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Posted to commits@tapestry.apache.org by bu...@apache.org on 2017/09/26 19:20:28 UTC
svn commit: r1018755 [15/15] - in /websites/production/tapestry/content: ./
cache/
Modified: websites/production/tapestry/content/uploading-files.html
==============================================================================
--- websites/production/tapestry/content/uploading-files.html (original)
+++ websites/production/tapestry/content/uploading-files.html Tue Sep 26 19:20:27 2017
@@ -27,16 +27,6 @@
</title>
<link type="text/css" rel="stylesheet" href="/resources/space.css" />
- <link href='/resources/highlighter/styles/shCoreCXF.css' rel='stylesheet' type='text/css' />
- <link href='/resources/highlighter/styles/shThemeCXF.css' rel='stylesheet' type='text/css' />
- <script src='/resources/highlighter/scripts/shCore.js' type='text/javascript'></script>
- <script src='/resources/highlighter/scripts/shBrushJava.js' type='text/javascript'></script>
- <script src='/resources/highlighter/scripts/shBrushXml.js' type='text/javascript'></script>
- <script src='/resources/highlighter/scripts/shBrushPlain.js' type='text/javascript'></script>
- <script>
- SyntaxHighlighter.defaults['toolbar'] = false;
- SyntaxHighlighter.all();
- </script>
<link href="/styles/style.css" rel="stylesheet" type="text/css"/>
@@ -77,24 +67,20 @@
</div>
<div id="content">
- <div id="ConfluenceContent"><p>Tapestry provides a file upload component based on <a class="external-link" href="http://commons.apache.org/fileupload/">Apache Commons FileUpload</a> to make it easier to handle files uploaded through web forms (via the standard <input type="file"> HTML element).</p><h1 id="UploadingFiles-Downloading">Downloading</h1><p><strong>tapestry-upload</strong> is not automatically included in Tapestry applications because of the additional dependencies it requires. To include it, just add the <code>tapestry-upload</code> dependency to the pom of your application, something like this:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<pre class="brush: xml; gutter: false; theme: Default" style="font-size:12px;"><dependency>
+ <div id="ConfluenceContent"><p>Tapestry provides a file upload component based on <a class="external-link" href="http://commons.apache.org/fileupload/">Apache Commons FileUpload</a> to make it easier to handle files uploaded through web forms (via the standard <input type="file"> HTML element).</p><h1 id="UploadingFiles-Downloading">Downloading</h1><p><strong>tapestry-upload</strong> is not automatically included in Tapestry applications because of the additional dependencies it requires. To include it, just add the <code>tapestry-upload</code> dependency to the pom of your application, something like this:</p><parameter ac:name="language">xml</parameter><plain-text-body><dependency>
<groupId>org.apache.tapestry</groupId>
<artifactId>tapestry-upload</artifactId>
<version>${tapestry-release-version}</version>
</dependency>
-</pre>
-</div></div><p>If you aren't using Maven, you'll have to download the jar and its dependencies yourself.</p><h1 id="UploadingFiles-Usage">Usage</h1><p>The upload component supports default value binding (based on id) and validation.</p><div class="navmenu" style="float:right; background:#eee; margin:3px; padding:0 1em">
-<p> <strong>JumpStart Demo:</strong><br clear="none">
- <a class="external-link" href="http://jumpstart.doublenegative.com.au/jumpstart/examples/javascript/fileupload" rel="nofollow">File Upload</a></p></div><h2 id="UploadingFiles-ComponentTemplate">Component Template</h2><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> <t:form>
+</plain-text-body><p>If you aren't using Maven, you'll have to download the jar and its dependencies yourself.</p><h1 id="UploadingFiles-Usage">Usage</h1><p>The upload component supports default value binding (based on id) and validation.</p><plain-text-body>{float:right|background=#eee|padding=0 1em}
+ *JumpStart Demo:*
+ [File Upload|http://jumpstart.doublenegative.com.au/jumpstart/examples/javascript/fileupload]
+{float}</plain-text-body><h2 id="UploadingFiles-ComponentTemplate">Component Template</h2><parameter ac:name="language">java</parameter><plain-text-body> <t:form>
<t:errors/>
<input t:type="upload" t:id="file" t:value="file" validate="required"/>
<br/>
<input type="submit" value="Upload"/>
- </t:form></pre>
-</div></div><p>Here, because the value parameter was not bound, the component used the file property of its container (because the component's id is 'file'). If you want to upload as a different property, either bind the value parameter or change the component's id.</p><h2 id="UploadingFiles-Pageclass">Page class</h2><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> public class UploadExample
+ </t:form></plain-text-body><p>Here, because the value parameter was not bound, the component used the file property of its container (because the component's id is 'file'). If you want to upload as a different property, either bind the value parameter or change the component's id.</p><h2 id="UploadingFiles-Pageclass">Page class</h2><parameter ac:name="language">java</parameter><plain-text-body> public class UploadExample
{
@Property
private UploadedFile file;
@@ -105,9 +91,7 @@
file.write(copied);
}
- }</pre>
