标签：JDBC java String 18 08 sql mysql import public

JDBC

一，JDBC

数据的持久化

把数据永久的保存起来，主要的方式是存在硬盘上。

持久化的实现过程大部分是通过数据库来完成的

JDBC

1.数据库的驱动

导入外部驱动

需要引入mysql的驱动（jar包）

java.sql.Driver接口，所有驱动需要实现的接口

mysql： com.mysql.jabc.Driver

8.0版本：com.mysql.cj.jdbc.Driver

oracle：oracle.jdbc.driver.OracleDriver

反射加载驱动，Class.forName("com.mysql.cj.jdbc.Driver")

2.URL地址

jdbc协议

jdbc:mysql://主机地址 : 端口号/数据库名

jdbc:mysql://127.0.0.1:3306/jiruan?useUnicode=true&characterEncoding=utf8

8.0版本还需要传参useSSL=false&serverTimezone=UTC

oracle:

jdbc:oracle:thin:@主机名称:oracle端口:数据库名

sqlServer:

jdbc:sqlServer://127.0.0.1端口号:DatabaseName=xxx

3.用户名

用户名：root

4.密码

密码：123

二，连接数据库

执行数据库的DML（增删改查）

java中3个接口定义了对数据库的调用

Statement：用来执行静态sql语句并返回生成的对象
PreparedStatement：预编译
CallableStatement

import com.mysql.jdbc.Driver;
import org.testng.annotations.Test;

import java.lang.reflect.InvocationTargetException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Objects;

public class TestJDBC {
    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, InvocationTargetException, InstantiationException, IllegalAccessException, SQLException {
        String url = "jdbc:mysql://127.0.0.1:3306/jiruan?useUnicode=true&characterEncoding=utf8";
        String username = "root";
        String password = "123";
        // 驱动的全类名
        String driverName = "com.mysql.jdbc.Driver";
        // 架载驱动类
        Class clazz= Class.forName(driverName);
        // 实例化Driver对象
        Driver driver = (Driver) clazz.getDeclaredConstructor().newInstance();
        // 注册驱动
        DriverManager.registerDriver(driver);
        // 获取链接
        Connection connection = DriverManager.getConnection(url, username, password);
        System.out.println(Objects.nonNull(connection) ? "连接成功" : "连接失败");
    }


    // 简化版
    @Test
    public void test() throws ClassNotFoundException, SQLException {
        String url = "jdbc:mysql://127.0.0.1:3306/jiruan?useUnicode=true&characterEncoding=utf8";
        String username = "root";
        String password = "123";
        // 驱动的全类名
        String driverName = "com.mysql.jdbc.Driver";
        
        // 架载驱动类,也可以省略，因为spi机制会自动加载META-INF下的services下的java.sql.Driver文件
        Class clazz= Class.forName(driverName);
        
        // 获取链接
        Connection connection = DriverManager.getConnection(url, username, password);
        System.out.println(Objects.nonNull(connection) ? "连接成功" : "连接失败");

    }
    
    //优化版
    @Test
    public void test02() throws ClassNotFoundException, SQLException, IOException {

    /*
      使用属性文件的好处：
       1、实现了代码和数据的分离，如果需要修改配置信息，直接在属性文件中修改即可，不需要深入代码
       2、如果修改了配置信息，省去了编译的过程
     */
        Properties properties = new Properties();

        // 读取外部的properties属性文件
        // 记住就好，复制粘贴就好
        properties.load(TestJDBC.class.getClassLoader().getResourceAsStream("db.properties"));

        String url = properties.getProperty("mysql.url");
        String driverName = properties.getProperty("mysql.driverName");
        String username = properties.getProperty("mysql.username");
        String password = properties.getProperty("mysql.password");

//    // 1.加载驱动类
        Class.forName(driverName);
//    // 4.获取连接
        Connection connection = DriverManager.getConnection(url, username, password);
        System.out.println(connection);
        System.out.println(Objects.nonNull(connection) ? "数据库连接成功" : "数据库连接失败");

