The process for creating a deployment descriptor for interceptors includes:

To illustrate the use of a deployment descriptor for a lifecycle method, we will modify the RegistrationApplication along with the SimpleInterceptor class developed in the first two recipes of Chapter 8, Interceptors. The SimpleInterceptor class has a method called constructed, as shown below, which we want to be a post construct method. Post construct methods will be executed after its class has been created and after any dependency injection has been performed. We could use the @PostConstruct annotation to mark the method as a post construct method. Instead we will use a deployment descriptor.

public class SimpleInterceptor {
private void constructed(InvocationContext invocationContext) {
System.out.println("SimpleInterceptor constructed: ");
}
...
}

Create an ejb-jar.xml file. The root element is<ejb-jar> as shown here:

<?xml version="1.0" encoding="UTF-8"?>
<ejb-jar xmlns = "http://java.sun.com/xml/ns/javaee"
version = "3.1"
xmlns:xsi = "http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation = "http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/ejb-jar_3_1.xsd">
...
</ejb-jar>

For a post construction life cycle callback, the<post-construct> element is used. Add an<interceptors> element within the<ejb-jar> element. Within this element you can add one or more<interceptor> elements to declare interceptors and their callback methods.

Add an<interceptor> element and within this element add the following two elements:

The following code illustrates the deployment code to affect the use of this lifecycle method.

<interceptors>
<interceptor>
<interceptor-class>packt.DefaultInterceptor</interceptor-class>
</interceptor>
<interceptor>
<interceptor-class>packt.SimpleInterceptor</interceptor-class>
<post-construct>
<lifecycle-callback-class>packt.SimpleInterceptor </lifecycle-callback-class>
<lifecycle-callback-method>constructed </lifecycle-callback-method>
</post-construct>
</interceptor>
</interceptors>

In the ejb-jar.xml file, the SimpleInterceptor was declared using the<interceptor> element. As part of this element, the<post-construct> element was used to associate the SimpleInterceptor with the constructed method. At deployment the server will effect these specifications.

There are other lifecycle methods which can be configured using a deployment descriptor. A list of common events is found in the following table:

When multiple lifecycle events are handled by the same class, the lifecycle elements follow each other within the same<interceptor> element for the same class. Here post-construct and pre-destroy methods are declared.

<interceptors>
<interceptor>
<interceptor-class>interceptorClass</interceptor-class>
<post-construct>
<lifecycle-callback-class>package.interceptorClassName </lifecycle-callback-class>
<lifecycle-callback-method>someMethodName </lifecycle-callback-method>
</post-construct>
<pre-destroy>
<lifecycle-callback-class>package.interceptorClassName </lifecycle-callback-class>
<lifecycle-callback-method>someMethodName </lifecycle-callback-method>
</pre-destroy>
</interceptor>
</interceptors>

The Using deployment descriptors for interceptors recipe covers the general aspects of using interceptors with business methods.