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| <a href="index.html" title="back to Plugins"><< back to Plugins</a> |
| |
| <h1 class="no_toc" id="plugins-architecture">Plugins architecture</h1> |
| |
| <ul id="markdown-toc"> |
| <li><a href="#static-resources" id="markdown-toc-static-resources">Static resources</a></li> |
| <li><a href="#extension-points" id="markdown-toc-extension-points">Extension Points</a></li> |
| <li><a href="#plugin-examples" id="markdown-toc-plugin-examples">Plugin Examples</a> <ul> |
| <li><a href="#sitemesh-plugin" id="markdown-toc-sitemesh-plugin">Sitemesh plugin</a></li> |
| <li><a href="#tiles-plugin" id="markdown-toc-tiles-plugin">Tiles plugin</a></li> |
| </ul> |
| </li> |
| <li><a href="#developing-new-extension-point" id="markdown-toc-developing-new-extension-point">Developing new extension point</a> <ul> |
| <li><a href="#extension-point-provided-by-the-core" id="markdown-toc-extension-point-provided-by-the-core">Extension point provided by the Core</a></li> |
| <li><a href="#plugin-ext" id="markdown-toc-plugin-ext">Plugin-defined extension points</a></li> |
| </ul> |
| </li> |
| <li><a href="#plugin-registry" id="markdown-toc-plugin-registry">Plugin Registry</a></li> |
| </ul> |
| |
| <p>Struts 2 plugins contain classes and configuration that extend, replace, or add to existing Struts framework |
| functionality. A plugin can be installed by adding its JAR file to the application’s class path, in addition to the JAR |
| files to fulfill whatever dependencies the plugin itself may have. To configure the plugin, the JAR should contain |
| a <code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> file and optionally a <code class="language-plaintext highlighter-rouge">struts-deferred.xml</code>, which follow the same format as an |
| ordinary <code class="language-plaintext highlighter-rouge">struts.xml</code> file.</p> |
| |
| <p>Since a plugin can contain these xml files, they have the ability to:</p> |
| <ul> |
| <li>Define new packages with results, interceptors, and/or actions</li> |
| <li>Override framework constants</li> |
| <li>Introduce new extension point implementation classes</li> |
| </ul> |
| |
| <p>Whilst configuration from <code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> is loaded prior to <code class="language-plaintext highlighter-rouge">struts.xml</code>, <code class="language-plaintext highlighter-rouge">struts-deferred.xml</code> is loaded after all |
| other configuration is loaded. This makes it useful for defining <a href="#plugin-ext">plugin extension points</a>.</p> |
| |
| <p>Many popular but optional features of the framework are distributed as plugins. An application can retain all the |
| plugins provided with the distribution, or just include the ones it uses. Plugins can be used to organize application |
| code or to distribute code to third-parties.</p> |
| |
| <p>Packages defined in a plugin can have parent packages that are defined in another plugin. Plugins may define |
| configuration elements with classes not contained in the plugin. Any classes not included in the plugin’s JAR must be on |
| the application’s classpath at runtime. As from Struts 2.3.5</p> |
| |
| <p>The framework loads its default configuration first, then any <code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> files found in others JARs on the |
| classpath, the “bootstrap” <code class="language-plaintext highlighter-rouge">struts.xml</code>, then finally any <code class="language-plaintext highlighter-rouge">struts-deferred.xml</code> files.</p> |
| |
| <ol> |
| <li><code class="language-plaintext highlighter-rouge">struts-default.xml</code> (bundled in the Core JAR)</li> |
| <li><code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> (as many as can be found in other JARs)</li> |
| <li><code class="language-plaintext highlighter-rouge">struts.xml</code> (provided by your application)</li> |
| <li><code class="language-plaintext highlighter-rouge">struts-deferred.xml</code> (as many as can be found in other JARs)</li> |
| </ol> |
| |
| <p>Since the <code class="language-plaintext highlighter-rouge">struts.xml</code> file is loaded between <code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> and before any potential plugin extension points |
| in <code class="language-plaintext highlighter-rouge">struts-deferred.xml</code>, it can make use of any resources provided by the plugins bundled with the distribution, or any |
| other plugins available to an application.</p> |
| |
| <h2 id="static-resources">Static resources</h2> |
| |
| <p>To include static resources in your plugins add them under “/static” in your jar. And include them in your page using |
