Struts1的处理流程

本文从收到一个请求开始讲述,忽略之前的filter等工作.

处理工作的主要承担者为RequestProcessor

1.处理请求的url. RequestProcessor.processPath(request,response)
　　String path = processPath(request, response);

     protected String processPath(HttpServletRequest request,
                                  HttpServletResponse response)
         throws IOException {

         String path = null;

         // For prefix matching, match on the path info (if any)
         path = (String) request.getAttribute(INCLUDE_PATH_INFO);
         if (path == null) {
             path = request.getPathInfo();
         }
         if ((path != null) && (path.length() > 0)) {
             return (path);
         }

         // For extension matching, strip the module prefix and extension
         path = (String) request.getAttribute(INCLUDE_SERVLET_PATH);
         if (path == null) {
             path = request.getServletPath();
         }
         String prefix = moduleConfig.getPrefix();
         if (!path.startsWith(prefix)) {
             String msg = getInternal().getMessage("processPath");

             log.error(msg + " " + request.getRequestURI());
             response.sendError(HttpServletResponse.SC_BAD_REQUEST, msg);

             return null;
         }

         path = path.substring(prefix.length());
         int slash = path.lastIndexOf("/");
         int period = path.lastIndexOf(".");
         if ((period >= 0) && (period > slash)) {
             path = path.substring(0, period);
         }
         return (path);

     }

　　从request中获取请求的url.path = request.getPathInfo();

　　在对获取的path进行处理:

         path = path.substring(prefix.length());
2         int slash = path.lastIndexOf("/");
3         int period = path.lastIndexOf(".");
         if ((period >= 0) && (period > slash)) {
             path = path.substring(0, period);
         }
         return (path);

2.根据获取的url-path来构建ActionMapping

　　ActionMapping mapping = processMapping(request, response, path);　　

　　

    protected ActionMapping processMapping(HttpServletRequest request,
                                            HttpServletResponse response,
                                            String path)
         throws IOException {

         // Is there a mapping for this path?
         ActionMapping mapping = (ActionMapping)
             moduleConfig.findActionConfig(path);

         // If a mapping is found, put it in the request and return it
         if (mapping != null) {
             request.setAttribute(Globals.MAPPING_KEY, mapping);
             return (mapping);
         }

         // Locate the mapping for unknown paths (if any)
         ActionConfig configs[] = moduleConfig.findActionConfigs();
         for (int i = 0; i < configs.length; i++) {
             if (configs[i].getUnknown()) {
                 mapping = (ActionMapping) configs[i];
                 request.setAttribute(Globals.MAPPING_KEY, mapping);
                 return (mapping);
             }
         }

         // No mapping can be found to process this request
         String msg = getInternal().getMessage("processInvalid");
         log.error(msg + " " + path);
         response.sendError(HttpServletResponse.SC_NOT_FOUND, msg);

         return null;
     }

　　这个过程主要是从struts-config.xml中读取<action-mapping>结点的action信息,将所有的<action>结点保存到ActionMapping中.

3.获取ActionForm,

　　 ActionForm form = processActionForm(request, response, mapping);

　　上一步通过url已经定位到了相应的action,然后通过 String name = mapping.getName(); 获取actionform(该项在<form-beans>中获取),同时设置该action的作用域(request/session默认session).再将创建号的actionform放到request/session中.

4.从actionform中获取相应的值,完成相应数据的赋值,这其中包括类型的转换,使用了第三方的工具类BeanUtils.

5.创建相应的action

　　protected Action processActionCreate(HttpServletRequest request,HttpServletResponse response,ActionMapping mapping)

　　actionform信息存在于actionmapping中。首先根据action类的完整名称（<action>标签下面的type），如果已经存在直接返回；否则再使用反射机制创建action。

6.最终执行action的execute方法。

　　ActionForward forward =processActionPerform(request, response,action, form, mapping);

　　从中执行action的execute方法，返回actinforward，再根据返回的actionforward来实现转发/转向。

具体的处理流程如下图：

附件一 struts-config.xml

<struts-config>
    <form-beans>
        <form-bean name="loginactionform" type="com.volshell.actionform.LoginActionForm"/>
    </form-beans>
    <action-mappings>
        <action path="/login"
                    name="loginactionform"
                    type="com.volshell.action.LoginAction"
                    scope="request">
            <forward name="error" path="/login_fail.jsp"></forward>
            <forward name="success" path="/login_success.jsp"></forward>
        </action>
    </action-mappings>
</struts-config>