8.3.
+ Embedded Mapping
+ </h3></div></div></div>
+
+ <a class="indexterm" name="d5e6395"></a>
+ <a class="indexterm" name="d5e6399"></a>
+ <p>
+<a class="xref" href="jpa_overview_meta.html" title="Chapter 5. Metadata">Chapter 5, <i>
+ Metadata
+ </i></a> describes JPA's concept of <span class="emphasis"><em>
+embeddable</em></span> objects. The field values of embedded objects are stored
+as part of the owning record, rather than as a separate database record. Thus,
+instead of mapping a relation to an embeddable object as a foreign key, you map
+all the fields of the embeddable instance to columns in the owning field's
+table.
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="309"><tr><td><img src="img/jpa-embedded.png"></td></tr></table></div>
+ <p>
+JPA defaults the embedded column names and descriptions to those of
+the embeddable class' field mappings. The <code class="classname"> AttributeOverride
+</code> annotation overrides a basic embedded mapping. This annotation has
+the following properties:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">String name</code>: The name of the embedded class' field being
+mapped to this class' table.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">Column column</code>: The column defining the mapping of the
+embedded class' field to this class' table.
+ </p>
+ </li></ul></div>
+ <p>
+The corresponding XML element is <code class="literal"> attribute-override</code>. It has
+a single <code class="literal">name</code> attribute to name the field being overridden,
+and a single <code class="literal">column</code> child element.
+ </p>
+ <p>
+To declare multiple overrides, use the <code class="classname">AttributeOverrides</code>
+annotation, whose value is an array of <code class="classname">AttributeOverride</code>
+s. In XML, simply list multiple <code class="literal">attribute-override</code> elements
+in succession.
+ </p>
+ <p>
+To override a many to one or one to one relationship, use the <code class="classname">
+AssociationOverride</code> annotation in place of <code class="classname">
+AttributeOverride</code>. <code class="classname"> AssociationOverride</code> has
+the following properties:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">String name</code>: The name of the embedded class' field being
+mapped to this class' table.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">JoinColumn[] joinColumns</code>: The foreign key columns joining to
+the related record.
+ </p>
+ </li></ul></div>
+ <p>
+The corresponding XML element is <code class="literal"> association-override</code>. It
+has a single <code class="literal">name</code> attribute to name the field being
+overridden, and one or more <code class="literal">join-column</code> child elements.
+ </p>
+ <p>
+To declare multiple relation overrides, use the <code class="classname"> AssociationOverrides
+</code> annotation, whose value is an array of <code class="classname">
+AssociationOverride</code> s. In XML, simply list multiple <code class="literal">
+association-override</code> elements in succession.
+ </p>
+ <div class="example"><a name="jpa_overview_mapping_embedex"></a><p class="title"><b>Example 13.12.
+ Embedded Field Mapping
+ </b></p><div class="example-contents">
+
+ <p>
+In this example, <code class="classname">Company</code> overrides the default mapping of
+<code class="literal">Address.street</code> and <code class="literal">Address.city</code>. All
+other embedded mappings are taken from the <code class="classname">Address</code>
+embeddable class.
+ </p>
+<pre class="programlisting">
+package org.mag.pub;
+
+@Entity
+@Table(name="COMP")
+public class Company {
+
+ @Embedded
+ @AttributeOverrides({
+ @AttributeOverride(name="street", column=@Column(name="STRT")),
+ @AttributeOverride(name="city", column=@Column(name="ACITY"))
+ })
+ private Address address;
+
+ ...
+}
+
+@Entity
+@Table(name="AUTH")
+public class Author {
+
+ // use all defaults from Address class mappings
+ private Address address;
+
+ ...
+}
+
+@Embeddable
+public class Address {
+
+ private String street;
+ private String city;
+ @Column(columnDefinition="CHAR(2)")
+ private String state;
+ private String zip;
+}
+</pre>
+ <p>
+The same metadata expressed in XML:
+ </p>
+<pre class="programlisting">
+<entity class="org.mag.pub.Company">
+ <table name="COMP"/>
+ <attributes>
+ ...
+ <embedded name="address">
+ <attribute-override name="street">
+ <column name="STRT"/>
+ </attribute-override>
+ <attribute-override name="city">
+ <column name="ACITY"/>
+ </attribute-override>
+ </embedded>
+ </attributes>
+</entity>
+<entity class="org.mag.pub.Author">
+ <table name="AUTH"/>
+ <attributes>
+ <embedded name="address">
+ <!-- use all defaults from Address -->
+ </embedded>
+ </attributes>
+</entity>
+<embeddable class="org.mag.pub.Address">
+ <attributes>
+ <basic name="street"/>
+ <basic name="city"/>
+ <basic name="state">
+ <column column-definition="CHAR(2)"/>
+ </basic>
+ <basic name="zip"/>
+ </attributes>
+</embeddable>
+</pre>
+ </div></div><br class="example-break">
+ <p>
+You can also use attribute overrides on an entity class to override mappings
+defined by its mapped superclass or table-per-class superclass. The example
+below re-maps the <code class="literal">Document.version</code> field to the <code class="classname">
+Contract</code> table's <code class="literal">CVERSION</code> column.
+ </p>
+ <div class="example"><a name="jpa_overview_mapping_joined_overex"></a><p class="title"><b>Example 13.13.
+ Mapping Mapped Superclass Field
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+@MappedSuperclass
+public abstract class Document {
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ ...
+}
+
+@Entity
+@Table(schema="CNTRCT")
+@Inheritance(strategy=InheritanceType.JOINED)
+@DiscriminatorColumn(name="CTYPE")
+@AttributeOverride(name="version", column=@Column(name="CVERSION"))
+public class Contract
+ extends Document {
+ ...