| “/static” as the path, like in the following example:</p> |
| |
| <div class="language-ftl highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="err"><!--</span><span class="w"> </span>Assuming /static/main.css is inside a plugin jar, to add it to the page: --><span class="w"> |
| |
| </span><span class="err"><@</span><span class="no">s</span><span class="na">.url</span><span class="w"> </span>value="/static/main.css" var="css" /><span class="w"> |
| </span><span class="err"><</span><span class="no">link</span><span class="w"> </span>rel="stylesheet" type="text/css" href="%<span class="p">{</span><span class="err">#</span><span class="no">css</span><span class="p">}</span>" /><span class="w"> |
| </span></code></pre></div></div> |
| |
| <p>Read also <a href="../core-developers/static-content">Static Content</a> and JavaDoc of <a href="https://struts.apache.org/maven/struts2-core/apidocs/org/apache/struts2/dispatcher/StaticContentLoader">StaticContentLoader</a>.</p> |
| |
| <h2 id="extension-points">Extension Points</h2> |
| |
| <p>Extension points allow a plugin to override a key class in the Struts framework with an alternate implementation. |
| For example, a plugin could provide a new class to create Action classes or map requests to Actions.</p> |
| |
| <p>The following extension points are available in Struts 2:</p> |
| |
| <table> |
| <thead> |
| <tr> |
| <th>Property</th> |
| <th>Description</th> |
| <th>Scope</th> |
| <th>Type</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td>struts.objectFactory</td> |
| <td>Creates actions, results, and interceptors</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.ObjectFactory</td> |
| </tr> |
| <tr> |
| <td>struts.objectFactory.actionFactory</td> |
| <td>Dedicated factory used to create Actions, you can implement/extend existing one instead of defining new ObjectFactory</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.factory.ActionFactory</td> |
| </tr> |
| <tr> |
| <td>struts.objectFactory.resultFactory</td> |
| <td>Dedicated factory used to create Results, you can implement/extend existing one instead of defining new ObjectFactory</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.factory.ResultFactory</td> |
| </tr> |
| <tr> |
| <td>struts.objectFactory.interceptorFactory</td> |
| <td>Dedicated factory used to create Interceptors, you can implement/extend existing one instead of defining new ObjectFactory</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.factory.InterceptorFactory</td> |
| </tr> |
| <tr> |
| <td>struts.objectFactory.converterFactory</td> |
| <td>Dedicated factory used to create TypeConverters, you can implement/extend existing one instead of defining new ObjectFactory</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.factory.ConverterFactory</td> |
| </tr> |
| <tr> |
| <td>struts.objectFactory.validatorFactory</td> |
| <td>Dedicated factory used to create Validators, you can implement/extend existing one instead of defining new ObjectFactory</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.factory.ValidatorFactory</td> |
| </tr> |
| <tr> |
| <td>struts.actionProxyFactory</td> |
| <td>Creates the ActionProxy</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.ActionProxyFactory</td> |
| </tr> |
| <tr> |
| <td>struts.objectTypeDeterminer</td> |
| <td>Determines what the key and element class of a Map or Collection should be</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.util.ObjectTypeDeterminer</td> |
| </tr> |
| <tr> |
| <td>struts.mapper.class</td> |
| <td>Determines the ActionMapping from a request and a URI from an ActionMapping</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.dispatcher.mapper.ActionMapper</td> |
| </tr> |
| <tr> |
| <td>struts.multipart.parser</td> |
| <td>Parses a multipart request (file upload)</td> |
| <td>per request</td> |
| <td>org.apache.struts2.dispatcher.multipart.MultiPartRequest</td> |
| </tr> |
| <tr> |
| <td>struts.freemarker.manager.classname</td> |
| <td>Loads and processes Freemarker templates</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.views.freemarker.FreemarkerManager</td> |
| </tr> |
| <tr> |
| <td>struts.velocity.manager.classname</td> |
| <td>Loads and processes Velocity templates</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.views.velocity.VelocityManagerInterface</td> |
| </tr> |
| <tr> |
| <td>struts.actionValidatorManager</td> |
| <td>Main interface for validation managers (regular and annotation based). Handles both the loading of configuration and the actual validation (since 2.1)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.validator.ActionValidatorManager</td> |
| </tr> |
| <tr> |
| <td>struts.valueStackFactory</td> |
