core/src/main/java/com/opensymphony/xwork2/interceptor/annotations/AnnotationWorkflowInterceptor.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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.annotations;

import com.opensymphony.xwork2.ActionInvocation;
import com.opensymphony.xwork2.interceptor.AbstractInterceptor;
import com.opensymphony.xwork2.interceptor.PreResultListener;
import org.apache.commons.lang3.reflect.MethodUtils;
import org.apache.struts2.StrutsException;

import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

/**
 * <!-- START SNIPPET: javadoc -->
 * <p>Invokes any annotated methods on the action. Specifically, it supports the following
 * annotations:</p>
 * <ul>
 * <li> &#64;{@link Before} - will be invoked before the action method. If the returned value is not null, it is
 * returned as the action result code</li>
 * <li> &#64;{@link BeforeResult} - will be invoked after the action method but before the result execution</li>
 * <li> &#64;{@link After} - will be invoked after the action method and result execution</li>
 * </ul>
 *
 * <p>There can be multiple methods marked with the same annotations, but the order of their execution
 * is not guaranteed. However, the annotated methods on the superclass chain are guaranteed to be invoked before the
 * annotated method in the current class in the case of a {@link Before} annotations and after, if the annotations is
 * {@link After}.</p>
 * <!-- END SNIPPET: javadoc -->
 *
 * <pre>
 * <!-- START SNIPPET: javacode -->
 *  public class BaseAnnotatedAction {
 *  	protected String log = "";
 *
 *  	&#64;Before
 *  	public String baseBefore() {
 *  		log = log + "baseBefore-";
 *  		return null;
 *  	}
 *  }
 *
 *  public class AnnotatedAction extends BaseAnnotatedAction {
 *  	&#64;Before
 *  	public String before() {
 *  		log = log + "before";
 *  		return null;
 *  	}
 *
 *  	public String execute() {
 *  		log = log + "-execute";
 *  		return Action.SUCCESS;
 *  	}
 *
 *  	&#64;BeforeResult
 *  	public void beforeResult() throws Exception {
 *  		log = log +"-beforeResult";
 *  	}
 *
 *  	&#64;After
 *  	public void after() {
 *  		log = log + "-after";
 *  	}
 *  }
 * <!-- END SNIPPET: javacode -->
 *  </pre>
 *
 * <!-- START SNIPPET: example -->
 * <p>With the interceptor applied and the action executed on <code>AnnotatedAction</code> the log
 * instance variable will contain <code>baseBefore-before-execute-beforeResult-after</code>.</p>
 * <!-- END SNIPPET: example -->
 *
 * <p>Configure a stack in xwork.xml that replaces the PrepareInterceptor with the AnnotationWorkflowInterceptor:</p>
 * <pre>
 * <!-- START SNIPPET: stack -->
 * &lt;interceptor-stack name="annotatedStack"&gt;
 * 	&lt;interceptor-ref name="staticParams"/&gt;
 * 	&lt;interceptor-ref name="params"/&gt;
 * 	&lt;interceptor-ref name="conversionError"/&gt;
 * 	&lt;interceptor-ref name="annotationWorkflow"/&gt;
 * &lt;/interceptor-stack&gt;
 *  <!-- END SNIPPET: stack -->
 * </pre>
 *
 * @author Zsolt Szasz, zsolt at lorecraft dot com
 * @author Rainer Hermanns
 * @author Dan Oxlade, dan d0t oxlade at gmail d0t c0m
 */
public class AnnotationWorkflowInterceptor extends AbstractInterceptor implements PreResultListener {

    /**
     * Discovers annotated methods on the action and calls them according to the workflow
     *
     * @see com.opensymphony.xwork2.interceptor.Interceptor#intercept(com.opensymphony.xwork2.ActionInvocation)
     */
    public String intercept(ActionInvocation invocation) throws Exception {
        final Object action = invocation.getAction();
        invocation.addPreResultListener(this);
        List<Method> methods = new ArrayList<>(MethodUtils.getMethodsListWithAnnotation(action.getClass(), Before.class,
                true, true));
        if (methods.size() > 0) {
            // methods are only sorted by priority
            Collections.sort(methods, new Comparator<Method>() {
                public int compare(Method method1, Method method2) {
                    return comparePriorities(MethodUtils.getAnnotation(method1, Before.class, true,
                            true).priority(), MethodUtils.getAnnotation(method2, Before.class, true,
                            true).priority());
                }
            });
            for (Method m : methods) {
                final String resultCode = (String) MethodUtils.invokeMethod(action, true, m.getName());
                if (resultCode != null) {
                    // shortcircuit execution
                    return resultCode;
                }
            }
        }

        String invocationResult = invocation.invoke();

        // invoke any @After methods
        methods = new ArrayList<Method>(MethodUtils.getMethodsListWithAnnotation(action.getClass(), After.class,
                true, true));

        if (methods.size() > 0) {
            // methods are only sorted by priority
            Collections.sort(methods, new Comparator<Method>() {
                public int compare(Method method1, Method method2) {
                    return comparePriorities(MethodUtils.getAnnotation(method1, After.class, true,
                            true).priority(), MethodUtils.getAnnotation(method2, After.class, true,
                            true).priority());
                }
            });
            for (Method m : methods) {
                MethodUtils.invokeMethod(action, true, m.getName());
            }
        }

        return invocationResult;
    }

    protected static int comparePriorities(int val1, int val2) {
        if (val2 < val1) {
            return -1;
        } else if (val2 > val1) {
            return 1;
        } else {
            return 0;
        }
    }

    /**
     * Invokes any &#64;BeforeResult annotated methods
     *
     * @see com.opensymphony.xwork2.interceptor.PreResultListener#beforeResult(com.opensymphony.xwork2.ActionInvocation,String)
     */
    public void beforeResult(ActionInvocation invocation, String resultCode) {
        Object action = invocation.getAction();
        List<Method> methods = new ArrayList<Method>(MethodUtils.getMethodsListWithAnnotation(action.getClass(),
                BeforeResult.class, true, true));

        if (methods.size() > 0) {
            // methods are only sorted by priority
            Collections.sort(methods, new Comparator<Method>() {
                public int compare(Method method1, Method method2) {
                    return comparePriorities(MethodUtils.getAnnotation(method1, BeforeResult.class, true,
                            true).priority(), MethodUtils.getAnnotation(method2, BeforeResult.class,
                            true, true).priority());
                }
            });
            for (Method m : methods) {
                try {
                    MethodUtils.invokeMethod(action, true, m.getName());
                } catch (Exception e) {
                    throw new StrutsException(e);
                }
            }
        }
    }

}