+}
+</pre>
+ <p>
+The same metadata expressed in XML form:
+ </p>
+<pre class="programlisting">
+<mapped-superclass class="org.mag.subcribe.Document">
+ <attributes>
+ <version name="version">
+ <column name="VERS">
+ </version>
+ ...
+ </attributes>
+</mapped-superclass>
+<entity class="org.mag.subcribe.Contract">
+ <table schema="CNTRCT"/>
+ <inheritance strategy="JOINED"/>
+ <discriminator-column name="CTYPE"/>
+ <attribute-override name="version">
+ <column name="CVERSION"/>
+ </attribute-override>
+ <attributes>
+ ...
+ </attributes>
+</entity>
+</pre>
+ </div></div><br class="example-break">
+ </div>
+ <div class="section" title="8.4. Direct Relations"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_rel">8.4.
+ Direct Relations
+ </h3></div></div></div>
+
+ <a class="indexterm" name="d5e6465"></a>
+ <a class="indexterm" name="d5e6469"></a>
+ <a class="indexterm" name="d5e6472"></a>
+ <a class="indexterm" name="d5e6475"></a>
+ <p>
+A direct relation is a non-embedded persistent field that holds a reference to
+another entity. <a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_manytoone" title="2.9. Many To One">many to one</a>
+and <a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_onetoone" title="2.11. One To One">one to one</a> metadata field
+types are mapped as direct relations. Our model has three direct relations:
+<code class="classname">Magazine</code>'s <code class="literal">publisher</code> field is a direct
+relation to a <code class="classname">Company</code>, <code class="classname">Magazine</code>'s
+<code class="literal">coverArticle</code> field is a direct relation to <code class="classname">
+Article</code>, and the <code class="literal">LineItem.magazine</code> field is a
+direct relation to a <code class="classname">Magazine</code>. Direct relations are
+represented in the database by foreign key columns:
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="249"><tr><td><img src="img/jpa-direct-relation.png"></td></tr></table></div>
+ <p>
+You typically map a direct relation with <code class="classname">JoinColumn</code>
+annotations describing how the local foreign key columns join to the primary key
+columns of the related record. The <code class="classname">JoinColumn</code> annotation
+exposes the following properties:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">String name</code>: The name of the foreign key column. Defaults to
+the relation field name, plus an underscore, plus the name of the referenced
+primary key column.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">String referencedColumnName</code>: The name of the primary key
+column being joined to. If there is only one identity field in the related
+entity class, the join column name defaults to the name of the identity field's
+column.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">boolean unique</code>: Whether this column is guaranteed to hold
+unique values for all rows. Defaults to false.
+ </p>
+ </li></ul></div>
+ <p>
+<code class="classname">JoinColumn</code> also has the same <code class="literal"> nullable</code>
+, <code class="literal">insertable</code>, <code class="literal"> updatable</code>, <code class="literal">
+columnDefinition</code>, and <code class="literal">table</code> properties as the
+<code class="classname"> Column</code> annotation. See
+<a class="xref" href="jpa_overview_mapping_column.html" title="3. Column">Section 3, “
+ Column
+ ”</a> for details on these
+properties.
+ </p>
+ <p>
+The <code class="literal">join-column</code> element represents a join column in XML. Its
+attributes mirror the above annotation's properties:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">name</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">referenced-column-name</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">unique</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">nullable</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">insertable</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">updatable</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">column-definition</code>
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">table</code>
+ </p>
+ </li></ul></div>
+ <p>
+When there are multiple columns involved in the join, as when a <code class="classname">
+LineItem</code> references a <code class="classname">Magazine</code> in our model,
+the <code class="classname">JoinColumns</code> annotation allows you to specify an array
+of <code class="classname">JoinColumn</code> values. In XML, simply list multiple
+<code class="literal">join-column</code> elements.
+ </p>
+ <div class="note" title="Note" style="margin-left: 0.5in; margin-right: 0.5in;"><h3 class="title">Note</h3>
+ <p>
+OpenJPA supports many non-standard joins. See
+<a class="xref" href="ref_guide_mapping_notes_nonstdjoins.html" title="6. Non-Standard Joins">Section 6, “
+ Non-Standard Joins
+ ”</a> in the Reference
+Guide for details.
+ </p>
+ </div>
+ <div class="example"><a name="jpa_overview_mapping_relex"></a><p class="title"><b>Example 13.14.
+ Direct Relation Field Mapping
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag;
+
+@Table(name="AUTH")
+public class Magazine {
+
+ @Column(length=9)
+ @Id private String isbn;
+ @Id private String title;
+
+ @OneToOne
+ @JoinColumn(name="COVER_ID" referencedColumnName="ID")
+ private Article coverArticle;
+
+ @ManyToOne
+ @JoinColumn(name="PUB_ID" referencedColumnName="CID")
+ private Company publisher;
+
+ ...
+}
+
+@Table(name="ART")
+public class Article {
+
+ @Id private long id;
+
+ ...
+}
+
+
+package org.mag.pub;
+
+@Table(name="COMP")
+public class Company {
+
+ @Column(name="CID")
+ @Id private long id;
+
+ ...
+}
+
+
+package org.mag.subscribe;
+
+public class Subscription {
+ ...
+
+ @Table(name="LINE_ITEM", schema="CNTRCT")
+ public static class LineItem
+ extends Contract {
+
+ @ManyToOne
+ @JoinColumns({
+ @JoinColumn(name="MAG_ISBN" referencedColumnName="ISBN"),
+ @JoinColumn(name="MAG_TITLE" referencedColumnName="TITLE")
+ })
+ private Magazine magazine;
+
+ ...
