Author: simonetripodi
Date: Tue Aug 31 09:35:30 2010
New Revision: 991130
URL: http://svn.apache.org/viewvc?rev=991130&view=rev
Log:
added the annotations package description
Added:
commons/proper/digester/trunk/src/site/xdoc/annotations.xml (with props)
Modified:
commons/proper/digester/trunk/src/site/site.xml
Modified: commons/proper/digester/trunk/src/site/site.xml
URL:
http://svn.apache.org/viewvc/commons/proper/digester/trunk/src/site/site.xml?rev=991130&r1=991129&r2=991130&view=diff
==============================================================================
--- commons/proper/digester/trunk/src/site/site.xml (original)
+++ commons/proper/digester/trunk/src/site/site.xml Tue Aug 31 09:35:30 2010
@@ -37,6 +37,7 @@
<item name="Plugins" href="/plugins.html"/>
<item name="Substitution" href="/substitution.html"/>
<item name="XML Rules" href="/xmlrules.html"/>
+ <item name="Annotations" href="/annotations.html"/>
<item name="FAQ" href="/faq.html"/>
</menu>
Added: commons/proper/digester/trunk/src/site/xdoc/annotations.xml
URL:
http://svn.apache.org/viewvc/commons/proper/digester/trunk/src/site/xdoc/annotations.xml?rev=991130&view=auto
==============================================================================
--- commons/proper/digester/trunk/src/site/xdoc/annotations.xml (added)
+++ commons/proper/digester/trunk/src/site/xdoc/annotations.xml Tue Aug 31
09:35:30 2010
@@ -0,0 +1,461 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!--
+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.
+-->
+<document xmlns="http://maven.apache.org/XDOC/2.0";
+ xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance";
+ xsi:schemaLocation="http://maven.apache.org/XDOC/2.0
http://maven.apache.org/xsd/xdoc-2.0.xsd";>
+ <properties>
+ <title>Download Commons Digester</title>
+ <author email="[email protected]">Commons Documentation Team</author>
+ </properties>
+ <body>
+ <section name="Annotations">
+ <p>The <code>annotations</code> package provides for Java5 Annotations
+ meta data-based definition of rules for <code>Digester</code>.
+ This improves maintainability of both Java code and XML documents, as
+ rules are now defined in POJOs and generating <code>Digester</code>
+ parsers at run-time, avoiding manual updates.</p>
+
+ <subsection name="Introduction">
+ <p>This is a brief overview of the digester-rules-in-Java5 Annotations
+ feature. Inspired by the basic idea behind the JPA, BeanValidation and
+ JAXB's specifications, this feature lets you define Digester rules
+ directly in target POJOs, instead of creating and initializing the
Rules
+ objects programmatically, which can become tedious.</p>
+ </subsection>
+
+ <subsection name="Annotation Rules">
+ <p>A digester rule on a POJO is expressed through one or more
annotations.
+ An annotation is considered a digester rule definition if its retention
+ policy contains RUNTIME and if the annotation itself is annotated with
+ <code>org.apache.commons.digester.annotations.DigesterRule</code>.</p>
+
+ <p>The <code>DigesterRule</code> is defined by the combination of:</p>
+ <ul>
+ <li>the reflected <code>Class<? extends
org.apache.commons.digester.Rule></code>
+ by the annotation;</li>
+ <li>the
<code>org.apache.commons.digester.annotations.DigesterLoaderHandler</code>
+ class that has to be invoked during the target class traversal
+ (if not specifyied, the annotation processor will supply the
+
<code>org.apache.commons.digester.annotations.handlers.DefaultLoaderHandler</code>);</li>
+ <li>the
<code>org.apache.commons.digester.annotations.AnnotationRuleProvider</code>
+ provider that produces the <code>pattern, rule</code> pair.</li>
+ </ul>
+
+ <p>Digester annotations can target any of the following
<code>ElementType</code>s:</p>
+ <ul>
+ <li><code>FIELD</code> for Digester rules concerning
attributes;</li>
+ <li><code>METHOD</code> for Digester rules concerning methods
calls;</li>
+ <li><code>PARAMETER</code> for Digester rules concerning methods
parameters setting;</li>
+ <li><code>TYPE</code> for Digester rules concerning types
creation.</li>
+ </ul>
+ <p>While other <code>ElementType</code>s are not forbidden, the
Digester
+ annotations processor does not have to recognize and process annotation
+ rules placed on such types.</p>
+
+ <p>Every Digester rule annotation <b>must</b> define a <i>pattern</i>
+ element of type <code>String</code> that represents the element
matching
+ path pattern.</p>
+
+ <source>@Documented
+...@retention(RetentionPolicy.RUNTIME)
+...@target(ElementType.TYPE)
+...@creationrule
+...@digesterrule(
+ reflectsRule = ObjectCreateRule.class,
+ providedBy = ObjectCreateRuleProvider.class
+)
+public @interface ObjectCreate {
+
+ String pattern();
+
+}</source>
+ </subsection>
+
+ <subsection name="Applying multiple annotation rule of the same type">
+ <p>It is often useful to declare the same annotation rule more than
once
+ to the same target, with different properties. To support this
requirement,
+ the Digester annotation processor treats annotations annotated by
+ <code>@org.apache.commons.digester.annotations.DigesterRuleList</code>
+ whose <code>value</code> element has a return type of an array of rule
+ annotations in a special way. Each element in the value array are
processed
+ by the Digester annotation processor as regular annotation rule
annotations.
