[大数据]JDBC笔记第一天

package connection;
import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
//url="jdbc:mysql://localhost:3306/test"  test指的是数据库
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

import org.junit.Test;



public class ConnectionText {
    @Test
    public void test() throws SQLException{
    	//方式一
    	 Driver d = new com.mysql.jdbc.Driver();
    	 String url = "jdbc:mysql://localhost:3306/test";
         Properties info = new Properties();
         info.setProperty("user", "mysqlChen");
         info.setProperty("password", "1234");
         Connection conn =  d.connect(url, info);
         System.out.println(conn);
         
    }
    //方式二
     @Test
     public void test1() throws ClassNotFoundException, InstantiationException, IllegalAccessException, SQLException {
    	 Class clazz = Class.forName("com.mysql.jdbc.Driver");
    	 Driver driver = (Driver) clazz.newInstance();
    	 String url = "jdbc:mysql://localhost:3306/test";
    	 Properties info = new Properties();
         info.setProperty("user", "mysqlChen");
         info.setProperty("password", "1234");
         Connection conn =  driver.connect(url, info);
         System.out.println(conn);
     }
     //方式三：使用driverMannager 替换Driver
     @Test
     public void test3() throws Exception {
    	 //1.获取Driver实现类的对象
    	 Class clazz = Class.forName("com.mysql.jdbc.Driver");
    	 Driver driver = (Driver) clazz.newInstance();
    	 //2.提供另外三个链接的基本信息
    	 String url ="jdbc:mysql://localhost:3306/test";
    	 String user = "mysqlChen";
    	 String password="1234";
    	 	//注册驱动
    	 DriverManager.registerDriver(driver);
    	 //获取链接
    	 Connection connection = DriverManager.getConnection(url, user, password);
    	 System.out.println(connection);
     }
     //方式四：在3的基础上优化
     @Test
     public void test4() throws Exception {
    	 //2.提供另外三个链接的基本信息
    	 String url ="jdbc:mysql://localhost:3306/test";
    	 String user = "mysqlChen";
    	 String password="1234";
    	 //2.获取Driver实现类的对象
    	 Class.forName("com.mysql.jdbc.Driver");
//    	 Driver driver = (Driver) clazz.newInstance();
//    	 //注册驱动，相较于方式三可以省略如下的操作
    	 //在mysql的Driver中声明了静态代码块自动帮我们注册驱动
//    	 DriverManager.registerDriver(driver);
    	 //3.获取链接
    	 Connection connection = DriverManager.getConnection(url, user, password);
    	 System.out.println(connection);
     }
     //方式五：将数据库需要的4哥基本信息生命在配置文件中，通过读取配置文件的方式，获取连接
     /*
      * 好处
      * 1.实现了数据与代码的法分离，实现了解耦
      * 2.如果需要修改配置文件信息，就可以避免程序重新打包。	
      * */
     @Test
     public void test5() throws Exception {
    	 //1.读取配置文件中的4个基本信息
    	 InputStream is = ConnectionText.class.getClassLoader().getResourceAsStream("jdbc.properties");
    	 Properties properties = new Properties();
    	 properties.load(is);
    	 String user = properties.getProperty("user");
    	 String password = properties.getProperty("password");
    	 String url =properties.getProperty("url");
    	 String driverClass = properties.getProperty("driverClass");
    	 //2.加载驱动
    	 Class.forName(driverClass);
    	 Connection connection = DriverManager.getConnection(url,user,password);
    	 System.out.println(connection);
     }
}

创建数据库与java程序的五种方式，以及statement 的弊端

statment：

Scanner scan = new Scanner(System.in);
//
//		System.out.print("用户名：");
//		String userName = scan.nextLine();
//		System.out.print("密   码：");
//		String password = scan.nextLine();
//
//		// SELECT user,password FROM user_table WHERE USER = '1' or ' AND PASSWORD = '
//		// ='1' or '1' = '1';
//		String sql = "SELECT user,password FROM user_table WHERE USER = '" + userName + "' AND PASSWORD = '" + password
//				+ "'";
//		User user = get(sql, User.class);
//		if (user != null) {
//			System.out.println("登陆成功!");
//		} else {
//			System.out.println("用户名或密码错误！");
//		}

user,password FROM user_table WHERE USER = '1' or ' AND PASSWORD = '
//		// ='1' or '1' = '1'

这段代码粘贴到mysql中显示就是statment的弊端

总体来说理解方式五即可