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<!DOCTYPE document PUBLIC "-//APACHE//DTD Documentation V1.2//EN" "document-v12.dtd">
<document>
<header>
<title>HOWTO - Stored Procedure Support</title>
<authors>
<person name="Ron Gallagher" email="rongallagher@bellsouth.net"/>
</authors>
</header>
<body>
<section>
<title>Introduction</title>
<p>
OJB supports the use of stored procedures to handle the basic DML
operations (INSERT, UPDATE, and DELETE). This document will describe
the entries that you'll need to add to your repository in order to get
OJB to utilize stored procedures instead of 'traditional' INSERT, UPDATE
or DELETE statements.
</p>
<p>
Please note that there will be references to 'stored procedures'
throughout this document. However, this is just a simplification for
the purposes of this document. Any place you see a reference to
'stored procedure', you can assume that either a stored procedure or
function can be used.
</p>
<p>
Information presented in this document includes the following:
</p>
<ul>
<li>
<link href="#Repository+entries">Basic repository entries</link>
</li>
<li>
<link href="#Common+attributes">Common attributes for all procedure
descriptors</link>
</li>
<li>An overview of the
<link href="#insert-procedure">insert procedure</link>,
<link href="#update-procedure">update procedure</link> and
<link href="#delete-procedure">delete procedure</link> descriptors.
</li>
<li>Information about the
<link href="#Argument+descriptors">argument descriptors</link>
that are supported for all procedure
</li>
<li>A
<link href="#A+simple+example">simple example</link> and a
<link href="#A+complex+example">more complex example</link>
</li>
</ul>
</section>
<section>
<title>Repository entries</title>
<p>
For any persistable class (i.e. "com.myproject.Customer") where you want to
utilize stored procedures to handle persistence operations instead of
traditional DML statements (i.e. INSERT, UPDATE or DELETE), you will need
to include one or more of the following descriptors within the
corresponding class-descriptor for the persistable class:
</p>
<ul>
<li>
<code>insert-procedure</code> - identifies the stored procedure that
is to be used whenever a class needs to be inserted into the database.
</li>
<li>
<code>update-procedure</code> - identifies the stored procedure that
is to be used whenever a class needs to be updated in the database.
</li>
<li>
<code>delete-procedure</code> - identifies the stored procedure that
is to be used whenever a class needs to be removed from the database.
</li>
</ul>
<p>
All of these descriptors must be nested within the class-descriptor that
they apply to. Here is an example of a simple class-descriptor that
includes each of the procedure descriptors listed above:
</p>
<source><![CDATA[
<class-descriptor class="com.myproject.Customer" table="CUSTOMER">
<field-descriptor column="ID" jdbc-type="DECIMAL" name="id" primarykey="true"/>
<field-descriptor column="NAME" jdbc-type="VARCHAR" name="name"/>
<insert-procedure name="CUSTOMER_PKG.ADD">
<runtime-argument field-ref="id" return="true"/>
<runtime-argument field-ref="name"/>
</insert-procedure>
<update-procedure name="CUSTOMER_PKG.CHG">
<runtime-argument field-ref="id"/>
<runtime-argument field-ref="name"/>
</update-procedure>
<delete-procedure name="CUSTOMER_PKG.CHG">
<runtime-argument field-ref="id"/>
</delete-procedure>
</class-descriptor>]]></source>
</section>
<section>
<title>Common attributes</title>
<p>
All three procedure descriptors have the following attributes in common:
</p>
<ul>
<li>
<code>name</code> - This is the name of the stored procedure that is to
be used to handle the specific persistence operation.
</li>
<li>
<code>return-field-ref</code> - This identifies the field in the class
where the return value from the stored procedure will be stored. If this
attribute is blank or not specified, then OJB will assume that the stored
procedure does not return a value and will format the SQL command
accordingly.
</li>
</ul>
<p>
The basic syntax that is used to call a procedure that has a return value
looks something like this:
</p>
<source><![CDATA[
{?= call <procedure-name>[<arg1>,<arg2>, ...]}]]></source>
<p>
The basic syntax that is used to call a procedure that
<strong>does not</strong>
include a return value looks something like this:
</p>
<source><![CDATA[
{call <procedure-name>[<arg1>,<arg2>, ...]}]]></source>
<p>
When OJB assembles the SQL to call a stored procedure, it will use the value
of the 'name' attribute in place of 'procedure-name' in these two examples.
