JDBC

本质:是官方定义的一套操作所有关系型数据库的规则,即接口,各个数据库厂商去实现这套接口,我们可以使用这套接口编程,真正执行的代码是驱动jar包中的实现类;

快速入门

• 导入jar包
• 实现案例

    public static void main(String[] args){
        Connection connection = null;
        Statement statement = null;
        //注册驱动
        try {
            Class.forName("com.mysql.cj.jdbc.Driver");
            //获取数据库连接对象
            connection = DriverManager.getConnection("jdbc:mysql://localhost:3306/test", "root", "root");
            //创建sql
            String sql = "insert into t_student values (null,'张三')";
            //获取执行sql的对象
            statement = connection.createStatement();
            //执行sql
            int i = statement.executeUpdate(sql);
            if (i > 0){
                System.out.println("运行成功");
            }else {
                System.out.println("运行失败");
            }
        } catch (ClassNotFoundException | SQLException e) {
            e.printStackTrace();
        } finally {
            //释放资源
            //避免空指针
            if (statement != null){
                try {
                    statement.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
            if (connection != null){
                try {
                    connection.close();
                } catch (SQLException throwables) {
                    throwables.printStackTrace();
                }
            }
        }
    }

JDBC各个对象

DriverManager 驱动管理对象

• 注册驱动
• 获取数据库链接

Connection 数据库连接对象

• 获取执行的sql对象
• 管理事务

Statement 执行sql对象

• 执行sql
  注意 : 真实开发会使用preparedStatement对象;
  防止sql注入,效率更高;

JDBCUtils

src下新建jdbc.properties

url=jdbc:mysql://localhost/test
user=root
password=root
driver=com.mysql.jdbc.Driver

import java.io.FileReader;
import java.io.IOException;
import java.net.URL;
import java.sql.*;
import java.util.Properties;

public class JDBCUtils {
    private static String URL;
    private static String USER;
    private static String PASSWORD;

    static {
        try {
            //创建properties对象
            Properties properties = new Properties();
            //获取scr路径下的配置文件
            ClassLoader classLoader = JDBCUtils.class.getClassLoader();
            URL resources = classLoader.getResource("jdbc.properties");
            String path = resources.getPath();
            //加载配置文件
            properties.load(new FileReader(path));
            //获得数据
            URL = properties.getProperty("url");
            USER = properties.getProperty("user");
            PASSWORD = properties.getProperty("password");
            Class.forName(properties.getProperty("driver"));
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }


    public static Connection connection() throws SQLException {

        return DriverManager.getConnection(URL, USER, PASSWORD);

    }

    /**
     * 释放资源
     * @param st
     * @param conn
     */
    public static void close(Statement st, Connection conn){
        if(st != null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }

    /**
     * 释放资源
     * @param rs
     * @param st
     * @param conn
     */
    public static void close(ResultSet rs, Statement st, Connection conn){
        if (rs != null){
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if(st != null){
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (conn != null){
            try {
                conn.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}