1、链接oracle

package cn.itcast.mybatis.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.Statement;
import java.text.SimpleDateFormat;
import java.util.TimeZone;
public class JDBCTest {
public static void main(String[] args) {
Connection con = null;
Connection conn = null;
PreparedStatement pst = null;
Statement sql_statement = null;
try {
Long startTime = System.currentTimeMillis();
SimpleDateFormat sdf = new SimpleDateFormat("HH:mm:ss:SS");
TimeZone t = sdf.getTimeZone();
t.setRawOffset(0);
sdf.setTimeZone(t);
Class.forName("oracle.jdbc.driver.OracleDriver");
String url = "jdbc:oracle:thin:@10.1.8.21:1521:QTDS";
conn = DriverManager.getConnection(url, "doudouqian", "doudouqian");
System.out.println("获取连接"+conn);
}catch(Exception e){

e.printStackTrace();
}
}

}

2、链接mysql：

package cn.itcast.mybatis.jdbc;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.SQLException;
/**
* @author muyeliubing 2016-11-10
* */
public class JdbcTest {

public static void main(String[] args) {

//数据库连接
Connection connection = null;
//预编译的Statement，使用预编译的Statement提高数据库性能
PreparedStatement preparedStatement = null;
//结果 集
ResultSet resultSet = null;

try {
//加载数据库驱动
Class.forName("com.mysql.jdbc.Driver");

//通过驱动管理类获取数据库链接
connection = DriverManager.getConnection("jdbc:mysql://10.138.60.64:3306/ddq?characterEncoding=utf-8", "JDev", "JDev");

System.out.println(connection);
//定义sql语句 ?表示占位符
String sql = "select * from user where username = ?";
//获取预处理statement
preparedStatement = connection.prepareStatement(sql);
//设置参数，第一个参数为sql语句中参数的序号（从1开始），第二个参数为设置的参数值
preparedStatement.setString(1, "aa");
//向数据库发出sql执行查询，查询出结果集
resultSet = preparedStatement.executeQuery();
//遍历查询结果集
while(resultSet.next()){
System.out.println(resultSet.getString("id")+" "+resultSet.getString("username")+" "
+ resultSet.getString("birthday"));
}
} catch (Exception e) {
e.printStackTrace();
}finally{
//释放资源
if(resultSet!=null){
try {
resultSet.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(preparedStatement!=null){
try {
preparedStatement.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if(connection!=null){
try {
connection.close();
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

}

}
}