Info

title	TODO

Update the info about the new interceptors

Interceptors

Interceptors allow arbitrary code to be included in the call stack for your action before and/or after processing the action, which can vastly simplify your code itself and provide excellent opportunities for code reuse. Many of the features of XWork and WebWork are implemented as interceptors and can be applied via external configuration along with your own Interceptors in whatever order you specify for any set of actions you define.

...

Note

title	Be Careful

Note that some interceptors will interrupt the stack/chain/flow... so the order is very important.

Interceptor configuration:

Code Block

	xml
	xml

<package name="default" extends="webwork-default">
   <interceptors>
       <interceptor name="timer" class=".."/>
       <interceptor name="logger" class=".."/>
   </interceptors>
   
   <action name="login"
      class="org.hibernate.auction.web.actions.users.Login">
        <interceptor-ref name="timer"/>
        <interceptor-ref name="logger"/>
         <result name="input">login.jsp</result>
         <result name="success"
            type="redirect">/secure/dashboard.action</result>
   </action>
</package>

Grouping interceptors as stacks

...

Code Block

	xml
	xml

<package name="default" extends="webwork-default">
   <interceptors>
        <interceptor name="timer" class=".."/>
        <interceptor name="logger" class=".."/>
        <interceptor-stack name="myStack">
           <interceptor-ref name="timer"/>
           <interceptor-ref name="logger"/>
        </interceptor-stack>
    </interceptors>

<action name="login"
     class="org.hibernate.auction.web.actions.users.Login">
         <interceptor-ref name="myStack"/>
         <result name="input">login.jsp</result>
         <result name="success"
             type="redirect">/secure/dashboard.action</result>
</action>
</package>

Looking inside webwork-default.xml we can see how it's done:

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Code Block

	xml
	xml

<!DOCTYPE xwork PUBLIC "-//OpenSymphony Group//XWork 1.0//EN" "http://www.opensymphony.com/xwork/xwork-1.1.dtd">

<!-- // START SNIPPET: webwork-default -->
<xwork>
    <package name="webwork-default">
        <result-types>
            <result-type name="chain" class="com.opensymphony.xwork.ActionChainResult"/>
            <result-type name="dispatcher" class="com.opensymphony.webwork.dispatcher.ServletDispatcherResult"
                         default="true"/>
            <result-type name="freemarker" class="com.opensymphony.webwork.views.freemarker.FreemarkerResult"/>
            <result-type name="httpheader" class="com.opensymphony.webwork.dispatcher.HttpHeaderResult"/>
            <result-type name="jasper" class="com.opensymphony.webwork.views.jasperreports.JasperReportsResult"/>
            <result-type name="redirect" class="com.opensymphony.webwork.dispatcher.ServletRedirectResult"/>
            <result-type name="redirect-action"
                         class="com.opensymphony.webwork.dispatcher.ServletActionRedirectResult"/>
            <result-type name="stream" class="com.opensymphony.webwork.dispatcher.StreamResult"/>
            <result-type name="velocity" class="com.opensymphony.webwork.dispatcher.VelocityResult"/>
            <result-type name="xslt" class="com.opensymphony.webwork.views.xslt.XSLTResult"/>
        </result-types>

