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Posted to commits@tapestry.apache.org by bu...@apache.org on 2018/02/13 03:21:20 UTC
svn commit: r1025321 [1/3] - in /websites/production/tapestry/content: ./
cache/
Author: buildbot
Date: Tue Feb 13 03:21:20 2018
New Revision: 1025321
Log:
Production update by buildbot for tapestry
Modified:
websites/production/tapestry/content/cache/main.pageCache
websites/production/tapestry/content/class-reloading.html
websites/production/tapestry/content/component-classes.html
websites/production/tapestry/content/component-reference.html
websites/production/tapestry/content/component-templates.html
websites/production/tapestry/content/ioc-cookbook-service-configurations.html
websites/production/tapestry/content/property-expressions.html
websites/production/tapestry/content/supported-environments-and-versions.html
Modified: websites/production/tapestry/content/cache/main.pageCache
==============================================================================
Binary files - no diff available.
Modified: websites/production/tapestry/content/class-reloading.html
==============================================================================
--- websites/production/tapestry/content/class-reloading.html (original)
+++ websites/production/tapestry/content/class-reloading.html Tue Feb 13 03:21:20 2018
@@ -131,7 +131,7 @@
</div></div><p>This is the intent of service builder methods; to do more than just injecting dependencies.</p><h2 id="ClassReloading-CheckingForUpdates">Checking For Updates</h2><p>The built in InvalidationEventHub services provide notifications of changes to component classes, to component templates, and to component message catalogs. If you wish to check some other resources (for example, files in a directory of the file system or rows in a database table), you should register as an <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/services/UpdateListener.html">UpdateListener</a> with the <a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/services/UpdateListenerHub.html">UpdateListenerHub</a> service.</p><p>Periodically (the frequency is configurable), UpdateListeners are notified that they should check for updates. Typically, UpdateListeners are also InvalidationEventHubs (or provide Invali
dationEventHubs), so that other interested parties can be alerted when underlying data changes.</p><h2 id="ClassReloading-TroubleshootingLiveClassReloading">Troubleshooting Live Class Reloading</h2><h3 id="ClassReloading-QuickChecklist">Quick Checklist</h3><ul><li>"Production Mode" must be false (in Tapestry 5.3 and later)</li><li>The class must be one that Tapestry instantiates (a page, component, or mixin class, or a Tapestry IOC service implementation that implements an interface)</li><li>Turn on "Build Automatically" in your IDE, or remember to build manually.</li><li>Turn <em>off</em> JVM hot code swapping, if your servlet container supports it.</li><li>Eclipse: Uncheck the "derived" checkbox for the Target dir (in the Project Explorer view, right click on "target", select properties, uncheck "derived" on the Resource tab)</li></ul><p>Some of these issues are described in more detail below.</p><h3 id="ClassReloading-IfLiveClassReloadingdoesn'twork">If Live Class Reloading doesn
't work</h3><h4 id="ClassReloading-ProductionMode">Production Mode</h4><p>Starting with Tapestry 5.3, Live Class Reloading only works when not in "Production Mode". Check your application module (usually AppModule.java) to be sure you have:</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;">configuration.add(SymbolConstants.PRODUCTION_MODE, "false");
</pre>
-</div></div><p>and that this isn't being overridden to "true" on your application's startup command line.</p><h4 id="ClassReloading-BuildPathIssues">Build Path Issues</h4><p>Live Class Reloading can fail if your build path isn't set correctly, and the exact configuration may differ between Maven plugin versions and Eclipse versions. The build process must be set to create classes in a folder which is in the servlet container's classpath.</p><p>Live Class Reloading won't work correctly with vanilla Tomcat without some tweaks (see below).</p><p>Non-Tapestry filters can interfere with LCR. Try disabling other filters in your web.xml file to see if that helps.</p><h4 id="ClassReloading-BuildingAutomatically">Building Automatically</h4><p>Although LCR allows you to see changes without restarting your app, you still need to "build" your project (to compile the Java source into byte code). Your IDE can be set to do this automatically every time you save a file. (In Eclipse, this is done us
