mybatis基于mapper开发(五)

朴灿烈づ我的快乐病毒、 2022-06-10 00:55 100阅读 0赞

基于mapper开发,只需写mapper接口(相当于Dao接口)  
基于mapper开发需要遵循一些mapper开发规范,mybatis可以自动生成mapper实现类的代理对象  
mapper代理开发规范  
1. mapper接口的全限定名要和mapper映射文件的namespace值一致。  
2. mapper接口的方法名称要和mapper映射文件的statement的id一致。  
3. mapper接口的方法参数类型要和mapper映射文件的statement的parameterType的值一致，而且它的参数是一个。  
4. mapper接口的方法返回值类型要和mapper映射文件的statement的resultType的值一致。

![这里写图片描述][SouthEast]

UserMapper接口

package com.test.mapper;
    
    import com.test.domain.User;
    
    public interface UserMapper { 
    
        User findUserById(int id);
        User findUserByUserName(String userName);
        void insertUser(User user);
    
    }

UserMapper.xml配置文件

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd">
    
    <mapper namespace="com.test.mapper.UserMapper">
        <select id="findUserById" parameterType="int" resultType="com.test.domain.User">
            SELECT * FROM USER WHERE id =#{id}
        </select>
        <select id="findUserByUserName" parameterType="String" resultType="com.test.domain.User">
            SELECT * FROM USER WHERE userName like '%${value}%'
        </select>
        <insert id="insertUser" parameterType="com.test.domain.User">
            <selectKey keyProperty="id" resultType="int" order="AFTER">
                SELECT LAST_INSERT_ID()
            </selectKey>
    
            INSERT INTO USER 
            (username,birthday,sex,address) 
            VALUES
            (#{username},#{birthday},#{sex},#{address})
        </insert>
    </mapper>

注:mapper.xml配置文件中的namespace需要与mapper接口的全类名一致

全局配置文件sqlMapConfig.xml

<?xml version="1.0" encoding="UTF-8" ?>
    <!DOCTYPE configuration PUBLIC "-//mybatis.org//DTD Config 3.0//EN" "http://mybatis.org/dtd/mybatis-3-config.dtd">
    <configuration>
        <environments default="development">
            <environment id="development">
                
                <transactionManager type="JDBC"></transactionManager>
                
                <dataSource type="POOLED">
                    <property name="driver" value="com.mysql.jdbc.Driver" />
                    <property name="url" value="jdbc:mysql://localhost:3306/test?useUnicode=true&characterEncoding=utf8" />
                    <property name="username" value="root" />
                    <property name="password" value="root" />
                </dataSource>
            </environment>
        </environments>
    
        
        <mappers>
            <mapper resource="mapper/UserMapper.xml" />
        </mappers>
    </configuration>

mappers标签用法

//相对于类路径的资源
    <mapper resource="mapper/UserMapper.xml" />

//完全限定路径
    <mapper url="file:///F:\work\store\mybatis_01\config\mapper\UserMapper.xml"/>

//mapper接口的全限定名
    //注：此种方法要求mapper接口和mapper映射文件要名称相同，且放到同一个目录下；
    <mapper class="com.test.mapper.UserMapper"/>

//指定包下的所有映射文件
    //注：此种方法要求mapper接口和mapper映射文件要名称相同，且放到同一个目录下；
    <package name="com.test.mapper"/>

测试代码

@org.junit.Test
        public void test_02() throws Exception{
            SqlSession sqlSession = sqlSessionFactory.openSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = mapper.findUserById(1);
            System.out.println(user);
        }
        @org.junit.Test
        public void test_03() throws Exception{
            SqlSession sqlSession = sqlSessionFactory.openSession();
            UserMapper mapper = sqlSession.getMapper(UserMapper.class);
            User user = new User();
            user.setUsername("不知火舞");
            user.setSex("1");
            user.setBirthday(new Date());
            user.setAddress("民治");
            mapper.insertUser(user);
    
            User user2 = mapper.findUserById(user.getId());
            sqlSession.commit();
            System.out.println(user2);
        }

[SouthEast]: /images/20220610/8554f0a5a6e04d5fb5be421031f159b3.png