        <interceptors>
            <interceptor name="alias" class="com.opensymphony.xwork.interceptor.AliasInterceptor"/>
            <interceptor name="autowiring"
                         class="com.opensymphony.xwork.spring.interceptor.ActionAutowiringInterceptor"/>
            <interceptor name="chain" class="com.opensymphony.xwork.interceptor.ChainingInterceptor"/>
            <interceptor name="component" class="com.opensymphony.xwork.interceptor.component.ComponentInterceptor"/>
            <interceptor name="conversionError"
                         class="com.opensymphony.webwork.interceptor.WebWorkConversionErrorInterceptor"/>
            <interceptor name="external-ref" class="com.opensymphony.xwork.interceptor.ExternalReferencesInterceptor"/>
            <interceptor name="execAndWait" class="com.opensymphony.webwork.interceptor.ExecuteAndWaitInterceptor"/>
            <interceptor name="exception" class="com.opensymphony.xwork.interceptor.ExceptionMappingInterceptor"/>
            <interceptor name="fileUpload" class="com.opensymphony.webwork.interceptor.FileUploadInterceptor"/>
            <interceptor name="i18n" class="com.opensymphony.xwork.interceptor.I18nInterceptor"/>
            <interceptor name="logger" class="com.opensymphony.xwork.interceptor.LoggingInterceptor"/>
            <interceptor name="model-driven" class="com.opensymphony.xwork.interceptor.ModelDrivenInterceptor"/>
            <interceptor name="params" class="com.opensymphony.xwork.interceptor.ParametersInterceptor"/>
            <interceptor name="prepare" class="com.opensymphony.xwork.interceptor.PrepareInterceptor"/>
            <interceptor name="static-params" class="com.opensymphony.xwork.interceptor.StaticParametersInterceptor"/>
            <interceptor name="servlet-config" class="com.opensymphony.webwork.interceptor.ServletConfigInterceptor"/>
            <interceptor name="sessionAutowiring"
                         class="com.opensymphony.webwork.spring.interceptor.SessionContextAutowiringInterceptor"/>
            <interceptor name="timer" class="com.opensymphony.xwork.interceptor.TimerInterceptor"/>
            <interceptor name="token" class="com.opensymphony.webwork.interceptor.TokenInterceptor"/>
            <interceptor name="token-session"
                         class="com.opensymphony.webwork.interceptor.TokenSessionStoreInterceptor"/>
            <interceptor name="validation" class="com.opensymphony.xwork.validator.ValidationInterceptor"/>
            <interceptor name="workflow" class="com.opensymphony.xwork.interceptor.DefaultWorkflowInterceptor"/>

            <!-- Basic stack -->
            <interceptor-stack name="basicStack">
                <interceptor-ref name="exception"/>
                <interceptor-ref name="servlet-config"/>
                <interceptor-ref name="prepare"/>
                <interceptor-ref name="static-params"/>
                <interceptor-ref name="params"/>
                <interceptor-ref name="conversionError"/>
            </interceptor-stack>

            <!-- Sample validation and workflow stack -->
            <interceptor-stack name="validationWorkflowStack">
                <interceptor-ref name="basicStack"/>
                <interceptor-ref name="validation"/>
                <interceptor-ref name="workflow"/>
            </interceptor-stack>

            <!-- Sample file upload stack -->
            <interceptor-stack name="fileUploadStack">
                <interceptor-ref name="fileUpload"/>
                <interceptor-ref name="basicStack"/>
            </interceptor-stack>

            <!-- Sample WebWork Inversion of Control stack
                 Note: WebWork's IoC is deprecated - please
                 look at alternatives such as Sprint -->
            <interceptor-stack name="componentStack">
                <interceptor-ref name="component"/>
                <interceptor-ref name="basicStack"/>
            </interceptor-stack>

            <!-- Sample model-driven stack  -->
            <interceptor-stack name="modelDrivenStack">
                <interceptor-ref name="model-driven"/>
                <interceptor-ref name="basicStack"/>
            </interceptor-stack>

            <!-- Sample action chaining stack -->
            <interceptor-stack name="chainStack">
                <interceptor-ref name="chain"/>
                <interceptor-ref name="basicStack"/>
            </interceptor-stack>

            <!-- Sample i18n stack -->
            <interceptor-stack name="chainStack">
                <interceptor-ref name="i18n"/>
                <interceptor-ref name="basicStack"/>
            </interceptor-stack>

            <!-- Sample execute and wait stack.
                 Note: execAndWait should always be the *last* interceptor. -->
            <interceptor-stack name="executeAndWaitStack">
                <interceptor-ref name="basicStack"/>
                <interceptor-ref name="execAndWait"/>
            </interceptor-stack>

            <!-- A complete stack with all the common interceptors in place.
                 Generally, this stack should be the one you use, though it
                 may process additional stuff you don't need, which could
                 lead to some performance problems. Also, the ordering can be
                 switched around (ex: if you wish to have your components
                 before prepare() is called, you'd need to move the component
                 interceptor up -->
            <interceptor-stack name="defaultStack">
                <interceptor-ref name="exception"/>
                <interceptor-ref name="alias"/>
                <interceptor-ref name="prepare"/>
                <interceptor-ref name="servlet-config"/>
                <interceptor-ref name="i18n"/>
                <interceptor-ref name="chain"/>
                <interceptor-ref name="model-driven"/>
                <interceptor-ref name="fileUpload"/>
                <interceptor-ref name="static-params"/>
                <interceptor-ref name="params"/>
                <interceptor-ref name="conversionError"/>
                <interceptor-ref name="validation"/>
                <interceptor-ref name="workflow"/>
            </interceptor-stack>

            <!-- The completeStack is here for backwards compatibility for
                 applications that still refer to the defaultStack by the
                 old name -->
            <interceptor-stack name="completeStack">
                <interceptor-ref name="defaultStack"/>
            </interceptor-stack>
        </interceptors>

        <default-interceptor-ref name="defaultStack"/>
    </package>
</xwork>
<!-- // END SNIPPET: webwork-default -->

Since we included webwork-default.xml in our xwork.xml, all the interceptors and stacks above are available for us to use in our actions. Here's what these interceptors do:

...

