纯JDBC代码连接实例 + 完整代码

Posted 2020-12-14 cugb

JDBC连接数据库实例

1、 数据库表

1.1、创建表

CREATE TABLE `users`(
`uid` INT NOT NULL AUTO_INCREMENT COMMENT ‘用户id‘,
`uname` VARCHAR(20) NOT NULL COMMENT ‘用户名‘,
`upass` VARCHAR(20) NOT NULL COMMENT ‘用户密码‘,
PRIMARY KEY (`uid`)
)ENGINE = INNODB DEFAULT CHARSET = utf8;

1.2、插入数据

INSERT INTO `users` (`uname`,`upass`) VALUES
(‘zhangwuji‘,‘123456‘),
(‘zhaomin‘,‘123456‘),
(‘zhouzhiruo‘,‘123456‘),
(‘xiaozhao‘,‘123456‘);

1.3、查看表

?

2、 java部分

2.1根据数据库表中的字段创建pojo对象

package com.cugb.pojo;

import lombok.ToString;

/**
 * @author huangjian
 * @data 2020/7/6 11:11
 */
public class Users {
    //用户id
    private  int uid;

    //用户名
    private String uname;

    //密码
    private String upass;

    public Users() {
    }

    public Users(int uid, String uname, String upass) {
        this.uid = uid;
        this.uname = uname;
        this.upass = upass;
    }

    public int getUid() {
        return uid;
    }

    public void setUid(int uid) {
        this.uid = uid;
    }

    public String getUname() {
        return uname;
    }

    public void setUname(String uname) {
        this.uname = uname;
    }

    public String getUpass() {
        return upass;
    }

    public void setUpass(String upass) {
        this.upass = upass;
    }

    @Override
    public String toString() {
        return "uid:" +  uid +  "	" +  "uname:" +  uname+  "	" +"upass:" +  upass;
    }
}

2.2、创建连接jdbc的工具类

package com.cugb.utils;

import java.sql.Connection;

import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;

import com.mysql.jdbc.Driver;

public class DBUTils {
	private static String url = "jdbc:mysql://localhost:3306/mybatis?characterEncoding=UTF8";
	private static String user = "root";
	private static String pass = "123456";
	
	static {
		try {
			new Driver();
		} catch (SQLException e) {
			e.printStackTrace();
		}
	}
	
	//连接数据库
	public static Connection getConnection()  {
		Connection conn =  null;
		try {
			
			conn = DriverManager.getConnection(url,user,pass);
		} catch (Exception e) {
			
			e.printStackTrace();
		}
		
	return conn;
	}
	
	//查询
	public static Object[] Query(String sql) {
		Connection conn = getConnection();
		PreparedStatement pst =null;
		ResultSet rs = null;
		try {
			pst = conn.prepareStatement(sql);
		
			rs = pst.executeQuery();
		} catch (SQLException e) {
			e.printStackTrace();
		}
		Object[] obj = new Object[]{rs,pst,conn};
		return obj;	
	}
	
	//增删改
	public static boolean DML(String sql, Object[] object) {
		Connection conn = getConnection();
		PreparedStatement pst = null;
		Boolean b = false;
		try {
			pst = conn.prepareStatement(sql);
			for(int i=0; i<object.length;i++){
				pst.setObject(i+1, object[i]);
			}
			
			b = pst.executeUpdate()==1;
		} catch (SQLException e) {	
			e.printStackTrace();
		}
		
		close(conn,pst,null);
	
	return b;
	}
	
	//关闭资源
	public static void close(Connection conn,PreparedStatement pst,ResultSet rs){
		try{
			if(rs != null && !rs.isClosed()) {
				rs.close();
			}
			if(pst != null && !pst.isClosed()){
				pst.close();
			}
			if(conn != null && !conn.isClosed()){
				conn.close();
			}
			
		}catch(Exception e){
			e.printStackTrace();
		}
	}
}

2.3、dao层创建接口，并添加增、删、改、查等方法

import com.cugb.pojo.Users;


import java.util.ArrayList;

public interface UsersDao {

	//查询用户
	public ArrayList<Users> queryUsers(String sql);

	//添加用户
	public boolean addUser(Users user);

	//修改用户
	public boolean changeUser(String sql,Object[] obj);
	

}

dao层创建接口实现类，并重写接口的方法

package com.cugb.dao;

import com.cugb.pojo.Users;
import com.cugb.utils.DBUTils;

import java.sql.Connection;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.util.ArrayList;

/**
 * @author huangjian
 * @data 2020/7/6 11:37
 */
public class UsersDaoImpl implements UsersDao {
    //查询用户
    public ArrayList<Users> queryUsers(String sql){
        Object[] obj = DBUTils.Query(sql);

        ResultSet rs = (ResultSet)obj[0];

        ArrayList<Users> list = new ArrayList<Users>();
        try {
            while(rs.next()){
                int uid = rs.getInt(1);
                String uname = rs.getString(2);
                String upass = rs.getString(3);

                Users user = new Users(uid,uname,upass);

                list.add(user);
            }
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        PreparedStatement pst = (PreparedStatement)obj[1];
        Connection conn = (Connection)obj[2];

        DBUTils.close(conn, pst, rs);
        return list;
    }

    //添加用户
    public boolean addUser(Users user) {
        String sql = "insert into Users (uname,upass values (?,?)";
        Object[] obj = new Object[]{user.getUname(),user.getUpass()};
        boolean flag = DBUTils.DML(sql, obj);

        return flag;
    };

    //修改用户
    public boolean changeUser(String sql,Object[] obj) {

        boolean flag = DBUTils.DML(sql, obj);

        return flag;
    }
}

2.4、测试类查询功能

package com.cugb.test;

import com.cugb.dao.UsersDaoImpl;
import com.cugb.pojo.Users;

import java.util.ArrayList;

/**
 * @author huangjian
 * @data 2020/7/6 11:49
 */
public class UsersTest {

    public static void main(String[] args) {
        UsersDaoImpl usersDao = new UsersDaoImpl();

        String sql = "select * from users";

        ArrayList<Users> list = usersDao.queryUsers(sql);

        for (Users users : list) {
            System.out.println(users);
        }
    }
}

3、结果

uid:1	uname:zhangwuji	upass:123456
uid:2	uname:zhaomin	upass:123456
uid:3	uname:zhouzhiruo	upass:123456
uid:4	uname:xiaozhao	upass:123456