技术开发 频道

设计模式:设计自己的MVC框架

    6。前端控制器(FrontController),它的任务我们已经很清楚,初始化配置文件;存储所有action到ServletContext供整个框架使用;得到发起请求的path,提供给Dispachter查找相应的action;调用Dispatcher,执行getNextPage方法得到下一个页面的url并转发:
public void init() throws ServletException { //初始化配置文件 ServletContext context=getServletContext(); String config_file =getServletConfig().getInitParameter("config"); String dispatcher_name=getServletConfig().getInitParameter("dispatcher"); if (config_file == null || config_file.equals("")) config_file = "/WEB-INF/strutslet-config.xml"; //默认是/WEB-INF/下面的strutslet-config if(dispatcher_name==null||dispatcher_name.equals("")) dispatcher_name=Constant.DEFAULT_DISPATCHER; try { Map<String, ActionModel> resources = ConfigUtil.newInstance() //工具类解析配置文件 .parse(config_file, context); context.setAttribute(Constant.ACTIONS_ATTR, resources); //存储在ServletContext中 log.info("初始化strutslet配置文件成功"); } catch (Exception e) { log.error("初始化strutslet配置文件失败"); e.printStackTrace(); } //实例化Dispacher try{ Class c = Class.forName(dispatcher_name); Dispatcher dispatcher = (Dispatcher) c.newInstance(); context.setAttribute(Constant.DISPATCHER_ATTR, dispatcher); //放在ServletContext log.info("初始化Dispatcher成功"); }catch(Exception e) { log.error("初始化Dispatcher失败"); e.printStackTrace(); } .....
    doGet()和doPost方法我们都让它调用process方法:
protected void process(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { ServletContext context = getServletContext(); //获取action的path String reqURI = request.getRequestURI(); int i=reqURI.lastIndexOf("."); String contextPath=request.getContextPath(); String path=reqURI.substring(contextPath.length(),i); request.setAttribute(Constant.REQUEST_ATTR, path); Dispatcher dispatcher = (Dispatcher) context.getAttribute(Constant.DISPATCHER_ATTR); // make sure we don't cache dynamic data response.setHeader("Cache-Control", "no-cache"); response.setHeader("Pragma", "no-cache"); // use the dispatcher to find the next page String nextPage = dispatcher.getNextPage(request, context);//调用Dispatcher的getNextPage // forward control to the view RequestDispatcher forwarder = request.getRequestDispatcher("/" + nextPage); forwarder.forward(request, response); //转发页面 }
    7。最后,web.xml的配置就非常简单了,配置前端控制器,提供启动参数(配置文件所在位置,为空就查找/WEB-INF/下面的strutslet-config.xml文件),我们把所有以action结尾的请求都交给FrontController处理:
<servlet> <servlet-name>StrutsletController</servlet-name> <servlet-class>com.strutslet.core.FrontController</servlet-class> <!-- <init-param> <param-name>config</param-name> <param-value>/WEB-INFstrutslet-config.xml</param-value> </init-param> --> <load-on-startup>0</load-on-startup> </servlet> <servlet-mapping> <servlet-name>StrutsletController</servlet-name> <url-pattern>*.action</url-pattern> </servlet-mapping>

    最后,让我们看看整个框架图:

 

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