Struts2源码分析--请求处理续

init_CustomConfigurationProviders方式初始自定义的Provider，配置类全名和实现ConfigurationProvider接口，用逗号隔开即可。
 

private void init_CustomConfigurationProviders() {
    String configProvs = initParams.get("configProviders");
    if (configProvs != null) {
        String[] classes = configProvs.split("\\s*[,]\\s*");
        for (String cname : classes) {
            try {
                Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
                ConfigurationProvider prov = (ConfigurationProvider)cls.newInstance();
                configurationManager.addConfigurationProvider(prov);
            }

        }
    }
}

    private void init_CustomConfigurationProviders() {
        String configProvs = initParams.get("configProviders");
        if (configProvs != null) {
            String[] classes = configProvs.split("\\s*[,]\\s*");
            for (String cname : classes) {
                try {
                    Class cls = ClassLoaderUtils.loadClass(cname, this.getClass());
                    ConfigurationProvider prov = (ConfigurationProvider)cls.newInstance();
                    configurationManager.addConfigurationProvider(prov);
                }
                
            }
        }
    }

   好了，现在再回到FilterDispatcher，每次发送一个Request，FilterDispatcher都会调用doFilter方法。
 

public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {

    HttpServletRequest request = (HttpServletRequest) req;
    HttpServletResponse response = (HttpServletResponse) res;
    ServletContext servletContext = getServletContext();

    String timerKey = "FilterDispatcher_doFilter: ";
    try {
        ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
        ActionContext ctx = new ActionContext(stack.getContext());
        ActionContext.setContext(ctx);

        UtilTimerStack.push(timerKey);
        //根据content type来使用不同的Request封装，可以参见Dispatcher的wrapRequest
        request = prepareDispatcherAndWrapRequest(request, response);
        ActionMapping mapping;
        try {
            //根据url取得对应的Action的配置信息--ActionMapping，actionMapper是通过Container的inject注入的
            mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());
        } catch (Exception ex) {
            log.error("error getting ActionMapping", ex);
            dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
            return;
        }
        //如果找不到对应的action配置，则直接返回。比如你输入***.jsp等等
        //这儿有个例外，就是如果path是以“/struts”开头，则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中，当然.class文件除外。如果再没有则跳转到404
        if (mapping == null) {
            // there is no action in this request, should we look for a static resource?
            String resourcePath = RequestUtils.getServletPath(request);

            if ("".equals(resourcePath) && null != request.getPathInfo()) {
                resourcePath = request.getPathInfo();
            }

            if (serveStatic && resourcePath.startsWith("/struts")) {
                String name = resourcePath.substring("/struts".length());
                findStaticResource(name, request, response);
            } else {
                chain.doFilter(request, response);
            }
            return;
        }
        //正式开始Action的方法了
        dispatcher.serviceAction(request, response, servletContext, mapping);

    } finally {
        try {
            ActionContextCleanUp.cleanUp(req);
        } finally {
            UtilTimerStack.pop(timerKey);
        }
    }
}

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) req;
        HttpServletResponse response = (HttpServletResponse) res;
        ServletContext servletContext = getServletContext();

        String timerKey = "FilterDispatcher_doFilter: ";
        try {
            ValueStack stack = dispatcher.getContainer().getInstance(ValueStackFactory.class).createValueStack();
            ActionContext ctx = new ActionContext(stack.getContext());
            ActionContext.setContext(ctx);
            
            UtilTimerStack.push(timerKey);
            //根据content type来使用不同的Request封装，可以参见Dispatcher的wrapRequest
            request = prepareDispatcherAndWrapRequest(request, response);
            ActionMapping mapping;
            try {
                //根据url取得对应的Action的配置信息--ActionMapping，actionMapper是通过Container的inject注入的
                mapping = actionMapper.getMapping(request, dispatcher.getConfigurationManager());
            } catch (Exception ex) {
                log.error("error getting ActionMapping", ex);
                dispatcher.sendError(request, response, servletContext, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, ex);
                return;
            }
            //如果找不到对应的action配置，则直接返回。比如你输入***.jsp等等
            //这儿有个例外，就是如果path是以“/struts”开头，则到初始参数packages配置的包路径去查找对应的静态资源并输出到页面流中，当然.class文件除外。如果再没有则跳转到404
            if (mapping == null) {
                // there is no action in this request, should we look for a static resource?
                String resourcePath = RequestUtils.getServletPath(request);

                if ("".equals(resourcePath) && null != request.getPathInfo()) {
                    resourcePath = request.getPathInfo();
                }

                if (serveStatic && resourcePath.startsWith("/struts")) {
                    String name = resourcePath.substring("/struts".length());
                    findStaticResource(name, request, response);
                } else {
                    chain.doFilter(request, response);
                }
                return;
            }
            //正式开始Action的方法了
            dispatcher.serviceAction(request, response, servletContext, mapping);

        } finally {
            try {
                ActionContextCleanUp.cleanUp(req);
            } finally {
                UtilTimerStack.pop(timerKey);
            }
        }
    }

    Dispatcher类的serviceAction方法：
 

public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,ActionMapping mapping) throws ServletException {

    Map<String, Object> extraContext = createContextMap(request, response, mapping, context);

    // 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);
    if (stack != null) {
        extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));
    }

    String timerKey = "Handling request from Dispatcher";
    try {
        UtilTimerStack.push(timerKey);
        String namespace = mapping.getNamespace();
        String name = mapping.getName();
        String method = mapping.getMethod();

        Configuration config = configurationManager.getConfiguration();
        ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
                namespace, name, method, extraContext, true, false);

        request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());

        // if the ActionMapping says to go straight to a result, do it!
        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 (stack != null) {
            request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
        }
    } catch (ConfigurationException e) {
        LOG.error("Could not find action or result", e);
        sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);
    } catch (Exception e) {
        sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
    } finally {
        UtilTimerStack.pop(timerKey);
    }
}

    public void serviceAction(HttpServletRequest request, HttpServletResponse response, ServletContext context,ActionMapping mapping) throws ServletException {

        Map<String, Object> extraContext = createContextMap(request, response, mapping, context);

        // 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);
        if (stack != null) {
            extraContext.put(ActionContext.VALUE_STACK, valueStackFactory.createValueStack(stack));
        }

        String timerKey = "Handling request from Dispatcher";
        try {
            UtilTimerStack.push(timerKey);
            String namespace = mapping.getNamespace();
            String name = mapping.getName();
            String method = mapping.getMethod();

            Configuration config = configurationManager.getConfiguration();
            ActionProxy proxy = config.getContainer().getInstance(ActionProxyFactory.class).createActionProxy(
                    namespace, name, method, extraContext, true, false);

            request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, proxy.getInvocation().getStack());

            // if the ActionMapping says to go straight to a result, do it!
            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 (stack != null) {
                request.setAttribute(ServletActionContext.STRUTS_VALUESTACK_KEY, stack);
            }
        } catch (ConfigurationException e) {
            LOG.error("Could not find action or result", e);
            sendError(request, response, context, HttpServletResponse.SC_NOT_FOUND, e);
        } catch (Exception e) {
            sendError(request, response, context, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, e);
        } finally {
            UtilTimerStack.pop(timerKey);
        }
    }

    第一句createContextMap()方法，该方法主要把Application、Session、Request的key value值拷贝到Map中，并放在HashMap<String,Object>中，可以参见createContextMap方法：
 

public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response,
        ActionMapping mapping, ServletContext context) {

    // request map wrapping the http request objects
    Map requestMap = new RequestMap(request);
    // parameters map wrapping the http parameters.  ActionMapping parameters are now handled and applied separately
    Map params = new HashMap(request.getParameterMap());
    // session map wrapping the http session
    Map session = new SessionMap(request);
    // application map wrapping the ServletContext
    Map application = new ApplicationMap(context);
    Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);
    extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
    return extraContext;
}

    public Map<String,Object> createContextMap(HttpServletRequest request, HttpServletResponse response,
            ActionMapping mapping, ServletContext context) {

        // request map wrapping the http request objects
        Map requestMap = new RequestMap(request);
        // parameters map wrapping the http parameters.  ActionMapping parameters are now handled and applied separately
        Map params = new HashMap(request.getParameterMap());
        // session map wrapping the http session
        Map session = new SessionMap(request);
        // application map wrapping the ServletContext
        Map application = new ApplicationMap(context);
        Map<String,Object> extraContext = createContextMap(requestMap, params, session, application, request, response, context);
        extraContext.put(ServletActionContext.ACTION_MAPPING, mapping);
        return extraContext;
    }

    后面才是最主要的--ActionProxy，ActionInvocation。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。归根到底，最后调用的是DefaultActionInvocation.invokeAction()方法。先看DefaultActionInvocation的init方法。
 

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);
    }
    //创建Action，可Struts2里是每次请求都新建一个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();
}

protected void createAction(Map contextMap) {
    // load action
    String timerKey = "actionCreate: "+proxy.getActionName();
    try {
        UtilTimerStack.push(timerKey);
        //这儿默认建立Action是StrutsObjectFactory，实际中我使用的时候都是使用Spring创建的Action，这个时候使用的是SpringObjectFactory
        action = objectFactory.buildAction(proxy.getActionName(), proxy.getNamespace(), proxy.getConfig(), contextMap);
    }
    ..
    } finally {
        UtilTimerStack.pop(timerKey);
    }

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