+ This means that each Digester rule specified in the <code>value</code>
+ element is applied to the target. The annotation must have retention
+ <code>RUNTIME</code> and can be applied on a type, field, method or
+ method parameter. It is recommended to use the same set of targets as
+ the initial Digester annotation rule.</p>
+
+ <p>Note to designers: each Digester annotation rule should be coupled
+ with its corresponding multi-valued annotation.
+ It is recommended, though not mandated, the definition of
+ an inner annotation named <code>List</code>.</p>
+
+ <source>@Documented
+...@retention(RetentionPolicy.RUNTIME)
+...@target(ElementType.TYPE)
+...@creationrule
+...@digesterrule(
+ reflectsRule = ObjectCreateRule.class,
+ providedBy = ObjectCreateRuleProvider.class
+)
+public @interface ObjectCreate {
+
+ String pattern();
+
+ @Documented
+ @Retention(RetentionPolicy.RUNTIME)
+ @Target(ElementType.TYPE)
+ @DigesterRuleList
+ @interface List {
+ ObjectCreate[] value();
+ }
+
+}</source>
+ </subsection>
+
+ <subsection name="Rule provider implementation">
+ <p>A Digester rule provider implementation performs the rule creation
+ of a given annotation for a given annotated element. The implementation
+ classes are specified by the <code>providedBy</code> element of the
+ <code>@DigesterRule</code> annotation that decorates the rule
annotation
+ definition. The rule provider implementation implements the
+
<code>org.apache.commons.digester.annotations.AnnotationRuleProvider<A
extends Annotation, E extends AnnotatedElement, R extends Rule></code>
+ interface.</p>
+
+ <source>class ObjectCreateRuleProvider implements
AnnotationRuleProvider<ObjectCreate, Class<?>, ObjectCreateRule> {
+
+ private Class<?> clazz;
+
+ public void init(ObjectCreate annotation, Class<?> element) {
+ this.clazz = element;
+ }
+
+ public ObjectCreateRule get() {
+ return new ObjectCreateRule(this.clazz);
+ }
+
+}</source>
+
+ <h5>Notes</h5>
+ <p>A new instance of the provider will be created each time the
Digester
+ annotations processor will meet the relative rule that requests it.</p>
+ <p>To supply the missing <code>AnnotatedElement</code> for methods
+ <code>PARAMETER</code>s, the Digester annotation processor come with
the
+
<code>org.apache.commons.digester.annotations.reflect.MethodArgument</code>
+ class.</p>
+ </subsection>
+
+ <subsection name="Digester loader handler implementation">
+ <p>The Digester loader handler is an <code>AnnotatedElement</code>
+ interceptor invoked when meeting a particular Digester rule annotation
+ while analyzing the target class.</p>
+
+ <p>By default, the Digester annotations processor, when meeting a
+ Digester annotation rule, extracts the rule pattern and the relative
+ rule provider to store it in the
+
<code>org.apache.commons.digester.annotations.FromAnnotationsRuleSet</code>,
+ an <code>org.apache.commons.digester.RuleSet</code> implementation.</p>
+
+ <p>If designers have the need of a more elaborate annottaion
processing,
+ they can specify the <code>handledBy</code> element of the
+ <code>@DigesterRule</code> annotation that decorates the rule
annotation
+ definition. The Digester loader handler implementation implements the
+ <code>DigesterLoaderHandler<A extends Annotation, E extends
AnnotatedElement></code>
+ interface. Follows below an example:</p>
+
+ <source>class SetPropertiesLoaderHandler implements
