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Struts example source code file (PrepareInterceptor.java)

This example Struts source code file (PrepareInterceptor.java) is included in the DevDaily.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" TM.

Java - Struts tags/keywords

alt_prepare_prefix, alt_prepare_prefix, error, exception, exception, methodfilterinterceptor, object, override, preparable, prepare_prefix, prepare_prefix, prepareinterceptor, reflection, string, string

The Struts PrepareInterceptor.java source code

/*
 * $Id: PrepareInterceptor.java 1060603 2011-01-18 22:42:54Z mcucchiara $
 * Copyright 2002-2007,2009 The Apache Software Foundation.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 * 
 *      http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.opensymphony.xwork2.interceptor;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.Preparable;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;

import java.lang.reflect.InvocationTargetException;


/**
 * <!-- START SNIPPET: description -->
 *
 * This interceptor calls <code>prepare() on actions which implement
 * {@link Preparable}. This interceptor is very useful for any situation where
 * you need to ensure some logic runs before the actual execute method runs.
 *
 * <p/> 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: <i>id and
 * <i>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 <i>user.name will be set, as desired, on the actual object
 * loaded from the database. See the example for more info.
 *
 * <p/>
 * <b>Note: Since XWork 2.0.2, this interceptor extends {@link MethodFilterInterceptor}, therefore being
 * able to deal with excludeMethods / includeMethods parameters. See [Workflow Interceptor]
 * (class {@link DefaultWorkflowInterceptor}) for documentation and examples on how to use this feature.
 *
 * <p/>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 {@link com.opensymphony.xwork2.ActionProxy}. For example, you can specify a
 * prepareInput() method that will be run before the invocation of the input method.
 *
 * <!-- END SNIPPET: description -->
 *
 * <p/> Interceptor parameters:
 *
 * <!-- START SNIPPET: parameters -->
 *
 * <ul>
 *
 * <li>alwaysInvokePrepare - Default to true. If true, prepare will always be invoked,
 * otherwise it will not.</li>
 *
 * </ul>
 *
 * <!-- END SNIPPET: parameters -->
 *
 * <p/> Extending the interceptor:
 *
 * <p/>
 *
 * <!-- START SNIPPET: extending -->
 *
 * There are no known extension points to this interceptor.
 *
 * <!-- END SNIPPET: extending -->
 *
 * <p/> Example code:
 *
 * <pre>
 * <!-- START SNIPPET: example -->
 * <!-- 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>
 * <!-- END SNIPPET: example -->
 * </pre>
 *
 * @author Jason Carreira
 * @author Philip Luppens
 * @author tm_jee
 * @see com.opensymphony.xwork2.Preparable
 */
public class PrepareInterceptor extends MethodFilterInterceptor {

    private static final long serialVersionUID = -5216969014510719786L;

    private final static String PREPARE_PREFIX = "prepare";
    private final static String ALT_PREPARE_PREFIX = "prepareDo";

    private boolean alwaysInvokePrepare = true;
    private boolean firstCallPrepareDo = false;

    /**
     * Sets if the <code>preapare method should always be executed.
     * <p/>
     * Default is <tt>true.
     *
     * @param alwaysInvokePrepare if <code>prepare should always be executed or not.
     */
    public void setAlwaysInvokePrepare(String alwaysInvokePrepare) {
        this.alwaysInvokePrepare = Boolean.parseBoolean(alwaysInvokePrepare);
    }

    /**
     * Sets if the <code>prepareDoXXX method should be called first
     * <p/>
     * Default is <tt>false for backward compatibility
     *
     * @param firstCallPrepareDo if <code>prepareDoXXX should be called first
     */
    public void setFirstCallPrepareDo(String firstCallPrepareDo) {
        this.firstCallPrepareDo = Boolean.parseBoolean(firstCallPrepareDo);
    }

    @Override
    public String doIntercept(ActionInvocation invocation) throws Exception {
        Object action = invocation.getAction();

        if (action instanceof Preparable) {
            try {
                String[] prefixes;
                if (firstCallPrepareDo) {
                    prefixes = new String[] {ALT_PREPARE_PREFIX, PREPARE_PREFIX};
                } else {
                    prefixes = new String[] {PREPARE_PREFIX, ALT_PREPARE_PREFIX};
                }
                PrefixMethodInvocationUtil.invokePrefixMethod(invocation, prefixes);
            }
            catch (InvocationTargetException e) {
                /*
                 * The invoked method threw an exception and reflection wrapped it
                 * in an InvocationTargetException.
                 * If possible re-throw the original exception so that normal
                 * exception handling will take place.
                 */
                Throwable cause = e.getCause();
                if (cause instanceof Exception) {
                    throw (Exception) cause;
                } else if(cause instanceof Error) {
                    throw (Error) cause;
                } else {
                    /*
                     * The cause is not an Exception or Error (must be Throwable) so
                     * just re-throw the wrapped exception.
                     */
                    throw e;
                }
            }

            if (alwaysInvokePrepare) {
                ((Preparable) action).prepare();
            }
        }

        return invocation.invoke();
    }

}

Other Struts examples (source code examples)

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