-</div></div><h1 id="UploadingFiles-UploadExceptions">Upload Exceptions</h1><p>In some cases, file uploads may fail. This can be because of a simple communication exception, or more likely, because the configured maximum upload size was exceeded.</p><p>When a file upload exception occurs, Tapestry will trigger a "uploadException" event on the page to notify it of the error. All other normal processing is skipped (no "activate" event, no form submission, etc.).</p><p>The event handler should return a non-null object, which will be handled as a navigational result. Example:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> @Persist(PersistenceConstants.FLASH)
+ }</plain-text-body><h1 id="UploadingFiles-UploadExceptions">Upload Exceptions</h1><p>In some cases, file uploads may fail. This can be because of a simple communication exception, or more likely, because the configured maximum upload size was exceeded.</p><p>When a file upload exception occurs, Tapestry will trigger a "uploadException" event on the page to notify it of the error. All other normal processing is skipped (no "activate" event, no form submission, etc.).</p><p>The event handler should return a non-null object, which will be handled as a navigational result. Example:</p><parameter ac:name="language">java</parameter><plain-text-body> @Persist(PersistenceConstants.FLASH)
@Property
private String message;
@@ -117,8 +101,7 @@
message = "Upload exception: " + ex.getMessage();
return this;
- }</pre>
-</div></div><p>Note the importance of <code>return this;</code>. A void event handler method, or one that returns null, will result in the FileUploadException being reported to the user as an uncaught runtime exception.</p><h1 id="UploadingFiles-Configuration">Configuration</h1><p>Four values may be configured as <a href="symbols.html">symbols</a>:</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.repository-location</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>The directory to which files that are too large to keep in memory will be written to. The default is from the java.io.tmpdir system property.</p></td></tr><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.repository-threshold</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>Upload size, in bytes, at which point the uploaded file is written to disk rather than kept in memory. The default is 10 kilobytes.</p></t
d></tr><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.requestsize-max</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>Maximim size, in bytes, for the overall request. If exceeded, a FileUploadException will occur. The default is no maximum.</p></td></tr><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.filesize-max</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>Maximum size, in bytes, for any individual uploaded file. Again, a FileUploadException will occur if exceeded. The default is no maximum.</p></td></tr></tbody></table></div><p>The class <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/upload/services/UploadSymbols.html">UploadSymbols</a> defines constants for all four of these.</p><h1 id="UploadingFiles-PotentialIssues">Potential Issues</h1><p>The Commons FileUpload library uses the CommonsIO file cleaner service to remove temporary files when they are no longer needed. This s
ervice creates a thread to carry out its work. If the commons-io library is shared amongst multiple applications (e.g. added to server classpath) it is possible for an application to terminate this thread prematurely and cause errors for the other applications. (see the <a class="external-link" href="http://jakarta.apache.org/commons/fileupload/using.html">Resource Cleanup</a> section in for more discussion)</p><p>Technically the file cleanup service is not needed by Tapestry Upload (which deletes temporary files at the end of request processing). However it is currently not possible to disable it (enhancement request has been filed as <a class="external-link" href="https://issues.apache.org/jira/browse/FILEUPLOAD-133">FILEUPLOAD-133</a>).</p></div>
+ }</plain-text-body><p>Note the importance of <code>return this;</code>. A void event handler method, or one that returns null, will result in the FileUploadException being reported to the user as an uncaught runtime exception.</p><h1 id="UploadingFiles-Configuration">Configuration</h1><p>Four values may be configured as <a href="symbols.html">symbols</a>:</p><div class="table-wrap"><table class="confluenceTable"><tbody><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.repository-location</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>The directory to which files that are too large to keep in memory will be written to. The default is from the java.io.tmpdir system property.</p></td></tr><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.repository-threshold</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>Upload size, in bytes, at which point the uploaded file is written to disk rather than kept in memory. The default is 10 kiloby