+ }
+}
+</pre>
+ <p>
+The same metadata expressed in XML form:
+ </p>
+<pre class="programlisting">
+<entity class="org.mag.Magazine">
+ <table name="MAG"/>
+ <id-class="org.mag.Magazine.MagazineId"/>
+ <attributes>
+ <id name="isbn">
+ <column length="9"/>
+ </id>
+ <id name="title"/>
+ <one-to-one name="coverArticle">
+ <join-column name="COVER_ID" referenced-column-name="ID"/>
+ </one-to-one>
+ <many-to-one name="publisher">
+ <join-column name="PUB_IC" referenced-column-name="CID"/>
+ </many-to-one>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.Article">
+ <table name="ART"/>
+ <attributes>
+ <id name="id"/>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.pub.Company">
+ <table name="COMP"/>
+ <attributes>
+ <id name="id">
+ <column name="CID"/>
+ </id>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.subscribe.Subscription.LineItem">
+ <table name="LINE_ITEM" schema="CNTRCT"/>
+ <primary-key-join-column name="ID" referenced-column-name="PK"/>
+ <attributes>
+ <many-to-one name="magazine">
+ <join-column name="MAG_ISBN" referenced-column-name="ISBN"/>
+ <join-column name="MAG_TITLE" referenced-column-name="TITLE"/>
+ </many-to-one>
+ ...
+ </attributes>
+</entity>
+</pre>
+ </div></div><br class="example-break">
+ <p>
+When the entities in a one to one relation join on shared primary key values
+rather than separate foreign key columns, use the <code class="classname">
+PrimaryKeyJoinColumn(s)</code> annotation or <code class="literal">
+primary-key-join-column</code> elements in place of <code class="classname">JoinColumn(s)
+</code> / <code class="literal"> join-column</code> elements.
+ </p>
+ </div>
+ <div class="section" title="8.5. Join Table"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_assoccoll">8.5.
+ Join Table
+ </h3></div></div></div>
+
+ <a class="indexterm" name="d5e6562"></a>
+ <a class="indexterm" name="d5e6566"></a>
+ <a class="indexterm" name="d5e6569"></a>
+ <a class="indexterm" name="d5e6571"></a>
+ <a class="indexterm" name="d5e6574"></a>
+ <p>
+A <span class="emphasis"><em>join table</em></span> consists of two foreign keys. Each row of a
+join table associates two objects together. JPA uses join tables to
+represent collections of entity objects: one foreign key refers back to the
+collection's owner, and the other refers to a collection element.
+ </p>
+ <p>
+<a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_onetomany" title="2.10. One To Many">one to many</a> and
+<a class="link" href="jpa_overview_meta_field.html#jpa_overview_meta_manytomany" title="2.12. Many To Many">many to many</a> metadata field
+types can map to join tables. Several fields in our model use join table
+mappings, including <code class="literal">Magazine.articles</code> and <code class="literal">
+Article.authors</code>.
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="261"><tr><td><img src="img/jpa-assoc-table.png"></td></tr></table></div>
+ <p>
+You define join tables with the <code class="classname">JoinTable</code> annotation.
+This annotation has the following properties:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">String name</code>: Table name. If not given, the name of the table
+defaults to the name of the owning entity's table, plus an underscore, plus the
+name of the related entity's table.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">String catalog</code>: Table catalog.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">String schema</code>: Table schema.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">JoinColumn[] joinColumns</code>: Array of <code class="classname">JoinColumn
+</code> showing how to associate join table records with the owning row in
+the primary table. This property mirrors the <code class="literal">pkJoinColumns</code>
+property of the <code class="classname"> SecondaryTable</code> annotation in
+functionality. See <a class="xref" href="jpa_overview_mapping_field.html#jpa_overview_mapping_secondary" title="8.2. Secondary Tables">Section 8.2, “
+ Secondary Tables
+ ”</a> to
+refresh your memory on secondary tables.
+ </p>
+ <p>
+If this is a bidirectional relation (see
+<a class="xref" href="jpa_overview_meta_field.html#jpa_overview_meta_mappedby" title="2.10.1. Bidirectional Relations">Section 2.10.1, “
+ Bidirectional Relations
+ ”</a> ), the name of a join column
+defaults to the inverse field name, plus an underscore, plus the referenced
+primary key column name. Otherwise, the join column name defaults to the field's
+owning entity name, plus an underscore, plus the referenced primary key column
+name.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">JoinColumn[] inverseJoinColumns</code>: Array of <code class="classname">
+JoinColumns</code> showing how to associate join table records with the
+records that form the elements of the collection. These join columns are used
+just like the join columns for direct relations, and they have the same naming
+defaults. Read <a class="xref" href="jpa_overview_mapping_field.html#jpa_overview_mapping_rel" title="8.4. Direct Relations">Section 8.4, “
+ Direct Relations
+ ”</a> for a review of
+direct relation mapping.
+ </p>
+ </li></ul></div>
+ <p>
+<code class="literal">join-table</code> is the corresponding XML element. It has the same
+attributes as the <code class="literal">table</code> element, but includes the ability to
+nest <code class="literal">join-column</code> and <code class="literal">inverse-join-column</code>
+elements as children. We have seen <code class="literal">join-column</code> elements
+already; <code class="literal">inverse-join-column</code> elements have the same
+attributes.
+ </p>
+ <p>
+Here are the join table mappings for the diagram above.
+ </p>
+ <div class="example"><a name="jpa_overview_mapping_assoccollex"></a><p class="title"><b>Example 13.15.
+ Join Table Mapping
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag;
+
+@Entity
+@Table(name="MAG")
+public class Magazine {
+
+ @Column(length=9)
+ @Id private String isbn;
+ @Id private String title;
+
+ @OneToMany(...)
