手写JDBC

1. 将数据库、驱动信息存储在配置文件

configure.properties

url=jdbc:mysql://localhost:3306/数据库名?serverTimezone=GMT&useSSL=false
user=用户名，一般是root
password=数据库密码
driver=com.mysql.cj.jdbc.Driver

2. JDBC工具类

MyDBUtil.java

import java.io.InputStream;
import java.sql.*;
import java.util.Properties;

/**
 * 手写实现JDBC工具类
 * @author Nemo
 * @version 1.0
 * @date 2019/4/10
 */
public class MyDBUtil {
    private static String url;
    private static Properties proterties;
    
    // 注册驱动
    static {
        proterties = new Properties;
        
        InputStream configureStream = MyDBUtil.class.getClassLoader.getResourceAsStream("configure.proterties");
        try {
            properties.load(configureStream);
            String driver = properties.getProperty("driver");
            class.forName(driver);
            
            url = properties.getProperty("url");
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
    
    // 获取连接
    public static Connection getConnection() throw SQLException{
        return DriverManager.getConnection(url, properties);
    }
    
    // 释放资源
    public static void release(Statement statement, Connection connection, ResultSet resultSet) {
        closeQuietly(statement);
        closeQuietly(connection);
        closeQuietly(resultSet);
    }
    // 重载释放资源
    public static void release(Statement statement, Connection connection) {
        closeQuietly(statement);
        closeQuietly(connection);
    }
    
    private static void closeQuietly(AutoCloseable closeable) {
        if (closeable != null) {
            try {
                closeable.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

3. 以实现数据库事务为例，演示工具类的使用

TranctionTest.java

import org.junit.Test;

import java.sql.Connection;
import java.sql.SQLException;
import java.sql.Savepoint;
import java.sql.Statement;

/**
 * 以数据库事务为例进行演示
 * @author Nemo
 * @version 1.0
 * @date 2019/4/13
 */
public class TranctionTest {
    @Test
    public void traction() throws SQLException {
        Connection conn = null;
        Statement stm = null;
        Savepoint savepoint = null;
        try {
            // 获取数据库连接
            conn = MyDBUtil.getConnection();
            
            // 关闭数据库自动commit功能
            conn.setAutoCommit(false);
            
            // 建立sql语句
            stm = conn.cteateStatement();
            
            // zs给lisi转账100
            String sql1 = "update user set money=money-100 where name='zs';";
            String sql2 = "update user set money=money+100 where name='lisi';";
            
            // wangwu给lisi转账100
            String sql3 = "update user set money=money-100 where name='wangwu';";
            String sql4 = "update user set money=money+100 where name='lisi';";
            
            // 提交sql语句
            stm.executeUpdate(sql1);
            stm.executeUpdate(sql2);
            
            // 设置savepoint
            savepoint = conn.setSavepoint();
            
            int i = 1/0;
            
            stm.executeUpdate(sql3);
            stm.executeUpdate(sql4);
            
            conn.commit();
        } catch (Exception e) {
            conn.rollback(savepoint);
            conn.commit();
        } finally {
            MyDBUtil.release(statement, connection);
        }
    }
}