WebWork 工作流程

WebWork 工作流程

1、处理客户端提交的请求
客户端提交的请求由com.opensymphony.xwork.dispatcher.ServletDispatcher进行处理。ServletDispatche是一个HttpServlet。
ServletDispatche接收到客户端的请求以后，首先调用init方法进行初始化工作：

 public void init(ServletConfig servletConfig) throws ServletException {
        super.init(servletConfig);

        // 进行各种初始化
    }

初始化完成之后，由service方法处理请求：

    public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException {
        try {

     // ....

            serviceAction(request, response, getNameSpace(request), getActionName(request), getRequestMap(request), getParameterMap(request), getSessionMap(request), getApplicationMap());
        } catch (IOException e) {
            String message = "Could not wrap servlet request with MultipartRequestWrapper!";
            log.error(message, e);
            sendError(request, response, HttpServletResponse.SC_INTERNAL_SERVER_ERROR, new ServletException(message, e));
        }
    }

这里，service方法把请求转交给了serviceAction方法：

    public void serviceAction(HttpServletRequest request, HttpServletResponse response, String namespace, String actionName, Map requestMap, Map parameterMap, Map sessionMap, Map applicationMap) {
        HashMap extraContext = createContextMap(requestMap, parameterMap, sessionMap, applicationMap, request, response, getServletConfig());
        extraContext.put(SERVLET_DISPATCHER, this);

 // ...

        try {
            ActionProxy proxy = ActionProxyFactory.getFactory().createActionProxy(namespace, actionName, extraContext);
            request.setAttribute(ServletActionContext.WEBWORK_VALUESTACK_KEY, proxy.getInvocation().getStack());
            proxy.execute();

     // ...

        } catch (ConfigurationException e) {
            log.error("Could not find action", e);
            sendError(request, response, HttpServletResponse.SC_NOT_FOUND, e);

     // ...
    }
到这里为止，WebWork就把处理Action的工作交给了XWork了，然后就等待XWork给结果了。

XWork怎么将结果返回给WebWork呢？

下面我们来看action部分的定义：

<action name="helloWebWorld" class="lesson03.HelloWebWorldAction">
 <result name="success" type="dispatcher">ex01-success.jsp</result>
</action>

这里的result结点有一个type属性，这表示此action的结果应该怎样处理。
再来看看dispatcher类型的result是怎么定义的：
<result-type name="dispatcher" class="com.opensymphony.webwork.dispatcher.ServletDispatcherResult" default="true"/>
到这里就可以知道了处理是交给ServletDispatcherResult类来做的。

ServletDispatcherResult类继承了WebWorkResultSupport类，而WebWorkResultSupport实现了com.opensymphony.xwork.Result接口，此接口用来处理action的结果。
WebWorkResultSupport类定义了一个抽象的方法 －－ doExecute，此方法用于实现对Result的处理。

下面来看看ServletDispatcherResult是怎么处理的：

 public void doExecute(String finalLocation, ActionInvocation invocation) throws Exception {

        PageContext pageContext = ServletActionContext.getPageContext();

        if (pageContext != null) {
            pageContext.include(finalLocation);
        } else {
            HttpServletRequest request = ServletActionContext.getRequest();
            HttpServletResponse response = ServletActionContext.getResponse();
            RequestDispatcher dispatcher = request.getRequestDispatcher(finalLocation);

            // if the view doesn't exist, let's do a 404
            if (dispatcher == null) {
                response.sendError(404, "result '" + finalLocation + "' not found");

                return;
            }

            // If we're included, then include the view
            // Otherwise do forward
            // This allow the page to, for example, set content type
            if (!response.isCommitted() && (request.getAttribute("javax.servlet.include.servlet_path") == null)) {
                request.setAttribute("webwork.view_uri", finalLocation);
                request.setAttribute("webwork.request_uri", request.getRequestURI());

                dispatcher.forward(request, response);
            } else {
                dispatcher.include(request, response);
            }
        }
    }

    我们看到，最终调用的是dispatcher.forward(request, response);
    这样就可以成功转到我们的目标页了。