DigesterLoaderHandler<SetProperty, Field> {
+
+ public void handle(SetProperty annotation, Field element,
FromAnnotationsRuleSet ruleSet) {
+ SetPropertiesRuleProvider ruleProvider =
ruleSet.getProvider(annotation.pattern(), SetPropertiesRuleProvider.class);
+
+ if (ruleProvider == null) {
+ ruleProvider = new SetPropertiesRuleProvider();
+ ruleSet.addRuleProvider(annotation.pattern(), ruleProvider);
+ }
+
+ ruleProvider.addAlias(annotation, element);
+ }
+
+}</source>
+ </subsection>
+
+ <subsection name="Built-in Rules">
+ <p>All built-in annotation rules are in the package
+ <code>org.apache.commons.digester.annotations.rules</code>.
+ Here is the list of annotations and their usage.</p>
+
+ <h4><code>TYPE</code> annotations</h4>
+ <table>
+ <thead>
+ <tr><th>Annotation</th><th>Reflect rule</th></tr>
+ </thead>
+ <tbody>
+
<tr><td>@ObjectCreate</td><td>org.apache.commons.digester.ObjectCreateRule</td></tr>
+
<tr><td>@FactoryCreate</td><td>org.apache.commons.digester.FactoryCreateRule</td></tr>
+ </tbody>
+ </table>
+
+ <h4><code>FIELD</code> annotations</h4>
+ <table>
+ <thead>
+ <tr><th>Annotation</th><th>Reflect rule</th></tr>
+ </thead>
+ <tbody>
+
<tr><td>@BeanPropertySetter</td><td>org.apache.commons.digester.BeanPropertySetterRule</td></tr>
+
<tr><td>@SetProperty</td><td>org.apache.commons.digester.SetPropertiesRule</td></tr>
+ </tbody>
+ </table>
+
+ <h4><code>METHOD</code> annotations</h4>
+ <table>
+ <thead>
+ <tr><th>Annotation</th><th>Reflect rule</th></tr>
+ </thead>
+ <tbody>
+
<tr><td>@CallMethod</td><td>org.apache.commons.digester.CallMethodRule</td></tr>
+
<tr><td>@SetNext</td><td>org.apache.commons.digester.SetNextRule</td></tr>
+
<tr><td>@SetRoot</td><td>org.apache.commons.digester.SetRootRule</td></tr>
+
<tr><td>@SetTop</td><td>org.apache.commons.digester.SetTopRule</td></tr>
+ </tbody>
+ </table>
+
+ <h4><code>PARAMETER</code> annotations</h4>
+ <table>
+ <thead>
+ <tr><th>Annotation</th><th>Reflect rule</th></tr>
+ </thead>
+ <tbody>
+
<tr><td>@AttributeCallParam</td><td>org.apache.commons.digester.Digester#addCallParam(String,
int, String)</td></tr>
+
<tr><td>@CallParam</td><td>org.apache.commons.digester.Digester#addCallParam(String,
int)</td></tr>
+
<tr><td>@PathCallParam</td><td>org.apache.commons.digester.Digester#addCallParamPath(String,
int)</td></tr>
+
<tr><td>@StackCallParam</td><td>org.apache.commons.digester.Digester#addCallParam(String,
int, int)</td></tr>
+ </tbody>
+ </table>
+ </subsection>
+
+ <subsection name="Bootstrapping">
+ <p>The core of Digester annotations rules processor is the
+ <code>org.apache.commons.digester.annotations.DigesterLoader</code>
class.</p>
+
+ <p>A <code>org.apache.commons.digester.annotations.DigesterLoader</code>
+ instance is able to analyze <code>Class<?></code> graphs and builds
+ the relative <code>org.apache.commons.digester.RuleSet</code> to create
+ <code>org.apache.commons.digester.Digester</code> instances.</p>
+
+ <p>The bootstrap sequence has been designed to be as simple as possible,
+ all that's needed is creating a new
+ <code>org.apache.commons.digester.annotations.DigesterLoaderBuilder</code>
+ instance, plugging the desired
+
<code>org.apache.commons.digester.annotations.spi.AnnotationRuleProviderFactory</code>
and
+
<code>org.apache.commons.digester.annotations.spi.DigesterLoaderHandlerFactory</code>.
