Servlet中实现多个功能案例

如何实现一个Servlet中的多个功能

前言：唉，打脸了，前脚刚说过要跟Servlet正式告别，后脚这不又来了，哈哈，总结出一点东西，纠结了一下还是做个分享吧，学习知识比面子重要，对吧，下回再也不约Servlet了。

需求分析

看下面代码，现在有一个UserServlet，里面有增删改查四个方法，按平常的思维，用一个Servlet实现一个功能，这没毛病，现在问题是一个Servlet中有四个功能，那这该如何去实现呢？

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package com.my.servlet;
 
import com.my.service.UserService;
import com.my.service.impl.UserServiceImpl;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
 
@WebServlet("/user")
public class UserServlet extends HttpServlet {
    private UserService userService = new UserServiceImpl();
 
  public String add(HttpServletRequest request,HttpServletResponse response){
      userService.add();
      request.setAttribute("mess","添加成功");
      return "r:add.jsp";
  }
 
    public String delete(HttpServletRequest request,HttpServletResponse response){
        userService.delete();
        request.setAttribute("mess","删除成功");
        return "f:add.jsp";
    }
    public String update(HttpServletRequest request,HttpServletResponse response){
        userService.update();
        request.setAttribute("mess","修改成功");
        return "add.jsp";
    }
    public String query(HttpServletRequest request,HttpServletResponse response){
        userService.query();
        request.setAttribute("mess","查询成功");
        return "add.jsp";
    }
 
}

解决思维

解决这个问题其实也简单，再写一个FatherServlet继承于HttpServlet,在这个父类Servlet中的service()方法中通过请求参数判断要调用的子类UserServlet中的哪个方法并执行，可能说到这有些朋友不懂了，如何用参数去判断大家一看下面的代码就明白了，我主要解释一下大家的疑惑，子类UserServlet如何去调用父类FatherServlet中的service()方法，其实秘诀就在这个参数上，在访问UserSerlvet时带上请求参数，访问过来后UserServlet中没有解决参数的方法，所以他会在父类FatherServlet中寻找响应的方法，找到后执行，这是继承的，子类继承父类的方法没毛病吧，所以就解决了。

 

解决完这个问题后我还在service()方法中加了判断是重定向还是转发的思维，这个就友情赠送了，不说了，来，看代码：

 

FatherServlet

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package com.my.servlet;
 
 
 
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.InvocationTargetException;
 
import java.lang.reflect.Method;
 
 
 
public class FatherServlet extends HttpServlet {
 
    @Override
 
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 
        String m = req.getParameter("m");
 
        if (m==null||"".equals(m)){
 
            throw new RuntimeException("参数不能为空");
 
        }
 
 
 
        Class c = this.getClass();
 
 
 
        try {
 
            Method method = c.getMethod(m,HttpServletRequest.class,HttpServletResponse.class);
 
            Object o =method.invoke(this,req,resp);
 
            String rel =String.valueOf(o);
 
 
 
            //判断返回值的前缀，默认转发，r:重定向  f:转发
 
            if (rel.startsWith("r:")){
 
               rel =  rel.substring(rel.indexOf(":")+1);
 
               resp.sendRedirect(rel);
 
            }else if(rel.startsWith("f:")){
 
                rel = rel.substring(rel.indexOf(":")+1);
 
                req.getRequestDispatcher(rel).forward(req,resp);
 
            }else {
 
                req.getRequestDispatcher(rel).forward(req,resp);
 
            }
 
        } catch (NoSuchMethodException e) {
 
            throw new RuntimeException("请求的方法不存在！！");
 
        } catch (IllegalAccessException e) {
 
            throw new RuntimeException("请求方法执行异常！！");
 
        } catch (InvocationTargetException e) {
 
            throw new RuntimeException("请求方法执行异常！！");
 
        }
 
    }
 
}

UserServlet

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package com.my.servlet;
 
 
 
import com.my.service.UserService;
 
import com.my.service.impl.UserServiceImpl;
 
import javax.servlet.annotation.WebServlet;
 
import javax.servlet.http.HttpServletRequest;
 
import javax.servlet.http.HttpServletResponse;
 
@WebServlet("/user")
 
public class UserServlet extends FatherServlet {
 
    private UserService userService = new UserServiceImpl();
 
 
 
  public String add(HttpServletRequest request,HttpServletResponse response){
 
      userService.add();
 
      request.setAttribute("mess","添加成功");
 
      return "r:add.jsp";
 
  }
 
 
 
    public String delete(HttpServletRequest request,HttpServletResponse response){
 
        userService.delete();
 
        request.setAttribute("mess","删除成功");
 
        return "f:add.jsp";
 
    }
 
    public String update(HttpServletRequest request,HttpServletResponse response){
 
        userService.update();
 
        request.setAttribute("mess","修改成功");
 
        return "add.jsp";
 
    }
 
    public String query(HttpServletRequest request,HttpServletResponse response){
 
        userService.query();
 
        request.setAttribute("mess","查询成功");
 
        return "add.jsp";
 
    }
 
 
 
}

完整演示

此篇主要是解决题目所示的需求，先在需求解决了，做戏还要做全呢，我就把我测试的代码都整理出来，方便新手去学习。

UserDao

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package com.my.dao;
 