</p>
<p>
In addition, if the procedure descriptor includes a value in the
'return-field-ref' attribute that is 'valid', then the syntax that OJB
builds will include the placeholder for the result parameter.
</p>
<p>
The previous section referred to the idea of a 'valid' value in the
'return-field-ref' attribute. A value is considered to be 'valid' if it
meets the following criteria:
</p>
<ul>
<li>The value is not blank</li>
<li>There is a field-descriptor with a 'name' that matches the value
in the 'return-field-ref' attribute.</li>
</ul>
<p>
If the 'return-field-ref' attribute is not 'valid', then the placeholder
for the result parameter will not be included in the SQL that OJB assembles.
</p>
</section>
<section>
<title>insert-procedure</title>
<p>
The insert-procedure descriptor identifies the stored procedure that should
be used whenever a class needs to be inserted into the database. In
addition to the
<link href="#Common+attributes">common attributes</link> listed
earlier, the insert-procedure includes the following attribute:
</p>
<ul>
<li>
<anchor id="include-all-fields"/>include-all-fields
</li>
</ul>
<p>
This attribute provides an efficient mechanism for passing all
attributes of a persistable class to a stored procedure. If this
attribute is set to true, then OJB will ignore any nested
<link href="#Argument+descriptors">argument descriptors</link>. Instead,
OJB will assume that the argument list for the stored procedure
includes arguments for all attributes of the persistable class and that
those arguments appear in the same order as the field-descriptors for
the persistable class.
</p>
<p>
The default value for this attribute is 'false'.
</p>
<note>
If the field-descriptors in your repository do not 'align'
exactly with the argument list for the stored procedure, or you want to
maintain explicit control over the values that are passed to the stored
procedure, then either set the 'include-all-fields' attribute to 'false'
or leave it off the insert-procedure descriptor.
</note>
</section>
<section>
<title>update-procedure</title>
<p>
The update-procedure descriptor identifies the stored procedure that should
be used whenever a class needs to be updated in the database. In addition to
the
<link href="#Common+attributes">common attributes</link> listed earlier, the
update-procedure includes the following attribute:
</p>
<ul>
<li>include-all-fields</li>
</ul>
<p>
This attribute provides the same capabilities and has the same caveats as
the
<link href="#include-all-fields">include-all-fields</link> attribute on
the
<link href="#insert-procedure">insert-procedure</link> descriptor.
</p>
</section>
<section>
<title>delete-procedure</title>
<p>
The delete-procedure descriptor identifies the stored procedure that should
be used whenever a class needs to be deleted from the database. In
addition to the
<link href="#Common+attributes">common attributes</link> listed
earlier, the delete-procedure includes the following attribute:
</p>
<ul>
<li>
<anchor id="include-pk-only"/>include-pk-only
<br/>
<br/>
This attribute provides an efficient mechanism for passing all of the
attributes that make up the primary key for a persistable class to the
specified stored procedure. If this attribute is set to true, then OJB
will ignore any nested
<link href="#Argument+descriptors">argument
descriptors</link>. Instead, OJB will assume that the argument list for
the stored procedure includes arguments for all attributes that make up
the primary key for the persistable class (i.e. those field-descriptors
where the 'primary-key' attribute is set to 'true'). OJB will also assume
that those arguments appear in the same order as the corresponding
field-descriptors for the persistable class.
<br/>
<br/>
The default value for this attribute is 'false'.
</li>
</ul>
<note>
If the field-descriptors in your repository that make up
the primary key for a persistable class do not 'align' exactly with the
argument list for the stored procedure, or you want to maintain explicit
control over the values that are passed to the stored procedure, then
either set the 'include-pk-only' attribute to 'false' or leave it off
the delete-procedure descriptor.
</note>
</section>
<section>
<title>Argument descriptors</title>
<p>
Argument descriptors are the mechanism that you will use to tell OJB two
things:
</p>
<ol>
<li>How many placeholders should be included in the argument list for a
stored procedure?</li>
<li>What value should be passed for each of those arguments?</li>
</ol>
<p>
There are two types of argument descriptors that can be defined in the
repository:
</p>
<ul>
<li>
<link href="#runtime-argument descriptors">runtime arguments</link>
used to set a stored procedure argument equal to a value that is only
known at runtime.