+ using a chaining builders pattern.</p>
+
+ <p>An
<code>org.apache.commons.digester.annotations.spi.AnnotationRuleProviderFactory</code>
+ implementation performs the creation of
+ <code>org.apache.commons.digester.annotations.AnnotationRuleProvider<A
extends Annotation, E extends AnnotatedElement, R extends Rule></code>
+ instances; the default implementation is limited to create the provider
+ by invoking the default empty constructor of the required class, but
+ users are free to give their implementation if they need a more complex
+ factory, i.e. providers requires components that could be injected from a
+ context, etc. etc.</p>
+
+ <h5>Note</h5>
+ <p>It is strongly descouraged caching <code>AnnotationRuleProvider</code>
+ instances!!!</p>
+
+ <p>Same thing for the
<code>org.apache.commons.digester.annotations.spi.DigesterLoaderHandlerFactory</code>,
+ which implementation performs the creation of
+ <code>DigesterLoaderHandler<A extends Annotation, E extends
AnnotatedElement></code>
+ instances; the default implementation is limited to create the handler
+ by invoking the default empty constructor of the required class, but
+ users are free to give their implementation if they need a more complex
+ factory, i.e. providers requires components that could be injected from a
+ context, etc. etc.</p>
+
+ <p>Said that, to obtain a fresh new
+ <code>org.apache.commons.digester.annotations.DigesterLoader</code>
instance
+ with default factories, it is enough invoking the default empty
constructor:</p>
+
+ <source>DigesterLoader digesterLoader = new DigesterLoaderBuilder()
+ .useDefaultAnnotationRuleProviderFactory()
+
.useDefaultDigesterLoaderHandlerFactory();</source>
+
+ <p>Otherwise, if users need specify theyr custom factories:</p>
+
+ <source>DigesterLoader digesterLoader = new DigesterLoaderBuilder()
+ .useAnnotationRuleProviderFactory(new
MyAnnotationRuleProviderFactory())
+ .useDigesterLoaderHandlerFactory(new
MyDigesterLoaderHandlerFactory());</source>
+ </subsection>
+
+ <subsection name="Example: a simple RSS parser">
+ <p>Let's assume there is the need to parse the following (simplified)
+ XML/RSS feed:</p>
+
+ <source><rss version="2.0">
+ <channel>
+
+ <title>Apache</title>
+ <link>http://www.apache.org</link>
+ <description>The Apache Software Foundation</description>
+ <language>en-US</language>
+ <rating>(PICS-1.1 "http://www.rsac.org/ratingsv01.html";
+ 2 gen true comment "RSACi North America Server"
+ for "http://www.rsac.org"; on "1996.04.16T08:15-0500"
+ r (n 0 s 0 v 0 l 0))</rating>
+
+ <image>
+ <title>Apache</title>
+
<url>http://jakarta.apache.org/images/jakarta-logo.gif</url>
+ <link>http://jakarta.apache.org</link>
+ <width>505</width>
+ <height>480</height>
+ <description>The Jakarta project. Open source, serverside
java.</description>
+ </image>
+
+ <item>
+ <title>Commons Attributes 2.1 Released</title>
+
<link>http://jakarta.apache.org/site/news/news-2004-2ndHalf.html#20040815.1</link>
+ <description>The Apache Commons team is happy to announce
the release of Commons Attributes 2.1. This is the first release of the new
Commons-Attributes code.</description>
+ </item>
+
+ <item>
+ <title>Cloudscape Becomes Apache Derby</title>
+
<link>http://jakarta.apache.org/site/news/elsewhere-2004-2ndHalf.html#20040803.1</link>
+ <description>IBM has submitted a proposal to the Apache DB
project for a Java-based package to be called 'Derby'.</description>
+ </item>
+
+ <item>
+ <title>Commons BeanUtils 1.7 Released</title>
+
<link>http://jakarta.apache.org/site/news/news-2004-2ndHalf.html#20040802.1</link>
+ <description/>
+ </item>
+
+ <item>
+ <title>Commons JXPath 1.2 Released</title>
+
<link>http://jakarta.apache.org/site/news/news-2004-2ndHalf.html#20040801.2</link>
+ <description/>
+ </item>
+ </channel>
+</rss></source>
+
+ <p>So, let's define the Java entities and annotate them; first the
<code>Channel</code> entity:</p>
+
+ <source>@ObjectCreate(pattern = "rss/channel")
+class Channel {
+
+ private final List<Item> items = new ArrayList<Item>();
+
+ @BeanPropertySetter(pattern = "rss/channel/title")
+ private String title;
+
+ @BeanPropertySetter(pattern = "rss/channel/link")
+ private String link;
+
+ @BeanPropertySetter(pattern = "rss/channel/description")
+ private String description;
+
+ @BeanPropertySetter(pattern = "rss/channel/language")
+ private String language;
+
+ private Image image;
+
+ // getters and setters
+
+ @SetNext
+ public void setImage(Image image) {
+ this.image = image;
+ }
+
+ @SetNext
+ public void addItem(Item item) {
+ this.items.add(item);
+ }
+
+}</source>
+
+ <p>Then the <code>Image</code> entity:</p>
+
+ <source>@ObjectCreate(pattern = "rss/channel/image")
+class Image {
+
+ @BeanPropertySetter(pattern = "rss/channel/image/description")
+ private String description;
+
+ @BeanPropertySetter(pattern = "rss/channel/image/width")
+ private int width;
+
+ @BeanPropertySetter(pattern = "rss/channel/image/height")
+ private int height;
+
+ @BeanPropertySetter(pattern = "rss/channel/image/link")
+ private String link;
+
+ @BeanPropertySetter(pattern = "rss/channel/image/title")
+ private String title;
+
+ @BeanPropertySetter(pattern = "rss/channel/image/url")
+ private String url;
+
+ // getters and setters
+
+}</source>
+
+ <p>and finally the <code>Item</code> entity:</p>
+
+ <source>@ObjectCreate(pattern = "rss/channel/item")
+class Item {
+
+ @BeanPropertySetter(pattern = "rss/channel/item/description")
+ private String description;
+
+ @BeanPropertySetter(pattern = "rss/channel/item/link")
+ private String link;
+
+ @BeanPropertySetter(pattern = "rss/channel/item/title")
+ private String title;
+
+ // getters and setters
+
+}</source>
+
+ <p>It is now possible to create the <code>Digester</code> instance and
parse the XML:</p>
+
+ <source>DigesterLoader digesterLoader = new DigesterLoaderBuilder()
+ .useDefaultAnnotationRuleProviderFactory()
+ .useDefaultDigesterLoaderHandlerFactory();
+...
+Digester digester = digesterLoader.createDigester(Channel.class);
+try {
+ Channel channel = (Channel) digester.parse(new
URL("http://www.myfeedprovider.com/rss.xml";).openStream());
+} catch (Exception e) {
+ // do something
+}
+ </source>
+
+ <h5>Notes</h5>
+ <p>If asking to the <code>DigesterLoader</code> instance more then twice
the
+ <code>Digester</code> for the same <code>Class<?></code>, the
+ <code>DigesterLoader</code> won't analize the target class for each
request,
+ but rather will reuse cached results.</p>
+
+ <p>The same <code>DigesterLoader</code> instance can be reused to create
+ other <code>Digester</code> instances.</p>
+ </subsection>
+ </section>
+ </body>
+</document>
Propchange: commons/proper/digester/trunk/src/site/xdoc/annotations.xml
------------------------------------------------------------------------------
svn:eol-style = native
Propchange: commons/proper/digester/trunk/src/site/xdoc/annotations.xml
------------------------------------------------------------------------------
svn:keywords = Date Revision Author HeadURL Id
Propchange: commons/proper/digester/trunk/src/site/xdoc/annotations.xml
------------------------------------------------------------------------------
svn:mime-type = text/xml
