Java使用JDBC连接MySQL方法详解

2020-02-01  本文已影响0人  3823丶

1. 概述

Java数据库连接,(Java Database Connectivity,简称JDBC)是Java语言中用来规范客户端程序如何来访问数据库的应用程序接口,提供了诸如查询和更新数据库中数据的方法。JDBC也是Sun Microsystems的商标。我们通常说的JDBC是面向关系型数据库的。
  JDBC API 允许用户访问任何形式的表格数据,尤其是存储在关系数据库中的数据。

执行流程:

2. JDBC 架构

分为双层架构和三层架构。   
双层    

双层    
作用:此架构中,Java Applet 或应用直接访问数据源。
条件:要求 Driver 能与访问的数据库交互。
机制:用户命令传给数据库或其他数据源,随之结果被返回。
部署:数据源可以在另一台机器上,用户通过网络连接,称为 C/S配置(可以是内联网或互联网)。   
三层 
三层    
侧架构特殊之处在于,引入中间层服务。
流程:命令和结构都会经过该层。
吸引:可以增加企业数据的访问控制,以及多种类型的更新;另外,也可简化应用的部署,并在多数情况下有性能优势。
历史趋势: 以往,因性能问题,中间层都用 C 或 C++ 编写,随着优化编译器(将 Java 字节码 转为 高效的 特定机器码)和技术的发展,如EJB,Java 开始用于中间层的开发这也让 Java 的优势突显出现出来,使用 Java 作为服务器代码语言,JDBC随之被重视。

3. JDBC使用详解

3.1 通过使用第三方类实现

@Test
public void testConnection1() throws SQLException {
    Driver driver = new com.mysql.jdbc.Driver();

    String url = "jdbc:mysql://localhost:3306/test";

    Properties info = new Properties();
    info.setProperty("user", "root");
    info.setProperty("password", "root");
        
    Connection conn = driver.connect(url, info);
        
    System.out.println(conn.toString());
}

3.2 使用反射机制加载驱动

@Test
public void testConnection2() 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", "root");
    info.setProperty("password", "root");
        
    Connection conn = driver.connect(url, info);
        
    System.out.println(conn.toString());
}

3.3 使用DriverManager类优化代码

@Test
public void testConnection3() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
    Class clazz = Class.forName("com.mysql.jdbc.Driver");
    Driver driver = (Driver) clazz.newInstance();
        
    String url = "jdbc:mysql://127.0.0.1:3306/test";
    String user = "root";
    String password = "root";
        
    DriverManager.registerDriver(driver);
    Connection connection = DriverManager.getConnection(url, user, password);
        
    System.out.println(connection);
}

3.4 MySQL驱动使用静态代码块自动加载

@Test
public void testConnection3() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
    Class clazz = Class.forName("com.mysql.jdbc.Driver");
    Driver driver = (Driver) clazz.newInstance();
        
    String url = "jdbc:mysql://127.0.0.1:3306/test";
    String user = "root";
    String password = "root";
        
    DriverManager.registerDriver(driver);
    Connection connection = DriverManager.getConnection(url, user, password);
        
    System.out.println(connection);
}

MySQL静态源码如下:

MySQL静态源码

3.5 终极配置文件版

优点:
1、实现了数据与代码的分离,是一种解耦的方式;
2、可移植性大大增强;
3、如果修改配置信息,可以避免程序重新打包;

jdbc.properties文件

user=root
password=root
url=jdbc:mysql://localhost:3306/test
driverClass=com.mysql.jdbc.Driver
@Test
public void testConnection5() throws IOException, ClassNotFoundException, SQLException {
    InputStream resource = ConnectionTest.class.getClassLoader().getResourceAsStream("jdbc.properties");
        
    Properties properties = new Properties();
    properties.load(resource);
        
    String user = properties.getProperty("user");
    String password = properties.getProperty("password");
    String url = properties.getProperty("url");
    String driverClass = properties.getProperty("driverClass");
        
    Class.forName(driverClass);
        
    Connection connection = DriverManager.getConnection(url, user, password);
        
    System.out.println(connection);
}

3.6 完整代码

import java.io.IOException;
import java.io.InputStream;
import java.net.URL;
import java.sql.Connection;
import java.sql.Driver;
import java.sql.DriverManager;
import java.sql.SQLException;
import java.util.Properties;

import org.junit.Test;

public class ConnectionTest {
    @Test
    public void testConnection1() throws SQLException {
        
        Driver driver = new com.mysql.jdbc.Driver();
        
        String url = "jdbc:mysql://localhost:3306/test";
        Properties info = new Properties();
        info.setProperty("user", "root");
        info.setProperty("password", "root");
        
        Connection conn = driver.connect(url, info);
        
        System.out.println(conn.toString());
    }
    
    @Test
    public void testConnection2() 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", "root");
        info.setProperty("password", "root");
        
        Connection conn = driver.connect(url, info);
        
        System.out.println(conn.toString());
    }
    
    @Test
    public void testConnection3() throws InstantiationException, IllegalAccessException, ClassNotFoundException, SQLException {
        Class clazz = Class.forName("com.mysql.jdbc.Driver");
        Driver driver = (Driver) clazz.newInstance();
        
        String url = "jdbc:mysql://127.0.0.1:3306/test";
        String user = "root";
        String password = "root";
        
        DriverManager.registerDriver(driver);
        Connection connection = DriverManager.getConnection(url, user, password);
        
        System.out.println(connection);
    }
    
    @Test
    public void testConnection4() throws ClassNotFoundException, SQLException {
        
        Class.forName("com.mysql.jdbc.Driver");
        
        String url = "jdbc:mysql://127.0.0.1:3306/test";
        String user = "root";
        String password = "root";
        
        Connection connection = DriverManager.getConnection(url, user, password);
        
        System.out.println(connection);
    }
    
    @Test
    public void testConnection5() throws IOException, ClassNotFoundException, SQLException {
        InputStream resource = ConnectionTest.class.getClassLoader().getResourceAsStream("jdbc.properties");
        
        Properties properties = new Properties();
        properties.load(resource);
        
        String user = properties.getProperty("user");
        String password = properties.getProperty("password");
        String url = properties.getProperty("url");
        String driverClass = properties.getProperty("driverClass");
        
        Class.forName(driverClass);
        
        Connection connection = DriverManager.getConnection(url, user, password);
        
        System.out.println(connection);
    }
}
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