ing <code>Project > Build Automatically</code>.) Alternatively, you can manually trigger a build after you save a file. (In Eclipse, this is done using <code>Project > Build</code>, or by pressing <code>Control-B</code>.)</p><h4 id="ClassReloading-TurnoffJVMhotcodeswapping&automaticrestarts">Turn off JVM hot code swapping & automatic restarts</h4><p>Many servlet containers, including Tomcat and Jetty, support various forms of hot code swapping and/or automatic restarts when file changes are detected. These are generally <strong>much slower</strong> than LCR and usually should be turned off with Tapestry applications. If you're using RunJettyRun plugin for Eclipse, for example, edit your Run Configuration, and on the Jetty tab, click Show Advanced Options and uncheck the Enable Scanner checkbox.</p><h3 id="ClassReloading-TomcatSpecifics">Tomcat Specifics</h3><p>See <a class="external-link" href="http://docs.codehaus.org/display/TYNAMO/Developing+with+Tomcat+and+Eclipse
" rel="nofollow">these Tomcat-specific hints</a></p><h3 id="ClassReloading-IfLiveClassReloadingworksbutisslow">If Live Class Reloading works but is slow</h3><p>If LCR works for you but is slow (more than a second or two), consider the following.</p><ul><li>Be sure your project source files (your workspace in Eclipse, for example), are on a local drive, NOT a network location. Network drives are always slower, and the file system scanning needed for LCR can add a noticable lag if I/O is slow. If you use Maven, be sure to put your local repository (e.g. ~/.m2/repository) on a local drive for similar reasons.</li><li>Since LCR adds classes to your PermGen space, you may be running low on PermGen memory (and may eventually get a "java.lang.OutOfMemoryError: PermGen space" error). Try increasing PermGen size with a JVM argument of something like <code>-XX:MaxPermSize=400m</code></li></ul><p></p></div>
+</div></div><p>and that this isn't being overridden to "true" on your application's startup command line.</p><h4 id="ClassReloading-BuildPathIssues">Build Path Issues</h4><p>Live Class Reloading can fail if your build path isn't set correctly, and the exact configuration may differ between Maven plugin versions and Eclipse versions. The build process must be set to create classes in a folder which is in the servlet container's classpath.</p><p>Live Class Reloading won't work correctly with vanilla Tomcat without some tweaks (see below).</p><p>Non-Tapestry filters can interfere with LCR. Try disabling other filters in your web.xml file to see if that helps.</p><h4 id="ClassReloading-BuildingAutomatically">Building Automatically</h4><p>Although LCR allows you to see changes without restarting your app, you still need to "build" your project (to compile the Java source into byte code). Your IDE can be set to do this automatically every time you save a file. (In Eclipse, this is done us
ing <code>Project > Build Automatically</code>.) Alternatively, you can manually trigger a build after you save a file. (In Eclipse, this is done using <code>Project > Build</code>, or by pressing <code>Control-B</code>.)</p><h4 id="ClassReloading-TurnoffJVMhotcodeswapping&automaticrestarts">Turn off JVM hot code swapping & automatic restarts</h4><p>Many servlet containers, including Tomcat and Jetty, support various forms of hot code swapping and/or automatic restarts when file changes are detected. These are generally <strong>much slower</strong> than LCR and usually should be turned off with Tapestry applications. If you're using RunJettyRun plugin for Eclipse, for example, edit your Run Configuration, and on the Jetty tab, click Show Advanced Options and uncheck the Enable Scanner checkbox.</p><h3 id="ClassReloading-TomcatSpecifics">Tomcat Specifics</h3><p>See <a class="external-link" href="http://docs.codehaus.org/display/TYNAMO/Developing+with+Tomcat+and+Eclipse
" rel="nofollow">these Tomcat-specific hints</a></p><h3 id="ClassReloading-IfLiveClassReloadingworksbutisslow">If Live Class Reloading works but is slow</h3><p>If LCR works for you but is slow (more than a second or two), consider the following.</p><ul><li>Be sure your project source files (your workspace in Eclipse, for example), are on a local drive, NOT a network location. Network drives are always slower, and the file system scanning needed for LCR can add a noticable lag if I/O is slow. If you use Maven, be sure to put your local repository (e.g. ~/.m2/repository) on a local drive for similar reasons.</li><li><p>Java 7 and below: Since LCR adds classes to your PermGen space, you may be running low on PermGen memory (and may eventually get a "java.lang.OutOfMemoryError: PermGen space" error). Try increasing PermGen size with a JVM argument of something like -XX:MaxPermSize=400m. (PermGen settings are not relevant for Java 8 and above.)</p></li></ul><p> </p></div>
</div>
<div class="clearer"></div>
Modified: websites/production/tapestry/content/component-classes.html
==============================================================================