</li>
<li>
<link href="#constant-argument descriptors">constant arguments</link>
used to set a stored procedure argument equal to constant value.
</li>
</ul>
<p>
You may notice that there is no argument descriptor specifically designed
to pass a
<em>null</em> value to the procedure. This capability is provided by
the
<link href="#runtime-argument descriptors">runtime argument</link>
descriptor.
</p>
<p>
The argument descriptors are essentially the 'mappings' between stored
procedure arguments and their runtime values. Each procedure descriptor
can include 0 or more argument descriptors in it's definition.
</p>
<p>
After reading that last comment, you may wonder why OJB allows you to
configure a procedure descriptor with no argument descriptors since the
primary focus of OJB is to handle object persistence. How could OJB perform
any sort persistence operation using a stored procedure that did not involve
the passage of at least one value to the stored procedure? To be honest, it
is extremely unlikely that you would ever set up a procedure descriptor with
no argument descriptors. However, since there is no minimum number of
arguments required for a stored procedure, we did not want to implement
within OJB a requirement on the number of arguments that was more
restrictive than the limits imposed by most/all database systems.
</p>
<section>
<title>runtime-argument descriptors</title>
<p>
A runtime-argument descriptor is used to set a stored procedure argument
equal to a value that is only known at runtime.
</p>
<p>
Two attributes can be specified for each runtime-argument descriptor:
</p>
<ul>
<li>field-ref
<br/>
<br/>
The 'field-ref' attribute identifies the specific field descriptor
that will provide the argument's value. If this attribute is not
specified or does not resolve to a valid field-descriptor, then a
null value will be passed to the stored procedure.
</li>
<li>return
<br/>
<br/>
The 'return' attribute is used to determine if the argument is used
by the stored procedure as an 'output' argument.
<br/>
<br/>
If this attribute is set to true, then the corresponding argument
will be registered as an output parameter. After execution of the
stored procedure, the value of the argument will be 'harvested' from
the CallableStatement and stored in the attribute identified by the
field-ref attribute.
<br/>
<br/>
If this attribute is not specified or set to false, then OJB assumes
that the argument is simply an 'input' argument, and it will do
nothing special to the argument.
</li>
</ul>
</section>
<section>
<title>constant-argument descriptors</title>
<p>
A constant-argument descriptor is used to set a stored procedure argument
equal to constant value.
</p>
<p>
There is one attribute that can be specified for the constant-argument
descriptor:
</p>
<ul>
<li>value
<br/>
<br/>
The 'value' attribute identifies the value for the argument.
</li>
</ul>
</section>
</section>
<section>
<title>A simple example</title>
<p>
This section provides background information and a simple example that
illustrates how OJB's support for stored procedures can be utilized.
</p>
<p>
The background information covers the following topics:
</p>
<ul>
<li>
<link href="#The+basic+requirements">The basic requirements</link>
</li>
<li>
<link href="#The+database+objects">The database objects</link>
including the
<link href="#The+table">table</link> that will be manipulated,
the
<link href="#The+sequence">sequence</link> that will be used by the stored
procedures to assign primary key falues, the
<link href="#The+insert+and+update+triggers">insert and update triggers</link>
that maintain the four 'audit' columns and the
<link href="#The+package">package</link> that provides the stored procedures that
will handle the persistence operations.
</li>
</ul>
<p>
Click
<link href="#The+implementation">here</link> to skip the background information
and go straight to the implementation.
</p>
<section>
<title>The basic requirements</title>
<p>
These are the requirements that must be satisfied by our example
</p>
<ol>
<li>
<p>
All insert, update and delete operations are to be performed
by stored procedures.
</p>
</li>
<li>
<p>
All primary key values are to be by the stored procedure that handles
the insert operation. The value that is assigned should be reflected
in the object that 'triggered' the insert operation.
</p>
</li>
<li>
For auditing purposes, all tables will include the following set of
columns:
<ul>
<li>
<code>USER_CREATED</code> - This will contain the id of the user
who created the record
</li>
<li>
<code>DATE_CREATED</code> - The date on which the record was created
created
</li>
<li>
<code>USER_UPDATED</code> - The id of the user who last modified the
record
</li>
<li>
<code>USER_UPDATED</code> - The date on which the record was last
modified
</li>
</ul>
In addition to the inclusion of these columns on each table, the
following requirements related to these columns had to be supported:
<ol>
<li>
The values of the two date-related audit columns were to be
maintained at the database level via insert and update triggers.
