Struts(十六)：通过CURD来学习Struts流程及ModelDriven的用法

• 背景：

从一个Member的增删改查，来了解Struts2的运行原理及学习ModelDriven拦截器、Preparable拦截器。

• 新建项目实现列表的展示及删除功能：

web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_9" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">

    <display-name>Struts 02</display-name>

    <filter>
        <filter-name>struts2</filter-name>
        <filter-class>org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter</filter-class>
    </filter>

    <filter-mapping>
        <filter-name>struts2</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>

    <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
    </welcome-file-list>

    <!-- Restricts access to pure JSP files - access available only via Struts 
        action <security-constraint> <display-name>No direct JSP access</display-name> 
        <web-resource-collection> <web-resource-name>No-JSP</web-resource-name> <url-pattern>*.jsp</url-pattern> 
        </web-resource-collection> <auth-constraint> <role-name>no-users</role-name> 
        </auth-constraint> </security-constraint> <security-role> <description>Don't 
        assign users to this role</description> <role-name>no-users</role-name> </security-role> -->
</web-app>

struts.xml

<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
    "-//Apache Software Foundation//DTD Struts Configuration 2.3//EN"
    "http://struts.apache.org/dtds/struts-2.3.dtd">

<struts>   
    <constant name="struts.ognl.allowStaticMethodAccess" value="true" />
    <constant name="struts.devMode" value="false" />

    <package name="default" namespace="/" extends="struts-default"> 
        <action name="member-*" class="com.dx.struts.actions.MemberAction" method="{1}">
            <result name="{1}">/member-{1}.jsp</result>       
            <result name="delete" type="redirectAction">member-list</result>
        </action>
    </package>
</struts>

Member.java

/**
 * @author Administrator
 *
 */
package com.dx.struts.entity;

public class Member{
    private Long id;
    private String name;
    private Integer age;
    private String gender;    

    public Member() {        
    }
    
    public Member(Long id, String name, Integer age, String gender) {
        super();
        this.id = id;
        this.name = name;
        this.age = age;
        this.gender = gender;
    }
    
    public Long getId() {
        return id;
    }
    public void setId(Long id) {
        this.id = id;
    }
    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public Integer getAge() {
        return age;
    }
    public void setAge(Integer age) {
        this.age = age;
    }
    public String getGender() {
        return gender;
    }
    public void setGender(String gender) {
        this.gender = gender;
    }
    
}

 MemberAction.java（暂时实现删除、列表功能）

package com.dx.struts.actions;

import java.util.Date;
import java.util.List;
import java.util.Map;

import org.apache.struts2.interceptor.RequestAware;

import com.dx.struts.dao.MemberDao;
import com.dx.struts.entity.Member;

public class MemberAction implements RequestAware {
    private MemberDao memberDao = new MemberDao();
    
    private Long id;

    public void setId(Long id) {
        this.id = id;
    }

    public String list() {
        List<Member> members = memberDao.getMembers();
        request.put("members", members);
        return "list";
    }

    public String delete() {
        memberDao.remove(this.id);
        // 返回结果的类型应该为：redirectAction
        // 也可以是chain：实际上chain是没有必要的，因为不需要在下一个action中保留啊当前action的状态
        // 若使用chain,则到达目标页面后，地址栏显示的依然是删除的那个链接，则刷新时会重复提交。
        return "delete";
    }


    private Map<String, Object> request;

    @Override
    public void setRequest(Map<String, Object> request) {
        this.request = request;
    }
    
}

注意：这里边根据id删除Member接收id参数是通过：在MemberAction类中添加了id属性，之后实现了id的set方法才实现了参数接收。

MemberDao.java

package com.dx.struts.dao;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;

import com.dx.struts.entity.Member;

public class MemberDao {
    private static HashMap<Long, Member> members = new HashMap<Long, Member>();

    static {
        members.put(1001L, new Member(1001L, "member1", 20, "male"));
        members.put(1002L, new Member(1002L, "member2", 20, "female"));
        members.put(1003L, new Member(1003L, "member3", 20, "male"));
        members.put(1004L, new Member(1004L, "member4", 20, "male"));
    }

    public List<Member> getMembers() {
        return new ArrayList<Member>(members.values());
    }

    public Member get(Long id) {
        return members.get(id);
    }

    public void add(Member member) {
        members.put(member.getId(), member);
    }
    
    public void remove(Long id){
        members.remove(id);
    }
}

member-list.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <s:a href="/Struts_02/member-add.jsp" >add</s:a><br>
    <table style="margin:0 auto;60%;" cellpadding="10" cellspacing="0" border="1">
        <tr style="">
            <td style="10%;">id</td>
            <td style="40%;">name</td>
            <td style="20%;">age</td>
            <td style="20%;">gender</td>
            <td style="10%;">view</td>
            <td style="10%;">edit</td>            
            <td style="10%;">delete</td>
        </tr>
        <s:iterator value="#request.members">
        <tr>
            <td>${id}</td>
            <td>${name}</td>
            <td>${age}</td>
            <td>${gender}</td>
            <td><s:a href="member-view.action?id=%{id}" >view</s:a></td>
            <td><s:a href="member-edit.action?id=%{id}" >edit</s:a></td>            
            <td><s:a href="member-delete.action?id=%{id}" >delete</s:a></td>
        </tr>
        </s:iterator>
    </table>
</body>
</html>

index.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<a href="member-list.action">index</a>
</body>
</html>

• 通过断点调试了解Action的运行原理：

把断点设置到delete方法内，断点调试代码的调用栈跟踪如下：

Daemon Thread [http-bio-8080-exec-7] (Suspended (breakpoint at line 52 in MemberAction))    
owns: Method  (id=91)    
owns: SocketWrapper<E>  (id=86)    
NativeMethodAccessorImpl.invoke0(Method, Object, Object[]) line: not available [native method]    
NativeMethodAccessorImpl.invoke(Object, Object[]) line: 62    
DelegatingMethodAccessorImpl.invoke(Object, Object[]) line: 43    
Method.invoke(Object, Object...) line: 498    
OgnlRuntime.invokeMethod(Object, Method, Object[]) line: 871    
OgnlRuntime.callAppropriateMethod(OgnlContext, Object, Object, String, String, List, Object[]) line: 1294    
XWorkMethodAccessor(ObjectMethodAccessor).callMethod(Map, Object, String, Object[]) line: 68    
XWorkMethodAccessor.callMethodWithDebugInfo(Map, Object, String, Object[]) line: 117    
XWorkMethodAccessor.callMethod(Map, Object, String, Object[]) line: 108    
OgnlRuntime.callMethod(OgnlContext, Object, String, Object[]) line: 1370    
ASTMethod.getValueBody(OgnlContext, Object) line: 91    
ASTMethod(SimpleNode).evaluateGetValueBody(OgnlContext, Object) line: 212    
ASTMethod(SimpleNode).getValue(OgnlContext, Object) line: 258    
Ognl.getValue(Object, Map, Object, Class) line: 467    
Ognl.getValue(Object, Map, Object) line: 431    
OgnlUtil$3.execute(Object) line: 352    
OgnlUtil.compileAndExecuteMethod(String, Map<String,Object>, OgnlTask<T>) line: 404    
OgnlUtil.callMethod(String, Map<String,Object>, Object) line: 350    
DefaultActionInvocation.invokeAction(Object, ActionConfig) line: 430    
DefaultActionInvocation.invokeActionOnly() line: 290    
DefaultActionInvocation.invoke() line: 251    
DeprecationInterceptor.intercept(ActionInvocation) line: 41    
DefaultActionInvocation.invoke() line: 245    
DebuggingInterceptor.intercept(ActionInvocation) line: 256    
DefaultActionInvocation.invoke() line: 245    
DefaultWorkflowInterceptor.doIntercept(ActionInvocation) line: 168    
DefaultWorkflowInterceptor(MethodFilterInterceptor).intercept(ActionInvocation) line: 98    
DefaultActionInvocation.invoke() line: 245    
AnnotationValidationInterceptor(ValidationInterceptor).doIntercept(ActionInvocation) line: 265    
AnnotationValidationInterceptor.doIntercept(ActionInvocation) line: 76    
AnnotationValidationInterceptor(MethodFilterInterceptor).intercept(ActionInvocation) line: 98    
DefaultActionInvocation.invoke() line: 245    
StrutsConversionErrorInterceptor(ConversionErrorInterceptor).intercept(ActionInvocation) line: 138    
DefaultActionInvocation.invoke() line: 245    
ParametersInterceptor.doIntercept(ActionInvocation) line: 229    
ParametersInterceptor(MethodFilterInterceptor).intercept(ActionInvocation) line: 98    
DefaultActionInvocation.invoke() line: 245    
ActionMappingParametersInteceptor(ParametersInterceptor).doIntercept(ActionInvocation) line: 229    
ActionMappingParametersInteceptor(MethodFilterInterceptor).intercept(ActionInvocation) line: 98    
DefaultActionInvocation.invoke() line: 245    
StaticParametersInterceptor.intercept(ActionInvocation) line: 191    
DefaultActionInvocation.invoke() line: 245    
MultiselectInterceptor.intercept(ActionInvocation) line: 73    
DefaultActionInvocation.invoke() line: 245    
DateTextFieldInterceptor.intercept(ActionInvocation) line: 125    
DefaultActionInvocation.invoke() line: 245    
CheckboxInterceptor.intercept(ActionInvocation) line: 91    
DefaultActionInvocation.invoke() line: 245    
FileUploadInterceptor.intercept(ActionInvocation) line: 253    
DefaultActionInvocation.invoke() line: 245    
ModelDrivenInterceptor.intercept(ActionInvocation) line: 100    
DefaultActionInvocation.invoke() line: 245    
ScopedModelDrivenInterceptor.intercept(ActionInvocation) line: 141    
DefaultActionInvocation.invoke() line: 245    
ChainingInterceptor.intercept(ActionInvocation) line: 145    
DefaultActionInvocation.invoke() line: 245    
PrepareInterceptor.doIntercept(ActionInvocation) line: 171    
PrepareInterceptor(MethodFilterInterceptor).intercept(ActionInvocation) line: 98    
DefaultActionInvocation.invoke() line: 245    
I18nInterceptor.intercept(ActionInvocation) line: 140    
DefaultActionInvocation.invoke() line: 245    
ServletConfigInterceptor.intercept(ActionInvocation) line: 164    
DefaultActionInvocation.invoke() line: 245    
AliasInterceptor.intercept(ActionInvocation) line: 193    
DefaultActionInvocation.invoke() line: 245    
ExceptionMappingInterceptor.intercept(ActionInvocation) line: 189    
DefaultActionInvocation.invoke() line: 245    
StrutsActionProxy.execute() line: 54    
Dispatcher.serviceAction(HttpServletRequest, HttpServletResponse, ActionMapping) line: 575    
ExecuteOperations.executeAction(HttpServletRequest, HttpServletResponse, ActionMapping) line: 81    
StrutsPrepareAndExecuteFilter.doFilter(ServletRequest, ServletResponse, FilterChain) line: 99    
ApplicationFilterChain.internalDoFilter(ServletRequest, ServletResponse) line: 241    
ApplicationFilterChain.doFilter(ServletRequest, ServletResponse) line: 208    
StandardWrapperValve.invoke(Request, Response) line: 218    
StandardContextValve.invoke(Request, Response) line: 110    
NonLoginAuthenticator(AuthenticatorBase).invoke(Request, Response) line: 506    
StandardHostValve.invoke(Request, Response) line: 169    
ErrorReportValve.invoke(Request, Response) line: 103    
AccessLogValve.invoke(Request, Response) line: 962    
StandardEngineValve.invoke(Request, Response) line: 116    
CoyoteAdapter.service(Request, Response) line: 452    
Http11Processor(AbstractHttp11Processor<S>).process(SocketWrapper<S>) line: 1087    
Http11Protocol$Http11ConnectionHandler(AbstractProtocol$AbstractConnectionHandler<S,P>).process(SocketWrapper<S>, SocketStatus) line: 637    
JIoEndpoint$SocketProcessor.run() line: 318    
ThreadPoolExecutor(ThreadPoolExecutor).runWorker(ThreadPoolExecutor$Worker) line: 1142    
ThreadPoolExecutor$Worker.run() line: 617    

在这里介绍下上边UML是使用的http://plantuml.com/在线UML来实现的：

http://plantuml.com/

@startuml
"浏览器" -> StrutsPrepareAndExecuteFilter : dofilter()
StrutsPrepareAndExecuteFilter -> StrutsActionProxy :execute()
StrutsActionProxy -> DefaultActionInvocation :invoke()
DefaultActionInvocation -> ExceptionMappingInterceptor : interceptor()
ExceptionMappingInterceptor -> DefaultActionInvocation : invoke()
DefaultActionInvocation -> XxxxInterceptor : interceptor()
XxxxInterceptor -> DefaultActionInvocation : invoke()
DefaultActionInvocation -> DebuggingInterceptor : interceptor()
DebuggingInterceptor -> DefaultActionInvocation : invoke()
DefaultActionInvocation -> DefaultActionInvocation : invokeAction()
DefaultActionInvocation -> MemberAction : delete()
@enduml

StrutsActionProxy
ActionProxy是Action的一个代理类，也就是说Action的调用是通过ActionProxy实现的，
其实就是调用了ActionProxy.execute()方法，而该方法又调用了ActionInvocation.invoke()方法，而该方法又调用了ActionInvocation

DefaultActionInvocation
ActionInvocation就是一个Action的调用者。
ActionInvocation在Action的执行过程中，负责Interceptor/Action/Result等一系列元素的调度。

具体代码请参考DefaultActionInvocation:

/*
 * Copyright 2002-2006,2009 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;

import com.opensymphony.xwork2.config.ConfigurationException;
import com.opensymphony.xwork2.config.entities.ActionConfig;
import com.opensymphony.xwork2.config.entities.InterceptorMapping;
import com.opensymphony.xwork2.config.entities.ResultConfig;
import com.opensymphony.xwork2.inject.Container;
import com.opensymphony.xwork2.inject.Inject;
import com.opensymphony.xwork2.interceptor.PreResultListener;
import com.opensymphony.xwork2.ognl.OgnlUtil;
import com.opensymphony.xwork2.util.ValueStack;
import com.opensymphony.xwork2.util.ValueStackFactory;
import com.opensymphony.xwork2.util.logging.Logger;
import com.opensymphony.xwork2.util.logging.LoggerFactory;
import com.opensymphony.xwork2.util.profiling.UtilTimerStack;
import ognl.MethodFailedException;
import ognl.NoSuchPropertyException;
import ognl.OgnlException;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.Map;


/**
 * The Default ActionInvocation implementation
 *
 * @author Rainer Hermanns
 * @author tmjee
 * @version $Date$ $Id$
 * @see com.opensymphony.xwork2.DefaultActionProxy
 */
public class DefaultActionInvocation implements ActionInvocation {

    private static final Logger LOG = LoggerFactory.getLogger(DefaultActionInvocation.class);

    protected Object action;
    protected ActionProxy proxy;
    protected List<PreResultListener> preResultListeners;
    protected Map<String, Object> extraContext;
    protected ActionContext invocationContext;
    protected Iterator<InterceptorMapping> interceptors;
    protected ValueStack stack;
    protected Result result;
    protected Result explicitResult;
    protected String resultCode;
    protected boolean executed = false;
    protected boolean pushAction = true;
    protected ObjectFactory objectFactory;
    protected ActionEventListener actionEventListener;
    protected ValueStackFactory valueStackFactory;
    protected Container container;
    protected UnknownHandlerManager unknownHandlerManager;
    protected OgnlUtil ognlUtil;

    public DefaultActionInvocation(final Map<String, Object> extraContext, final boolean pushAction) {
        this.extraContext = extraContext;
        this.pushAction = pushAction;
    }

    @Inject
    public void setUnknownHandlerManager(UnknownHandlerManager unknownHandlerManager) {
        this.unknownHandlerManager = unknownHandlerManager;
    }

    @Inject
    public void setValueStackFactory(ValueStackFactory fac) {
        this.valueStackFactory = fac;
    }

    @Inject
    public void setObjectFactory(ObjectFactory fac) {
        this.objectFactory = fac;
    }

    @Inject
    public void setContainer(Container cont) {
        this.container = cont;
    }

    @Inject(required=false)
    public void setActionEventListener(ActionEventListener listener) {
        this.actionEventListener = listener;
    }

    @Inject
    public void setOgnlUtil(OgnlUtil ognlUtil) {
        this.ognlUtil = ognlUtil;
    }

    public Object getAction() {
        return action;
    }

    public boolean isExecuted() {
        return executed;
    }

    public ActionContext getInvocationContext() {
        return invocationContext;
    }

    public ActionProxy getProxy() {
        return proxy;
    }

    /**
     * If the DefaultActionInvocation has been executed before and the Result is an instance of ActionChainResult, this method
     * will walk down the chain of ActionChainResults until it finds a non-chain result, which will be returned. If the
     * DefaultActionInvocation's result has not been executed before, the Result instance will be created and populated with
     * the result params.
     *
     * @return a Result instance
     * @throws Exception
     */
    public Result getResult() throws Exception {
        Result returnResult = result;

        // If we've chained to other Actions, we need to find the last result
        while (returnResult instanceof ActionChainResult) {
            ActionProxy aProxy = ((ActionChainResult) returnResult).getProxy();

            if (aProxy != null) {
                Result proxyResult = aProxy.getInvocation().getResult();

                if ((proxyResult != null) && (aProxy.getExecuteResult())) {
                    returnResult = proxyResult;
                } else {
                    break;
                }
            } else {
                break;
            }
        }

        return returnResult;
    }

    public String getResultCode() {
        return resultCode;
    }

    public void setResultCode(String resultCode) {
        if (isExecuted())
            throw new IllegalStateException("Result has already been executed.");

        this.resultCode = resultCode;
    }


    public ValueStack getStack() {
        return stack;
    }

    /**
     * Register a com.opensymphony.xwork2.interceptor.PreResultListener to be notified after the Action is executed and before the
     * Result is executed. The ActionInvocation implementation must guarantee that listeners will be called in the order
     * in which they are registered. Listener registration and execution does not need to be thread-safe.
     *
     * @param listener to register
     */
    public void addPreResultListener(PreResultListener listener) {
        if (preResultListeners == null) {
            preResultListeners = new ArrayList<PreResultListener>(1);
        }

        preResultListeners.add(listener);
    }

    public Result createResult() throws Exception {
        LOG.trace("Creating result related to resultCode [#0]", resultCode);

        if (explicitResult != null) {
            Result ret = explicitResult;
            explicitResult = null;

            return ret;
        }
        ActionConfig config = proxy.getConfig();
        Map<String, ResultConfig> results = config.getResults();

        ResultConfig resultConfig = null;

        try {
            resultConfig = results.get(resultCode);
        } catch (NullPointerException e) {
            if (LOG.isDebugEnabled()) {
                LOG.debug("Got NPE trying to read result configuration for resultCode [#0]", resultCode);
            }
        }
        
        if (resultConfig == null) {
            // If no result is found for the given resultCode, try to get a wildcard '*' match.
            resultConfig = results.get("*");
        }

        if (resultConfig != null) {
            try {
                return objectFactory.buildResult(resultConfig, invocationContext.getContextMap());
            } catch (Exception e) {
                if (LOG.isErrorEnabled()) {
                    LOG.error("There was an exception while instantiating the result of type #0", e, resultConfig.getClassName());
                }
                throw new XWorkException(e, resultConfig);
            }
        } else if (resultCode != null && !Action.NONE.equals(resultCode) && unknownHandlerManager.hasUnknownHandlers()) {
            return unknownHandlerManager.handleUnknownResult(invocationContext, proxy.getActionName(), proxy.getConfig(), resultCode);
        }
        return null;
    }

    /**
     * @throws ConfigurationException If no result can be found with the returned code
     */
    public String invoke() throws Exception {
        String profileKey = "invoke: ";
        try {
            UtilTimerStack.push(profileKey);

            if (executed) {
                throw new IllegalStateException("Action has already executed");
            }

            if (interceptors.hasNext()) {
                final InterceptorMapping interceptor = interceptors.next();
                String interceptorMsg = "interceptor: " + interceptor.getName();
                UtilTimerStack.push(interceptorMsg);
                try {
                                resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);
                            }
                finally {
                    UtilTimerStack.pop(interceptorMsg);
                }
            } else {
                resultCode = invokeActionOnly();
            }

            // this is needed because the result will be executed, then control will return to the Interceptor, which will
            // return above and flow through again
            if (!executed) {
                if (preResultListeners != null) {
                    LOG.trace("Executing PreResultListeners for result [#0]", result);

                    for (Object preResultListener : preResultListeners) {
                        PreResultListener listener = (PreResultListener) preResultListener;

                        String _profileKey = "preResultListener: ";
                        try {
                            UtilTimerStack.push(_profileKey);
                            listener.beforeResult(this, resultCode);
                        }
                        finally {
                            UtilTimerStack.pop(_profileKey);
                        }
                    }
                }

                // now execute the result, if we're supposed to
                if (proxy.getExecuteResult()) {
                    executeResult();
                }

                executed = true;
            }

            return resultCode;
        }
        finally {
            UtilTimerStack.pop(profileKey);
        }
    }

    public String invokeActionOnly() throws Exception {
        return invokeAction(getAction(), proxy.getConfig());
    }

    protected void createAction(Map<String, Object> contextMap) {
        // load action
        String timerKey = "actionCreate: " + proxy.getActionName();
        try {
            UtilTimerStack.push(timerKey);
            action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
        } catch (InstantiationException e) {
            throw new XWorkException("Unable to intantiate Action!", e, proxy.getConfig());
        } catch (IllegalAccessException e) {
            throw new XWorkException("Illegal access to constructor, is it public?", e, proxy.getConfig());
        } catch (Exception e) {
            String gripe;

            if (proxy == null) {
                gripe = "Whoa!  No ActionProxy instance found in current ActionInvocation.  This is bad ... very bad";
            } else if (proxy.getConfig() == null) {
                gripe = "Sheesh.  Where'd that ActionProxy get to?  I can't find it in the current ActionInvocation!?";
            } else if (proxy.getConfig().getClassName() == null) {
                gripe = "No Action defined for '" + proxy.getActionName() + "' in namespace '" + proxy.getNamespace() + "'";
            } else {
                gripe = "Unable to instantiate Action, " + proxy.getConfig().getClassName() + ",  defined for '" + proxy.getActionName() + "' in namespace '" + proxy.getNamespace() + "'";
            }

            gripe += (((" -- " + e.getMessage()) != null) ? e.getMessage() : " [no message in exception]");
            throw new XWorkException(gripe, e, proxy.getConfig());
        } finally {
            UtilTimerStack.pop(timerKey);
        }

        if (actionEventListener != null) {
            action = actionEventListener.prepare(action, stack);
        }
    }

    protected Map<String, Object> createContextMap() {
        Map<String, Object> contextMap;

        if ((extraContext != null) && (extraContext.containsKey(ActionContext.VALUE_STACK))) {
            // In case the ValueStack was passed in
            stack = (ValueStack) extraContext.get(ActionContext.VALUE_STACK);

            if (stack == null) {
                throw new IllegalStateException("There was a null Stack set into the extra params.");
            }

            contextMap = stack.getContext();
        } else {
            // create the value stack
            // this also adds the ValueStack to its context
            stack = valueStackFactory.createValueStack();

            // create the action context
            contextMap = stack.getContext();
        }

        // put extraContext in
        if (extraContext != null) {
            contextMap.putAll(extraContext);
        }

        //put this DefaultActionInvocation into the context map
        contextMap.put(ActionContext.ACTION_INVOCATION, this);
        contextMap.put(ActionContext.CONTAINER, container);

        return contextMap;
    }

    /**
     * Uses getResult to get the final Result and executes it
     *
     * @throws ConfigurationException If not result can be found with the returned code
     */
    private void executeResult() throws Exception {
        result = createResult();

        String timerKey = "executeResult: " + getResultCode();
        try {
            UtilTimerStack.push(timerKey);
            if (result != null) {
                result.execute(this);
            } else if (resultCode != null && !Action.NONE.equals(resultCode)) {
                throw new ConfigurationException("No result defined for action " + getAction().getClass().getName()
                        + " and result " + getResultCode(), proxy.getConfig());
            } else {
                if (LOG.isDebugEnabled()) {
                    LOG.debug("No result returned for action " + getAction().getClass().getName() + " at " + proxy.getConfig().getLocation());
                }
            }
        } finally {
            UtilTimerStack.pop(timerKey);
        }
    }

    public void init(ActionProxy proxy) {
        this.proxy = proxy;
        Map<String, Object> contextMap = createContextMap();

