废话不多说，先直接上代码：
package com.study.jdbc.jdbc.create;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.Driver;
import java.sql.SQLException;
import java.util.Properties;
public class JdbcConnection {
public static void main(String[] args) throws Exception {
//Connection con = getSqlConnection();
JdbcConnection con = new JdbcConnection();
//Connection connection = con.getConnection();
Connection connection = con.getMysqlConnection();
System.out.println(con);
}
public static Connection getSqlConnection() {
//1.JDBC所需的四个参数4个准备：user,password,url,driverClass(连接数据库所需的驱动)
String url = "jdbc:mysql://localhost:3306/test";
String user = "root";
String password = "root";
String driverClass = "com.mysql.jdbc.Driver";//这个是mysql-connector-java-5.1.8-bin.jar包中的，不是JDK自带的Driver。
Connection connection = null;
try {
//2.加载JDBC驱动程序
Class.forName(driverClass);
//3.创建数据库连接:三种连接方案
//方案一：connection = DriverManager.getConnection(jdbcUrl);
//方案二：connection = DriverManager.getConnection(url,user,password);
//方案三：connection = DriverManager.getConnection(url,info);
Properties info = new Properties();
info.setProperty("user",user);//property的key必须是"user"
info.setProperty("password",password);//property的key必须是"password"
connection = DriverManager.getConnection(url,info);
return connection;
} catch (ClassNotFoundException e) {
//log.error("Not found driver class, load driver failed.");
} catch (SQLException e) {
//log.error("create db connection error,",e);
}
return null;
}
public Connection getConnection() throws Exception{
//1.准备连接数据库的4个字符串
//1).创建Properties对象
Properties info = new Properties();
//2).获取jdbc.properties对应的输入流
InputStream in = getClass().getClassLoader().getResourceAsStream("com/conf/properties/jdbc-conf.properties");
//3).加载2)对应的输入流
info.load(in);
//4).具体决定user、password、url、driver这4个字符串
String driverClass = info.getProperty("driverClass");
String jdbcUrl = info.getProperty("jdbcUrl");
String user = info.getProperty("user");
String password = info.getProperty("password");
/**
* Driver实现类中注册的静态代码块:
*
* static {
* try {
* DriverManager.registerDriver(new Driver());
* } catch (SQLException var1) {
* throw new RuntimeException("Can't register driver!");
* }
* }
*/
//2.加载数据库驱动程序(对应的Driver实现类中有注册的静态代码块)
Class.forName(driverClass);
//3.通过DriverManager的getConnection()方法获取Connection连接
return DriverManager.getConnection(jdbcUrl,user,password);
}
public Connection getMysqlConnection() throws Exception {
InputStream in = getClass().getClassLoader().getResourceAsStream("com/conf/properties/jdbc-conf.properties");
Properties info = new Properties();
info.load(in);
String driverClass = info.getProperty("driverClass");
String jdbcUrl = info.getProperty("jdbcUrl");
String user = info.getProperty("user");
String password = info.getProperty("password");
info.put("user",user);
info.put("password",password);
Driver driver = (Driver)Class.forName(driverClass).newInstance();
Connection connection = driver.connect(jdbcUrl, info);
return connection;
}
}
连接属性放在配置文件中，方便统一管理：jdbc-conf.properties
jdbcUrl=jdbc:mysql://localhost:3306/test user=root password=root driverClass=com.mysql.jdbc.Driver
来一个驱动Driver的源码：
package com.mysql.jdbc;
import java.sql.DriverManager;
import java.sql.SQLException;
public class Driver extends NonRegisteringDriver implements java.sql.Driver {
public Driver() throws SQLException {
}
static {
try {
DriverManager.registerDriver(new Driver());
} catch (SQLException var1) {
throw new RuntimeException("Can't register driver!");
}
}
}
使用driver实例获取connection(简称方法一)和使用DriverManager获取connection(简称方法二)方法比较：
1、方法一中要(Driver)Class.forName(driverClass).newInstance();实例化返回驱动Driver的一个实例对象，然后调用方法connect(jdbcUrl, info);
2、在方法二中，只需要手动的加载数据库驱动程序就行，不需要再手动的去实例化驱动了。然后，通过DriverManager的getConnection(jdbcUrl,user,password)方法获取Connection连接。
3、这里不再手动的去实例化驱动是有原因的，因为在加载驱动时，Driver有一段static代码，这段代码在类加载时会自动执行，所以就把自己注册到DriverManager的registerDriver。
4、而registerDriver是通过遍历registerDrivers中所有已经注册的驱动来常识获取连接。查看源码就能看出这里是怎么实现了。
DriverManager的获取Connection的部分源码：
for(DriverInfo aDriver : registeredDrivers) {
// If the caller does not have permission to load the driver then
// skip it.
if(isDriverAllowed(aDriver.driver, callerCL)) {
try {
println(" trying " + aDriver.driver.getClass().getName());
Connection con = aDriver.driver.connect(url, info);
if (con != null) {
// Success!
println("getConnection returning " + aDriver.driver.getClass().getName());
return (con);
}
} catch (SQLException ex) {
if (reason == null) {
reason = ex;
}
}
} else {
println(" skipping: " + aDriver.getClass().getName());
}
}
可进一步参考：java中连接mysql时添加Class.forName("com.mysql.jdbc.Driver")的作用？
关于Class.forName(“com.mysql.jdbc.Driver”)