<ul>
<li>
The insert trigger will set both
<code>DATE_CREATED</code> and
<code>DATE_UPDATED</code> to the current system date.
</li>
<li>
The update trigger will set
<code>DATE_UPDATED</code> to the
current system date. The update trigger will also ensure that
the original value of
<code>DATE_CREATED</code> is never
modified.
</li>
</ul>
</li>
<li>
The values of the two user-related audit columns are to be
maintained at the database level via insert and update triggers.
<ul>
<li>
The insert and update triggers will ensure that
<code>USER_CREATED</code> and
<code>USER_UPDATED</code> are
appropriately populated.
</li>
<li>
The update trigger will ensure that the original value of
<code>USER_CREATED</code> is never modified.
</li>
</ul>
</li>
<li>
Any changes that are made by the insert or update triggers to any of
the four 'audit' columns had to be reflected in the object that
caused the insert or update operation to occur.
</li>
</ol>
</li>
</ol>
</section>
<section>
<title>The database objects</title>
<p>
The database objects that are described in this section utilize Oracle
specific syntax. However, you should not infer from this that the
stored procedure support provided by OJB can only be used to access data
that is stored in an Oracle database. In reality, stored procedures can
be used for persistence operations in any database that supports stored
procedures.
</p>
<ul>
<li>The
<link href="#The+table">table</link> that will be manipulated,
</li>
<li>The
<link href="#The+sequence">sequence</link> that will be used by the stored
procedures to assign primary key values
</li>
<li>The
<link href="#The+insert+and+update+triggers">insert and update
triggers</link> that maintain the four 'audit' columns
</li>
<li>The
<link href="#The+package">package</link> that provides the stored
procedures that will handle the persistence operations.
</li>
</ul>
<p>
Click
<link href="#The+implementation">here</link> to skip the information about
the database objects and go straight to the implementation.
</p>
</section>
<section>
<title>The CUSTOMER table</title>
<p>
This example will deal exclusively with persistence operations related
to the a table named 'CUSTOMER' that is built using the following DDL:
</p>
<source><![CDATA[
CREATE TABLE CUSTOMER
( ID NUMBER(18) NOT NULL
, NAME VARCHAR2(50) NOT NULL
, USER_CREATED VARCHAR2(30)
, DATE_CREATED DATE
, USER_UPDATED VARCHAR2(30)
, DATE_UPDATED DATE
, CONSTRAINT PK_CUSTOMER PRIMARY KEY (ID)
);]]></source>
</section>
<section>
<title>The sequence</title>
<p>
This sequence will be used to assign unique values to
<code>CUSTOMER.ID</code>.
</p>
<source><![CDATA[
CREATE SEQUENCE CUSTOMER_SEQ;]]></source>
</section>
<section>
<title>The insert and update triggers</title>
<p>
These two triggers will implement all of the requirements listed
above that are related to the four audit columns:
</p>
<source><![CDATA[
CREATE OR REPLACE TRIGGER CUSTOMER_ITR
BEFORE INSERT ON CUSTOMER
FOR EACH ROW
BEGIN
--
-- Populate the audit dates
--
SELECT SYSDATE, SYSDATE
INTO :NEW.DATE_CREATED, :NEW.DATE_UPDATED
FROM DUAL;
--
-- Make sure the user created column is populated.
--
IF :NEW.USER_CREATED IS NULL
THEN
SELECT SYS_CONTEXT('USERENV','TERMINAL')
INTO :NEW.USER_CREATED
FROM DUAL;
END IF;
--
-- Make sure the user updated column is populated.
--
IF :NEW.USER_UPDATED IS NULL
THEN
SELECT SYS_CONTEXT('USERENV','TERMINAL')
INTO :NEW.USER_UPDATED
FROM DUAL;
END IF;
END;
/
CREATE OR REPLACE TRIGGER CUSTOMER_UTR
BEFORE UPDATE ON CUSTOMER
FOR EACH ROW
BEGIN
--
-- Populate the date updated
--
SELECT SYSDATE
INTO :NEW.DATE_UPDATED
FROM DUAL;
--
-- Make sure the user updated column is populated.
