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     <h1>Constructor Injection

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 <p>For those of you who would like to use final fields, wish to avoid numerous
 setters, or dislike private field injection and would like nothing more
 than to just use plan old java constructors, your wish has come true.  This
 is a feature we intended to add to OpenEJB 3.0 but didn't have time for.
 We're happy to bring it to the OpenEJB 3.1 release and with a bit of luck
 and support from people like yourself, we'll see this as an EJB 3.1 feature
 as well.</p>

 <pre><code>@Stateless
 public class WidgetBean implements Widget {

     @EJB(beanName = "FooBean")
     private final Foo foo;

     @Resource(name = "count")
     private final int count;

     @Resource
     private final DataSource ds;

     public WidgetBean(Integer count, Foo foo, DataSource ds) {
     this.count = count;
     this.foo = foo;
     this.ds = ds;
     }

     public int getCount() {
     return count;
     }

     public Foo getFoo() {
     return foo;
     }
 }
 </code></pre>

 <p>The @EJB, @Resource, @PersistenceUnit, and @PersistenceContext annotations
 can be placed at the class-level instead such as:</p>

 <pre><code>@Stateless
 @EJB(name = "foo", beanInterface = Foo.class, beanName = "FooBean")
 @Resource(name = "count", type = int.class)
 @Resource(name = "ds", type = DataSource.class)
 public class WidgetBean implements Widget {

     public WidgetBean(Integer count, Foo foo, DataSource ds) {
        // do something
     }

     public int getCount() {
     return count;
     }

     public Foo getFoo() {
     return foo;
     }
 }
 </code></pre>

 <p>Currently this functionality relies on classes being compiled with debug
 symbols (the default compile setting for javac) as we use the debug table
 in the byte code to discover the constructor arg names.  Additionally, you
 must not have a no-arg constructor.  If a no-arg constructor is present,
 that constructor will be used instead.</p>

 <p>Ideally, we would like the annotations to be used on the parameters
 directly as shown below.  Unfortunately, this does not work as the Java EE
 annotation classes do not permit usage on parameters.  If you'd like to see
 that change as much as we do, definitely voice your support by sending note
 to <a href="mailto:jsr-316-comments@jcp.org.html">jsr-316-comments@jcp.org</a></p>

 <p>Not yet possible</p>

 <pre><code>@Stateless

 public class WidgetBean implements Widget {

     public WidgetBean(@Resource(name = "count") Integer count, @EJB Foo foo, @Resource DataSource ds) {
        // do something
     }

     public int getCount() {
         return count;
     }

     public Foo getFoo() {
         return foo;
     }
 }
 </code></pre>


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	<h1>Constructor Injection

	<div style="float: right; position: relative; bottom: -10px; ">
	<a onclick="javascript:gpshare()" class="gp-share sprite" title="Share on Google+">share [gp]</a>
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	<p>For those of you who would like to use final fields, wish to avoid numerous
	setters, or dislike private field injection and would like nothing more
	than to just use plan old java constructors, your wish has come true. This
	is a feature we intended to add to OpenEJB 3.0 but didn't have time for.
	We're happy to bring it to the OpenEJB 3.1 release and with a bit of luck
	and support from people like yourself, we'll see this as an EJB 3.1 feature
	as well.</p>

	<pre><code>@Stateless
	public class WidgetBean implements Widget {

	@EJB(beanName = "FooBean")
	private final Foo foo;

	@Resource(name = "count")
	private final int count;

	@Resource
	private final DataSource ds;

	public WidgetBean(Integer count, Foo foo, DataSource ds) {
	this.count = count;
	this.foo = foo;
	this.ds = ds;
	}

	public int getCount() {
	return count;
	}

	public Foo getFoo() {
	return foo;
	}
	}
	</code></pre>

	<p>The @EJB, @Resource, @PersistenceUnit, and @PersistenceContext annotations
	can be placed at the class-level instead such as:</p>

	<pre><code>@Stateless
	@EJB(name = "foo", beanInterface = Foo.class, beanName = "FooBean")
	@Resource(name = "count", type = int.class)
	@Resource(name = "ds", type = DataSource.class)
	public class WidgetBean implements Widget {

	public WidgetBean(Integer count, Foo foo, DataSource ds) {
	// do something
	}

	public int getCount() {
	return count;
	}

	public Foo getFoo() {
	return foo;
	}
	}
	</code></pre>

	<p>Currently this functionality relies on classes being compiled with debug
	symbols (the default compile setting for javac) as we use the debug table
	in the byte code to discover the constructor arg names. Additionally, you
	must not have a no-arg constructor. If a no-arg constructor is present,
	that constructor will be used instead.</p>

	<p>Ideally, we would like the annotations to be used on the parameters
	directly as shown below. Unfortunately, this does not work as the Java EE
	annotation classes do not permit usage on parameters. If you'd like to see
	that change as much as we do, definitely voice your support by sending note
	to <a href="mailto:jsr-316-comments@jcp.org.html">jsr-316-comments@jcp.org</a></p>

	<p>Not yet possible</p>

	<pre><code>@Stateless

	public class WidgetBean implements Widget {

	public WidgetBean(@Resource(name = "count") Integer count, @EJB Foo foo, @Resource DataSource ds) {
	// do something
	}

	public int getCount() {
	return count;
	}

	public Foo getFoo() {
	return foo;
	}
	}
	</code></pre>




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	<small>NOTICE: unless indicated otherwise on the pages in question, all editable content available from apache.org is presumed to be licensed under the Apache License (AL) version 2.0 and hence all submissions to apache.org treated as formal Contributions under the license terms.</small>
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