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>