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<title>Declaring an EJB reference</title><link rel="stylesheet" href="styles.css" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/styles.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets Vimages/callouts/"><link rel="home" href="index.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/index.html" title="JBoss 3.0 Documentation"><link rel="up" href="ch07.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07.html" title="Chapter 7. Advanced container configuration : use of jboss.xml"><link rel="previous" href="ch07s10.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07s10.html" title="Specifying the deployment name of your beans"><link rel="next" href="ch07s16.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07s16.html" title="Container configuration"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><table border="0" cellpadding="0" cellspacing="0" height="65"><tr height="65"><td rowspan="2"><img src="jboss.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/jboss.gif" border="0"></td><td rowspan="2" background="gbar.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/gbar.gif" width="100%" align="right" valign="top"><a href="index.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/index.html"><img src="doc.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/doc.gif" border="0"></a><a href="ch07.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07.html"><img src="toc.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/toc.gif" border="0"></a><a href="ch07s10.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07s10.html"><img src="prev.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/prev.gif" border="0"></a><a href="ch07s16.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07s16.html"><img src="next.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/next.gif" border="0"></a></td></tr><tr></tr></table><div class="section"><a name="d0e2657"></a><div class="titlepage"><div><h2 class="title" style="clear: both"><a name="d0e2657"></a>Declaring an EJB reference</h2></div></div><p>An EJB reference (see ejb1.1 specification, 14.3, p207) is when a bean A wants
to call methods on a bean B.
We are talking about intra-bean calls also called B2B calls. This is not for
clients (that is covered in
the beginner trails) this is for bean calls all on the server. Most of these
calls are done inside the
server VM.</p><p>This call will look like this:</p><pre class="programlisting">public class ABean implements SessionBean {
public void businessMethod(...) {
...
InitialContext namingContext = new InitialContext();
Object ref = namingContext.lookup("java:comp/env/ejb/myBean");
BHome home = (BHome)PortableRemoteObject(ref);
B bean = home.create(pk);
...
}
}</pre><p>You can also have a lookup relative to "java:comp/env" like this :</p><pre class="programlisting">public class ABean implements SessionBean {
public void businessMethod(...) {
...
InitialContext namingContext = new InitialContext();
Object ref = namingContext.lookup("ejb/myBean");
BHome home = (BHome)PortableRemoteObject(ref);
B bean = home.create(pk);
...
}
}</pre><p>This notation let better understand the redirection done by JBoss for the JNDI lookup. As we will see,
where the bean lives is not specified in the source code but in the deployment descriptor.</p><p>To be allowed this call, the bean A must declare it in the its deployment
descriptor. This is done by an <ejb-ref>
tag in the bean section of the ejb-jar.xml file. 2 cases may occur:
</p><div class="section"><a name="d0e2674"></a><div class="titlepage"><div><h3 class="title"><a name="d0e2674"></a>Internal EJB reference</h3></div></div><p>An EJB reference is called internal when the bean B is in the same application unit as the bean
A. This means that the beans are
physically packaged in the same jar. In this case, you must provide the <ejb-link> tag, and its value must
match the <ejb-name> of bean B. You don't have to provide anything
in the jboss.xml file. Your ejb-jar.xml
file will look like this:
</p><pre class="programlisting">
<ejb-jar>
<enterprise-beans>
<session>
<ejb-name>Bean A</ejb-name>
<home>AHome</home>
<remote>A</remote>
<ejb-class>ABean</ejb-class>
<session-type>Stateful</session-type>
<transaction-type>Container</transaction-type>
<ejb-ref>
<ejb-ref-name>ejb/myBean</ejb-ref-name>
<ejb-ref-type>Entity</ejb-ref-type>
<home>BHome</home>
<remote>B</remote>
<ejb-link>Bean B</ejb-link>
</ejb-ref>
</session>
<entity>
<ejb-name>Bean B</ejb-name>
<home>BHome</home>
<remote>B</remote>
<ejb-class>BBean</ejb-class>
<persistence-type>Bean</persistence-type>
<prim-key-class>myPK</prim-key-class>
<reentrant>True</reentrant>
</entity>
</enterprise-beans>
</ejb-jar>
</pre></div><div class="section"><a name="d0e2681"></a><div class="titlepage"><div><h3 class="title"><a name="d0e2681"></a>External EJB reference</h3></div></div><p>An EJB reference is called external when the bean B comes from another application unit, it may
even be deployed on another server.
This means that the beans live in different jars on different systems. In this
case, you cannot rely on the
standard <ejb-link> tag in ejb-jar.xml since there the beans are
not covered in the same file. Instead, you must
provide the full JNDI name of the bean B in jboss.xml. This is necessary to
map the names from different ejb-jar.xml
files since the 2 beans are defined in different application units. A full
name is of the form:
</p><p>protocol://host:1234/name/in/other/server
Note that the <ejb-ref-name> tags in the 2 xml files must match.
</p><p>ejb-jar.xml:</p><pre class="programlisting">
<ejb-jar>
<enterprise-beans>
<session>
<ejb-name>Bean A</ejb-name>
<home>AHome</home>
<remote>A</remote>
<ejb-class>ABean</ejb-class>
<session-type>Stateful</session-type>
<transaction-type>Container</transaction-type>
<ejb-ref>
<ejb-ref-name>ejb/myBean</ejb-ref-name>
<ejb-ref-type>Entity</ejb-ref-type>
<home>BHome</home>
<remote>B</remote>
</ejb-ref>
</session>
</enterprise-beans>
</ejb-jar>
</pre><p>jboss.xml: </p><pre class="programlisting">
<jboss>
<enterprise-beans>
<session>
<ejb-name>Bean A</ejb-name>
<ejb-ref>
<ejb-ref-name>ejb/myBean</ejb-ref-name>
<jndi-name>jnp://otherserver/application/beanB</jndi-name>
</ejb-ref>
</session>
<enterprise-beans>
</jboss>
</pre><p>If bean B is deployed in another application, but on the same jboss server,
the jndi-name you provide must be
the name under which bean B is deployed.</p><p>IMPORTANT NOTE: this will tell jboss where to look for bean B. You also have
to tell jboss what bean B is:
in case of an external ejb-reference, be sure to include bean B's home and
remote interface in bean A's ejb-jar. </p></div></div><table border="0" cellpadding="0" cellspacing="0" height="65"><tr height="65"><td rowspan="2"><img src="gbar.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/gbar.gif" width="432" height="79"></td><td rowspan="2" background="gbar.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/gbar.gif" width="100%" align="right" valign="top"><a href="index.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/index.html"><img src="doc.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/doc.gif" border="0"></a><a href="ch07.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07.html"><img src="toc.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/toc.gif" border="0"></a><a href="ch07s10.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07s10.html"><img src="prev.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/prev.gif" border="0"></a><a href="ch07s16.html" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/ch07s16.html"><img src="next.gif" tppabs="http://www.huihoo.org/jboss/online_manual/3.0/next.gif" border="0"></a></td></tr><tr></tr></table></body></html>⌨️ 快捷键说明
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