--- websites/production/tapestry/content/component-classes.html (original)
+++ websites/production/tapestry/content/component-classes.html Tue Feb 13 03:21:20 2018
@@ -171,13 +171,13 @@ public class HelloWorld
}
}
</pre>
-</div></div><p>In this example, just like the first one, the component's only job is to write out a fixed message. The @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/BeginRender.html">BeginRender</a> annotation is a type of <em><a href="component-classes.html">render phase annotation</a></em>, a method annotation that instructs Tapestry when and under what circumstances to invoke methods of your class.</p><p>These methods are not necessarily public; they can have any access level you like (unlike in Tapestry 4). By convention they usually have package-private access level (the default).</p><h2 id="ComponentClasses-ComponentPackages">Component Packages</h2><p>Component classes must exist within an appropriate package (this is necessary for runtime code transformation and class reloading to operate).</p><p>These packages exist under the application's root package, as follows:</p><ul><li>For pages, place classes in <em>root
</em>.<strong>pages</strong>. Page names are mapped to classes within this package.</li><li>For mixins, place classes in <em>root</em>.<strong>mixins</strong>. Mixin types are mapped to classes within this package.</li><li>For other components, place classes in <em>root</em>.<strong>components</strong>. Component types are mapped to classes within this package.</li></ul><p>In addition, it is common for an application to have base classes, often <em>abstract</em> base classes, that should not be directly referenced. These should <em>not</em> go in the <strong>pages</strong>, <strong>components</strong> or <strong>mixins</strong> packages, because they then look like valid pages, components or mixins. Instead, use the <em>root</em>.<strong>base</strong> package to store such base classes.</p><div class="confluence-information-macro confluence-information-macro-warning"><span class="aui-icon aui-icon-small aui-iconfont-error confluence-information-macro-icon"></span><div class="conflue
nce-information-macro-body"><p>Only component classes should go in any of these controlled packages; classes representing data, or interfaces, or anything that isn't precisely a component class, must go elsewhere. Any top-level class in any of the controlled packages will be transformed at runtime. The only exception is inner classes (anonymous or not), which are loaded by the same class loader as the component class loader, but not transformed as components.</p></div></div><h2 id="ComponentClasses-Sub-Folders/Sub-Packages">Sub-Folders / Sub-Packages</h2><p>Classes do not have to go directly inside the package (pages, components, mixins, etc.). It is valid to create a sub-package to store some of the classes. The sub-package name becomes part of the page name or component type. Thus you might define a page component <code>com.example.myapp.pages.admin.CreateUser</code> and the logical page name (which often shows up inside URLs) will be <strong>admin/CreateUser</strong>.</p><p>Tapes
try performs some simple optimizations of the logical page name (or component type, or mixin type). It checks to see if the package name is either a prefix or a suffix of the unqualified class name (case insensitively, of course) and removes the prefix or suffix if so. The net result is that a class name such as <code>com.example.myapp.pages.user.EditUser</code> will have a page name of <code>user/Edit</code> (instead of user<code>/EditUser</code>). The goal here is to provide shorter, more natural URLs.</p><h2 id="ComponentClasses-IndexPages">Index Pages</h2><p>One special simplification exists for Index pages: if the logical page name is Index after removing the package name from the unqualified class name, it will map to the root of that folder. A class such as <code>com.example.myapp.pages.user.IndexUser</code> or <code>com.example.myapp.pages.user.UserIndex</code> will have a page name of <code>user/</code>.</p><p>In previous versions of Tapestry there was also the concept of a
start page configured with the <code><a href="component-classes.html">tapestry.start-page-name</a></code> configuration symbol (defaults to "start"). If a page with a name as configured with that symbol exists at the root level, this page is used as the root URL. This has precedence over an existing Index page. If for example you have a page class <code>com.example.myapp.pages.Start</code> it will map to <code>/</code>.</p><div class="confluence-information-macro confluence-information-macro-warning"><span class="aui-icon aui-icon-small aui-iconfont-error confluence-information-macro-icon"></span><div class="confluence-information-macro-body"><p>Use of start-pages is discouraged and support for it will eventually be removed. Use an Index page instead.</p></div></div><h2 id="ComponentClasses-Pagesvs.Components">Pages vs. Components</h2><p>The distinction between pages and component is very, very small. The primary difference is the package name: <em>root</em>.<strong>pages</strong>
