Javaweb实现数据库简单的增删改查

JDBC介绍

JDBC工作原理

JDBC应用编程

1、准备工作

2、JDBC编程步骤

（1）注册JDBC驱动程序

Class.forName("com.mysql.jdbc.Driver");

或者DriverManager.registerDriver(new com.mysql.jdbc.Driver());

（2）建立数据库连接Connection

String url="jdbc:mysql://localhost:3306/db";

String user="root";

String password="mysqladmin";

Connection conn=DriverManager.getConnection(url, user, password);

（3）创建并执行SQL语句Statement实际应用我们用的是PreparedStatement 

Statement stmt=conn.createStatement(); //conn为上一步创建的连接

String sql="select * from user";

ResultSet rs=stmt.executeQuery(sql);

（4）处理执行结果集ResultSet

while(rs.next()){ //rs为上一步返回的结果集

    String name=rs.getString("username");

    String pass=rs.getString("password");

    System.out.printf("用户名：%s,口令：%s\n",name,pass);

}

结果集的getString(String columnLabel) ，该方法根据表中的列名获取当前记录指定列的值

（5）释放资源

rs.close();      //关闭结果集

stmt.close();  //关闭语句

conn.close();  //关闭连接

JDBC实现增加、删除和修改操作

开发工具：myeclipse2014、MySQL8.0【MySQL】MySQL8.0安装教程： https://blog.csdn.net/Trista_1999/article/details/132678207

文件结构：

User类：

package javabean;
 
public class User {
	private String username;
	private String password;
	public String getUsername() {
		return username;
	}
	public void setUsername(String username) {
		this.username = username;
	}
	public String getPassword() {
		return password;
	}
	public void setPassword(String password) {
		this.password = password;
	}
}

UserDAO类：实现数据库连接和增删改查

package javabean;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
public class UserDAO {
	//查询
	public static List searchAll() throws ClassNotFoundException, SQLException{
		
		Listusers=new ArrayList<>();
		//注册JDBC驱动程序
		Connection conn = getConnection();
		//创建并执行SQL语句PreparedStatement
		String sql="select* from user";
		PreparedStatement ps=conn.prepareStatement(sql);
		
		ResultSet rs = ps.executeQuery();
		//处理执行结果集ResultSet
		while(rs.next()){
			String username = rs.getString("username");
			String password = rs.getString("password");
			User user=new User();
			user.setUsername(username);
			user.setPassword(password);
			users.add(user);
		}
		//释放资源
		rs.close();
		ps.close();
		conn.close();
		
		return users;
	}
	//getConnection函数，注册JDBC驱动程序并建立数据库连接Connection
	private static Connection getConnection() throws ClassNotFoundException,
			SQLException {
		//注册JDBC驱动程序
		Class.forName("com.mysql.cj.jdbc.Driver");
		String url="jdbc:mysql://localhost:3306/db";
		//建立数据库连接Connection
		Connection conn=DriverManager.getConnection(url, "root", "root");
		return conn;
	}
	//添加
	public boolean add(User user) throws SQLException, ClassNotFoundException{
		Connection conn = getConnection();
		String sql="insert into user(username,password) values (?,?)";
		
		PreparedStatement ps=conn.prepareStatement(sql);
		ps.setString(1, user.getUsername());
		ps.setString(2, user.getPassword());
		
		System.out.print(sql);
		int res=ps.executeUpdate();
		ps.close();
		conn.close();
		return res==1;
	}
	//更新
	public boolean update(User user) throws SQLException, ClassNotFoundException{
		Connection conn = getConnection();
		String sql="update user  password=? where username=?";
		
		PreparedStatement ps=conn.prepareStatement(sql);
		ps.setString(1, user.getPassword());
		ps.setString(2, user.getUsername());
		
		System.out.print(sql);
		int res=ps.executeUpdate();
		ps.close();
		conn.close();
		return res==1;
	}
	//删除
	public boolean delete(String username) throws SQLException, ClassNotFoundException{
		Connection conn = getConnection();
		String sql="delete from user where username=?";
		
		PreparedStatement ps=conn.prepareStatement(sql);
		ps.setString(1, username);
		
		System.out.print(sql);
		int res=ps.executeUpdate();
		ps.close();
		conn.close();
		return res==1;
	}
 
	
}