--
IF :NEW.USER_UPDATED IS NULL
THEN
SELECT SYS_CONTEXT('USERENV','TERMINAL')
INTO :NEW.USER_UPDATED
FROM DUAL;
END IF;
--
-- Make sure the date/user created are never changed
--
SELECT :OLD.DATE_CREATED, :OLD.USER_CREATED
INTO :NEW.DATE_CREATED, :NEW.USER_CREATED
FROM DUAL;
END;
/]]></source>
</section>
<section>
<title>The package</title>
<p>
This Oracle package will handle all INSERT, UPDATE and DELETE operations
involving the
<code>CUSTOMER</code> table.
</p>
<source><![CDATA[
CREATE OR REPLACE PACKAGE CUSTOMER_PKG AS
--
-- This procedure should be used to add a record to the CUSTOMER table.
--
PROCEDURE ADD ( AID IN OUT CUSTOMER.ID%TYPE
, ANAME IN CUSTOMER.NAME%TYPE
, AUSER_CREATED IN OUT CUSTOMER.USER_CREATED%TYPE
, ADATE_CREATED IN OUT CUSTOMER.DATE_CREATED%TYPE
, AUSER_UPDATED IN OUT CUSTOMER.USER_UPDATED%TYPE
, ADATE_UPDATED IN OUT CUSTOMER.DATE_UPDATED%TYPE );
--
-- This procedure should be used to change a record on the CUSTOMER table.
--
PROCEDURE CHANGE ( AID IN CUSTOMER.ID%TYPE
, ANAME IN CUSTOMER.NAME%TYPE
, AUSER_CREATED IN OUT CUSTOMER.USER_CREATED%TYPE
, ADATE_CREATED IN OUT CUSTOMER.DATE_CREATED%TYPE
, AUSER_UPDATED IN OUT CUSTOMER.USER_UPDATED%TYPE
, ADATE_UPDATED IN OUT CUSTOMER.DATE_UPDATED%TYPE );
--
-- This procedure should be used to delete a record from the CUSTOMER table.
--
PROCEDURE DELETE ( AID IN CUSTOMER.ID%TYPE );
END CUSTOMER_PKG;
/
CREATE OR REPLACE PACKAGE BODY CUSTOMER_PKG AS
--
-- This procedure should be used to add a record to the CUSTOMER table.
--
PROCEDURE ADD ( AID IN OUT CUSTOMER.ID%TYPE
, ANAME IN CUSTOMER.NAME%TYPE
, AUSER_CREATED IN OUT CUSTOMER.USER_CREATED%TYPE
, ADATE_CREATED IN OUT CUSTOMER.DATE_CREATED%TYPE
, AUSER_UPDATED IN OUT CUSTOMER.USER_UPDATED%TYPE
, ADATE_UPDATED IN OUT CUSTOMER.DATE_UPDATED%TYPE )
IS
NEW_SEQUENCE_1 CUSTOMER.ID%TYPE;
BEGIN
SELECT CUSTOMER_SEQ.NEXTVAL
INTO NEW_SEQUENCE_1
FROM DUAL;
INSERT INTO CUSTOMER ( ID, NAME, USER_CREATED, USER_UPDATED )
VALUES ( NEW_SEQUENCE_1, ANAME, AUSER_CREATED, AUSER_UPDATED )
RETURNING ID, USER_CREATED, DATE_CREATED, USER_UPDATED, DATE_UPDATED
INTO AID, AUSER_CREATED, ADATE_CREATED, AUSER_UPDATED, ADATE_UPDATED;
END ADD;
--
-- This procedure should be used to change a record on the CUSTOMER table.
--
PROCEDURE CHANGE ( AID IN CUSTOMER.ID%TYPE
, ANAME IN CUSTOMER.NAME%TYPE
, AUSER_CREATED IN OUT CUSTOMER.USER_CREATED%TYPE
, ADATE_CREATED IN OUT CUSTOMER.DATE_CREATED%TYPE
, AUSER_UPDATED IN OUT CUSTOMER.USER_UPDATED%TYPE
, ADATE_UPDATED IN OUT CUSTOMER.DATE_UPDATED%TYPE )
IS
BEGIN
UPDATE CUSTOMER
SET NAME = ANAME
, USER_CREATED = USER_CREATED
, USER_UPDATED = AUSER_UPDATED
WHERE ID = AID
RETURNING USER_CREATED, DATE_CREATED, USER_UPDATED, DATE_UPDATED
INTO AUSER_CREATED, ADATE_CREATED, AUSER_UPDATED, ADATE_UPDATED;
END CHANGE;
--
-- This procedure should be used to delete a record from the CUSTOMER table.
--
PROCEDURE DELETE ( AID IN CUSTOMER.ID%TYPE )
IS
BEGIN
DELETE
FROM CUSTOMER
WHERE ID = AID;
END DELETE;
END CUSTOMER_PKG;
/]]></source>
<p>
Please note the following about the structure of the
<code>CUSTOMER_PKG</code> package:
</p>
<ul>
<li>
The
<code>AID</code> argument that is passed to the the
<code>ADD</code> procedure is defined as
<code>IN OUT</code>. This
allows the procedure to return the newly assigned
<code>ID</code> to the caller.
</li>
<li>
In the
<code>ADD</code> and
<code>CHANGE</code> procedures, the
arguments that correspond to the four 'audit' columns are defined as
<code>IN OUT</code>. This allows the procedure to return the current
value of these columns to the 'caller'.
</li>
</ul>
</section>
<section>
<title>The implementation</title>
<p>
Getting OJB to utilize the stored procedures described earlier in this
document is as simple as adding a few descriptors to the repository. Here
is a class-descriptor related to the
<code>CUSTOMER</code> table that
includes all of the necessary descriptors.
</p>
<source><![CDATA[
<class-descriptor class="com.myproject.Customer" table="CUSTOMER">
<field-descriptor column="ID" jdbc-type="DECIMAL" name="id" primarykey="true"/>
<field-descriptor column="NAME" jdbc-type="VARCHAR" name="name"/>
<field-descriptor column="USER_CREATED" jdbc-type="VARCHAR" name="userCreated"/>
<field-descriptor column="DATE_CREATED" jdbc-type="TIMESTAMP" name="dateCreated"/>
<field-descriptor column="USER_UPDATED" jdbc-type="VARCHAR" name="userUpdated"/>
<field-descriptor column="DATE_UPDATED" jdbc-type="TIMESTAMP" name="dateUpdated"/>
<insert-procedure name="CUSTOMER_PKG.ADD">
<runtime-argument field-ref="id" return="true"/>
<runtime-argument field-ref="name"/>
<runtime-argument field-ref="userCreated" return="true"/>
<runtime-argument field-ref="dateCreated" return="true"/>
<runtime-argument field-ref="userUpdated" return="true"/>
<runtime-argument field-ref="dateUpdated" return="true"/>
</insert-procedure>
<update-procedure name="CUSTOMER_PKG.CHG">
<runtime-argument field-ref="id"/>
<runtime-argument field-ref="name"/>
<runtime-argument field-ref="userCreated" return="true"/>
<runtime-argument field-ref="dateCreated" return="true"/>
<runtime-argument field-ref="userUpdated" return="true"/>
<runtime-argument field-ref="dateUpdated" return="true"/>
</update-procedure>
<delete-procedure name="CUSTOMER_PKG.CHG">
<runtime-argument field-ref="id"/>
</delete-procedure>
</class-descriptor>]]></source>
<p>
Some things to note about this class-descriptor:
</p>
<ol>
<li>
In the insert-procedure descriptor, the first runtime-argument descriptor
correspnds to the "AID" argument that is passed to the CUSTOMER_PKG.ADD
routine. The "return" attribute on this runtime-argument is set to
"true". With this configuration, OJB will 'harvest' the value that is
returned by the CUSTOMER_PKG.ADD stored procedure and store the value in
the "id" attribute on the com.myproject.Customer class.
</li>
<li>
In both the insert-procedure and update-procedure descriptors, the
runtime-argument descriptors that correspond to the four 'audit' columns
all have the "return" argument set to "true". This allows any updates that
are made by the procedure or the insert/update triggers to be reflected in
the "Customer" object that caused the insert/update operation to occur.
</li>
</ol>
</section>
</section>
<section>
<title>A complex example</title>
<p>
This example builds upon the
<link href="#A+simple+example">simple example</link>
that was presented earlier by introducing some additional requirements
beyond those that were specified in the simple example. Some of these
additional requirements may seem a little contrived. To be honest, they
are. The only purpose of these additional requirements is to create
situations that illustrate how the additional capabilities provided by OJB's
support for stored procedures can be utilized.