.<em>PageName</em> for pages, and <em>root</em>.<strong>components</strong>.<em>ComponentType</em> for components. Conceptually, page components are simply the <em>root component</em> of a page's component tree.</p><p><em>For Tapestry 4 users: there was a much greater distinction in Tapestry 4 between pages and components, which showed up as separate interfaces and a hierarchy of abstract implementations to extend your classes from.</em></p><h2 id="ComponentClasses-ClassTransformation">Class Transformation</h2><p>Tapestry uses your class as a starting point. It <em>transforms</em> your class at runtime. This is necessary for a number of reasons, including to address how Tapestry shares pages between requests.</p><p>For the most part, these transformations are both sensible and invisible. In a few limited cases, they comprise a marginally <a class="external-link" href="http://www.joelonsoftware.com/printerFriendly/articles/LeakyAbstractions.html" rel="nofollow">leaky abstractio
n</a> – for instance, the scope restrictions on instance variables described below – but the programming model in general supports a very high level of developer productivity.</p><p>Because transformation doesn't occur until <em>runtime</em>, the build stage of your application is not affected by the fact that you are creating a Tapestry application. Further, your classes are absolutely simple POJOs during unit testing.</p><h2 id="ComponentClasses-LiveClassReloading">Live Class Reloading</h2><p>Main Article: <a href="component-classes.html">Component Classes</a></p><p>Component classes are monitored for changes by the framework. <a href="component-classes.html">Classes are reloaded when changed</a>. This allows you to build your application with a speed approaching that of a scripting environment, without sacrificing any of the power of the Java platform.</p><p>And it's fast! You won't even notice that this magic class reloading has occurred.</p><p>The net result:
super productivity — change your class, see the change instantly. This is designed to be a blend of the best of scripting environments (such as Python or Ruby) with all the speed and power of Java backing it up.</p><p>However, class reloading <em>only</em> applies to component classes (pages, components and mixins) and, starting in 5.2, Tapestry IOC-based service implementations (with some restrictions). Other classes, such as service interfaces, entity/model classes, and other data objects, are loaded by the normal class loader and not subject to live class reloading.</p><h2 id="ComponentClasses-InstanceVariables">Instance Variables</h2><p>Tapestry components may have instance variables (unlike Tapestry 4, where you had to use <em>abstract properties</em>).</p><p>Since release 5.3.2, instance variables may be protected, or package private (that is, no access modifier). Under specific circumstances they may even be public (public fields must either be final, or have the @<a
class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Retain.html">Retain</a> annotation).</p><p><span>Be aware that you will need to either provide getter and setter methods to access your classes' instance variables, or else annotate the fields with</span><span> @</span><a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Property.html">Property</a>.</p><h2 id="ComponentClasses-TransientInstanceVariables">Transient Instance Variables</h2><p>Unless an instance variable is decorated with an annotation, it will be a <em>transient</em> instance variable. This means that its value resets to its default value at the end of reach request (when the <a href="component-classes.html">page is detached from the request</a>).</p><div class="confluence-information-macro confluence-information-macro-note"><p class="title">About initialization</p><span class="aui-icon aui-icon-small
aui-iconfont-warning confluence-information-macro-icon"></span><div class="confluence-information-macro-body"><p>Never initialize an instance field to a <em>mutable</em> object at the point of declaration. If this is done, the instance created from that initializer becomes the default value for that field and is reused inside the component on every request. This could cause state to inadvertently be shared between different sessions in an application.</p></div></div>