tes.</p></td></tr><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.requestsize-max</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>Maximim size, in bytes, for the overall request. If exceeded, a FileUploadException will occur. The default is no maximum.</p></td></tr><tr><th colspan="1" rowspan="1" class="confluenceTh"><p>upload.filesize-max</p></th><td colspan="1" rowspan="1" class="confluenceTd"><p>Maximum size, in bytes, for any individual uploaded file. Again, a FileUploadException will occur if exceeded. The default is no maximum.</p></td></tr></tbody></table></div><p>The class <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/upload/services/UploadSymbols.html">UploadSymbols</a> defines constants for all four of these.</p><h1 id="UploadingFiles-PotentialIssues">Potential Issues</h1><p>The Commons FileUpload library uses the CommonsIO file cleaner service to remove temporary files when they are no longer nee
ded. This service creates a thread to carry out its work. If the commons-io library is shared amongst multiple applications (e.g. added to server classpath) it is possible for an application to terminate this thread prematurely and cause errors for the other applications. (see the <a class="external-link" href="http://jakarta.apache.org/commons/fileupload/using.html">Resource Cleanup</a> section in for more discussion)</p><p>Technically the file cleanup service is not needed by Tapestry Upload (which deletes temporary files at the end of request processing). However it is currently not possible to disable it (enhancement request has been filed as <a class="external-link" href="https://issues.apache.org/jira/browse/FILEUPLOAD-133">FILEUPLOAD-133</a>).</p></div>
</div>
<div class="clearer"></div>
Modified: websites/production/tapestry/content/using-select-with-a-list.html
==============================================================================
--- websites/production/tapestry/content/using-select-with-a-list.html (original)
+++ websites/production/tapestry/content/using-select-with-a-list.html Tue Sep 26 19:20:27 2017
@@ -27,16 +27,6 @@
</title>
<link type="text/css" rel="stylesheet" href="/resources/space.css" />
- <link href='/resources/highlighter/styles/shCoreCXF.css' rel='stylesheet' type='text/css' />
- <link href='/resources/highlighter/styles/shThemeCXF.css' rel='stylesheet' type='text/css' />
- <script src='/resources/highlighter/scripts/shCore.js' type='text/javascript'></script>
- <script src='/resources/highlighter/scripts/shBrushJava.js' type='text/javascript'></script>
- <script src='/resources/highlighter/scripts/shBrushXml.js' type='text/javascript'></script>
- <script src='/resources/highlighter/scripts/shBrushPlain.js' type='text/javascript'></script>
- <script>
- SyntaxHighlighter.defaults['toolbar'] = false;
- SyntaxHighlighter.all();
- </script>
<link href="/styles/style.css" rel="stylesheet" type="text/css"/>
@@ -77,15 +67,13 @@
</div>
<div id="content">
- <div id="ConfluenceContent"><h1 id="UsingSelectWithaList-UsingSelectWithaList">Using Select With a List</h1><p>The documentation for the <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Select.html">Select Component</a> and the <a href="tutorial.html">Tapestry Tutorial</a> provide simplistic examples of populating a drop-down menu (as the (X)HTML <em>Select</em> element) using comma-delimited strings and enums. However, most real-world Tapestry applications need to populate such menus using values from a database, commonly in the form of java.util.List objects. Doing so generally requires a <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/SelectModel.html">SelectModel</a> and a <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/ValueEncoder.html">ValueEncoder</a> bound to the Select component with its "model" a
nd "encoder" parameters:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"><t:select t:id="colorMenu" value="selectedColor" model="ColorSelectModel" encoder="colorEncoder" />
-</pre>
-</div></div><p>In the above example, ColorSelectModel must be of type SelectModel, or anything that Tapestry knows how to <a href="parameter-type-coercion.html">coerce</a> into a SelectModel, such as a List or a Map or a "value=label,value=label,..." delimited string, or anything Tapestry knows how to coerce into a List or Map, such as an Array or a comma-delimited String.</p><h2 id="UsingSelectWithaList-SelectModel">SelectModel</h2><div class="navmenu" style="float:right; background:#eee; margin:3px; padding:0 1em">
-<p> <strong>JumpStart Demos:</strong><br clear="none">
- <a class="external-link" href="http://jumpstart.doublenegative.com.au/jumpstart/examples/select/totalcontrolobject" rel="nofollow">Total Control Object Select</a><br clear="none">
- <a class="external-link" href="http://jumpstart.doublenegative.com.au/jumpstart/examples/select/id" rel="nofollow">ID Select</a><br clear="none">
- <a class="external-link" href="http://jumpstart.doublenegative.com.au/jumpstart/examples/select/easyid" rel="nofollow">Easy ID Select</a></p></div><p>A SelectModel is a collection of options (specifically <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/OptionModel.html">OptionModel</a> objects) for a drop-down menu. Basically, each option is a value (an object) and a label (presented to the user).</p><p>If you provide a property of type List for the "model" parameter, Tapestry automatically builds a SelectModel that uses each object's toString() for both the select option value and the select option label. For database-derrived lists this is rarely useful, however, since after form submission you would then have to look up the selected object using that label.</p><p>If you provide a Map, Tapestry builds a SelectModel that uses each item's key as the encoded value and its value as the user-visible label. This is more useful, but if
