这是利用action模仿请求Servelet(单例)
作用:
java构造方法重载。1.减少web.xml代码量
2.将servelet中的代码转移到action中,只需要在action中定义业务逻辑则可。
java servlet、1.定义一个过滤器
package com.struts2.filter;import java.io.IOException;import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import com.struts2.action.Action;
import com.struts2.action.HelloWorldAction;
import com.struts2.utils.ServletUtils;public class DispatchFilter implements Filter {private HttpServletRequest request;private HttpServletResponse response;@Overridepublic void destroy() {// TODO Auto-generated method stub}@Overridepublic void doFilter(ServletRequest request, ServletResponse response,FilterChain arg2) throws IOException, ServletException {/*** 1.先获取HttpServletRequest,HttpServletResponse* 2.获取HelloWorldAction.action中的HelloWorldAction* 3.利用java的反射机制进行调用*/this.request=(HttpServletRequest) request;this.response=(HttpServletResponse) response;String requestURI = this.request.getRequestURI();System.out.println(requestURI);String actionName = ServletUtils.convert(requestURI);//利用java的反射机制调用该方法try {//利用java反射机制创建一个新的HelloWorldAction对象HelloWorldAction action = (HelloWorldAction) Class.forName("com.struts2.action."+actionName).newInstance();String forward = action.execute(this.request, this.response);/*** 2种跳转方法* *重定向* request里的参数不起作用* this.response.sendRedirect(jsp页面)* *转发* 放在 request中的值可以取出来* this.request.getRequestDispatcher("index.jsp").forward(this.request, this.response);* */this.request.getRequestDispatcher("index.jsp").forward(this.request, this.response);} catch (InstantiationException e) {e.printStackTrace();} catch (IllegalAccessException e) {e.printStackTrace();} catch (ClassNotFoundException e) {e.printStackTrace();}}@Overridepublic void init(FilterConfig arg0) throws ServletException {}}
web.xml中配置为:
<filter><filter-name>DispatchFilter</filter-name><filter-class>com.struts2.filter.DispatchFilter</filter-class></filter><filter-mapping><filter-name>DispatchFilter</filter-name><url-pattern>*.action</url-pattern></filter-mapping>
struts2的执行过程、
当接受到一个请求后
<a href="HelloWorldAction.action">请求一个action</a>
当过滤器接受到一个请求以后,进行过滤
1.先取出请求uri.
2.根据java反射机制取出action
package com.struts2.action;import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class HelloWorldAction implements Action {@Overridepublic String execute(HttpServletRequest request,HttpServletResponse response) {System.out.println("Hello World Struts2");return "index.jsp";}}
3.取出action以后,就可以执行action中的方法
4.利用request/response转发
/*** 2种跳转方法* *重定向* request里的参数不起作用* this.response.sendRedirect(jsp页面)* *转发* 放在 request中的值可以取出来* this.request.getRequestDispatcher("index.jsp").forward(this.request, this.response);* */this.request.getRequestDispatcher("index.jsp").forward(this.request, this.response); // 这句话的意思是,上面返回了一个字符串"index.jsp",那么这里就是去寻找这个index.jsp,并将request和response放进去。