</p>
<p>
The additional requirements for this example include the following:
</p>
<ul>
<li>
All procedures will include two additional arguments. These two new
arguments will be added to the end of the argument list for all existing
procedures.
<ul>
<li>
<code>ASOURCE_SYSTEM</code> - identifies the system that initiated the
persistence operation. This will provide a higher level of audit
tracking capability. In our example, this will always be "SAMPLE".
</li>
<li>
<code>ACOST_CENTER</code> - identifies the 'cost center' that should
be charged for the persistence operation. In our example, this argument
will always be null.
</li>
</ul>
</li>
<li>
For all "ADD" and "CHG" stored procedures, the value that was assigned to
the "DATE_UPDATED" column will no longer be returned to the caller via an
"IN OUT" argument. Instead, it will be returend to the caller via the
procedure's return value.
</li>
</ul>
<p>
Based on these new requirements, the class-descriptor for the
"com.myproject.Customer" class will look like this. The specific changes
are detailed below.
</p>
<source><![CDATA[
<class-descriptor class="com.myproject.Customer" table="CUSTOMER">
<field-descriptor column="ID" jdbc-type="DECIMAL" name="id" primarykey="true"/>
<field-descriptor column="NAME" jdbc-type="VARCHAR" name="name"/>
<field-descriptor column="USER_CREATED" jdbc-type="VARCHAR" name="userCreated"/>
<field-descriptor column="DATE_CREATED" jdbc-type="TIMESTAMP" name="dateCreated"/>
<field-descriptor column="USER_UPDATED" jdbc-type="VARCHAR" name="userUpdated"/>
<field-descriptor column="DATE_UPDATED" jdbc-type="TIMESTAMP" name="dateUpdated"/>
<insert-procedure name="CUSTOMER_PKG.ADD"
return-field-ref="dateUpdated"> <!-- See note 1 -->
<runtime-argument field-ref="id" return="true"/>
<runtime-argument field-ref="name"/>
<runtime-argument field-ref="userCreated" return="true"/>
<runtime-argument field-ref="dateCreated" return="true"/>
<runtime-argument field-ref="userUpdated" return="true"/>
<runtime-argument field-ref="dateUpdated"/> <!-- See note 2 -->
<constant-argument value="SAMPLE"/> <!-- See note 3 -->
<runtime-argument/> <!-- See note 4 -->
</insert-procedure>
<update-procedure name="CUSTOMER_PKG.CHG"
return-field-ref="dateUpdated"> <!-- See note 1 -->
<runtime-argument field-ref="id"/>
<runtime-argument field-ref="name"/>
<runtime-argument field-ref="userCreated" return="true"/>
<runtime-argument field-ref="dateCreated" return="true"/>
<runtime-argument field-ref="userUpdated" return="true"/>
<runtime-argument field-ref="dateUpdated"/> <!-- See note 2 -->
<constant-argument value="SAMPLE"/> <!-- See note 3 -->
<runtime-argument/> <!-- See note 4 -->
</update-procedure>
<delete-procedure name="CUSTOMER_PKG.CHG">
<runtime-argument field-ref="id"/>
<constant-argument value="SAMPLE"/> <!-- See note 3 -->
<runtime-argument/> <!-- See note 4 -->
</delete-procedure>
</class-descriptor>]]></source>
<p>
Here are an explanation of each modification:
</p>
<ul>
<li>
<strong>Note 1:</strong>
The value that is returned by the "ADD" and "CHG" stored procedures will
now be stored in the "dateUpdated" attribute on the
"com.myproject.Customer" class.
</li>
<li>
<strong>Note 2:</strong>
Since the ADATE_UPDATED argument is no longer defined as an "IN OUT"
argument, we have removed the "return" attribute from the corresponding
runtime-argument descriptor.
</li>
<li>
<strong>Note 3:</strong>
This is the first of two new arguments that were added to the argument
list of each procedure. This argument represents the 'source system',
the system that initiated the persistence operation. In our example,
we will always pass a value of 'SAMPLE'.
</li>
<li>
<strong>Note 4:</strong>
This is the second of two new arguments that were added to the argument
list of each procedure. This argument represents the 'cost center' that
should be charged for the persistence operation. In our example, we
have no cost center, so we need to pass a null value. This is
accomplished by including a 'runtime-argument' descriptor that has
no 'field-ref' specified.
</li>
</ul>
</section>
</body>
</document>
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