        //测试
        Statement stmt = null;
        stmt = connection.createStatement();
        // 2.执行sql语句
        String sql = "INSERT INTO teacher (name) VALUES ('Jay')";
        // 返回值是执行sql语句影响的行数
        int i = stmt.executeUpdate(sql);
        // 3.处理执行sql的返回值
        System.out.println(i);
        System.out.println("操作成功...");

        connection.close();
        stmt.close();
    }

    @Test
    public void test01(){
        // 1.获取连接
        Connection conn = null;
        Statement stmt = null;
        try {
            conn = GetConnection.test();
            System.out.println(conn);
            stmt = conn.createStatement();
            // 2.执行sql语句
            String sql = "INSERT INTO teacher (name) VALUES ('Jay')";
            // 返回值是执行sql语句影响的行数
            int i = stmt.executeUpdate(sql);
            // 3.处理执行sql的返回值
            System.out.println(i);
            System.out.println("操作成功...");
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            //GetConnection.close(conn,stmt);
        }
    }

    //查询
    @Test
    public void test03() throws SQLException {
        // 1.获取连接
        Connection conn = null;
        Statement stmt = null;
        ResultSet re = null;
        try {
            conn = GetConnection.test();
            System.out.println(conn);
            stmt = conn.createStatement();
            // 2.执行sql语句
            String sql = "select * from teacher";

            //返回结果集合
             re = stmt.executeQuery(sql);
            // ResultSet封装了结果集的对象
            while (re.next()){
                int id = re.getInt("id");//索引从1开始
                String name = re.getString("name");
                System.out.println(id + " " + name);
            }
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } finally {
            re.close();
            stmt.close();
            conn.close();
            //GetConnection.close(conn,stmt);
        }
    }
    
}

db.properties文件（放在src根目录下）

mysql.url = jdbc:mysql://127.0.0.1:3306/jiruan?useUnicode=true&characterEncoding=utf8
mysql.username = root
mysql.password = 123
mysql.driverName = com.mysql.jdbc.Driver

GetConnection（连接数据库封装类）

import java.io.IOException;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

public class GetConnection {
    public static Connection test(){
        Connection conn = null;
        Properties properties = new Properties();
        try {
            properties.load(GetConnection.class.getClassLoader().getResourceAsStream("db.properties"));
            String url = properties.getProperty("mysql.url");
            String driverName = properties.getProperty("mysql.driverName");
            String username = properties.getProperty("mysql.username");
            String password = properties.getProperty("mysql.password");
            Class.forName(driverName);
            conn = DriverManager.getConnection(url, username, password);
        } catch (IOException e) {
            throw new RuntimeException(e);
        } catch (SQLException e) {
            throw new RuntimeException(e);
        } catch (ClassNotFoundException e) {
            throw new RuntimeException(e);
        }
        return conn;
    }

}

案例：连接数据库改变数据库

Teacher类

package jdbc;

public class Teacher {
    private int id;
    private String name;

    public Teacher(int id, String name) {
        this.id = id;
        this.name = name;
    }

    public int getId() {
        return id;
    }

    public void setId(int id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        this.name = name;
    }
}

TeacherDao类

import java.sql.Connection;
import java.sql.ResultSet;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;

public class TeacherDao {

    Connection conn = null;
    Statement stmt = null;

    {
        conn = GetConnection.test();
        try {
            stmt = conn.createStatement();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }

    // 增删改
    public int update(String sql,Object ... args) throws SQLException {
        int i = stmt.executeUpdate(sql);
        conn.close();
        stmt.close();
        return i;
    }

    //查询所有
    public List<Teacher> queryAll(String sql,Object ... args) throws SQLException {
        List<Teacher> teachers = new ArrayList<>();
        ResultSet re = stmt.executeQuery(sql);
        while(re.next()){
            int id = re.getInt("id");
            String name = re.getString("name");
            Teacher teacher = new Teacher(id,name);
            teachers.add(teacher);
        }
        conn.close();
        stmt.close();
        return  teachers;
    }

}

实现类

import java.sql.SQLException;

public class TestTeacher {

    private static   TeacherDao teacherDao = new TeacherDao();

    public static void main(String[] args) throws SQLException {
        int update = teacherDao.update("delete from teacher where id =6 ");

    }
}

标签：JDBC,java,String,18,08,sql,mysql,import,public
From： https://www.cnblogs.com/shenmimao/p/16598439.html

2022-08-18 第二小组张晟源（JDBC）

JDBC

一，JDBC

数据的持久化

JDBC

二，连接数据库

案例：连接数据库改变数据库

相关文章

赞助商

阅读排行

2022-08-18 第二小组 张晟源（JDBC）

JDBC

一，JDBC

数据的持久化

JDBC

二，连接数据库

案例：连接数据库改变数据库

相关文章

赞助商

阅读排行

2022-08-18 第二小组张晟源（JDBC）