将JAVA程序连接至数据库****
1. 下载 mysql 驱动 jar 包
2. 添加入JAVA程序文件中
3. 添加到 library 库中
获取数据库的五种方式
mysqL驱动5.1.6可以无需CLass . forName(“com.mysql.jdbc.Driver”);
从jdk1.5以后使用了jdbc4,不再需要显示调用class.forName()注册驱动而是自动调用驱动jar包下META-INF\services\java .sql.Driver文本中的类名称去注册
建议还是写上 CLass . forName(“com.mysql.jdbc.Driver”),更加明确 `package com.ftn.jdbc.myjdbc;
//数据库的不同连接方式
import com.mysql.cj.jdbc.Driver;
import org.junit.jupiter.api.Test;
import java.io.FileInputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;
public class JdbcConn {
public static void main(String[] args) {
}
//方式一
//直接加载Driver对象，获取连接
@Test
public void connect01() throws SQLException {
Driver driver = new Driver();
Properties properties = new Properties();
properties.setProperty("user","root");
properties.setProperty("password","122800");
Connection connect = driver.connect("jdbc:mysql://localhost:3306/db_03", properties);
System.out.println("第三种连接方式：" + connect);
connect.close();
}
//方式二
//使用反射加载 Driver 类，动态加载，更加灵活，减少依赖性
@Test
public void connect02() throws Exception {
Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
Driver driver =(Driver) aClass.newInstance();
//创建 url，user和 password
Properties properties = new Properties();
properties.setProperty("user","root");
properties.setProperty("password","122800");
Connection connect = driver.connect("jdbc:mysql://localhost:3306/db_03", properties);
System.out.println("第三种连接方式：" + connect);
connect.close();
}
//方式三
//使用DriverManager代替Driver进行统一管理
@Test
public void connect03() throws Exception {
//使用反射加载 Driver
Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
Driver driver = (Driver) aClass.newInstance();
//创建 url，user和 password
String url = "jdbc:mysql://localhost:3306/db_03";
String user = "root";
String password = "122800";
DriverManager.registerDriver(driver); //注册 Driver 驱动
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第三种连接方式：" + connection);
connection.close();
}
//方式四
//使用 Class.forName 自动完成注册驱动，简化代码
/*
1. mysqL驱动 5.1.6可以无需 CLass . forName("com.mysql.jdbc.Driver");
2. 从jdk1.5以后使用了jdbc4,不再需要显示调用class.forName()注册驱动而是自动调用驱动
jar包下 META-INF\services\java .sql.Driver文本中的类名称去注册
3. 建议还是写上CLass . forName("com.mysql.jdbc.Driver"), 更加明确
*/
@Test
public void connect04() throws Exception {
//使用反射加载 Driver
/*
Driver 类源码中的静态代码块
1. 在类加载时，会执行 DriverManager.registerDriver(new Driver());
2. 即 Driver 会自动注册
static {
try {
DriverManager.registerDriver(new Driver());
} catch (SQLException var1) {
throw new RuntimeException("Can't register driver!");
}
}
*/
Class<?> aClass = Class.forName("com.mysql.cj.jdbc.Driver");
//创建 url，user和 password
String url = "jdbc:mysql://localhost:3306/db_03";
String user = "root";
String password = "122800";
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第四种方式：" + connection);
connection.close();
}
//方式五
//在方式四基础上改进，增加配置文件，让连接 mysql 更加灵活
@Test
public void connect05() throws Exception {
//通过 Properties 对象获取配置文件的信息
Properties properties = new Properties();
properties.load(new FileInputStream("src\mysql.properties"));
//获取相关的值
String url = properties.getProperty("url");
String user = properties.getProperty("user");
String password = properties.getProperty("password");
String driver = properties.getProperty("driver");
Class<?> aClass = Class.forName(driver);
Connection connection = DriverManager.getConnection(url, user, password);
System.out.println("第五种方式：" + connection);
connection.close();
}
}`
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