+</div></div><p>In this example, just like the first one, the component's only job is to write out a fixed message. The @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/BeginRender.html">BeginRender</a> annotation is a type of <em><a href="component-classes.html">render phase annotation</a></em>, a method annotation that instructs Tapestry when and under what circumstances to invoke methods of your class.</p><p>These methods are not necessarily public; they can have any access level you like (unlike in Tapestry 4). By convention they usually have package-private access level (the default).</p><h2 id="ComponentClasses-ComponentPackages">Component Packages</h2><p>Component classes must exist within an appropriate package (this is necessary for runtime code transformation and class reloading to operate).</p><p>These packages exist under the application's root package, as follows:</p><ul><li>For pages, place classes in <em>root
</em>.<strong>pages</strong>. Page names are mapped to classes within this package.</li><li>For mixins, place classes in <em>root</em>.<strong>mixins</strong>. Mixin types are mapped to classes within this package.</li><li>For other components, place classes in <em>root</em>.<strong>components</strong>. Component types are mapped to classes within this package.</li></ul><p>In addition, it is common for an application to have base classes, often <em>abstract</em> base classes, that should not be directly referenced. These should <em>not</em> go in the <strong>pages</strong>, <strong>components</strong> or <strong>mixins</strong> packages, because they then look like valid pages, components or mixins. Instead, use the <em>root</em>.<strong>base</strong> package to store such base classes.</p><div class="confluence-information-macro confluence-information-macro-warning"><span class="aui-icon aui-icon-small aui-iconfont-error confluence-information-macro-icon"></span><div class="conflue
nce-information-macro-body"><p>Only component classes should go in any of these controlled packages; classes representing data, or interfaces, or anything that isn't precisely a component class, must go elsewhere. Any top-level class in any of the controlled packages will be transformed at runtime. The only exception is inner classes (anonymous or not), which are loaded by the same class loader as the component class loader, but not transformed as components.</p></div></div><h2 id="ComponentClasses-Sub-Folders/Sub-Packages">Sub-Folders / Sub-Packages</h2><p>Classes do not have to go directly inside the package (pages, components, mixins, etc.). It is valid to create a sub-package to store some of the classes. The sub-package name becomes part of the page name or component type. Thus you might define a page component <code>com.example.myapp.pages.admin.CreateUser</code> and the logical page name (which often shows up inside URLs) will be <strong>admin/CreateUser</strong>.</p><p>Tapes
try performs some simple optimizations of the logical page name (or component type, or mixin type). It checks to see if the package name is either a prefix or a suffix of the unqualified class name (case insensitively, of course) and removes the prefix or suffix if so. The net result is that a class name such as <code>com.example.myapp.pages.user.EditUser</code> will have a page name of <code>user/Edit</code> (instead of user<code>/EditUser</code>). The goal here is to provide shorter, more natural URLs.</p><h2 id="ComponentClasses-IndexPages">Index Pages</h2><p>One special simplification exists for Index pages: if the logical page name is Index after removing the package name from the unqualified class name, it will map to the root of that folder. A class such as <code>com.example.myapp.pages.user.IndexUser</code> or <code>com.example.myapp.pages.user.UserIndex</code> will have a page name of <code>user/</code>.</p><p>In previous versions of Tapestry there was also the concept of a
start page configured with the <code><a href="component-classes.html">tapestry.start-page-name</a></code> configuration symbol (defaults to "start"). If a page with a name as configured with that symbol exists at the root level, this page is used as the root URL. This has precedence over an existing Index page. If for example you have a page class <code>com.example.myapp.pages.Start</code> it will map to <code>/</code>.</p><div class="confluence-information-macro confluence-information-macro-warning"><span class="aui-icon aui-icon-small aui-iconfont-error confluence-information-macro-icon"></span><div class="confluence-information-macro-body"><p>Use of start-pages is discouraged and support for it will eventually be removed. Use an Index page instead.</p></div></div><h2 id="ComponentClasses-Pagesvs.Components">Pages vs. Components</h2><p>The distinction between pages and component is very, very small. The primary difference is the package name: <em>root</em>.<strong>pages</strong>
