<select id="findUserById" parameterType="int" resultType="com.vg.entity.User">
    select * from user where id = #{id};
  </select>

package com.vg.test;



import com.vg.dao.UserMapper;
import com.vg.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.Test;

import java.io.InputStream;
import java.util.List;

/**
 * 測(cè)試類
 */
public class TestUserMapper {

	/**
	 * 測(cè)試方法：查詢所有學(xué)生
	 * SqlSessionFactoryBuilder => SqlSessionFactory => SqlSession：相當(dāng)于JDBC中的Connection對(duì)象，提供了操作數(shù)據(jù)庫(kù)的CRUD方法
	 */
	@Test
	public void testFindAllUsers()throws Exception{
		// 1. 通過(guò)Resources類，加載sqlMapConfig.xml，得到文件輸入流對(duì)象
		// Resources類作用：專門讀取src目錄下的資源文件
		InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
		// 2. 實(shí)例化會(huì)話工廠創(chuàng)建類SqlSessionFactoryBuilder
		SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
		// 3. 通過(guò)會(huì)話工廠創(chuàng)建類，讀取上面的輸入流，得到會(huì)話工廠SqlSessionFactory類
		SqlSessionFactory sqlSessionFactory = builder.build(in);
		// 4. 使用SqlSessionFactory對(duì)象，創(chuàng)建SqlSession對(duì)象
		// a) 它相當(dāng)于JDBC中的Connection對(duì)象，提供了操作數(shù)據(jù)庫(kù)的CRUD方法
		// b) 它提供了一個(gè)getMapper()方法，獲取接口的實(shí)現(xiàn)對(duì)象。
		SqlSession sqlSession = sqlSessionFactory.openSession();

		// 5. 獲取接口 UserMapper 實(shí)現(xiàn)類對(duì)象（代理對(duì)象）
		UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
		System.out.println("userMapper = " +userMapper);
		// 6. 執(zhí)行數(shù)據(jù)庫(kù)的查詢操作，輸出用戶信息
		List<User> userList = userMapper.findAllUsers();
		for (User user : userList) {
			System.out.println(user);
		}
		// 7. 關(guān)閉會(huì)話，釋放資源。
		sqlSession.close();
	}
	@Test
	public void testFindUserById()throws Exception{
		// 1. 通過(guò)Resources類，加載sqlMapConfig.xml，得到文件輸入流對(duì)象
		// Resources類作用：專門讀取src目錄下的資源文件
		InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
		// 2. 實(shí)例化會(huì)話工廠創(chuàng)建類SqlSessionFactoryBuilder
		SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
		// 3. 通過(guò)會(huì)話工廠創(chuàng)建類，讀取上面的輸入流，得到會(huì)話工廠SqlSessionFactory類
		SqlSessionFactory sqlSessionFactory = builder.build(in);
		// 4. 使用SqlSessionFactory對(duì)象，創(chuàng)建SqlSession對(duì)象
		// a) 它相當(dāng)于JDBC中的Connection對(duì)象，提供了操作數(shù)據(jù)庫(kù)的CRUD方法
		// b) 它提供了一個(gè)getMapper()方法，獲取接口的實(shí)現(xiàn)對(duì)象。
		SqlSession sqlSession = sqlSessionFactory.openSession();

		// 5. 獲取接口 UserMapper 實(shí)現(xiàn)類對(duì)象（代理對(duì)象）
		UserMapper userMapper = sqlSession.getMapper(UserMapper.class);
		System.out.println("userMapper = " +userMapper);
		// 6. 調(diào)用接口的方法根據(jù)id查詢用戶
		User user = userMapper.findUserById(1);
		System.out.println("user = " + user);
		// 7. 關(guān)閉會(huì)話，釋放資源。
		sqlSession.close();
	}
}

package com.vg.test;

import com.vg.dao.UserMapper;
import com.vg.entity.User;
import org.apache.ibatis.io.Resources;
import org.apache.ibatis.session.SqlSession;
import org.apache.ibatis.session.SqlSessionFactory;
import org.apache.ibatis.session.SqlSessionFactoryBuilder;
import org.junit.After;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

import java.io.IOException;
import java.io.InputStream;
import java.util.List;

/**
 * 測(cè)試類
 */
public class TestUserMapper {
	private static SqlSessionFactory sqlSessionFactory =null;
	private SqlSession sqlSession =null;
	private UserMapper userMapper =null;

	// 該方法在所有測(cè)試方法執(zhí)行之前執(zhí)行1次
	@BeforeClass
	public static void init() throws Exception {
		// 1. 通過(guò)Resources類，加載sqlMapConfig.xml，得到文件輸入流對(duì)
		InputStream in = Resources.getResourceAsStream("sqlMapConfig.xml");
		// 2. 實(shí)例化會(huì)話工廠創(chuàng)建類SqlSessionFactoryBuilder對(duì)象
		SqlSessionFactoryBuilder builder = new SqlSessionFactoryBuilder();
		// 3. 根據(jù)字節(jié)輸入流獲取SqlSessionFactory對(duì)象
		sqlSessionFactory = builder.build(in);
	}
	// 該方法會(huì)在每個(gè)測(cè)試方法執(zhí)行之前執(zhí)行1次
	@Before
	public void before(){
		// 4. 獲取SqlSession對(duì)象，等價(jià)連接對(duì)象
		// true:事務(wù)自動(dòng)提交，false:不自動(dòng)提交,默認(rèn)值
		sqlSession = sqlSessionFactory.openSession();
		// 5. 創(chuàng)建接口 實(shí)現(xiàn)類對(duì)象
		 userMapper = sqlSession.getMapper(UserMapper.class);

	}

	/**
	 * 測(cè)試方法：查詢所有學(xué)生
	 * SqlSessionFactoryBuilder => SqlSessionFactory => SqlSession：相當(dāng)于JDBC中的Connection對(duì)象，提供了操作數(shù)據(jù)庫(kù)的CRUD方法
	 */
	@Test
	public void testFindAllUsers() throws Exception{
		List<User> userList = userMapper.findAllUsers();
		for (User user : userList) {
			System.out.println(user);
		}
	}

	@Test
	public void testFindUserById()throws Exception{
		// 6. 調(diào)用接口的方法根據(jù)id查詢用戶
		User user = userMapper.findUserById(1);
		System.out.println("user = " + user);

	}

	@After
	public void after() {
		// 7. 關(guān)閉會(huì)話，釋放資源。

		sqlSession.close();
	}
}