you are going to build a copy of the list as a map just for this purpose, you may as well let Tapestry do it for you, using SelectModelFactory.</p><h2 id="UsingSelectWithaList-SelectModelFactory">SelectModelFactory</h2><p>To have Tapestry create a SelectModel for you, use the <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/services/SelectModelFactory.html">SelectModelFactory</a> service. SelectModelFactory creates a SelectModel from a List of objects (of whatever type) and a label property name that you choose:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>SelectWithListDemo.java (a page class)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">@Property
+ <div id="ConfluenceContent"><plain-text-body>{scrollbar}</plain-text-body><parameter ac:name="hidden">true</parameter><parameter ac:name="atlassian-macro-output-type">BLOCK</parameter><rich-text-body><p>Using SelectModel, SelectModelFactory and ValueEncoder for Select menus populated from a database</p></rich-text-body><h1 id="UsingSelectWithaList-UsingSelectWithaList">Using Select With a List</h1><p>The documentation for the <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/corelib/components/Select.html">Select Component</a> and the <a href="tutorial.html">Tapestry Tutorial</a> provide simplistic examples of populating a drop-down menu (as the (X)HTML <em>Select</em> element) using comma-delimited strings and enums. However, most real-world Tapestry applications need to populate such menus using values from a database, commonly in the form of java.util.List objects. Doing so generally requires a <a class="external-lin
k" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/SelectModel.html">SelectModel</a> and a <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/ValueEncoder.html">ValueEncoder</a> bound to the Select component with its "model" and "encoder" parameters:</p><plain-text-body><t:select t:id="colorMenu" value="selectedColor" model="ColorSelectModel" encoder="colorEncoder" />
+</plain-text-body><p>In the above example, ColorSelectModel must be of type SelectModel, or anything that Tapestry knows how to <a href="parameter-type-coercion.html">coerce</a> into a SelectModel, such as a List or a Map or a "value=label,value=label,..." delimited string, or anything Tapestry knows how to coerce into a List or Map, such as an Array or a comma-delimited String.</p><h2 id="UsingSelectWithaList-SelectModel">SelectModel</h2><plain-text-body>{float:right|background=#eee|padding=0 1em}
+ *JumpStart Demos:*
+ [Total Control Object Select|http://jumpstart.doublenegative.com.au/jumpstart/examples/select/totalcontrolobject]
+ [ID Select|http://jumpstart.doublenegative.com.au/jumpstart/examples/select/id]
+ [Easy ID Select|http://jumpstart.doublenegative.com.au/jumpstart/examples/select/easyid]
+{float}</plain-text-body><p>A SelectModel is a collection of options (specifically <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/OptionModel.html">OptionModel</a> objects) for a drop-down menu. Basically, each option is a value (an object) and a label (presented to the user).</p><p>If you provide a property of type List for the "model" parameter, Tapestry automatically builds a SelectModel that uses each object's toString() for both the select option value and the select option label. For database-derrived lists this is rarely useful, however, since after form submission you would then have to look up the selected object using that label.</p><p>If you provide a Map, Tapestry builds a SelectModel that uses each item's key as the encoded value and its value as the user-visible label. This is more useful, but if you are going to build a copy of the list as a map just for this purpose, you may as well let Tapestry do it for you, using Se
lectModelFactory.</p><h2 id="UsingSelectWithaList-SelectModelFactory">SelectModelFactory</h2><p>To have Tapestry create a SelectModel for you, use the <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/services/SelectModelFactory.html">SelectModelFactory</a> service. SelectModelFactory creates a SelectModel from a List of objects (of whatever type) and a label property name that you choose:</p><parameter ac:name="title">SelectWithListDemo.java (a page class)</parameter><plain-text-body>@Property
private SelectModel colorSelectModel;
@Inject
SelectModelFactory selectModelFactory;
@@ -97,18 +85,15 @@ void setupRender() {
// create a SelectModel from my list of colors
colorSelectModel = selectModelFactory.create(colors, "name");
}
-</pre>
-</div></div><p>The resulting SelectModel has a selectable option (specifically, an OptionModel) for every object in the original List. The label property name (the "name" property, in this example) determines the user-visible text of each menu option, and your ValueEncoder's toClient() method provides the encoded value (most commonly a simple number). If you don't provide a ValueEncoder, the result of the objects' toString() method (Color#toString() in this example) is used. Although not a recommended practice, you <em>could</em> set your toString() to return the object's ID for this purpose:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>Color.java (partial)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">...