If none of the above interceptors suit your particular need, you will have to implement your own interceptor. Fortunately, this is an easy task to accomplish. Suppose we need an interceptor that places a greeting in the Session according to the time of the day (morning, afternoon or evening). Here's how we could implement it:

But let's see how it works from scracth:

Create an interceptor class, which is a class that implements the com.opensymphony.xwork.interceptor.Interceptor interface (bundled in xwork-1.1.jar);
Declare the class in your XML configuration file (xwork.xml) using the element <interceptor /> nested within <interceptors />;
Create stacks of interceptors, using the <interceptor-stack /> element (optional);
Determine which interceptors are used by which action, using <interceptor-ref /> or <default-interceptor-ref />. The former defines the interceptors to be used in a specific action, while the latter determines the default interceptor stack to be used by all actions that do not specify their own <interceptor-ref />.

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Code Block

	java
	java

package lesson05;

import java.util.Calendar;
import com.opensymphony.xwork.interceptor.Interceptor;
import com.opensymphony.xwork.ActionInvocation;

public class GreetingInterceptor implements Interceptor {
	public void init() { }
	public void destroy() { }
	public String intercept(ActionInvocation invocation) throws Exception {
		Calendar calendar = Calendar.getInstance();
		int hour = calendar.get(Calendar.HOUR_OF_DAY);
		String greeting = (hour < 6) ? "Good evening" : 
			((hour < 12) ? "Good morning": 
			((hour < 18) ? "Good afternoon": "Good evening"));

		invocation.getInvocationContext().getSession().put("greeting", greeting);

		String result = invocation.invoke();

		return result;
	}
}

xwork.xml:

Code Block

	xml
	xml

<!DOCTYPE xwork PUBLIC "-//OpenSymphony Group//XWork 1.0//EN" 
"http://www.opensymphony.com/xwork/xwork-1.0.dtd">

<xwork>
	<!-- Include webwork defaults (from WebWork JAR). -->
	<include file="webwork-default.xml" />
	
	<!-- Configuration for the default package. -->
	<package name="default" extends="webwork-default">
		<interceptors> 
			<interceptor name="greeting" class="section02.lesson05.GreetingInterceptor" /> 
		</interceptors> 
		
		<!-- Action: Lesson 5: GreetingInterceptor. --> 
		<action name="greetingAction" class="lesson05.GreetingAction"> 
			<result name="success" type="velocity">ex01-result.vm</result> 
			<interceptor-ref name="greeting" /> 
		</action> 
	</package>
</xwork>

GreetingAction.java:

Code Block

	java
	java

package lesson05;

import com.opensymphony.xwork.ActionSupport;

public class GreetingAction extends ActionSupport {
	public String execute() throws Exception {
		return SUCCESS;
	}
}

ex01-result.vm:

Code Block

	html
	html

<html>
<head>
<title>WebWork Tutorial - Lesson 5 - Example 1</title>
</head>
<body>

#set ($ses = $req.getSession())
<p><b>${ses.getAttribute('greeting')}!</b></p>

</body>
</html>

Let's take a look at our interceptor class first. As explained before, the interceptor must implement com.opensymphony.xwork.interceptor.Interceptor's methods: init(), called during interceptor initialization, destroy(), called during destruction, and most importantly, intercept(ActionInvocation invocation), which is where we place the code that does the work.

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Child pages

Versions Compared

Old Version 13

New Version 14

Key

Interceptors

Interceptor configuration:

Grouping interceptors as stacks

xwork.xml:

GreetingAction.java:

ex01-result.vm:

Child pages

Page History

Versions Compared

Old Version 13

New Version 14

Key

Interceptors

Interceptor configuration:

Grouping interceptors as stacks

xwork.xml:

GreetingAction.java:

ex01-result.vm: