最近工作任务不是很紧，时间也不能白白浪费，以前常用的struts2框架源码没去了解过，所以就跟踪一下struts2的整个执行过程.由于本人也是抱着学习的态度来阅读掩码，若文章在表述和代码方面如有不妥之处，欢迎批评指正。留下你的脚印，欢迎评论！希望能互相学习。

 我这里的struts2源码是maven导jar包来查看源码的，这样方便多了，可以在IDE下查看源码。pom.xml文件如下

       
      
       4.0.0
        
      
       Struts_test_lishun
        
      
       Struts_test_lishun
        
      
       0.0.1-SNAPSHOT
        
      
       war
         
          
               
        
         commons-logging
                
        
         commons-logging
                
        
         1.2
            
           
               
        
         org.apache.struts
                
        
         struts2-core
                
        
         2.3.24
            
         
      
     

1.实现从web.xml说起：

     
          
          
              
       
        action2
               
               
       
        org.apache.struts2.dispatcher.ng.filter.StrutsPrepareAndExecuteFilter
               
                   
        
         struts.serve.static.browserCache
                    
        
         true
                
               
                
                   
        
         struts.action.extension
                    
        
         do
                
           
          
              
       
        action2
               
               
       
        /*
           
      
     

2：开始查看StrutsPrepareAndExecuteFilter 过滤器

2-1:初始化：(tomcat一启动就会执行到这里)

public void init(FilterConfig filterConfig) throws ServletException {        InitOperations init = new InitOperations();        Dispatcher dispatcher = null;        try {　　　　　　　//封装filterConfig，便于对xml文件的操作            FilterHostConfig config = new FilterHostConfig(filterConfig);　　　　　　　//初始化日志            init.initLogging(config);　　　　　　　//初始化dispatcher，struts2的核心类，大部分的操作都是在这里完成的            dispatcher = init.initDispatcher(config);            init.initStaticContentLoader(config, dispatcher);       　　 //初始化当前类属性：prepare 、execute(这两个属性会在doFilter里设置ActionContext和encoding的值)            prepare = new PrepareOperations(dispatcher);            execute = new ExecuteOperations(dispatcher);            this.excludedPatterns = init.buildExcludedPatternsList(dispatcher);　　　　　　　//这是是空函数。说是回调方法，这里不太懂，有了解可以给小弟指引下            postInit(dispatcher, filterConfig);        } finally {            if (dispatcher != null) {                dispatcher.cleanUpAfterInit();            }            init.cleanup();        }    }

2-2:对上面init.initDispatcher(config)的跟踪：

public Dispatcher initDispatcher( HostConfig filterConfig ) {        //这里主要是对新建一个dispatcher，并加载配置文件中的初始化参数        Dispatcher dispatcher = createDispatcher(filterConfig);        //初始化dispatcher        dispatcher.init();        return dispatcher;}

2-2-1：dispatcher.init()跟踪：

public void init() {        if (configurationManager == null) {            //把struts.xml文件进行封装(默认是名字是struts)            configurationManager = createConfigurationManager(DefaultBeanSelectionProvider.DEFAULT_BEAN_NAME);        }        try {
                init_FileManager();            //加载org/apache/struts2/default.properties            init_DefaultProperties(); // [1]            //加载struts-default.xml,struts-plugin.xml,struts.xml            init_TraditionalXmlConfigurations(); // [2]            //下面的初始化代码。没去研究，到此已经把web.xml,和struts.xml文件给加载进来了            init_LegacyStrutsProperties(); // [3]            init_CustomConfigurationProviders(); // [5]            init_FilterInitParameters() ; // [6]            init_AliasStandardObjects() ; // [7]            Container container = init_PreloadConfiguration();            //注入dispatcher            container.inject(this);            init_CheckWebLogicWorkaround(container);            if (!dispatcherListeners.isEmpty()) {                for (DispatcherListener l : dispatcherListeners) {                    l.dispatcherInitialized(this);                }            }            errorHandler.init(servletContext);        } catch (Exception ex) {            if (LOG.isErrorEnabled())                LOG.error("Dispatcher initialization failed", ex);            throw new StrutsException(ex);        }    }

初始化就在此告一段落了。

----------------------华丽的分割线-------------------------

3-1：访问某个action，StrutsPrepareAndExecuteFilter对所有的的请求都会过滤，此事就跟踪到；

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {        HttpServletRequest request = (HttpServletRequest) req;        HttpServletResponse response = (HttpServletResponse) res;        try {            if (excludedPatterns != null && prepare.isUrlExcluded(request, excludedPatterns)) {                chain.doFilter(request, response);            } else {                //设置类属性编码和国际化                prepare.setEncodingAndLocale(request, response);                //设置类属性action的上下文                prepare.createActionContext(request, response);                prepare.assignDispatcherToThread();                //对request进行封装，继续跟踪下去代码会发现这里的作用就是根据不同的请求返回不同request的封装类(这里就是用到装饰者模式)                request = prepare.wrapRequest(request);　　　　　　　　　//返回ActionMapping：里面有通过struts.xml文件通过反射获取到action对应的类和方法                ActionMapping mapping = prepare.findActionMapping(request, response, true);　　　　　　　　　//若返回的ActionMapping为null，则表示不是调用action                if (mapping == null) {                    boolean handled = execute.executeStaticResourceRequest(request, response);                    if (!handled) {                        chain.doFilter(request, response);                    }                } else {                    //这里进行了很多操作，比较重要就是页面参数值的注入，和执行action                    execute.executeAction(request, response, mapping);                }            }        } finally {            prepare.cleanupRequest(request);        }    }

3-2：追踪代码-生成映射action的映射：

ActionMapping mapping = prepare.findActionMapping(request, response, true);在PrepareOperations中,主要执行ActionMapper的getMapping(..)方法public ActionMapping findActionMapping(HttpServletRequest request, HttpServletResponse response, boolean forceLookup) {        ActionMapping mapping = (ActionMapping) request.getAttribute(STRUTS_ACTION_MAPPING_KEY);        if (mapping == null || forceLookup) {            try {　　　　　　　　　//new一个ActionMapper实例并执行getMapping(..)方法                mapping = dispatcher.getContainer().getInstance(ActionMapper.class).getMapping(request, dispatcher.getConfigurationManager());                if (mapping != null) {                    request.setAttribute(STRUTS_ACTION_MAPPING_KEY, mapping);                }            } catch (Exception ex) {                dispatcher.sendError(request, response, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);            }        }        return mapping;    }

3-2-1:追踪到ActionMapper的getMapping(..)方法；而ActionMapper是一个接口，方法由DefaultActionMapper类实现；

定位到DefaultActionMapper类的getMapping(..);

public ActionMapping getMapping(HttpServletRequest request, ConfigurationManager configManager) {        ActionMapping mapping = new ActionMapping();        //获取到请求的url        String uri = RequestUtils.getUri(request);        //截取url，把含有";"的后面的字符截取掉        int indexOfSemicolon = uri.indexOf(";");        uri = (indexOfSemicolon > -1) ? uri.substring(0, indexOfSemicolon) : uri;                  //继续截取url，url的后缀截取掉(如.action和.do等)，在这里就可以看见extensions变量，struts默认的后缀名就是.action        uri = dropExtension(uri, mapping);        if (uri == null) {            return null;        }        //从url获取namespace和name并和mapping匹配        parseNameAndNamespace(uri, mapping, configManager);        handleSpecialParameters(request, mapping);        return parseActionName(mapping);    }

3-3：现在返回到doFilter方法，追踪到

execute.executeAction(request, response, mapping);方法；

public void executeAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping) throws ServletException {        dispatcher.serviceAction(request, response, mapping);    }

最终调用的是Dispatcher的serviceAction(...)方法，

 

public void serviceAction(HttpServletRequest request, HttpServletResponse response, ActionMapping mapping)            throws ServletException {        //封转上下文环境，主要将request、params、session等Map封装成为一个上下文Map、        Map
     
       extraContext = createContextMap(request, response, mapping);        // If there was a previous value stack, then create a new copy and pass it in to be used by the new Action        ValueStack stack = (ValueStack) request.getAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY);        boolean nullStack = stack == null;        if (nullStack) {            ActionContext ctx = ActionContext.getContext();            if (ctx != null) {                stack = ctx.getValueStack();            }        }        if (stack != null) {            extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));        }        String timerKey = "Handling request from Dispatcher";        try {            UtilTimerStack.push(timerKey);            //从mapping(这里是已经封装好的mapping，struts.xml与请求url共同映射出来的数据)中获取命名空间            String namespace = mapping.getNamespace();　　　　　　  //从mapping中获取action的name            String name = mapping.getName();　　　　　　　//从mapping中获取请求方法（是获取动态的请求方法：在url后面加上 ‘!+方法名’）            String method = mapping.getMethod();　　　　　　　//生成action的代理类，执行页面参数值和根据反射执行请求方法            ActionProxy proxy = getContainer().getInstance(ActionProxyFactory.class).createActionProxy(                    namespace, name, method, extraContext, true, false);            request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());            //如果配置文件中执行的这个action配置了result，就直接转到result            if (mapping.getResult() != null) {                Result result = mapping.getResult();                result.execute(proxy.getInvocation());            } else {                proxy.execute();            }            // If there was a previous value stack then set it back onto the request            if (!nullStack) {                request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);            }        } catch (ConfigurationException e) {            logConfigurationException(request, e);            sendError(request, response, HttpServletResponse.SC_NOT_FOUND, e);        } catch (Exception e) {            if (handleException || devMode) {                sendError(request, response, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);            } else {                throw new ServletException(e);            }        } finally {            UtilTimerStack.pop(timerKey);        }    }
     

 

3-3-1：追踪  ActionProxy proxy = getContainer().getInstance(ActionProxyFactory.class).createActionProxy(

                    namespace, name, method, extraContext, true, false);

创建ActionProxy是由ActionProxyFactory实现类完成

DefaultActionProxyFactory createActionProxy方法

public ActionProxy createActionProxy(String namespace, String actionName, String methodName, Map
     
       extraContext, boolean executeResult, boolean cleanupContext) {                ActionInvocation inv = new DefaultActionInvocation(extraContext, true);        container.inject(inv);        //StrutsActionProxyFactory 的createActionProxy方法,   StrutsActionProxyFactory是DefaultActionProxyFactory的子类，调用的是StrutsActionProxyFactory的方法        return createActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);    }
     

--------- StrutsActionProxyFactory-----------------

public class StrutsActionProxyFactory extends DefaultActionProxyFactory {    @Override    public ActionProxy createActionProxy(ActionInvocation inv, String namespace, String actionName, String methodName, boolean executeResult, boolean cleanupContext) {                StrutsActionProxy proxy = new StrutsActionProxy(inv, namespace, actionName, methodName, executeResult, cleanupContext);        container.inject(proxy);//继续跟踪代码: prepare()调用的是父类DefaultActionProxy的prepare()方法        proxy.prepare();        return proxy;    }}

--------------------DefaultActionProxy-------------------

protected void prepare() {        String profileKey = "create DefaultActionProxy: ";        try {            UtilTimerStack.push(profileKey);            config = configuration.getRuntimeConfiguration().getActionConfig(namespace, actionName);            if (config == null && unknownHandlerManager.hasUnknownHandlers()) {                config = unknownHandlerManager.handleUnknownAction(namespace, actionName);            }            if (config == null) {                throw new ConfigurationException(getErrorMessage());            }              //获取执行method为空的方法名， 若为空则默认设置为"execute"             resolveMethod();            if (!config.isAllowedMethod(method)) {                throw new ConfigurationException("Invalid method: " + method + " for action " + actionName);            }              //创建action            invocation.init(this);        } finally {            UtilTimerStack.pop(profileKey);        }    }

----------------- invocation.init(this)--------------

public void init(ActionProxy proxy) {        this.proxy = proxy;        Map
     
       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);        }         //这里开始创建action        createAction(contextMap);        if (pushAction) {            stack.push(action);            contextMap.put("action", action);        }        invocationContext = new ActionContext(contextMap);        invocationContext.setName(proxy.getActionName());        // get a new List so we don't get problems with the iterator if someone changes the list        List
      
        interceptorList = new ArrayList
       
        (proxy.getConfig().getInterceptors());        interceptors = interceptorList.iterator();    }
       
      
     

至此action就创建成功了，然后就是给action的属性赋值和执行action里的方法

3-4：重新回到Dispatcher的serviceAction(...)方法，当mapping.getResult() != null此时就跟踪到

proxy.execute();方法

ActionProxy是接口，execute()由StrutsActionProxy实现；

public String execute() throws Exception {        ActionContext previous = ActionContext.getContext();        ActionContext.setContext(invocation.getInvocationContext());        try {            //开始执行action和注入属性值，由DefaultActionInvocation实现这个方法            return invocation.invoke();        } finally {            if (cleanupContext)                ActionContext.setContext(previous);        }    }

---------------DefaultActionInvocation--------------------------------

.....其他代码省略try {　　　　//最主要执行了intercept方法，这里就是执行设置action的属性值和执行方法，由接口Interceptor的抽象类AbstractInterceptor的子类MethodFilterInterceptor执行intercept方法， 　　　　//由于AbstractInterceptor的实现类很多，所以这段代码会执行很多次，至于为什么会执行多次，本人也还在研究，若有仁兄了解可以给小弟一点指引         resultCode = interceptor.getInterceptor().intercept(DefaultActionInvocation.this);    }    finally {    　　UtilTimerStack.pop(interceptorMsg);    }.....其他代码省略

---------------MethodFilterInterceptor---------------------------------

@Override    public String intercept(ActionInvocation invocation) throws Exception {        if (applyInterceptor(invocation)) {          //执行了ParametersInterceptor的doIntercept方法， return doIntercept(invocation);        }         return invocation.invoke();    }

---------------ParametersInterceptor---------------------

 

@Override    public String doIntercept(ActionInvocation invocation) throws Exception {        Object action = invocation.getAction();        if (!(action instanceof NoParameters)) {            ActionContext ac = invocation.getInvocationContext();            final Map
     
       parameters = retrieveParameters(ac);            if (LOG.isDebugEnabled()) {                LOG.debug("Setting params " + getParameterLogMap(parameters));            }            if (parameters != null) {                Map
      
        contextMap = ac.getContextMap();                try {                    ReflectionContextState.setCreatingNullObjects(contextMap, true);                    ReflectionContextState.setDenyMethodExecution(contextMap, true);                    ReflectionContextState.setReportingConversionErrors(contextMap, true);                    ValueStack stack = ac.getValueStack();//给action的参数赋值                    setParameters(action, stack, parameters);                } finally {                    ReflectionContextState.setCreatingNullObjects(contextMap, false);                    ReflectionContextState.setDenyMethodExecution(contextMap, false);                    ReflectionContextState.setReportingConversionErrors(contextMap, false);                }            }        }//最后执行action        return invocation.invoke();    }
      
     

至此，整个action的请求就结束了；