+</plain-text-body><p>The resulting SelectModel has a selectable option (specifically, an OptionModel) for every object in the original List. The label property name (the "name" property, in this example) determines the user-visible text of each menu option, and your ValueEncoder's toClient() method provides the encoded value (most commonly a simple number). If you don't provide a ValueEncoder, the result of the objects' toString() method (Color#toString() in this example) is used. Although not a recommended practice, you <em>could</em> set your toString() to return the object's ID for this purpose:</p><parameter ac:name="title">Color.java (partial)</parameter><plain-text-body>...
@Override
public String toString() {
return String.valueOf(this.getId());
}
-</pre>
-</div></div><p>But that is contorting the purpose of the toString() method, and if you go to that much trouble you're already half way to the recommended practice: creating a ValueEncoder.</p><h2 id="UsingSelectWithaList-ValueEncoder">ValueEncoder</h2><p>In addition to a SelectModel, your Select menu is likely to need a ValueEncoder. While a SelectModel is concerned only with how to construct a Select menu, a ValueEncoder is used when constructing the Select menu <em>and</em> when interpreting the encoded value that is submitted back to the server. A ValueEncoder is a converter between the type of objects you want to represent as options in the menu and the client-side encoded values that uniquely identify them, and vice-versa.</p><div class="navmenu" style="float:right; background:#eee; margin:3px; padding:0 1em">
-<p> <strong>JumpStart Demo:</strong><br clear="none">
- <a class="external-link" href="http://jumpstart.doublenegative.com.au/jumpstart/examples/select/easyobject" rel="nofollow">Easy Object Select</a></p></div><p>Most commonly, your ValueEncoder's toClient() method will return a unique ID (e.g. a database primary key, or perhaps a UUID) of the given object, and its toValue() method will return the <em>object</em> matching the given ID by doing a database lookup (ideally using a service or DAO method).</p><p>If you're using one of the ORM integration modules (<a href="hibernate.html">Tapestry-Hibernate</a>, <a href="integrating-with-jpa.html">Tapestry-JPA</a>, or <a class="external-link" href="http://code.google.com/p/tapestry5-cayenne/wiki/ValueEncoder" rel="nofollow">Tapestry-Cayenne</a>), the ValueEncoder is automatically provided for each of your mapped entity classes. The Hibernate module's implementation is typical: the primary key field of the object (converted to a String) is used as the client-side value, and that same p
rimary key is used to look up the selected object.</p><p>That's exactly what you should do in your own ValueEncoders too:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>ColorEncoder.java (perhaps in your com.example.myappname.encoders package)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">public class ColorEncoder implements ValueEncoder<Color>, ValueEncoderFactory<Color> {
+</plain-text-body><p>But that is contorting the purpose of the toString() method, and if you go to that much trouble you're already half way to the recommended practice: creating a ValueEncoder.</p><h2 id="UsingSelectWithaList-ValueEncoder">ValueEncoder</h2><p>In addition to a SelectModel, your Select menu is likely to need a ValueEncoder. While a SelectModel is concerned only with how to construct a Select menu, a ValueEncoder is used when constructing the Select menu <em>and</em> when interpreting the encoded value that is submitted back to the server. A ValueEncoder is a converter between the type of objects you want to represent as options in the menu and the client-side encoded values that uniquely identify them, and vice-versa.</p><plain-text-body>{float:right|background=#eee|padding=0 1em}
+ *JumpStart Demo:*
+ [Easy Object Select|http://jumpstart.doublenegative.com.au/jumpstart/examples/select/easyobject]