        // Setting this so that other classes, like object factories, can use the ActionProxy and other
        // contextual information to operate
        ActionContext actionContext = ActionContext.getContext();

        if (actionContext != null) {
            actionContext.setActionInvocation(this);
        }

        createAction(contextMap);

        if (pushAction) {
            stack.push(action);
            contextMap.put("action", action);
        }

        invocationContext = new ActionContext(contextMap);
        invocationContext.setName(proxy.getActionName());

        createInterceptors(proxy);
    }

    protected void createInterceptors(ActionProxy proxy) {
        // get a new List so we don't get problems with the iterator if someone changes the list
        List<InterceptorMapping> interceptorList = new ArrayList<InterceptorMapping>(proxy.getConfig().getInterceptors());
        interceptors = interceptorList.iterator();
    }

    protected String invokeAction(Object action, ActionConfig actionConfig) throws Exception {
        String methodName = proxy.getMethod();

        if (LOG.isDebugEnabled()) {
            LOG.debug("Executing action method = #0", methodName);
        }

        String timerKey = "invokeAction: " + proxy.getActionName();
        try {
            UtilTimerStack.push(timerKey);

            Object methodResult;
            try {
                methodResult = ognlUtil.callMethod(methodName + "()", getStack().getContext(), action);
            } catch (MethodFailedException e) {
                // if reason is missing method, try find version with "do" prefix
                if (e.getReason() instanceof NoSuchMethodException) {
                    try {
                        String altMethodName = "do" + methodName.substring(0, 1).toUpperCase() + methodName.substring(1) + "()";
                        methodResult = ognlUtil.callMethod(altMethodName, getStack().getContext(), action);
                    } catch (MethodFailedException e1) {
                        // if still method doesn't exist, try checking UnknownHandlers
                        if (e1.getReason() instanceof NoSuchMethodException) {
                            if (unknownHandlerManager.hasUnknownHandlers()) {
                                try {
                                    methodResult = unknownHandlerManager.handleUnknownMethod(action, methodName);
                                } catch (NoSuchMethodException e2) {
                                    // throw the original one
                                    throw e;
                                }
                            } else {
                                // throw the original one
                                throw e;
                            }
                            // throw the original exception as UnknownHandlers weren't able to handle invocation as well
                            if (methodResult == null) {
                                throw e;
                            }
                        } else {
                            // exception isn't related to missing action method, throw it
                            throw e1;
                        }
                    }
                } else {
                    // exception isn't related to missing action method, throw it
                    throw e;
                }
            }
            return saveResult(actionConfig, methodResult);
        } catch (NoSuchPropertyException e) {
            throw new IllegalArgumentException("The " + methodName + "() is not defined in action " + getAction().getClass() + "");
        } catch (MethodFailedException e) {
            // We try to return the source exception.
            Throwable t = e.getCause();

            if (actionEventListener != null) {
                String result = actionEventListener.handleException(t, getStack());
                if (result != null) {
                    return result;
                }
            }
            if (t instanceof Exception) {
                throw (Exception) t;
            } else {
                throw e;
            }
        } finally {
            UtilTimerStack.pop(timerKey);
        }
    }

    /**
     * Save the result to be used later.
     * @param actionConfig current ActionConfig
     * @param methodResult the result of the action.
     * @return the result code to process.
     */
    protected String saveResult(ActionConfig actionConfig, Object methodResult) {
        if (methodResult instanceof Result) {
            this.explicitResult = (Result) methodResult;

            // Wire the result automatically
            container.inject(explicitResult);
            return null;
        } else {
            return (String) methodResult;
        }
    }

    /**
     * Version ready to be serialize
     *
     * @return instance without reference to {@link Container}
     */
    public ActionInvocation serialize() {
        DefaultActionInvocation that = this;
        that.container = null;
        return that;
    }

    /**
     * Restoring Container
     *
     * @param actionContext current {@link ActionContext}
     * @return instance which can be used to invoke action
     */
    public ActionInvocation deserialize(ActionContext actionContext) {
        DefaultActionInvocation that = this;
        that.container = actionContext.getContainer();
        return that;
    }