.<em>PageName</em> for pages, and <em>root</em>.<strong>components</strong>.<em>ComponentType</em> for components. Conceptually, page components are simply the <em>root component</em> of a page's component tree.</p><p><em>For Tapestry 4 users: there was a much greater distinction in Tapestry 4 between pages and components, which showed up as separate interfaces and a hierarchy of abstract implementations to extend your classes from.</em></p><h2 id="ComponentClasses-ClassTransformation">Class Transformation</h2><p>Tapestry uses your class as a starting point. It <em>transforms</em> your class at runtime. This is necessary for a number of reasons, including to address how Tapestry shares pages between requests.</p><p>For the most part, these transformations are both sensible and invisible. In a few limited cases, they comprise a marginally <a class="external-link" href="http://www.joelonsoftware.com/printerFriendly/articles/LeakyAbstractions.html" rel="nofollow">leaky abstractio
n</a> – for instance, the scope restrictions on instance variables described below – but the programming model in general supports a very high level of developer productivity.</p><p>Because transformation doesn't occur until <em>runtime</em>, the build stage of your application is not affected by the fact that you are creating a Tapestry application. Further, your classes are absolutely simple POJOs during unit testing.</p><h2 id="ComponentClasses-LiveClassReloading">Live Class Reloading</h2><p>Main Article: <a href="class-reloading.html">Class Reloading</a></p><p>Component classes are monitored for changes by the framework. <a href="component-classes.html">Classes are reloaded when changed</a>. This allows you to build your application with a speed approaching that of a scripting environment, without sacrificing any of the power of the Java platform.</p><p>And it's fast! You won't even notice that this magic class reloading has occurred.</p><p>The net result: sup
er productivity — change your class, see the change instantly. This is designed to be a blend of the best of scripting environments (such as Python or Ruby) with all the speed and power of Java backing it up.</p><p>However, class reloading <em>only</em> applies to component classes (pages, components and mixins) and, starting in 5.2, Tapestry IOC-based service implementations (with some restrictions). Other classes, such as service interfaces, entity/model classes, and other data objects, are loaded by the normal class loader and not subject to live class reloading.</p><h2 id="ComponentClasses-InstanceVariables">Instance Variables</h2><p>Tapestry components may have instance variables (unlike Tapestry 4, where you had to use <em>abstract properties</em>).</p><p>Since release 5.3.2, instance variables may be protected, or package private (that is, no access modifier). Under specific circumstances they may even be public (public fields must either be final, or have the @<a clas
s="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Retain.html">Retain</a> annotation).</p><p><span>Be aware that you will need to either provide getter and setter methods to access your classes' instance variables, or else annotate the fields with</span><span> @</span><a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Property.html">Property</a>.</p><h2 id="ComponentClasses-TransientInstanceVariables">Transient Instance Variables</h2><p>Unless an instance variable is decorated with an annotation, it will be a <em>transient</em> instance variable. This means that its value resets to its default value at the end of reach request (when the <a href="component-classes.html">page is detached from the request</a>).</p><div class="confluence-information-macro confluence-information-macro-note"><p class="title">About initialization</p><span class="aui-icon aui-icon-small aui-
iconfont-warning confluence-information-macro-icon"></span><div class="confluence-information-macro-body"><p>Never initialize an instance field to a <em>mutable</em> object at the point of declaration. If this is done, the instance created from that initializer becomes the default value for that field and is reused inside the component on every request. This could cause state to inadvertently be shared between different sessions in an application.</p></div></div>
<div class="aui-message aui-message-warning">
Deprecated since 5.2 |
For Tapestry 5.1 and earlier, in the rare event that you have a variable that can keep its value between requests and you would like to defeat that reset logic, then you can add a @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Retain.html">Retain</a> annotation to the field. You should take care that no client-specific data is stored into such a field, since on a later request the same page <em>instance</em> may be used for a different user. Likewise, on a later request for the <em>same</em> client, a <em>different</em> page instance may be used.
