java JDBC

DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
//注意，mysql5时用com.mysql.jdbc.Driver
//但是mysql8以后要用com.mysql.cj.jdbc.Driver

Connection conn = DriverManager.getConnection(url, user, password);
/*
user和password没什么好说的
url的格式为：
"jdbc:mysql://localhost:3306/数据库名？useSSL=false&serverTimezone=UTC"
但是在mysql5的时候，url要写成：
"jdbc:mysql://localhost:3306/数据库名"
*/

Statement st = conn.createStatement();

String sql = "select * from users;";
ResultSet rs = st.executeQuery(sql);

while(rs.next()) {
    String name = rs.getString("name");
    int age = rs.getInt("age");

    System.out.println("name=" + name + ", age=" + age);
}

rs.close();
st.close();
conn.close();

package com.wbytts.util;

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.Statement;
import java.util.Properties;

public class JDBCUtils {
    
    static String driverClass = null;
    static String url = null;
    static String name = null;
    static String password = null;
    
    static {        
        try {
            //建立一个属性配置对象
            Properties properties = new Properties();
            //使用类加载器，去获取src底下的文件
            InputStream is = JDBCUtils.class.getClassLoader().getResourceAsStream("jdbc.properties");
            //导入输入流
            properties.load(is);
            //读取属性
            driverClass = properties.getProperty("driverClass");
            url = properties.getProperty("url");
            name = properties.getProperty("name");
            password = properties.getProperty("password");
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    
    public static Connection getConn() {    
        Connection conn = null;
        try {
            Class.forName(driverClass);
            conn = DriverManager.getConnection(
                    "jdbc:mysql://localhost:3306/test?useSSL=false&serverTimezone=UTC", 
                    name, password);
        } catch (Exception e) {
            e.printStackTrace();
        }
        
        return conn;
    }
    
    /**
     *  释放资源
     * @param conn
     * @param st
     * @param rs
     */
    public static void release(Connection conn, Statement st, ResultSet rs) {
        closeRs(rs);
        closeSt(st);
        closeConn(conn);
    }
    
    public static void release(Connection  conn, Statement st) {
        closeSt(st);
        closeConn(conn);
    }
    
    private static void closeRs(ResultSet rs) {
        try {
            if(rs != null) {
                rs.close();
            }
            rs = null;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            rs = null;
        }
    }
    
    private static void closeSt(Statement st) {
        try {
            if(st != null) {
                st.close();
            }
            st = null;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            st = null;
        }
    }
    
    private static void closeConn(Connection conn) {
        try {
            if(conn != null) {
                conn.close();
            }
            conn = null;
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            conn = null;
        }
    }
}