| <td>Creates value stacks (since 2.1)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.util.ValueStackFactory</td> |
| </tr> |
| <tr> |
| <td>struts.reflectionProvider</td> |
| <td>Provides reflection services, key place to plug in a custom expression language (since 2.1)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.reflection.ReflectionProvider</td> |
| </tr> |
| <tr> |
| <td>struts.reflectionContextFactory</td> |
| <td>Creates reflection context maps used for reflection and expression language operations (since 2.1)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.reflection.ReflectionContextFactory</td> |
| </tr> |
| <tr> |
| <td>N/A</td> |
| <td>All beans registered as PackageProvider implementations will be automatically included in configuration building (since 2.1)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.config.PackageProvider</td> |
| </tr> |
| <tr> |
| <td>struts.patternMatcher</td> |
| <td>Matches patterns, such as action names, generally used in configuration (since 2.1)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.util.PatternMatcher</td> |
| </tr> |
| <tr> |
| <td>struts.staticContentLoader</td> |
| <td>Loads static resources (since 2.1)</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.views.dispatcher.DefaultStaticContentLoader</td> |
| </tr> |
| <tr> |
| <td>struts.xworkConverter</td> |
| <td>Handles conversion logic and allows to load custom converters per class or per action</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.impl.XWorkConverter</td> |
| </tr> |
| <tr> |
| <td>struts.localeProviderFactory</td> |
| <td>Allows provide custom LocaleProvider for whole application</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.LocaleProviderFactory</td> |
| </tr> |
| <tr> |
| <td>struts.urlRenderer</td> |
| <td>Allows provide custom implementation of environment specific URL rendering/creating class</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.components.UrlRenderer</td> |
| </tr> |
| <tr> |
| <td>struts.unknownHandlerManager</td> |
| <td>Implementation of this interface allows handle logic of unknown Actions, Methods or Results</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.UnknownHandlerManager</td> |
| </tr> |
| <tr> |
| <td>struts.view.urlHelper</td> |
| <td>Helper class used with URLRenderer to provide exact logic for building URLs</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.views.util.UrlHelper</td> |
| </tr> |
| <tr> |
| <td>struts.fileManagerFactory</td> |
| <td>Used to create FileManager instance to access files on the File System as also to monitor if reload is needed, can be implemented / overwritten to meet specific an application server needs</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.FileManagerFactory</td> |
| </tr> |
| <tr> |
| <td>struts.converter.collection</td> |
| <td>Converter used to convert any object to Collection and back</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.impl.CollectionConverter</td> |
| </tr> |
| <tr> |
| <td>struts.converter.array</td> |
| <td>Converter used to convert any object to Array and back</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.impl.ArrayConverter</td> |
| </tr> |
| <tr> |
| <td>struts.converter.date</td> |
| <td>Converter used to convert any object to Date and back</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.impl.DateConverter</td> |
| </tr> |
| <tr> |
| <td>struts.converter.number</td> |
| <td>Converter used to convert any object to Number and back</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.impl.NumberConverter</td> |
| </tr> |
| <tr> |
| <td>struts.converter.string</td> |
| <td>Converter used to convert any object to String and back</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.impl.StringConverter</td> |
| </tr> |
| <tr> |
| <td>struts.conversion.properties.processor</td> |
| <td>Process Properties to create converters</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.ConversionPropertiesProcessor</td> |
| </tr> |
| <tr> |
| <td>struts.converter.file.processor</td> |
| <td>Process {class}-conversion.properties file create converters</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.ConversionPropertiesProcessor</td> |
| </tr> |
| <tr> |
| <td>struts.converter.annotation.processor</td> |
| <td>Process TypeConversion annotation to create converters</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.ConversionAnnotationProcessor</td> |
| </tr> |
| <tr> |
| <td>struts.converter.creator</td> |
| <td>Creates user converters</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.TypeConverterCreator</td> |
| </tr> |
| <tr> |
| <td>struts.converter.holder</td> |
| <td>Holds user converters’ instances</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.conversion.TypeConverterHolder</td> |
