04mybatis mapper使用方法

向右看齐 2022-06-02 02:27 185阅读 0赞

# mybatis mapper使用方法 #

**mapper方式的组成部分：pojo.java、mapper.java（相当于传统的statementid的dao接口）和mapper.xml**

## 具体实现 ##

**重点：**  
mapper使用方式要遵循以下四个规范：

1.  mapper.xml的namespace的ID要和mapper的包路径一样

如下

1.  mapper.java的方法名要和mapper.xml中的statementid一致
2.  mapper.java的方法输入参数要和mapper.xml中的paramterType类型一致
3.  mapper.java的方法的返回值要和mapper.xml中的resultType类型一致  
    细节如下：  
    2.1 pojo.java如下

@Getter
    @Setter
    @ToString
    public class BusinessApply { 
        private Integer id;
        private String name;
        private String businessNo;
        private String businessType;
        private Integer businessSum;
    }

2.2 mapper.xml如下

<?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.cmhy.mapper.BusinessApplyMapper">
        <select id="findByNo" parameterType="java.lang.String" resultType="com.cmhy.model.BusinessApply">
            select * from business_apply where business_no = #{value}
        </select>
        <select id="findByName" parameterType="java.lang.String" resultType="com.cmhy.model.BusinessApply">
            select * from business_apply where name like '%${value}%'
        </select>
        <select id="findIdByName" parameterType="java.lang.String" resultType="java.lang.Integer">
            select id from business_apply where name like #{value}
        </select>
        <update id="updateById" parameterType="int">
            update business_apply set business_sum = 12.00 where id = #{value}
        </update>
        <update id="deleteById" parameterType="int">
            delete from business_apply where id = #{value}
        </update>
    </mapper>

2.3 mapper.java文件如下：

package com.cmhy.mapper;
    
    import java.util.List;
    import com.cmhy.model.BusinessApply;
    
    public interface BusinessApplyMapper { 
        public BusinessApply findByNo(String businessNo);
        public List<BusinessApply> findByName(String name);
        public List<Integer> findIdByName(String name);
        public void updateById(Integer id);
        public void deleteById(Integer id);
    }

2.4 测试类如下：

package com.cmhy.dao;
    
    import java.io.IOException;
    import java.io.InputStream;
    
    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.cmhy.mapper.BusinessApplyMapper;
    
    public class BusinessApplyDaoTest { 
        private SqlSessionFactory sqlSessionFactory;
        @Before
        public void sqlSessionFactory() throws IOException {
            InputStream in = Resources.getResourceAsStream("SqlMapConfig.xml");
            sqlSessionFactory = new SqlSessionFactoryBuilder().build(in);
        }
        @Test
        public void testFindByNo() {
    
        }
    
        @Test
        public void testFindByName() {
            SqlSession sqlSession = sqlSessionFactory.openSession();
            BusinessApplyMapper baMapper = sqlSession.getMapper(BusinessApplyMapper.class);
            baMapper.findByName("个贷");
            System.out.println("***********"+baMapper.findByName("个贷"));
            sqlSession.close();
        }
    
        @Test
        public void testFindIdByName() {
        }
    
        @Test
        public void testUpdateById() {
        }
    
        @Test
        public void testDeleteById() {
        }
    
    }

**总结**  
mapper.java接口方法参数只能有一个，所以使用包装类型的pojo满足不同的业务需求。系统使用不是太方便。  
注意：service层的方法入参不建议使用包装类型