Java使用JDBC连接MySQL方法详解
2020-02-01 本文已影响0人
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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:
- 连接数据源,如:数据库。
- 为数据库传递查询和更新指令。
- 处理数据库响应并返回的结果。
2. JDBC 架构
分为双层架构和三层架构。
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:
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);
}
}