+{float}</plain-text-body><p>Most commonly, your ValueEncoder's toClient() method will return a unique ID (e.g. a database primary key, or perhaps a UUID) of the given object, and its toValue() method will return the <em>object</em> matching the given ID by doing a database lookup (ideally using a service or DAO method).</p><p>If you're using one of the ORM integration modules (<a href="hibernate.html">Tapestry-Hibernate</a>, <a href="integrating-with-jpa.html">Tapestry-JPA</a>, or <a class="external-link" href="http://code.google.com/p/tapestry5-cayenne/wiki/ValueEncoder" rel="nofollow">Tapestry-Cayenne</a>), the ValueEncoder is automatically provided for each of your mapped entity classes. The Hibernate module's implementation is typical: the primary key field of the object (converted to a String) is used as the client-side value, and that same primary key is used to look up the selected object.</p><p>That's exactly what you should do in your own ValueEncoders too:</p><parameter
ac:name="title">ColorEncoder.java (perhaps in your com.example.myappname.encoders package)</parameter><plain-text-body>public class ColorEncoder implements ValueEncoder<Color>, ValueEncoderFactory<Color> {
@Inject
private ColorService colorService;
@@ -131,9 +116,7 @@ public String toString() {
return this;
}
}
-</pre>
-</div></div><p>Alternatively, if you don't expect to need a particular ValueEncoder more than once in your app, you might want to just create it on demand, using an anonymous inner class, from the getter method in the component class where it is needed. For example:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>SelectWithListDemo.java (a page class, partial)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"> . . .
+</plain-text-body><p>Alternatively, if you don't expect to need a particular ValueEncoder more than once in your app, you might want to just create it on demand, using an anonymous inner class, from the getter method in the component class where it is needed. For example:</p><parameter ac:name="title">SelectWithListDemo.java (a page class, partial)</parameter><plain-text-body> . . .
public ValueEncoder<Color> getColorEncoder() {
@@ -152,35 +135,26 @@ public String toString() {
}
};
}
-</pre>
-</div></div><p>Notice that the body of this anonymous inner class is the same as the body of the ColorEncoder top level class, except that we don't need a <code>create</code> method.</p><h2 id="UsingSelectWithaList-ApplyingyourValueEncoderAutomatically">Applying your ValueEncoder Automatically</h2><p>If your ValueEncoder <em>implements ValueEncoderFactory</em> (as the ColorEncoder top level class does, above), you can associate your custom ValueEncoder with your entity class so that Tapestry will automatically use it every time a ValueEncoder is needed for items of that type (such as with the Select, RadioGroup, Grid, Hidden and AjaxFormLoop components). Just add lines like the following to your module class (usually AppModule.java):</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>AppModule.java (partial)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">...
+</plain-text-body><p>Notice that the body of this anonymous inner class is the same as the body of the ColorEncoder top level class, except that we don't need a <code>create</code> method.</p><h2 id="UsingSelectWithaList-ApplyingyourValueEncoderAutomatically">Applying your ValueEncoder Automatically</h2><p>If your ValueEncoder <em>implements ValueEncoderFactory</em> (as the ColorEncoder top level class does, above), you can associate your custom ValueEncoder with your entity class so that Tapestry will automatically use it every time a ValueEncoder is needed for items of that type (such as with the Select, RadioGroup, Grid, Hidden and AjaxFormLoop components). Just add lines like the following to your module class (usually AppModule.java):</p><parameter ac:name="title">AppModule.java (partial)</parameter><plain-text-body>...
public static void contributeValueEncoderSource(MappedConfiguration<Class<Color>,
ValueEncoderFactory<Color>> configuration) {
configuration.addInstance(Color.class, ColorEncoder.class);
}
-</pre>
-</div></div><p>If you are contributing more than one ValueEncoder, you'll have to use raw types, like this:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>AppModule.java (partial)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">...
