struts1 flow

在web.xml中配置有  

    <servlet-mapping>
        <servlet-name>action</servlet-name>
        <url-pattern>*.do</url-pattern>
    </servlet-mapping>

<servlet-class>org.apache.struts.action.ActionServlet</servlet-class>

当页面请求到来时， ActionServlet进行初始化，  执行该Servlet的init()方法，

            initModuleMessageResources(moduleConfig);
            initModulePlugIns(moduleConfig);
            initModuleFormBeans(moduleConfig);
            initModuleForwards(moduleConfig);
            initModuleExceptionConfigs(moduleConfig);
            initModuleActions(moduleConfig);

完成初始化操作。

之后， 调用该Servlet的doGet 、doPost方法，

    public void doGet(HttpServletRequest request, HttpServletResponse response)
        throws IOException, ServletException {
        process(request, response);
    }
.....

继续方法调用

processor.process(request, response);

其中获取processor方法为：

    /**
     * <p>Returns the RequestProcessor for the given module or null if one
     * does not exist.  This method will not create a RequestProcessor.</p>
     *
     * @param config The ModuleConfig.
     * @return The <code>RequestProcessor</code> for the given module, or
     *         <code>null</code> if one does not exist.
     */
    private RequestProcessor getProcessorForModule(ModuleConfig config) {
        String key = Globals.REQUEST_PROCESSOR_KEY + config.getPrefix();
 
        return (RequestProcessor) getServletContext().getAttribute(key);
    }

下面简要分析一下上面提及的processor.process(request, response)

public void process(HttpServletRequest request, HttpServletResponse response) {
   // 处理文件上传
   request = processMultipart(request);
  // 得到ActionMapping 
  ActionMapping mapping = processMapping(request, response, path);
  // 得到ActionForm 
  ActionForm form = processActionForm(request, response, mapping); 
  //  得到action 
  Action action = processActionCreate(request, response, mapping);
  // 得到forward 
  ActionForward forward =
            processActionPerform(request, response, action, form, mapping);
  .... 
  processForwardConfig(request, response, forward);
 
 
  
}

processForwardConfig(request, response, forward) 又会调用RequestDispatcher的forward等方法， 完成
此次转发。



关于action的获取方法 processActionCreate

    protected Action processActionCreate(HttpServletRequest request,
        HttpServletResponse response, ActionMapping mapping)
        throws IOException {
        // Acquire the Action instance we will be using (if there is one)
        String className = mapping.getType();
 
        if (log.isDebugEnabled()) {
            log.debug(" Looking for Action instance for class " + className);
        }
 
        // If there were a mapping property indicating whether
        // an Action were a singleton or not ([true]),
        // could we just instantiate and return a new instance here?
        Action instance;
        synchronized (actions) {
            // Return any existing Action instance of this class
            instance = (Action) actions.get(className);

  可见action是单例的