MyBatis開發(fā)原始Dao層請(qǐng)閱讀我的上一篇博客：MyBatis開發(fā)Dao層的兩種方式（原始Dao層開發(fā)）
接上一篇博客繼續(xù)介紹MyBatis開發(fā)Dao層的第二種方式：Mapper動(dòng)態(tài)代理方式
Mapper接口開發(fā)方法只需要程序員編寫Mapper接口（相當(dāng)于Dao接口），由Mybatis框架根據(jù)接口定義創(chuàng)建接口的動(dòng)態(tài)代理對(duì)象，代理對(duì)象的方法體同上一篇博客中Dao接口實(shí)現(xiàn)類方法。
Mapper接口開發(fā)需要遵循以下規(guī)范：
（1）Mapper.xml文件中的namespace與mapper接口的類路徑相同。
（2）Mapper接口方法名和Mapper.xml中定義的每個(gè)statement的id相同
（3）Mapper接口方法的輸入?yún)?shù)類型和mapper.xml中定義的每個(gè)sql 的parameterType的類型相同
（4）Mapper接口方法的輸出參數(shù)類型和mapper.xml中定義的每個(gè)sql的resultType的類型相同
1、定義mapper映射文件UserMapper.xml（內(nèi)容同User.xml），需要修改namespace的值為 UserMapper接口路徑。將UserMapper.xml放在classpath 下sqlmapperr目錄下。
<?xml version="1.0" encoding="UTF-8" ?><!DOCTYPE mapperPUBLIC "-//mybatis.org//DTD Mapper 3.0//EN""http://mybatis.org/dtd/mybatis-3-mapper.dtd"><mapper namespace="com.xyfer.mapper.UserMapper"> <!-- 根據(jù)id查詢用戶 --> <select id="getUserById" parameterType="int" resultType="com.xyfer.po.User"> select * from user where id = #{id} </select> <!-- 添加用戶 --> <insert id="insertUser" parameterType="com.xyfer.po.User"> <selectKey keyProperty="id" order="AFTER" resultType="java.lang.Integer"> select LAST_INSERT_ID() </selectKey> insert into user(username,birthday,sex,address) values(#{username},#{birthday},#{sex},#{address}) </insert> <!-- 修改用戶 --> <update id="updateUser" parameterType="com.xyfer.po.User"> update user set username=#{username},birthday=#{birthday},sex=#{sex},address=#{address} where id=#{id} </update> <!-- 刪除用戶 --> <delete id="deleteUserById" parameterType="int"> delete from user where id=#{id} </delete> </mapper>2、UserMapper.java接口文件
package com.xyfer.mapper;import com.xyfer.po.User;public interface UserMapper { public User getUserById(int id); //根據(jù)id值查詢一個(gè)用戶 public void insertUser(User user); //新增一個(gè)用戶 public void updateUser(User user); //修改一個(gè)用戶 public void deleteUser(int id); //刪除一個(gè)用戶}接口定義有如下特點(diǎn)：
（1）UserMapper接口方法名和Mapper.xml中定義的statement的id相同
（2）UserMapper接口方法的輸入?yún)?shù)類型和mapper.xml中定義的statement的parameterType的類型相同
（3） UserMapper接口方法的輸出參數(shù)類型和mapper.xml中定義的statement的resultType的類型相同
3、在SqlMapConfig.xml文件中加載UserMapper.xml文件
<mappers> <mapper resource="UserMapper.xml"/></mappers>
4、測(cè)試
package com.xyfer.mapper;import static org.junit.Assert.*;import java.io.InputStream;import java.util.Date;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.Before;import org.junit.Test;import com.xyfer.po.User;import junit.framework.TestCase;public class UserMapperTest extends TestCase{ private SqlSessionFactory sqlSessionFactory; protected void setUp() throws Exception { SqlSessionFactoryBuilder sessionFactoryBuilder = new SqlSessionFactoryBuilder(); InputStream inputStream = Resources.getResourceAsStream("SqlMapConfig.xml"); sqlSessionFactory = sessionFactoryBuilder.build(inputStream); } @Test public void testGetUserById() { //獲取sqlsession SqlSession sqlsession = sqlSessionFactory.openSession(); //獲取UserMapper接口代理對(duì)象 UserMapper userMapper = sqlsession.getMapper(UserMapper.class); //調(diào)用代理對(duì)象方法 User user = userMapper.getUserById(10); //打印結(jié)果 System.out.println(user); //關(guān)閉sqlsession sqlsession.close(); } @Test public void testInsertUser() { //獲取sqlsession SqlSession sqlsession = sqlSessionFactory.openSession(); //獲取UserMapper接口代理對(duì)象 UserMapper userMapper = sqlsession.getMapper(UserMapper.class); //新建一個(gè)對(duì)象 User user = new User(); user.setUsername("小謝"); user.setSex("男"); user.setBirthday(new Date()); user.setAddress("浙江省杭州市"); //調(diào)用代理對(duì)象方法 userMapper.insertUser(user); //關(guān)閉sqlsession sqlsession.close(); } @Test public void testUpdateUser() { //獲取sqlsession SqlSession sqlsession = sqlSessionFactory.openSession(); //獲取UserMapper接口代理對(duì)象 UserMapper userMapper = sqlsession.getMapper(UserMapper.class); //新建一個(gè)對(duì)象 User user = new User(); user.setUsername("小謝"); user.setSex("男"); user.setBirthday(new Date()); user.setAddress("上海市"); //調(diào)用代理對(duì)象方法 userMapper.updateUser(user); //關(guān)閉sqlsession sqlsession.close(); } @Test public void testDeleteUser() { //獲取sqlsession SqlSession sqlsession = sqlSessionFactory.openSession(); //獲取UserMapper接口代理對(duì)象 UserMapper userMapper = sqlsession.getMapper(UserMapper.class); //調(diào)用代理對(duì)象方法 userMapper.deleteUser(6); //關(guān)閉sqlsession sqlsession.close(); }}以上步驟，完成mybatis框架以Mapper動(dòng)態(tài)代理方式開發(fā)Dao層，并對(duì)數(shù)據(jù)庫進(jìn)行增刪改查操作。
需要注意的是，上文提到的config文件夾和sqlmapper文件夾均為資源文件夾（source folder），默認(rèn)會(huì)加載該路徑下的文件。希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持VeVb武林網(wǎng)。
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