+</plain-text-body><p>If you are contributing more than one ValueEncoder, you'll have to use raw types, like this:</p><parameter ac:name="title">AppModule.java (partial)</parameter><plain-text-body>...
public static void contributeValueEncoderSource(MappedConfiguration<Class,
ValueEncoderFactory> configuration)
{
configuration.addInstance(Color.class, ColorEncoder.class);
configuration.addInstance(SomeOtherType.class, SomeOtherTypeEncoder.class);
}
-</pre>
-</div></div><h2 id="UsingSelectWithaList-WhatifIomittheValueEncoder?">What if I omit the ValueEncoder?</h2><p>The Select component's "encoder" parameter is optional, but if the "value" parameter is bound to a complex object (not a simple String, Integer, etc.) and you don't provide a ValueEncoder with the "encoder" parameter (and one isn't provided automatically by, for example, the Tapestry Hibernate integration), you'll receive a "Could not find a coercion" exception (when you submit the form) as Tapestry tries to convert the selected option's encoded value back to the <em>object</em> in your Select's "value" parameter. To fix this, you'll either have to 1) provide a ValueEncoder, 2) provide a <a href="type-coercion.html">Coercion</a>, or 3) use a simple value (String, Integer, etc.) for your Select's "value" parameter, and then you'll have to add logic in the corresponding onSuccess event listener method:</p><div class="code panel pdl" style="border-width: 1px;"><div class="code
Header panelHeader pdl" style="border-bottom-width: 1px;"><b>SelectWithListDemo.tml (partial)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;"><t:select t:id="colorMenu" value="selectedColorId" model="ColorSelectModel" />
-</pre>
-</div></div><div class="code panel pdl" style="border-width: 1px;"><div class="codeHeader panelHeader pdl" style="border-bottom-width: 1px;"><b>SelectWithListDemo.java (partial)</b></div><div class="codeContent panelContent pdl">
-<pre class="brush: java; gutter: false; theme: Default" style="font-size:12px;">...
+</plain-text-body><h2 id="UsingSelectWithaList-WhatifIomittheValueEncoder?">What if I omit the ValueEncoder?</h2><p>The Select component's "encoder" parameter is optional, but if the "value" parameter is bound to a complex object (not a simple String, Integer, etc.) and you don't provide a ValueEncoder with the "encoder" parameter (and one isn't provided automatically by, for example, the Tapestry Hibernate integration), you'll receive a "Could not find a coercion" exception (when you submit the form) as Tapestry tries to convert the selected option's encoded value back to the <em>object</em> in your Select's "value" parameter. To fix this, you'll either have to 1) provide a ValueEncoder, 2) provide a <a href="type-coercion.html">Coercion</a>, or 3) use a simple value (String, Integer, etc.) for your Select's "value" parameter, and then you'll have to add logic in the corresponding onSuccess event listener method:</p><parameter ac:name="title">SelectWithListDemo.tml (partial)</para
meter><plain-text-body><t:select t:id="colorMenu" value="selectedColorId" model="ColorSelectModel" />
+</plain-text-body><parameter ac:name="title">SelectWithListDemo.java (partial)</parameter><plain-text-body>...
public void onSuccessFromMyForm() {
// look up the color object from the ID selected
selectedColor = colorService.findById(selectedColorId);
...
}
-</pre>
-</div></div><p>But then again, you may as well create a ValueEncoder instead.</p><h2 id="UsingSelectWithaList-Whyisthissohard?">Why is this so hard?</h2><p>Actually, it's really pretty easy if you follow the examples above. But why is Tapestry designed to use SelectModels and ValueEncoders anyway? Well, in short, this design allows you to avoid storing (via @Persist, @SessionAttribute or @SessionState) the entire (potentially large) list of objects in the session or rebuilding the whole list of objects again (though only one is needed) when the form is submitted. The chief benefits are reduced memory use and <a href="performance-and-clustering.html">more scalable clustering</a> due to having far less HTTP session data to replicate across the nodes of a cluster.</p></div>
+</plain-text-body><p>But then again, you may as well create a ValueEncoder instead.</p><h2 id="UsingSelectWithaList-Whyisthissohard?">Why is this so hard?</h2><p>Actually, it's really pretty easy if you follow the examples above. But why is Tapestry designed to use SelectModels and ValueEncoders anyway? Well, in short, this design allows you to avoid storing (via @Persist, @SessionAttribute or @SessionState) the entire (potentially large) list of objects in the session or rebuilding the whole list of objects again (though only one is needed) when the form is submitted. The chief benefits are reduced memory use and <a href="performance-and-clustering.html">more scalable clustering</a> due to having far less HTTP session data to replicate across the nodes of a cluster.</p></div>
</div>
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