用jsp和servlet实现增删改查

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"%>

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);

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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);

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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 +"'");

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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;
	
}

}