-</div><p>Use <a href="component-classes.html">persistent fields</a> to hold client-specific information from one request to the next.</p><p>Further, final fields are (in fact) final, and will not be reset between requests.</p><h2 id="ComponentClasses-Constructors">Constructors</h2><p>Tapestry will instantiate your class using the default, no arguments constructor. Other constructors will be ignored.</p><h2 id="ComponentClasses-Injection">Injection</h2><p>Main Article: <a href="component-classes.html">Component Classes</a></p><p>Injection of dependencies occurs at the field level, via additional annotations. At runtime, fields that contain injections become read-only.</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
+</div><p>Use <a href="component-classes.html">persistent fields</a> to hold client-specific information from one request to the next.</p><p>Further, final fields are (in fact) final, and will not be reset between requests.</p><h2 id="ComponentClasses-Constructors">Constructors</h2><p>Tapestry will instantiate your class using the default, no arguments constructor. Other constructors will be ignored.</p><h2 id="ComponentClasses-Injection">Injection</h2><p>Main Article: <a href="injection.html">Injection</a></p><p>Injection of dependencies occurs at the field level, via additional annotations. At runtime, fields that contain injections become read-only.</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;">@Inject // inject a resource
private ComponentResources componentResources;
@@ -191,7 +191,7 @@ private Asset banner;
@Inject // inject a service
private AjaxResponseRenderer ajaxResponseRenderer;
</pre>
-</div></div><h2 id="ComponentClasses-Parameters">Parameters</h2><p>Main Article: <a href="component-classes.html">Component Classes</a></p><p>Component parameters are private fields of your component class annotated with @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Parameter.html">Parameter</a>. Component parameters represent a two-way binding of a field of your component and a property or resource of its containing component or page.</p><h2 id="ComponentClasses-PersistentFields">Persistent Fields</h2><p>Main Article: <a href="component-classes.html">Component Classes</a></p><p>Most fields in component classes are automatically cleared at the end of each request. However, fields may be annotated so that they retain their value across requests, using the @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Persist.html">Persist</a> annotation.</p><h2 id="Component
Classes-Embedded_ComponentsEmbeddedComponents"><span class="confluence-anchor-link" id="ComponentClasses-Embedded_Components"></span>Embedded Components</h2><p>Components often contain other components. Components inside another component's template are called <em>embedded components</em>. The containing component's <a href="component-classes.html">template</a> will contain special elements, in the Tapestry namespace, identifying where the the embedded components go.</p><p>You can define the type of component inside template, or you can create an instance variable for the component and use the @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Component.html">Component</a> annotation to define the component type and parameters.</p><p>Example:</p><div class="code panel pdl" style="border-width: 1px;"><div class="codeContent panelContent pdl">
+</div></div><h2 id="ComponentClasses-Parameters">Parameters</h2><p>Main Article: <a href="component-parameters.html">Component Parameters</a></p><p>Component parameters are private fields of your component class annotated with @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Parameter.html">Parameter</a>. Component parameters represent a two-way binding of a field of your component and a property or resource of its containing component or page.</p><h2 id="ComponentClasses-PersistentFields">Persistent Fields</h2><p>Main Article: <a href="persistent-page-data.html">Persistent Page Data</a></p><p>Most fields in component classes are automatically cleared at the end of each request. However, fields may be annotated so that they retain their value across requests, using the @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Persist.html">Persist</a> annotation.</p><h2 i
d="ComponentClasses-Embedded_ComponentsEmbeddedComponents"><span class="confluence-anchor-link" id="ComponentClasses-Embedded_Components"></span>Embedded Components</h2><p>Components often contain other components. Components inside another component's template are called <em>embedded components</em>. The containing component's <a href="component-classes.html">template</a> will contain special elements, in the Tapestry namespace, identifying where the the embedded components go.</p><p>You can define the type of component inside template, or you can create an instance variable for the component and use the @<a class="external-link" href="http://tapestry.apache.org/current/apidocs/org/apache/tapestry5/annotations/Component.html">Component</a> annotation to define the component type and parameters.</p><p>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;">package org.example.app.pages;
import org.apache.tapestry5.annotations.Component;