java.lang.Object
   com.opensymphony.xwork2.interceptor.AbstractInterceptor
      com.opensymphony.xwork2.interceptor.MethodFilterInterceptor
         com.opensymphony.xwork2.interceptor.PrepareInterceptor

All Implemented Interfaces:
    Interceptor

A typical use of this is to run some logic to load an object from the database so that when parameters are set they can be set on this object. For example, suppose you have a User object with two properties: id and name. Provided that the params interceptor is called twice (once before and once after this interceptor), you can load the User object using the id property, and then when the second params interceptor is called the parameter user.name will be set, as desired, on the actual object loaded from the database. See the example for more info.

Note: Since XWork 2.0.2, this interceptor extends MethodFilterInterceptor , therefore being able to deal with excludeMethods / includeMethods parameters. See [Workflow Interceptor] (class DefaultWorkflowInterceptor ) for documentation and examples on how to use this feature.

Update: Added logic to execute a prepare{MethodName} and conditionally the a general prepare() Method, depending on the 'alwaysInvokePrepare' parameter/property which is by default true. This allows us to run some logic based on the method name we specify in the com.opensymphony.xwork2.ActionProxy . For example, you can specify a prepareInput() method that will be run before the invocation of the input method.

Interceptor parameters:

• alwaysInvokePrepare - Default to true. If true, prepare will always be invoked, otherwise it will not.

Extending the interceptor:

There are no known extension points to this interceptor.

Example code:

<!-- Calls the params interceptor twice, allowing you to
      pre-load data for the second time parameters are set -->
 <action name="someAction" class="com.examples.SomeAction">
     <interceptor-ref name="params"/>
     <interceptor-ref name="prepare"/>
     <interceptor-ref name="basicStack"/>
     <result name="success">good_result.ftl</result>
 </action>

Also see:

com.opensymphony.xwork2.Preparable
author: Jason - Carreira

author: Philip - Luppens

author: tm_jee -

 public String doIntercept(ActionInvocation invocation) throws Exception 
{
        Object action = invocation.getAction();
        if (action instanceof Preparable) {
            try {
                PrefixMethodInvocationUtil.invokePrefixMethod(invocation,
                        new String[]{PREPARE_PREFIX, ALT_PREPARE_PREFIX});
            }
            catch (InvocationTargetException e) {
                // just in case there's an exception while doing reflection,
                // we still want prepare() to be able to get called.
                LOG.warn("an exception occured while trying to execute prefixed method", e);
            }
            catch (IllegalAccessException e) {
                // just in case there's an exception while doing reflection,
                // we still want prepare() to be able to get called.
                LOG.warn("an exception occured while trying to execute prefixed method", e);
            } catch (Exception e) {
                // just in case there's an exception while doing reflection,
                // we still want prepare() to be able to get called.
                LOG.warn("an exception occured while trying to execute prefixed method", e);
            }
            if (alwaysInvokePrepare) {
                ((Preparable) action).prepare();
            }
        }
        return invocation.invoke();
}

 public  void setAlwaysInvokePrepare(String alwaysInvokePrepare) 
{
        this.alwaysInvokePrepare = Boolean.parseBoolean(alwaysInvokePrepare);
}