| </tr> |
| <tr> |
| <td>struts.expression.parser</td> |
| <td>Used to parse expressions like ${foo.bar} or %{bar.foo} but it is up tp the TextParser’s implementation what kind of opening char to use (#, $, %, etc)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.util.TextParser</td> |
| </tr> |
| <tr> |
| <td>struts.excludedPatterns.checker</td> |
| <td>Used across different interceptors to check if given string matches one of the excluded patterns</td> |
| <td>request</td> |
| <td>com.opensymphony.xwork2.ExcludedPatternsChecker</td> |
| </tr> |
| <tr> |
| <td>struts.acceptedPatterns.checker</td> |
| <td>Used across different interceptors to check if given string matches one of the accepted patterns</td> |
| <td>request</td> |
| <td>com.opensymphony.xwork2.AcceptedPatternsChecker</td> |
| </tr> |
| <tr> |
| <td>struts.contentTypeMatcher</td> |
| <td>Matches content type of uploaded files (since 2.3.22)</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.util.ContentTypeMatcher</td> |
| </tr> |
| <tr> |
| <td>struts.localizedTextProvider</td> |
| <td>Provides access to resource bundles used to localise messages (since 2.5.11)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.LocalizedTextProvider</td> |
| </tr> |
| <tr> |
| <td>struts.date.formatter</td> |
| <td>Allow define a date formatter used by <code class="language-plaintext highlighter-rouge"><s:date/></code> tag (since 6.0.0)</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.components.date.DateFormatter</td> |
| </tr> |
| <tr> |
| <td>struts.ognlGuard</td> |
| <td>Define a custom OgnlGuard implementation to block raw or compiled OGNL expressions (since 6.4.0)</td> |
| <td>singleton</td> |
| <td>org.apache.struts2.ognl.OgnlGuard</td> |
| </tr> |
| <tr> |
| <td>struts.securityMemberAccess</td> |
| <td>Define a custom SecurityMemberAccess implementation, used to restrict OGNL evaluations based on classes involved (since 6.4.0)</td> |
| <td>prototype</td> |
| <td>com.opensymphony.xwork2.ognl.SecurityMemberAccess</td> |
| </tr> |
| <tr> |
| <td>struts.compoundRootAccessor</td> |
| <td>Define a custom CompoundRootAccessor implementation, used to resolve classes and manipulate the CompoundRoot (since 6.4.0)</td> |
| <td>singleton</td> |
| <td>com.opensymphony.xwork2.ognl.accessor.RootAccessor</td> |
| </tr> |
| <tr> |
| <td>struts.methodAccessor</td> |
| <td>Define a custom MethodAccessor implementation, used to evaluate OGNL method calls (since 6.4.0)</td> |
| <td>singleton</td> |
| <td>ognl.MethodAccessor</td> |
| </tr> |
| </tbody> |
| </table> |
| |
| <h2 id="plugin-examples">Plugin Examples</h2> |
| |
| <p>Let’s look at two similar but different plugins bundled with the core distribution.</p> |
| |
| <h3 id="sitemesh-plugin">Sitemesh plugin</h3> |
| |
| <p><a href="http://opensymphony.com/sitemesh/">SiteMesh</a> is a popular alternative to Tiles. SiteMesh provides a common look-and-feel |
| to an application’s pages by automatically wrapping a plain page with common elements like headers and menubars.</p> |
| |
| <p>The <code class="language-plaintext highlighter-rouge">sitemesh-plugin.jar</code> contains several classes, a standard JAR manifest, and a plugin configuration file.</p> |
| |
| <div class="language-text highlighter-rouge"><div class="highlight"><pre class="highlight"><code> + META-INF/ |
| + manifest.mf |
| + org |
| + apache |
| + struts2 |
| + sitemesh |
| + FreeMarkerPageFilter.class |
| + TemplatePageFilter.class |
| + VelocityPageFilter.class |
| + struts-plugin.xml |
| </code></pre></div></div> |
| |
| <p>While the SiteMesh Plugin doesn’t provide any new results, interceptors, or actions, or even extend any Struts integration |
| points, it does need to know what settings have been enabled in the Struts framework. Therefore, its <code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> looks like this:</p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="cp"><?xml version="1.0" encoding="UTF-8" ?></span> |
| <span class="c"><!-- |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one |
| * or more contributor license agreements. See the NOTICE file |
| * distributed with this work for additional information |
| * regarding copyright ownership. The ASF licenses this file |
| * to you under the Apache License, Version 2.0 (the |
| * "License"); you may not use this file except in compliance |
| * with the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, |
| * software distributed under the License is distributed on an |
| * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY |
| * KIND, either express or implied. See the License for the |
| * specific language governing permissions and limitations |
| * under the License. |
| */ |
| --></span> |
| <span class="cp"><!DOCTYPE struts PUBLIC |
| "-//Apache Software Foundation//DTD Struts Configuration 2.5//EN" |
| "http://struts.apache.org/dtds/struts-2.5.dtd"></span> |
| |
| <span class="nt"><struts></span> |
| <span class="nt"><bean</span> <span class="na">class=</span><span class="s">"org.apache.struts2.sitemesh.FreemarkerPageFilter"</span> <span class="na">static=</span><span class="s">"true"</span> <span class="na">optional=</span><span class="s">"true"</span><span class="nt">/></span> |
| <span class="nt"><bean</span> <span class="na">class=</span><span class="s">"org.apache.struts2.sitemesh.VelocityPageFilter"</span> <span class="na">static=</span><span class="s">"true"</span> <span class="na">optional=</span><span class="s">"true"</span><span class="nt">/></span> |
| <span class="nt"></struts></span> |
| |
| </code></pre></div></div> |
| |
| <p>The two bean elements, with the “static” flag enabled, tell Struts to inject the current settings and framework objects |
| into static property setters on startup. This allows, for example, the FreeMarkerPageFilter class to get an instance |
| of the Struts FreemarkerManager and the current encoding setting.</p> |
| |
| <h3 id="tiles-plugin">Tiles plugin</h3> |
| |
| <p><a href="http://struts.apache.org/struts-sandbox/tiles/index">Tiles</a> is a popular alternative to SiteMesh. Tiles provides |
| a common look-and-feel to an application’s pages by breaking the page down into common fragments or “tiles”.</p> |
| |
| <p>The <code class="language-plaintext highlighter-rouge">tiles-plugin.jar</code> contains several classes, a standard JAR manifest, and a configuration file.</p> |
| |
| <div class="language-text highlighter-rouge"><div class="highlight"><pre class="highlight"><code> + META-INF/ |
| + manifest.mf |
| + org |
| + apache |
| + struts2 |
| + tiles |
| + StrutsTilesListener.class |
| + StrutsTileUtilImpl.class |
| + views |
| + tiles |
| + TilesResult.class |
| + struts-plugin.xml |
| </code></pre></div></div> |
| |
| <p>Since the Tiles Plugin does need to register configuration elements, a result class, it provides a <code class="language-plaintext highlighter-rouge">struts-plugin.xml</code> file.</p> |
| |
| <h2 id="developing-new-extension-point">Developing new extension point</h2> |
| |
| <p>An extension point it’s a name which will be used to locate other beans by the name and inject them into a given place. |
| Extension point isn’t a bean, you cannot inject it. It’s a bridge between your interface/class and the final implementation, |
| provided either by a plugin or by a user.</p> |
| |
| <p>If needed you can define your own extension point. This can happen in two ways: either define it in the Struts Core, |
| or define the extension in the plugin you are developing.</p> |
| |
| <h3 id="extension-point-provided-by-the-core">Extension point provided by the Core</h3> |
| |
| <p>First step is to name your extension point, basically we are using a pattern like follow:</p> |
| <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.<component | functionallity>.<name of the extebsion point> |
| </code></pre></div></div> |
| |
| <p>e.g.: <code class="language-plaintext highlighter-rouge">struts.date.formatter</code>.</p> |
| |
| <p>Now you must provide an interface or a class as the extension point, it will be used by others to implement they own behaviour |
| of the extension point, e.g.: <code class="language-plaintext highlighter-rouge">org.apache.struts2.components.date.DateFormatter</code>.</p> |
| |
| <p>The next step is to tie the name of the extension point with the interface/class. It happens in <code class="language-plaintext highlighter-rouge">StrutsBeanSelectionProvider</code></p> |
| |
| <p>by using <code class="language-plaintext highlighter-rouge">alias()</code> method as below:</p> |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">alias</span><span class="o">(</span><span class="nc">DateFormatter</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="nc">StrutsConstants</span><span class="o">.</span><span class="na">STRUTS_DATE_FORMATTER</span><span class="o">,</span> <span class="n">builder</span><span class="o">,</span> <span class="n">props</span><span class="o">,</span> <span class="nc">Scope</span><span class="o">.</span><span class="na">SINGLETON</span><span class="o">);</span> |
| </code></pre></div></div> |
| |
| <p>as you can see you must provide:</p> |
| <ul> |
| <li><code class="language-plaintext highlighter-rouge">Class<?></code> class behind the extension point, which is used by users to implement the extension point</li> |
| <li><code class="language-plaintext highlighter-rouge">String</code> a key, the name of the extension point</li> |
| <li><code class="language-plaintext highlighter-rouge">ContainerBuilder</code> builder used to setup the Container</li> |
| <li><code class="language-plaintext highlighter-rouge">Properties</code> additional properties when needed</li> |
| <li><code class="language-plaintext highlighter-rouge">Scope</code> scope of the extension point, all the beans extneding the extension point must have the same scope</li> |
| </ul> |
| |
| <p>Having all that set, you can define where to use the extension point by injecting beans implementing it by using <code class="language-plaintext highlighter-rouge">@Inject</code></p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nd">@Inject</span> |
| <span class="kd">public</span> <span class="kt">void</span> <span class="nf">setDateFormatter</span><span class="o">(</span><span class="nc">DateFormatter</span> <span class="n">dateFormatter</span><span class="o">)</span> <span class="o">{</span> |
| <span class="k">this</span><span class="o">.</span><span class="na">dateFormatter</span> <span class="o">=</span> <span class="n">dateFormatter</span><span class="o">;</span> |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| <p>you can use <code class="language-plaintext highlighter-rouge">optional = true</code> if the implementation is not required, yet please remember to handle <code class="language-plaintext highlighter-rouge">null</code> in such case.</p> |
| |
| <p>All the above steps have defined a new extension point, now you can implement a bean which will be <em>bridged</em> throughout |
| the extension point with the <code class="language-plaintext highlighter-rouge">@Inject</code>. Just implement the interface/class used to define the extension point and define |
| the bean in <code class="language-plaintext highlighter-rouge">struts-default.xml</code>:</p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">public</span> <span class="kd">class</span> <span class="nc">DateTimeFormatterAdapter</span> <span class="kd">implements</span> <span class="nc">DateFormatter</span> <span class="o">{</span> |
| |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="nc">String</span> <span class="nf">format</span><span class="o">(</span><span class="nc">TemporalAccessor</span> <span class="n">temporal</span><span class="o">,</span> <span class="nc">String</span> <span class="n">format</span><span class="o">)</span> <span class="o">{</span> |
| <span class="nc">DateTimeFormatter</span> <span class="n">dtf</span><span class="o">;</span> |
| <span class="nc">Locale</span> <span class="n">locale</span> <span class="o">=</span> <span class="nc">ActionContext</span><span class="o">.</span><span class="na">getContext</span><span class="o">().</span><span class="na">getLocale</span><span class="o">();</span> |
| <span class="k">if</span> <span class="o">(</span><span class="n">format</span> <span class="o">==</span> <span class="kc">null</span><span class="o">)</span> <span class="o">{</span> |
| <span class="n">dtf</span> <span class="o">=</span> <span class="nc">DateTimeFormatter</span><span class="o">.</span><span class="na">ofLocalizedDateTime</span><span class="o">(</span><span class="nc">FormatStyle</span><span class="o">.</span><span class="na">MEDIUM</span><span class="o">)</span> |
| <span class="o">.</span><span class="na">withLocale</span><span class="o">(</span><span class="n">locale</span><span class="o">);</span> |
| <span class="o">}</span> <span class="k">else</span> <span class="o">{</span> |
| <span class="n">dtf</span> <span class="o">=</span> <span class="nc">DateTimeFormatter</span><span class="o">.</span><span class="na">ofPattern</span><span class="o">(</span><span class="n">format</span><span class="o">,</span> <span class="n">locale</span><span class="o">);</span> |
| <span class="o">}</span> |
| <span class="k">return</span> <span class="n">dtf</span><span class="o">.</span><span class="na">format</span><span class="o">(</span><span class="n">temporal</span><span class="o">);</span> |
| <span class="o">}</span> |
| |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><bean</span> <span class="na">type=</span><span class="s">"org.apache.struts2.components.date.DateFormatter"</span> |
| <span class="na">name=</span><span class="s">"dateTimeFormatter"</span> |
| <span class="na">class=</span><span class="s">"org.apache.struts2.components.date.DateTimeFormatterAdapter"</span> |
| <span class="na">scope=</span><span class="s">"singleton"</span><span class="nt">/></span> |
| </code></pre></div></div> |
| |
| <p>The <code class="language-plaintext highlighter-rouge">name</code> attribute it’s of your choice, it just needs to be unique.</p> |
| |
| <p>And the final step is to use the new bean with the extension point, this will happen in <code class="language-plaintext highlighter-rouge">default.properties</code>:</p> |
| |
| <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.date.formatter=dateTimeFormatter |
| </code></pre></div></div> |
| |
| <p>and done!</p> |
| |
| <p>If a user would like to provide its own implementation they just needs to implement the interface, define a bean |
| in <code class="language-plaintext highlighter-rouge">struts.xml</code> with a name and then tie it to the extension point overriding the one provided by the framework:</p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><bean</span> <span class="na">type=</span><span class="s">"org.apache.struts2.components.date.DateFormatter"</span> |
| <span class="na">name=</span><span class="s">"myDateTimeFormatter"</span> |
| <span class="na">class=</span><span class="s">"com.company.date.MyDateTimeFormatterAdapter"</span> |
| <span class="na">scope=</span><span class="s">"singleton"</span><span class="nt">/></span> |
| </code></pre></div></div> |
| |
| <div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>struts.date.formatter=myDateTimeFormatter |
| </code></pre></div></div> |
| |
| <h3 id="plugin-ext">Plugin-defined extension points</h3> |
| |
| <p>It’s very much like above except that the plugin must provide a <code class="language-plaintext highlighter-rouge">bean-selection</code> configuration option |
| in <code class="language-plaintext highlighter-rouge">struts-deferred.xml</code>. The <code class="language-plaintext highlighter-rouge">bean-selection</code> option represents an implementation of a |
| class <code class="language-plaintext highlighter-rouge">org.apache.struts2.config.AbstractBeanSelectionProvider</code> |
| with <em>no-arguments</em> constructor:</p> |
| |
| <div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">public</span> <span class="kd">class</span> <span class="nc">VelocityBeanSelectionProvider</span> <span class="kd">extends</span> <span class="nc">AbstractBeanSelectionProvider</span> <span class="o">{</span> |
| |
| <span class="nd">@Override</span> |
| <span class="kd">public</span> <span class="kt">void</span> <span class="nf">register</span><span class="o">(</span><span class="nc">ContainerBuilder</span> <span class="n">builder</span><span class="o">,</span> <span class="nc">LocatableProperties</span> <span class="n">props</span><span class="o">)</span> <span class="kd">throws</span> <span class="nc">ConfigurationException</span> <span class="o">{</span> |
| <span class="n">alias</span><span class="o">(</span><span class="nc">VelocityManagerInterface</span><span class="o">.</span><span class="na">class</span><span class="o">,</span> <span class="nc">VelocityConstants</span><span class="o">.</span><span class="na">STRUTS_VELOCITY_MANAGER_CLASSNAME</span><span class="o">,</span> <span class="n">builder</span><span class="o">,</span> <span class="n">props</span><span class="o">);</span> |
| <span class="o">}</span> |
| |
| <span class="o">}</span> |
| </code></pre></div></div> |
| |
| <p>The class defines extension points by implementing <code class="language-plaintext highlighter-rouge">register()</code> method and using <code class="language-plaintext highlighter-rouge">alias()</code> method to register them.</p> |
| |
| <p>And finally it must be added to the <code class="language-plaintext highlighter-rouge">struts-deferred.xml</code>:</p> |
| |
| <div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="cp"><?xml version="1.0" encoding="UTF-8" ?></span> |
| <span class="cp"><!DOCTYPE struts PUBLIC |
| "-//Apache Software Foundation//DTD Struts Configuration 2.6//EN" |
| "http://struts.apache.org/dtds/struts-2.6.dtd"></span> |
| |
| <span class="nt"><struts></span> |
| ... |
| |
| <span class="nt"><bean-selection</span> <span class="na">name=</span><span class="s">"velocityBeans"</span> <span class="na">class=</span><span class="s">"org.apache.struts2.views.velocity.VelocityBeanSelectionProvider"</span><span class="nt">/></span> |
| |
| <span class="nt"></struts></span> |
| </code></pre></div></div> |
| |
| <p>And now other plugins or user application can use the new extension point represented by <code class="language-plaintext highlighter-rouge">VelocityConstants.STRUTS_VELOCITY_MANAGER_CLASSNAME</code>.</p> |
| |
| <h2 id="plugin-registry">Plugin Registry</h2> |
| |
| <blockquote> |
| <p>For a list of bundled plugins, see the <a href="index">Plugin Reference Documentation</a>. For more about bundled and third-party |
| plugins, visit the <a href="http://cwiki.apache.org/S2PLUGINS/home">Apache Struts Plugin Registry</a>.</p> |
| </blockquote> |
| |
| </section> |
| </article> |
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