java JDBC 通过物理连接数据库和通过获取数据库连接池进行链接

package com.nhfc99.login;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.SQLException;

//import javax.activation.DataSource;
import javax.naming.Context;
import javax.naming.InitialContext;
import javax.naming.NamingException;
import javax.sql.DataSource;

import com.MySQL.jdbc.Statement;

public class ConnectSql {
public void connectMysql() throws ClassNotFoundException, SQLException, NamingException {
// 基本的连接数据库方式
Connection conn = null;
Statement stmt = null;
// 注册 JDBC 驱动器
Class.forName("com.mysql.jdbc.Driver");
// 打开一个连接
conn = DriverManager.getConnection("jdbc:mysql://127.0.0.1:3306/mysql?characterEncoding=utf8&useSSL=true",
"root", "****");
if (conn == null) {
System.out.println("连接失败");
} else {
System.out.println("连接成功");
String sql = "SELECT * FROM user";
stmt = (Statement) conn.createStatement();
ResultSet rs = stmt.executeQuery(sql);
while (rs.next()) {
System.out.println("User = " + rs.getString("User") + "\n");
System.out.println("Host = " + rs.getString("Host"));
}
}

// 使用数据库连接池进行获取数据库的连接
Context context = new InitialContext();
Context envContext = (Context) context.lookup("java:comp/env");
DataSource ds = (DataSource) envContext.lookup("jdbc/mysqlds");
Connection conn = ds.getConnection();
if (conn == null) {
System.out.println("连接数据库失败\n");
} else {
System.out.println("连接数据库成功\n");
}
}
}

//context.xml配置
/*
<?xml version="1.0" encoding="UTF-8"?>
<Context reloadable="true">
<Resource
name="jdbc/mysqlds"
auth="Container"
type="javax.sql.DataSource"
maxActive="100"
maxIdle="30"
maxWaite="10000"
username="root"
password="****"
driverClassName="com.mysql.jdbc.Driver"
url="jdbc:mysql://127.0.0.1:3306/TestDatabase" />
</Context>
*/