DriverManager

//1.加载驱动
//DriverManager.registerDriver(new com.mysql.jdbc.Driver());
//推荐这种写法加载驱动
Class.forName("com.mysql.jdbc.Driver");
 
Connection connection = DriverManager.getConnection(url, userName, passWord);
// connection代表数据库
// 数据库设置自动提交
// 事务提交
// 事务回滚
connection.setAutoCommit(true);
connection.commit();
connection.rollback();

  URL

String url = "jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=false";
 
// mysql默认端口3306
// 协议://主机地址:端口号/数据库名?参数1&参数2&参数3
// oracle默认端口1521
// jdbc:oracle:thin:@localhost:1521:sid

Statement 执行sql对象  、  PreparedStatement 执行sql对象

String sql = "SELECT * FROM users";//编写SQL
 
statement.executeQuery();//执行查询 返回ResultSet
statement.executeUpdate();//新增，删除，修改，都用这个，返回受影响的行数
statement.execute();//执行任何SQL

ResultSet 查询的结果集，封装了所有的查询结果

获得指定的数据类型

//在不知道列类型的情况下使用
resultSet.getObject();
//如果知道列类型，就使用指定的类型
resultSet.getString();
resultSet.getInt();
resultSet.getDouble();
resultSet.getBigDecimal();
resultSet.getFloat();
resultSet.getDate();
//...

遍历，指针

resultSet.beforeFirst();//移动到最前面
resultSet.afterLast();//移动到最后面
resultSet.next();//移动到下一个数据
resultSet.previous();//移动到前一行
resultSet.absolute(row);//移动到指定行

释放资源

resultSet.close();
statement.close();
connection.close();//消耗资源

---

statement对象

        jdbc中的statement对象用于向数据库发送SQL语句，想完成对数据库的增删改查，只需要通过这个对象向数据库发送增删改查语句即可。

        Statement对象的executeUpdate方法，用于向数据库发送增、删、改的SQL语句，executeUpdate执行完后，将会返回一个整数（即增删改语句导致了数据库几行数据发送了变化）。

        Statement.executeQuery方法用于向数据库发送查询语句，executeQuery方法返回代表查询结果的ResultSet对象。

CRUD操作-create

使用executeUpdate(String sql)方法完成数据添加操作，示例操作：

Statement statement = connection.createStatement();
String sql = "insert into user(...) values(...)";
int num = statement.executeUpdate(sql);
if (num > 0) {
    System.out.println("插入成功~");
}

CRUD操作-delete

Statement statement = connection.createStatement();
String sql = "delete from user where id=1";
int num = statement.executeUpdate(sql);
if (num > 0) {
    System.out.println("删除成功~");
}

CRUD操作-update

Statement statement = connection.createStatement();
String sql = "update user set name='' where name =''";
int num = statement.executeUpdate(sql);
if (num > 0) {
    System.out.println("修改成功~");
}

CRUD操作-read

Statement statement = connection.createStatement();
String sql = "SELECT * FROM users";
ResultSet resultSet = statement.executeQuery(sql);
while (resultSet.next()) {
    //根据获取列的数据类型，分别调用resultSet的相应方法映射到java对象中
}

例：

        提取工具类

        配置文件db.properties

driver=com.mysql.jdbc.Driver
url=jdbc:mysql://localhost:3306/jdbcstudy?useUnicode=true&characterEncoding=utf8&useSSL=false
username=root
password=123456

        JdbcUtils 

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.Properties;
 
 
public class JdbcUtils {
    private static String driver = null;
    private static String url = null;
    private static String username = null;
    private static String password = null;
 
    static {
        try {
            InputStream in = JdbcUtils.class.getClassLoader().getResourceAsStream("db.properties");
            Properties properties = new Properties();
            properties.load(in);
 
            driver = properties.getProperty("driver");
            url = properties.getProperty("url");
            username = properties.getProperty("username");
            password = properties.getProperty("password");
 
            //驱动只用加载一次
            Class.forName(driver);
        } catch (IOException e) {
            e.printStackTrace();
        } catch (ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
 
    /**
     * 获取连接
     */
    public static Connection getConnection() throws SQLException {
        return DriverManager.getConnection(url, username, password);
    }
 
    /**
     * 释放资源
     */
    public static void release(Connection con, Statement st, ResultSet rs) {
        if (rs != null) {
            try {
                rs.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (st != null) {
            try {
                st.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
        if (con != null) {
            try {
                con.close();
            } catch (SQLException e) {
                e.printStackTrace();
            }
        }
    }
}

        编写增、删、改的方法，executeUpdate

import com.yuan.lesson02.utils.JdbcUtils;
 
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class TestInsert {
    public static void main(String[] args) {
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
        try {
            con = JdbcUtils.getConnection();
            st = con.createStatement();
            String sql = "UPDATE INTO users(`id`,`name`,`password`,`email`,`birthday`)\n" +
                    "VALUES (4,'牛六','123456','niuliu@sina.com','1988-12-04')";
            int num = st.executeUpdate(sql);
            if (num > 0) {
                System.out.println("插入成功！");
            }
 
        } catch (SQLException e) {
            e.printStackTrace();
        } finally {
            JdbcUtils.release(con,st,rs);
        }
 
    }
}

import com.yuan.lesson02.utils.JdbcUtils;
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class TestDelete {
    public static void main(String[] args) {
        Connection con = null;
        Statement st = null;
        ResultSet rs = null;
 
        try {
            con = JdbcUtils.getConnection();
            st = con.createStatement();
            String sql = "DELETE FROM users WHERE `id`=4";
            int num = st.executeUpdate(sql);
            if(num > 0){
                System.out.println("删除成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally{
            JdbcUtils.release(con,st,rs);
        } 
    }
}

import com.yuan.lesson02.utils.JdbcUtils;
 
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class TestUpdate {
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
 
        try {
            connection = JdbcUtils.getConnection();
            statement = connection.createStatement();
            String sql = "UPDATE users SET birthday='1990-12-01' WHERE id=1";
            int num = statement.executeUpdate(sql);
            if (num > 0){
                System.out.println("更新成功");
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.release(connection,statement,resultSet);
        }
    }

        查询

import com.yuan.lesson02.utils.JdbcUtils;
 
import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
 
public class TestSelect {
    public static void main(String[] args) {
        Connection connection = null;
        Statement statement = null;
        ResultSet resultSet = null;
 
        try {
            connection = JdbcUtils.getConnection();
            statement = connection.createStatement();
            String sql = "SELECT * FROM users WHERE id=1";
            resultSet = statement.executeQuery(sql);
            while (resultSet.next()){
                System.out.println("id="+resultSet.getInt("id"));
                System.out.println("name="+resultSet.getString("name"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }finally {
            JdbcUtils.release(connection,statement,resultSet);
        }
    }
}