通用Servlet(反射实现)+网上商城实战篇

代码仓库地址+教程：https://gitee.com/DerekAndroid/ServletStore.git

实现一个通用的servlet对应多个请求路径的jsp

效果：

思路：

1 一个路径一个servlet

2 多个路径对应一个servlet，通过method请求参数与if语句进行分流

3 编写BaseServlet，使用反射执行当前类的指定方法

4 方法返回-请求转发时需要的jsp路径

 实现：

package cn.itcast.web;


import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
import java.lang.reflect.Method;

public class BaseServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        try {
            //1.获取请求参数method
            String methodName = req.getParameter("method");
            //2设置默认方法名
            if (methodName == null) {
                methodName = "execute";
            }
            Method method = this.getClass().getMethod(methodName, HttpServletRequest.class, HttpServletResponse.class);
            //3执行方法
            String jspPath = (String) method.invoke(this, req, resp);
            //4如果子类有返回值，将请求到指定的jsp中
            if (jspPath != null) {
                req.getRequestDispatcher(jspPath).forward(req, resp);
            }
        } catch (Exception e) {
            e.printStackTrace();
            throw new RuntimeException(e);
        }
    }

    public String execute(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        System.out.println("execute");
        return null;
    }
}

测试：

package cn.itcast.web;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class AllServlet extends BaseServlet {
    private static final long serialVersionUID = 1L;

    public String findAll(HttpServletRequest request, HttpServletResponse response) {
        System.out.println("findAll");
        return "/all.jsp";
    }
}

web.xml配置

  <servlet>
    <description></description>
    <display-name>AllServlet</display-name>
    <servlet-name>AllServlet</servlet-name>
    <servlet-class>cn.itcast.web.AllServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>AllServlet</servlet-name>
    <url-pattern>/all</url-pattern>
  </servlet-mapping>

测试路径：

http://localhost:8080/ProxyServlet/all?method=findAll