}

• 通过新增用户、修改用户、查看用户及删除用户功能来学习ModelDriven拦截器

 从上边实现删除代码中我们知道，我们可以通过在MemberAction类中添加一个id属性，并实现set方法，就可以实现在删除用户功能中接收传递到后台的id参数。不过，现在我们尝试学习一种新的方式：通过ModelDriven

修改struts.xml

        <action name="member-*" class="com.dx.struts.actions.MemberAction" method="{1}">
            <result name="{1}">/member-{1}.jsp</result>            
            <result name="delete" type="redirectAction">member-list</result>            
            <result name="modify" type="redirectAction">member-list</result>            
            <result name="create" type="redirectAction">member-list</result>
        </action>

 修改MemberAction.java

package com.dx.struts.actions;

import java.util.Date;
import java.util.List;
import java.util.Map;
import org.apache.struts2.interceptor.RequestAware;
import com.opensymphony.xwork2.ModelDriven;
import com.dx.struts.dao.MemberDao;
import com.dx.struts.entity.Member;

public class MemberAction implements RequestAware, ModelDriven<Member> {
    private MemberDao memberDao = new MemberDao();
    private Member member;

    public String list() {
        List<Member> members = memberDao.getMembers();
        request.put("members", members);
        return "list";
    }

    public String view() {
        Member member_ = memberDao.get(this.member.getId());
        this.member.setAge(member_.getAge());
        this.member.setName(member_.getName());
        this.member.setGender(member_.getGender());

        return "view";
    }

    public String delete() {
        memberDao.remove(this.member.getId());
        // 返回结果的类型应该为：redirectAction
        // 也可以是chain：实际上chain是没有必要的，因为不需要在下一个action中保留啊当前action的状态
        // 若使用chain,则到达目标页面后，地址栏显示的依然是删除的那个链接，则刷新时会重复提交。
        return "delete";
    }

    public String edit() {
        Member member_ = memberDao.get(this.member.getId());
        this.member.setAge(member_.getAge());
        this.member.setName(member_.getName());
        this.member.setGender(member_.getGender());

        return "edit";
    }

    public String modify() {
        Member member_ = memberDao.get(this.member.getId());
        member_.setAge(this.member.getAge());
        member_.setName(this.member.getName());
        member_.setGender(this.member.getGender());

        return "modify";
    }

    public String create() {
        member.setId(new Date().getTime());
        memberDao.add(member);

        return "create";
    }

    private Map<String, Object> request;

    @Override
    public void setRequest(Map<String, Object> request) {
        this.request = request;
    }

    @Override
    public Member getModel() {
        this.member = new Member();
        return this.member;
    }
}

注意：

这里是如果把member的所有属性都copy一份到MemberAction其实也是可以实现接收表单提交的参数的；

不过，实现了ModelDriven<Member>接口之后，不光是可以实现form表单提交的参数，也可以接收url提交的参数等。

member-view.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <s:debug></s:debug>
    <s:form>
        <s:textfield name="id" label="ID"></s:textfield>
        <s:textfield name="name" label="Name"></s:textfield>
        <s:textfield name="age" label="Age"></s:textfield>
        <s:radio list="#{'male':'male','female':'female' }" name="gender" label="Gender"></s:radio>
    </s:form>
</body>
</html>

member-add.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
<s:debug></s:debug>
    <s:form action="member-create.action">
        <s:textfield name="name" label="Name"></s:textfield>
        <s:textfield name="age" label="Age"></s:textfield>
        <s:radio list="#{'male':'male','female':'female' }" name="gender" label="Gender"></s:radio>
        <s:submit name="submit" label="提交"></s:submit>
    </s:form>
</body>
</html>

member-edit.jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ taglib prefix="s" uri="/struts-tags" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>Insert title here</title>
</head>
<body>
    <s:debug></s:debug>
    <s:form action="member-modify.action">
        <s:textfield name="id" label="ID"></s:textfield>
        <s:textfield name="name" label="Name"></s:textfield>
        <s:textfield name="age" label="Age"></s:textfield>
        <s:radio list="#{'male':'male','female':'female' }" name="gender" label="Gender"></s:radio>
        <s:submit name="submit" label="提交"></s:submit>
    </s:form>
</body>
</html>