+ @OrderBy
+ @JoinTable(name="MAG_ARTS",
+ joinColumns={
+ @JoinColumn(name="MAG_ISBN", referencedColumnName="ISBN"),
+ @JoinColumn(name="MAG_TITLE", referencedColumnName="TITLE")
+ },
+ inverseJoinColumns=@JoinColumn(name="ART_ID", referencedColumnName="ID"))
+ private Collection<Article> articles;
+
+ ...
+}
+
+@Entity
+@Table(name="ART")
+public class Article {
+
+ @Id private long id;
+
+ @ManyToMany(cascade=CascadeType.PERSIST)
+ @OrderBy("lastName, firstName")
+ @JoinTable(name="ART_AUTHS",
+ joinColumns=@JoinColumn(name="ART_ID", referencedColumnName="ID"),
+ inverseJoinColumns=@JoinColumn(name="AUTH_ID", referencedColumnName="AID"))
+ private Collection<Author> authors;
+
+ ...
+}
+
+
+package org.mag.pub;
+
+@Entity
+@Table(name="AUTH")
+public class Author {
+
+ @Column(name="AID", columnDefinition="INTEGER64")
+ @Id private long id;
+
+ ...
+}
+</pre>
+ <p>
+The same metadata expressed in XML:
+ </p>
+<pre class="programlisting">
+<entity class="org.mag.Magazine">
+ <table name="MAG"/>
+ <attributes>
+ <id name="isbn">
+ <column length="9"/>
+ </id>
+ <id name="title"/>
+ <one-to-many name="articles">
+ <order-by/>
+ <join-table name="MAG_ARTS">
+ <join-column name="MAG_ISBN" referenced-column-name="ISBN"/>
+ <join-column name="MAG_TITLE" referenced-column-name="TITLE"/>
+ <inverse-join-column name="ART_ID" referenced-column-name="ID"/>
+ </join-table>
+ </one-to-many>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.Article">
+ <table name="ART"/>
+ <attributes>
+ <id name="id"/>
+ <many-to-many name="authors">
+ <order-by>lastName, firstName</order-by>
+ <join-table name="ART_AUTHS">
+ <join-column name="ART_ID" referenced-column-name="ID"/>
+ <inverse-join-column name="AUTH_ID" referenced-column-name="AID"/>
+ </join-table>
+ <cascade>
+ <cascade-persist/>
+ </cascade>
+ </many-to-many>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.pub.Author">
+ <table name="AUTH"/>
+ <attributes>
+ <id name="id">
+ <column name="AID" column-definition="INTEGER64"/>
+ </id>
+ ...
+ </attributes>
+</entity>
+</pre>
+ </div></div><br class="example-break">
+ </div>
+ <div class="section" title="8.6. Bidirectional Mapping"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_bidi">8.6.
+ Bidirectional Mapping
+ </h3></div></div></div>
+
+ <a class="indexterm" name="d5e6628"></a>
+ <p>
+<a class="xref" href="jpa_overview_meta_field.html#jpa_overview_meta_mappedby" title="2.10.1. Bidirectional Relations">Section 2.10.1, “
+ Bidirectional Relations
+ ”</a> introduced bidirectional
+relations. To map a bidirectional relation, you map one field normally using the
+annotations we have covered throughout this chapter. Then you use the <code class="literal">
+mappedBy</code> property of the other field's metadata annotation or the
+corresponding <code class="literal">mapped-by</code> XML attribute to refer to the mapped
+field. Look for this pattern in these bidirectional relations as you peruse the
+complete mappings below:
+ </p>
+ <div class="itemizedlist"><ul class="itemizedlist" type="disc"><li class="listitem">
+ <p>
+<code class="literal">Magazine.publisher</code> and <code class="literal">Company.mags</code>.
+ </p>
+ </li><li class="listitem">
+ <p>
+<code class="literal">Article.authors</code> and <code class="literal">Author.articles</code>.
+ </p>
+ </li></ul></div>
+ </div>
+ <div class="section" title="8.7. Map Mapping"><div class="titlepage"><div><div><h3 class="title" id="jpa_overview_mapping_map">8.7.
+ Map Mapping
+ </h3></div></div></div>
+
+ <a class="indexterm" name="d5e6646"></a>
+ <a class="indexterm" name="d5e6649"></a>
+ <p>
+All map fields in JPA are modeled on either one to many or many to
+many associations. The map key is always derived from an associated entity's
+field. Thus map fields use the same mappings as any one to many or many to many
+fields, namely dedicated <a class="link" href="jpa_overview_mapping_field.html#jpa_overview_mapping_assoccoll" title="8.5. Join Table">join
+tables</a> or <a class="link" href="jpa_overview_mapping_field.html#jpa_overview_mapping_bidi" title="8.6. Bidirectional Mapping">bidirectional
+relations</a>. The only additions are the <code class="classname">MapKey</code>
+annotation and <code class="literal">map-key</code> element to declare the key field. We
+covered these additions in <a class="xref" href="jpa_overview_meta_field.html#jpa_overview_meta_mapkey" title="2.14. Map Key">Section 2.14, “
+ Map Key
+ ”</a>.
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="255"><tr><td><img src="img/jpa-map.png"></td></tr></table></div>
+ <p>
+The example below maps <code class="classname">Subscription</code>'s map of <code class="classname">
+LineItem</code>s to the <code class="literal">SUB_ITEMS</code> join table. The key
+for each map entry is the <code class="classname"> LineItem</code>'s <code class="literal">num
+</code> field value.
+ </p>
+ <div class="example"><a name="jpa_overview_mapping_mapex"></a><p class="title"><b>Example 13.16.
+ Join Table Map Mapping
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag.subscribe;
+
+@Entity
+@Table(name="SUB", schema="CNTRCT")
+public class Subscription {
+
+ @OneToMany(cascade={CascadeType.PERSIST,CascadeType.REMOVE})
+ @MapKey(name="num")
+ @JoinTable(name="SUB_ITEMS", schema="CNTRCT",
+ joinColumns=@JoinColumn(name="SUB_ID"),
+ inverseJoinColumns=@JoinColumn(name="ITEM_ID"))
+ private Map<Long,LineItem> items;
+
+ ...
+
+ @Entity
+ @Table(name="LINE_ITEM", schema="CNTRCT")
+ public static class LineItem
+ extends Contract {
+
+ private long num;
+
+ ...
+ }
+}
+</pre>
+ <p>
+The same metadata expressed in XML:
+ </p>
+<pre class="programlisting">
+<entity class="org.mag.subscribe.Subscription">
+ <table name="SUB" schema="CNTRCT"/>
+ <attributes>
+ ...
+ <one-to-many name="items">
+ <map-key name="num">
+ <join-table name="SUB_ITEMS" schema="CNTRCT">
+ <join-column name="SUB_ID"/>
+ <inverse-join-column name="ITEM_ID"/>
+ </join-table>
+ <cascade>
+ <cascade-persist/>
+ <cascade-remove/>
+ </cascade>
+ </one-to-many>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.subscribe.Subscription.LineItem">
+ <table name="LINE_ITEM" schema="CNTRCT"/>
+ <attributes>
+ ...
+ <basic name="num"/>
+ ...
+ </attributes>
+</entity>
+</pre>
+ </div></div><br class="example-break">
+ </div>
+ </div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="jpa_overview_mapping_discrim.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="jpa_overview_mapping.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="jpa_overview_mapping_full.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">7.
+ Discriminator
+ </td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top"> 9.
+ The Complete Mappings
+ </td></tr></table></div></body></html>
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+<html><head>
+ <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
+ <title>9. The Complete Mappings</title><base href="display"><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"><link rel="home" href="manual.html" title="Apache OpenJPA 2.4 User's Guide"><link rel="up" href="jpa_overview_mapping.html" title="Chapter 13. Mapping Metadata"><link rel="prev" href="jpa_overview_mapping_field.html" title="8. Field Mapping"><link rel="next" href="jpa_overview_conclusion.html" title="Chapter 14. Conclusion"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">9.
+ The Complete Mappings
+ </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="jpa_overview_mapping_field.html">Prev</a> </td><th width="60%" align="center">Chapter 13.
+ Mapping Metadata
+ </th><td width="20%" align="right"> <a accesskey="n" href="jpa_overview_conclusion.html">Next</a></td></tr></table><hr></div><div class="section" title="9. The Complete Mappings"><div class="titlepage"><div><div><h2 class="title" style="clear: both" id="jpa_overview_mapping_full">9.
+ The Complete Mappings
+ </h2></div></div></div>
+
+ <p>
+We began this chapter with the goal of mapping the following object model:
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="369"><tr><td><img src="img/jpa-meta-model.png"></td></tr></table></div>
+ <p>
+That goal has now been met. In the course of explaining JPA's object-relational
+mapping metadata, we slowly built the requisite schema and mappings for the
+complete model. First, the database schema:
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="326"><tr><td><img src="img/jpa-data-model.png"></td></tr></table></div>
+ <p>
+And finally, the complete entity mappings. We have trimmed the mappings to take
+advantage of JPA defaults where possible.
+ </p>
+ <div class="example"><a name="jpa_overview_mapping_fullex"></a><p class="title"><b>Example 13.17.
+ Full Entity Mappings
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag;
+
+@Entity
+@IdClass(Magazine.MagazineId.class)
+@Table(name="MAG")
+@DiscriminatorValue("Mag")
+public class Magazine {
+
+ @Column(length=9)
+ @Id private String isbn;
+ @Id private String title;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ private String name;
+ private double price;
+
+ @Column(name="COPIES")
+ private int copiesSold;
+
+ @OneToOne(fetch=FetchType.LAZY,
+ cascade={CascadeType.PERSIST,CascadeType.REMOVE})
+ @JoinColumn(name="COVER_ID")
+ private Article coverArticle;
+
+ @OneToMany(cascade={CascadeType.PERSIST,CascadeType.REMOVE})
+ @OrderBy
+ @JoinTable(name="MAG_ARTS",
+ joinColumns={
+ @JoinColumn(name="MAG_ISBN", referencedColumnName="ISBN"),
+ @JoinColumn(name="MAG_TITLE", referencedColumnName="TITLE")
+ },
+ inverseJoinColumns=@JoinColumn(name="ART_ID"))
+ private Collection<Article> articles;
+
+ @ManyToOne(fetch=FetchType.LAZY, cascade=CascadeType.PERSIST)
+ @JoinColumn(name="PUB_ID")
+ private Company publisher;
+
+ @Transient private byte[] data;
+
+
+ ...
+
+ public static class MagazineId {
+ ...
+ }
+}
+
+@Entity
+@Table(name="ART", uniqueConstraints=@Unique(columnNames="TITLE"))
+@SequenceGenerator(name="ArticleSeq", sequenceName="ART_SEQ")
+public class Article {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.SEQUENCE, generator="ArticleSeq")
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ private String title;
+ private byte[] content;
+
+ @ManyToMany(cascade=CascadeType.PERSIST)
+ @OrderBy("lastName, firstName")
+ @JoinTable(name="ART_AUTHS",
+ joinColumns=@JoinColumn(name="ART_ID"),
+ inverseJoinColumns=@JoinColumn(name="AUTH_ID"))
+ private Collection<Author> authors;
+
+ ...
+}
+
+
+package org.mag.pub;
+
+@Entity
+@Table(name="COMP")
+public class Company {
+
+ @Column(name="CID")
+ @Id private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ private String name;
+
+ @Column(name="REV")
+ private double revenue;
+
+ @Embedded
+ @AttributeOverrides({
+ @AttributeOverride(name="street", column=@Column(name="STRT")),
+ @AttributeOverride(name="city", column=@Column(name="ACITY"))
+ })
+ private Address address;
+
+ @OneToMany(mappedBy="publisher", cascade=CascadeType.PERSIST)
+ private Collection<Magazine> mags;
+
+ @OneToMany(cascade=CascadeType.PERSIST,CascadeType.REMOVE)
+ @JoinTable(name="COMP_SUBS",
+ joinColumns=@JoinColumn(name="COMP_ID"),
+ inverseJoinColumns=@JoinColumn(name="SUB_ID"))
+ private Collection<Subscription> subscriptions;
+
+ ...
+}
+
+@Entity
+@Table(name="AUTH")
+public class Author {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.TABLE, generator="AuthorGen")
+ @TableGenerator(name="AuthorGen", tableName="AUTH_GEN", pkColumnName="PK",
+ valueColumnName="AID")
+ @Column(name="AID", columnDefinition="INTEGER64")
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ @Column(name="FNAME")
+ private String firstName;
+
+ @Column(name="LNAME")
+ private String lastName;
+
+ private Address address;
+
+ @ManyToMany(mappedBy="authors", cascade=CascadeType.PERSIST)
+ private Collection<Article> arts;
+
+ ...
+}
+
+@Embeddable
+public class Address {
+
+ private String street;
+ private String city;
+ @Column(columnDefinition="CHAR(2)")
+ private String state;
+ private String zip;
+}
+
+
+package org.mag.subscribe;
+
+@MappedSuperclass
+public abstract class Document {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.IDENTITY)
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ ...
+}
+
+@Entity
+@Table(schema="CNTRCT")
+@Inheritance(strategy=InheritanceType.JOINED)
+@DiscriminatorColumn(name="CTYPE")
+public class Contract
+ extends Document {
+
+ @Lob
+ private String terms;
+
+ ...
+}
+
+@Entity
+@Table(name="SUB", schema="CNTRCT")
+@DiscriminatorColumn(name="KIND", discriminatorType=DiscriminatorType.INTEGER)
+@DiscriminatorValue("1")
+public class Subscription {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.IDENTITY)
+ private long id;
+
+ @Column(name="VERS")
+ @Version private int version;
+
+ @Column(name="START")
+ private Date startDate;
+
+ @Column(name="PAY")
+ private double payment;
+
+ @OneToMany(cascade={CascadeType.PERSIST,CascadeType.REMOVE})
+ @MapKey(name="num")
+ @JoinTable(name="SUB_ITEMS", schema="CNTRCT",
+ joinColumns=@JoinColumn(name="SUB_ID"),
+ inverseJoinColumns=@JoinColumn(name="ITEM_ID"))
+ private Map<Long,LineItem> items;
+
+ ...
+
+ @Entity
+ @Table(name="LINE_ITEM", schema="CNTRCT")
+ public static class LineItem
+ extends Contract {
+
+ @Column(name="COMM")
+ private String comments;
+
+ private double price;
+ private long num;
+
+ @ManyToOne
+ @JoinColumns({
+ @JoinColumn(name="MAG_ISBN", referencedColumnName="ISBN"),
+ @JoinColumn(name="MAG_TITLE", referencedColumnName="TITLE")
+ })
+ private Magazine magazine;
+ ...
+ }
+}
+
+@Entity(name="Lifetime")
+@DiscriminatorValue("2")
+public class LifetimeSubscription
+ extends Subscription {
+
+ @Basic(fetch=FetchType.LAZY)
+ @Column(name="ELITE")
+ private boolean getEliteClub() { ... }
+ public void setEliteClub(boolean elite) { ... }
+
+ ...
+}
+
+@Entity(name="Trial")
+@DiscriminatorValue("3")
+public class TrialSubscription
+ extends Subscription {
+
+ @Column(name="END")
+ public Date getEndDate() { ... }
+ public void setEndDate(Date end) { ... }
+
+ ...
+}
+</pre>
+ <p>
+The same metadata expressed in XML form:
+ </p>
+<pre class="programlisting">
+<entity-mappings xmlns="http://java.sun.com/xml/ns/persistence/orm"
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+ xsi:schemaLocation="http://java.sun.com/xml/ns/persistence/orm orm_1_0.xsd"
+ version="1.0">
+ <mapped-superclass class="org.mag.subscribe.Document">
+ <attributes>
+ <id name="id">
+ <generated-value strategy="IDENTITY"/>
+ </id>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ </attributes>
+ </mapped-superclass>
+ <entity class="org.mag.Magazine">
+ <table name="MAG"/>
+ <id-class="org.mag.Magazine.MagazineId"/>
+ <discriminator-value>Mag</discriminator-value>
+ <attributes>
+ <id name="isbn">
+ <column length="9"/>
+ </id>
+ <id name="title"/>
+ <basic name="name"/>
+ <basic name="price"/>
+ <basic name="copiesSold">
+ <column name="COPIES"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ <many-to-one name="publisher" fetch="LAZY">
+ <join-column name="PUB_ID"/>
+ <cascade>
+ <cascade-persist/>
+ </cascade>
+ </many-to-one>
+ <one-to-many name="articles">
+ <order-by/>
+ <join-table name="MAG_ARTS">
+ <join-column name="MAG_ISBN" referenced-column-name="ISBN"/>
+ <join-column name="MAG_TITLE" referenced-column-name="TITLE"/>
+ <inverse-join-column name="ART_ID"/>
+ </join-table>
+ <cascade>
+ <cascade-persist/>
+ <cascade-remove/>
+ </cascade>
+ </one-to-many>
+ <one-to-one name="coverArticle" fetch="LAZY">
+ <join-column name="COVER_ID"/>
+ <cascade>
+ <cascade-persist/>
+ <cascade-remove/>
+ </cascade>
+ </one-to-one>
+ <transient name="data"/>
+ </attributes>
+ </entity>
+ <entity class="org.mag.Article">
+ <table name="ART">
+ <unique-constraint>
+ <column-name>TITLE</column-name>
+ </unique-constraint>
+ </table>
+ <sequence-generator name="ArticleSeq", sequenceName="ART_SEQ"/>
+ <attributes>
+ <id name="id">
+ <generated-value strategy="SEQUENCE" generator="ArticleSeq"/>
+ </id>
+ <basic name="title"/>
+ <basic name="content"/>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ <many-to-many name="articles">
+ <order-by>lastName, firstName</order-by>
+ <join-table name="ART_AUTHS">
+ <join-column name="ART_ID" referenced-column-name="ID"/>
+ <inverse-join-column name="AUTH_ID" referenced-column-name="AID"/>
+ </join-table>
+ </many-to-many>
+ </attributes>
+ </entity>
+ <entity class="org.mag.pub.Company">
+ <table name="COMP"/>
+ <attributes>
+ <id name="id">
+ <column name="CID"/>
+ </id>
+ <basic name="name"/>
+ <basic name="revenue">
+ <column name="REV"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ <one-to-many name="mags" mapped-by="publisher">
+ <cascade>
+ <cascade-persist/>
+ </cascade>
+ </one-to-many>
+ <one-to-many name="subscriptions">
+ <join-table name="COMP_SUBS">
+ <join-column name="COMP_ID"/>
+ <inverse-join-column name="SUB_ID"/>
+ </join-table>
+ <cascade>
+ <cascade-persist/>
+ <cascade-remove/>
+ </cascade>
+ </one-to-many>
+ <embedded name="address">
+ <attribute-override name="street">
+ <column name="STRT"/>
+ </attribute-override>
+ <attribute-override name="city">
+ <column name="ACITY"/>
+ </attribute-override>
+ </embedded>
+ </attributes>
+ </entity>
+ <entity class="org.mag.pub.Author">
+ <table name="AUTH"/>
+ <attributes>
+ <id name="id">
+ <column name="AID" column-definition="INTEGER64"/>
+ <generated-value strategy="TABLE" generator="AuthorGen"/>
+ <table-generator name="AuthorGen" table="AUTH_GEN"
+ pk-column-name="PK" value-column-name="AID"/>
+ </id>
+ <basic name="firstName">
+ <column name="FNAME"/>
+ </basic>
+ <basic name="lastName">
+ <column name="LNAME"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ <many-to-many name="arts" mapped-by="authors">
+ <cascade>
+ <cascade-persist/>
+ </cascade>
+ </many-to-many>
+ <embedded name="address"/>
+ </attributes>
+ </entity>
+ <entity class="org.mag.subcribe.Contract">
+ <table schema="CNTRCT"/>
+ <inheritance strategy="JOINED"/>
+ <discriminator-column name="CTYPE"/>
+ <attributes>
+ <basic name="terms">
+ <lob/>
+ </basic>
+ </attributes>
+ </entity>
+ <entity class="org.mag.subcribe.Subscription">
+ <table name="SUB" schema="CNTRCT"/>
+ <inheritance strategy="SINGLE_TABLE"/>
+ <discriminator-value>1</discriminator-value>
+ <discriminator-column name="KIND" discriminator-type="INTEGER"/>
+ <attributes>
+ <id name="id">
+ <generated-value strategy="IDENTITY"/>
+ </id>
+ <basic name="payment">
+ <column name="PAY"/>
+ </basic>
+ <basic name="startDate">
+ <column name="START"/>
+ </basic>
+ <version name="version">
+ <column name="VERS"/>
+ </version>
+ <one-to-many name="items">
+ <map-key name="num">
+ <join-table name="SUB_ITEMS" schema="CNTRCT">
+ <join-column name="SUB_ID"/>
+ <inverse-join-column name="ITEM_ID"/>
+ </join-table>
+ <cascade>
+ <cascade-persist/>
+ <cascade-remove/>
+ </cascade>
+ </one-to-many>
+ </attributes>
+ </entity>
+ <entity class="org.mag.subscribe.Subscription.LineItem">
+ <table name="LINE_ITEM" schema="CNTRCT"/>
+ <attributes>
+ <basic name="comments">
+ <column name="COMM"/>
+ </basic>
+ <basic name="price"/>
+ <basic name="num"/>
+ <many-to-one name="magazine">
+ <join-column name="MAG_ISBN" referenced-column-name="ISBN"/>
+ <join-column name="MAG_TITLE" referenced-column-name="TITLE"/>
+ </many-to-one>
+ </attributes>
+ </entity>
+ <entity class="org.mag.subscribe.LifetimeSubscription" name="Lifetime">
+ <discriminator-value>2</discriminator-value>
+ <attributes>
+ <basic name="eliteClub" fetch="LAZY">
+ <column name="ELITE"/>
+ </basic>
+ </attributes>
+ </entity>
+ <entity class="org.mag.subscribe.TrialSubscription" name="Trial">
+ <discriminator-value>3</discriminator-value>
+ <attributes>
+ <basic name="endDate">
+ <column name="END"/>
+ </basic>
+ </attributes>
+ </entity>
+ <embeddable class="org.mag.pub.Address">
+ <attributes>
+ <basic name="street"/>
+ <basic name="city"/>
+ <basic name="state">
+ <column column-definition="CHAR(2)"/>
+ </basic>
+ <basic name="zip"/>
+ </attributes>
+ </embeddable>
+</entity-mappings>
+</pre>
+ </div></div><br class="example-break">
+ </div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="jpa_overview_mapping_field.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="jpa_overview_mapping.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="jpa_overview_conclusion.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">8.
