SPR-7858
This commit is contained in:
Michael Isvy
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e5d8fa0771
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE section PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd">
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<section id="beans-standard-annotations">
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<title>Using JSR 330 standard annotations</title>
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<para>Starting from Spring 3.0, Spring offers support for JSR-330 standard annotations (Dependency Injection).
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Those annotations are scanned in the same way as the Spring annotations. You just need to have the relevant jars in your classpath.
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</para>
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<note>
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If you are using Maven, the <interfacename>javax.inject</interfacename> artifact is available on the standard Maven repository (<ulink url="http://repo1.maven.org/maven2/javax/inject/javax.inject/1/">http://repo1.maven.org/maven2/javax/inject/javax.inject/1/</ulink>). You just need to add the following dependency to your file pom.xml:
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<programlisting language="xml">
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<dependency>
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<groupId>javax.inject</groupId>
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<artifactId>javax.inject</artifactId>
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<version>1</version>
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</dependency>
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</programlisting>
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</note>
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<section id="beans-inject-named">
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<title>Dependency Injection with <interfacename>@Inject</interfacename> and <interfacename>@Named</interfacename></title>
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<para>
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Instead of <interfacename>@Autowired</interfacename>, <interfacename>javax.inject.Inject</interfacename> may be used as follows:
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<programlisting language="java">
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import javax.inject.Inject;
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public class SimpleMovieLister {
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private MovieFinder movieFinder;
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@Inject
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public void setMovieFinder(MovieFinder movieFinder) {
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this.movieFinder = movieFinder;
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}
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<lineannotation>// ...</lineannotation>
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}</programlisting>
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As for <interfacename>@Autowired</interfacename>, it is possible to use <interfacename>@Inject</interfacename> at the class-level, field-level, method-level and constructor-argument level.
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If you would like to use a qualified name for the dependency that should be injected, you should use the <interfacename>@Named</interfacename> annotation as follows:
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<programlisting language="java">
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import javax.inject.Inject;
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import javax.inject.Named;
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public class SimpleMovieLister {
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private MovieFinder movieFinder;
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@Inject
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public void setMovieFinder(@Named("main") MovieFinder movieFinder) {
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this.movieFinder = movieFinder;
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}
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<lineannotation>// ...</lineannotation>
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}</programlisting>
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</para>
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</section>
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<section id="beans-named">
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<title><interfacename>@Named</interfacename>: a standard equivalent to the <interfacename>@Component</interfacename> annotation</title>
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<para>
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Instead of <interfacename>@Component</interfacename>, <interfacename>javax.inject.Named</interfacename> may be used as follows:
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<programlisting language="java">
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import javax.inject.Inject;
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import javax.inject.Named;
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@Named("movieListener")
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public class SimpleMovieLister {
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private MovieFinder movieFinder;
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@Inject
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public void setMovieFinder(MovieFinder movieFinder) {
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this.movieFinder = movieFinder;
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}
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<lineannotation>// ...</lineannotation>
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}</programlisting>
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</para>
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<para>
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It is very common to use <interfacename>@Component</interfacename> without specifying a name for the component. <interfacename>@Named</interfacename> can be used in a similar fashion:
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<programlisting language="java">
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import javax.inject.Inject;
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import javax.inject.Named;
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@Named
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public class SimpleMovieLister {
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private MovieFinder movieFinder;
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@Inject
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public void setMovieFinder(MovieFinder movieFinder) {
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this.movieFinder = movieFinder;
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}
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<lineannotation>// ...</lineannotation>
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}
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</programlisting>
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</para>
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<para>
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When using <interfacename>@Named</interfacename>, it is possible to use component-scanning in the exact same way as when using Spring annotations:
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<programlisting language="xml">
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<beans>
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<context:component-scan base-package="org.example"/>
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</beans>
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</programlisting>
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</para>
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</section>
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<section id="beans-standard-annotations-limitations">
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<title>Limitations of the standard approach</title>
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<para>When working with standard annotations, it is important to know that some significant features are not available as shown in the table below:</para>
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<para><table id="annotations-comparison">
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<title>Spring annotations vs standard annotations</title>
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<tgroup cols="3">
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<colspec colnum="1" colwidth="0.7*" />
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<colspec colnum="2" colwidth="0.6*" />
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<colspec colnum="3" colwidth="1.5*" />
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<thead>
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<row>
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<entry>Spring</entry>
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<entry>javax.inject.*</entry>
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<entry>javax.inject restrictions / comments</entry>
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</row>
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</thead>
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<tbody>
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<row>
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<entry>@Autowired</entry>
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<entry>@Inject</entry>
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<entry>@Inject has no 'required' attribute</entry>
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</row>
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<row>
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<entry>@Component</entry>
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<entry>@Named</entry>
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<entry></entry>
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</row>
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<row>
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<entry>@Scope("singleton")</entry>
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<entry>@Singleton</entry>
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<entry>
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<para>
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jsr-330 default scope is like Spring's <interfacename>prototype</interfacename>. However, in order to keep it consistent with Spring's general defaults, a jsr-330 bean declared in the Spring container is a <interfacename>singleton</interfacename> by default. In order to use another scope than <interfacename>singleton</interfacename>, you should use Spring's <interfacename>@Scope</interfacename> annotation.
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</para>
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<para>
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<interfacename>javax.inject</interfacename> also provides a <ulink url="http://download.oracle.com/javaee/6/api/javax/inject/Scope.html">@Scope</ulink> annotation. Nevertheless, this one only aims to be used for creating your own annotations.
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</para>
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</entry>
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</row>
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<row>
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<entry>@Qualifier</entry>
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<entry>@Named</entry>
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<entry></entry>
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</row>
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<row>
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<entry>@Value</entry>
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<entry>-</entry>
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<entry>no equivalent</entry>
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</row>
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<row>
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<entry>@Required</entry>
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<entry>-</entry>
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<entry>no equivalent</entry>
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</row>
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<row>
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<entry>@Lazy</entry>
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<entry>-</entry>
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<entry>no equivalent</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</para>
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</section>
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</section>
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@ -942,6 +942,9 @@ List userList service.getUsernameList();
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<xi:include href="beans-classpath-scanning.xml"
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xmlns:xi="http://www.w3.org/2001/XInclude"/>
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<xi:include href="beans-standard-annotations.xml"
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xmlns:xi="http://www.w3.org/2001/XInclude"/>
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<xi:include href="beans-java.xml" xmlns:xi="http://www.w3.org/2001/XInclude"/>
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