 
 
public interface UserDao {
 
    public void add();
 
    public void delete();
 
    public void update();
 
    public void query();
 
}

UserDaoImpl

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package com.my.dao.impl;
 
 
 
import com.my.dao.UserDao;
 
 
 
public class UserDaoImpl implements UserDao {
 
    @Override
 
    public void add() {
 
        System.out.println("UserDao中的添加功能实现了");
 
    }
 
 
 
    @Override
 
    public void delete() {
 
        System.out.println("UserDao中的删除功能实现了");
 
    }
 
 
 
    @Override
 
    public void update() {
 
        System.out.println("UserDao中的修改功能实现了");
 
    }
 
 
 
    @Override
 
    public void query() {
 
        System.out.println("UserDao中的查询功能实现了");
 
    }
 
}

UserService

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package com.my.service;
 
 
 
public interface UserService {
 
    public void add();
 
    public void delete();
 
    public void update();
 
    public void query();
 
}

UserServiceImpl

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package com.my.service.impl;
 
 
 
import com.my.dao.UserDao;
 
import com.my.dao.impl.UserDaoImpl;
 
import com.my.service.UserService;
 
 
 
public class UserServiceImpl implements UserService {
 
 
 
    private UserDao userDao = new UserDaoImpl();
 
    @Override
 
    public void add() {
 
        userDao.add();
 
    }
 
 
 
    @Override
 
    public void delete() {
 
        userDao.delete();
 
    }
 
 
 
    @Override
 
    public void update() {
 
        userDao.update();
 
    }
 
 
 
    @Override
 
    public void query() {
 
        userDao.query();
 
    }
 
}

UserServlet

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package com.my.servlet;
 
 
 
import com.my.service.UserService;
 
import com.my.service.impl.UserServiceImpl;
 
import javax.servlet.annotation.WebServlet;
 
import javax.servlet.http.HttpServletRequest;
 
import javax.servlet.http.HttpServletResponse;
 
@WebServlet("/user")
 
public class UserServlet extends FatherServlet {
 
    private UserService userService = new UserServiceImpl();
 
 
 
  public String add(HttpServletRequest request,HttpServletResponse response){
 
      userService.add();
 
      request.setAttribute("mess","添加成功");
 
      return "r:add.jsp";
 
  }
 
 
 
    public String delete(HttpServletRequest request,HttpServletResponse response){
 
        userService.delete();
 
        request.setAttribute("mess","删除成功");
 
        return "f:add.jsp";
 
    }
 
    public String update(HttpServletRequest request,HttpServletResponse response){
 
        userService.update();
 
        request.setAttribute("mess","修改成功");
 
        return "add.jsp";
 
    }
 
    public String query(HttpServletRequest request,HttpServletResponse response){
 
        userService.query();
 
        request.setAttribute("mess","查询成功");
 
        return "add.jsp";
 
    }
 
 
 
}

FatherServlet

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package com.my.servlet;
 
 
 
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.InvocationTargetException;
 
import java.lang.reflect.Method;
 
 
 
public class FatherServlet extends HttpServlet {
 
    @Override
 
    protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
 
        String m = req.getParameter("m");
 
        if (m==null||"".equals(m)){
 
            throw new RuntimeException("参数不能为空");
 
        }
 
 
 
        Class c = this.getClass();
 
 
 
        try {
 
            Method method = c.getMethod(m,HttpServletRequest.class,HttpServletResponse.class);
 
            Object o =method.invoke(this,req,resp);
 
            String rel =String.valueOf(o);
 
 
 
            //判断返回值的前缀，默认转发，r:重定向  f:转发
 
            if (rel.startsWith("r:")){
 
               rel =  rel.substring(rel.indexOf(":")+1);
 
               resp.sendRedirect(rel);
 
            }else if(rel.startsWith("f:")){
 
                rel = rel.substring(rel.indexOf(":")+1);
 
                req.getRequestDispatcher(rel).forward(req,resp);
 
            }else {
 
                req.getRequestDispatcher(rel).forward(req,resp);
 
            }
 
        } catch (NoSuchMethodException e) {
 
            throw new RuntimeException("请求的方法不存在！！");
 
        } catch (IllegalAccessException e) {
 
            throw new RuntimeException("请求方法执行异常！！");
 
        } catch (InvocationTargetException e) {
 
            throw new RuntimeException("请求方法执行异常！！");
 
        }
 
    }
 
}

add.jsp

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<%@ page contentType="text/html;charset=UTF-8" language="java" isELIgnored="false" %>
 
<%@ taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %>
 
<%@ taglib prefix="z" uri="http://mycompany.com" %>
 
<html>
 
<head>
 
    <title>测试页面</title>
 
</head>
 
<body>
 
 
 
<h1>测试</h1>
 
${mess}
 
 
 
</body>
 
</html>

测试展示

 

越努力越幸运

最后来点鸡汤吧，好久没说了，吃苦的年龄就不要选择安逸，别白了少年头，空悲切，人生赢在转折处，改变从现在开始，分享的越多，你的价值增值越大。。。。。。。。。

*****************************************************************************************************

我的博客园地址：https://www.cnblogs.com/zyx110/

posted @   泰斗贤若如  阅读(781)  评论(0)  编辑  收藏  举报
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