+ Field Mapping
+ </td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top"> Chapter 14.
+ Conclusion
+ </td></tr></table></div></body></html>
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+<html><head>
+ <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
+ <title>4. Identity Mapping</title><base href="display"><link rel="stylesheet" type="text/css" href="css/docbook.css"><meta name="generator" content="DocBook XSL-NS Stylesheets V1.76.1"><link rel="home" href="manual.html" title="Apache OpenJPA 2.4 User's Guide"><link rel="up" href="jpa_overview_mapping.html" title="Chapter 13. Mapping Metadata"><link rel="prev" href="jpa_overview_mapping_column.html" title="3. Column"><link rel="next" href="jpa_overview_mapping_sequence.html" title="5. Generators"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">4.
+ Identity Mapping
+ </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="jpa_overview_mapping_column.html">Prev</a> </td><th width="60%" align="center">Chapter 13.
+ Mapping Metadata
+ </th><td width="20%" align="right"> <a accesskey="n" href="jpa_overview_mapping_sequence.html">Next</a></td></tr></table><hr></div><div class="section" title="4. Identity Mapping"><div class="titlepage"><div><div><h2 class="title" style="clear: both" id="jpa_overview_mapping_id">4.
+ Identity Mapping
+ </h2></div></div></div>
+
+ <a class="indexterm" name="d5e5629"></a>
+ <a class="indexterm" name="d5e5631"></a>
+ <a class="indexterm" name="d5e5634"></a>
+ <p>
+With our new knowledge of columns, we can map the identity fields of our
+entities. The diagram below now includes primary key columns for our model's
+tables. The primary key column for <code class="classname">Author</code> uses
+nonstandard type <code class="literal"> INTEGER64</code>, and the <code class="literal">Magazine.isbn
+</code> field is mapped to a <code class="literal">VARCHAR(9)</code> column instead of
+a <code class="literal">VARCHAR(255)</code> column, which is the default for string
+fields. We do not need to point out either one of these oddities to the JPA
+implementation for runtime use. If, however, we want to use the JPA
+implementation to create our tables for us, it needs to know about
+any desired non-default column types. Therefore, the example following the
+diagram includes this data in its encoding of our mappings.
+ </p>
+ <div class="mediaobject"><table border="0" summary="manufactured viewport for HTML img" cellspacing="0" cellpadding="0" width="341"><tr><td><img src="img/jpa-mapping-identity.png"></td></tr></table></div>
+ <p>
+Note that many of our identity fields do not need to specify column information,
+because they use the default column name and type.
+ </p>
+ <div class="example"><a name="jpa_overview_mapping_identityex"></a><p class="title"><b>Example 13.3.
+ Identity Mapping
+ </b></p><div class="example-contents">
+
+<pre class="programlisting">
+package org.mag;
+
+@Entity
+@IdClass(Magazine.MagazineId.class)
+@Table(name="MAG")
+public class Magazine {
+
+ @Column(length=9)
+ @Id private String isbn;
+ @Id private String title;
+
+ ...
+
+ public static class MagazineId {
+ ...
+ }
+}
+
+@Entity
+@Table(name="ART", uniqueConstraints=@Unique(columnNames="TITLE"))
+public class Article {
+
+ @Id private long id;
+
+ ...
+}
+
+
+package org.mag.pub;
+
+@Entity
+@Table(name="COMP")
+public class Company {
+
+ @Column(name="CID")
+ @Id private long id;
+
+ ...
+}
+
+@Entity
+@Table(name="AUTH")
+public class Author {
+
+ @Column(name="AID", columnDefinition="INTEGER64")
+ @Id private long id;
+
+ ...
+}
+
+@Embeddable
+public class Address {
+ ...
+}
+
+
+package org.mag.subscribe;
+
+@MappedSuperclass
+public abstract class Document {
+
+ @Id
+ @GeneratedValue(strategy=GenerationType.IDENTITY)
+ private long id;
+
+ ...
+}
+
+@Entity
+@Table(schema="CNTRCT")
+public class Contract
+ extends Document {
+ ...
+}
+
+@Entity
+@Table(name="SUB", schema="CNTRCT")
+public class Subscription {
+
+ @Id private long id;
+
+ ...
+
+ @Entity
+ @Table(name="LINE_ITEM", schema="CNTRCT")
+ public static class LineItem
+ extends Contract {
+ ...
+ }
+}
+
+@Entity(name="Lifetime")
+public class LifetimeSubscription
+ extends Subscription {
+ ...
+}
+
+@Entity(name="Trial")
+public class TrialSubscription
+ extends Subscription {
+ ...
+}
+</pre>
+ <p>
+The same metadata for <code class="literal">Magazine</code> and <code class="literal">Company</code>
+expressed in XML form:
+ </p>
+<pre class="programlisting">
+<entity class="org.mag.Magazine">
+ <id-class class="org.mag.Magazine.Magazine.MagazineId"/>
+ <table name="MAG"/>
+ <attributes>
+ <id name="isbn">
+ <column length="9"/>
+ </id>
+ <id name="title"/>
+ ...
+ </attributes>
+</entity>
+<entity class="org.mag.pub.Company">
+ <table name="COMP"/>
+ <attributes>
+ <id name="id">
+ <column name="CID"/>
+ </id>
+ ...
+ </attributes>
+</entity>
+</pre>
+ </div></div><br class="example-break">
+ </div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="jpa_overview_mapping_column.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="jpa_overview_mapping.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="jpa_overview_mapping_sequence.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">3.
+ Column
+ </td><td width="20%" align="center"><a accesskey="h" href="manual.html">Home</a></td><td width="40%" align="right" valign="top"> 5.
+ Generators
+ </td></tr></table></div></body></html>
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