数据库问题？？？

package cn.itcast.demo;



import java.sql.Connection;

import java.sql.PreparedStatement;

import java.sql.ResultSet;

import java.sql.SQLException;



import org.junit.Test;



import cn.itcast.utils.JdbcUtils;



public class Demo4 {

	/**

	 * 获取自动生成的主键

	 create table test1

	 (

	 	id int primary key auto_increment,

	 	name varchar(20)

	 );

	 */

	@Test

	public void test(){

		Connection conn=null;

		PreparedStatement st=null;

		ResultSet rs=null;

		

		try {

			conn=JdbcUtils.getConnection();

			String sql="insert into test1(name) values(?)";

			st=conn.prepareStatement(sql);

			st.setString(1,"aaa");

			st.executeUpdate();

			

			rs=st.getGeneratedKeys();

			if(rs.next()){

				System.out.println(rs.getInt(1));

				//System.out.println(rs.getInt("id"));//为什么不能这样写呢？？？

			}

		} catch (Exception e) {

			

			e.printStackTrace();

		}

		

	}

}

java中对于id的值为什么不能这样取呢，System.out.println(rs.getInt("id"));
错误提示是：java.sql.SQLException: Column 'id' not found.
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:910)
at com.mysql.jdbc.ResultSet.findColumn(ResultSet.java:987)
at com.mysql.jdbc.ResultSet.getInt(ResultSet.java:2749)
at cn.itcast.demo.Demo4.test(Demo4.java:37)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.junit.internal.runners.TestMethodRunner.executeMethodBody(TestMethodRunner.java:99)
at org.junit.internal.runners.TestMethodRunner.runUnprotected(TestMethodRunner.java:81)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestMethodRunner.runMethod(TestMethodRunner.java:75)
at org.junit.internal.runners.TestMethodRunner.run(TestMethodRunner.java:45)
at org.junit.internal.runners.TestClassMethodsRunner.invokeTestMethod(TestClassMethodsRunner.java:66)
at org.junit.internal.runners.TestClassMethodsRunner.run(TestClassMethodsRunner.java:35)
at org.junit.internal.runners.TestClassRunner$1.runUnprotected(TestClassRunner.java:42)
at org.junit.internal.runners.BeforeAndAfterRunner.runProtected(BeforeAndAfterRunner.java:34)
at org.junit.internal.runners.TestClassRunner.run(TestClassRunner.java:52)
at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:38)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:460)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:673)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:386)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:196)