用jsp和servlet实现增删改查

最终实现的效果如下（并没有加上css修饰，就实现最简单功能）
在这里插入图片描述
先要事先新建一个jsp文件，和4个servler文件，4个是调用ajax方法给予回调函数，一个是sql方法函数我命名为SqlConnection

jsp

<%@ page language="java" contentType="text/html; charset=UTF-8"
	pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
<script type="text/javascript">
	function checkUsername(increase) {
		createRequest("Mysql?increase=" + increase.value);
	}
	function checkUsername2(strikeout) {
		createRequest("Mysql2?strikeout=" + strikeout.value);
	}
	function checkUsername3(modify) {
		createRequest("Mysql3?modify=" + modify.value);
	}
	function checkUsername4(inquire) {
		createRequest("Mysql4?inquire=" + inquire.value);
	}

	function createRequest(url) {

		http_request = new XMLHttpRequest();
		http_request.onreadystatechange = function() {
			if (http_request.readyState == 4) {

				if (http_request.status == 200) {
					//alert("1");
					if (http_request.responseText == 1) {
						alert("列表中存在此数据");
					}
					if (http_request.responseText == 2) {
						alert("列表中不存在此数据");
					}
				}
			}

		};

		http_request.open("POST", url, true);
		http_request.send(null);

	}
</script>
</head>
<body>
	<form action="">
		<li><input name="increase" type="text" value=""> <input
			type="button" class="login-btn" value="增"
			onclick="checkUsername(this.form.increase)"></li>
		<li><input type="text" name="strikeout" value=""> <input
			type="button" class="login-btn" value="删"
			onclick="checkUsername2(this.form.strikeout)"></li>
		<li><input type="text" name="modify" value=""> <input
			type="button" class="login-btn" value="改"
			onclick="checkUsername3(this.form.modify)"></li>
		<li><input type="text" name="inquire" value=""> <input
			type="button" class="login-btn" value="查"
			onclick="checkUsername4(this.form.inquire)"></li>
	</form>
</body>
</html>

Mysql.java(增，全部代码)

package com.lyq;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;




/**
 * Servlet implementation class Mysql
 */
@WebServlet("/Mysql")
public class Mysql extends HttpServlet {
	private static final long serialVersionUID = -286431665770754787L;
    
	
		

		public void doGet(HttpServletRequest request, HttpServletResponse response)
				throws ServletException, IOException {
			this.doPost(request, response);
		}
	
	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
	
		PrintWriter out = response.getWriter();
		response.setContentType("text/html");
		response.setCharacterEncoding("UTF-8");
		
		
		// 获取表单参数
		request.setCharacterEncoding("UTF-8");
		String increase= new String(request.getParameter("increase").getBytes("utf-8"),"UTF-8");
		
		String sql2 = new String("INSERT INTO t_student (c_sn) VALUES ('"+increase+"')");
		ResultSet rs=SqlConnection.add(sql2);
		System.out.println(sql2);
		
		
		try{
			if(rs.next()) {
				out.println(1); //no
			}
			
			else {
				out.println(2);//yes
		
				
			}
		}catch(Exception e) {
			out.println(3);//no
		}
		
		out.flush();
		out.close();
	}

}

Mysql2（删，主要代码）

	String strikeout= new String(request.getParameter("strikeout").getBytes("utf-8"),"UTF-8");
		
		String sql3 = new String("delete from t_student where c_sn='"+strikeout+"'");
		ResultSet rs=SqlConnection.delete(sql3);

Mysql3（改，主要代码）

			String modify= new String(request.getParameter("modify").getBytes("utf-8"),"UTF-8");
		
		String sql4 = new String("update t_student set c_sn='"+modify+"'where id='448'");
		ResultSet rs=SqlConnection.update(sql4);

Mysql4（查，主要代码）

		String inquire= new String(request.getParameter("inquire").getBytes("utf-8"),"UTF-8");
		
		String sql = new String("select * from t_student where c_sn='"+ inquire +"'");

SqlConnection.java

package com.lyq;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;

public class SqlConnection {

    public static final String url = "jdbc:mysql://localhost:3306/jwdb?useUnicode=true&characterEncoding=UTF-8";
    public static final	String username = "root";
    public static final String password = "761027";
    
    public static Connection conn =null;
    public static Statement stmt = null;
    public static ResultSet rs = null;
    
    //安装驱动
    
    
    
    public static void init() {
    	if(conn==null) {
    		try {
        		
    			Class.forName("com.mysql.jdbc.Driver");
    			conn = DriverManager.getConnection(url,username,password);
    			if(conn!=null){
    				System.out.println("数据库连接正常");
    			}else{
    				System.out.println("数据库连接失败");
    			}
    		} catch (Exception e) {
    			e.printStackTrace();
    		}
    	}
    }
    
    //查询方法
    public static ResultSet query(String sql){
    	init();
    	try {
    		System.out.println(conn);
			stmt = conn.createStatement();
			
			rs = stmt.executeQuery(sql);
			
			

		} catch (SQLException e) {
			e.printStackTrace();
		}
		finally{
			
			//relaseResourse();
			
		}
    	return rs;
    }
    
    //释放资源
    public static void relaseResourse(){
    	try {
			if(rs!=null){
				rs.close();
				rs = null;
			}
			if(stmt!=null){
				stmt.close();
				stmt = null;
			}
			if(conn!=null){
				conn.close();
				conn=null;
			}
		} catch (Exception e) {
			e.printStackTrace();
		}
		
    }
     //增加数据操作
    public static ResultSet add(String sql2){
    	init();
    	try {
			stmt = conn.createStatement();
			
		    int result = stmt.executeUpdate(sql2);
			
			 if(result>0){ System.out.println("添加数据成功");
			 }else{
			 System.out.println("添加数据失败"); }
			
		} catch (SQLException e) {
			e.printStackTrace();
		}finally{
			//relaseResourse();
		}
		return rs;
    	
    }
    //删除数据操作方法
    public static ResultSet delete(String sql3){
    	init();
       try {
		stmt = conn.createStatement();
		int result = stmt.executeUpdate(sql3);
		//执行
		
		if(result>0){
			System.out.println("删除成功");
		}else{
			System.out.println("删除数据失败");
			
		}
		
	} catch (SQLException e) {
		e.printStackTrace();
	}finally{
		//relaseResourse();
	}
	return rs;
       
    }
    
    //修改方法
    public static ResultSet update(String sql4){
    	init();
    	try {
			stmt = conn.createStatement();
			//String sql = "update user set name = 'xiaoxiao' where id='6'";
			int result = stmt.executeUpdate(sql4);
			if(result>0){
				System.out.println("修改成功");
			}else{
				System.out.println("修改数据失败");
				
			}
		} catch (SQLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}finally{
			//relaseResourse();
		}
		return rs;
    	
    }
    

}

原文链接：https://blog.csdn.net/hh1297240789/article/details/88748083