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public interface UserMapper extends BaseMapper<User> {}
public class MapperTest {@Autowiredprivate UserMapper userMapper;@Testpublic void getAll() {List<User> users = userMapper.selectList(null);users.forEach(System.out::println);} }
只是用到了usermapper中的selectList()方法,而UserMapper继承了BaseMapper这个接口,这个接口便是MybatisPlus提供给我们的
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条件构造器wrapper
@Testpublic void test01(){QueryWrapper<User> wrapper = new QueryWrapper<>();//查询名字和邮箱都不为空、且年龄大于18岁的用户wrapper.isNotNull("name").isNotNull("email").ge("age",18);userMapper.selectList(wrapper).forEach(System.out::println);}
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xml映射文件
<!DOCTYPE mapper PUBLIC "-//mybatis.org//DTD Mapper 3.0//EN" "http://mybatis.org/dtd/mybatis-3-mapper.dtd"> <mapper namespace="com.xxx.mapper.UserMapper"><select id="selectAdultUsers" resultType="com.xxx.entity.User">SELECT * FROM users <where><if test="status != null">status = #{status}</if>age >= 18</where></select><resultMap id="userDetailMap" type="com.xxx.entity.User"><id property="id" column="user_id"/><result property="createTime" column="create_time"/></resultMap><select id="selectUserDetail" resultMap="userDetailMap">SELECT u.id AS user_id, u.create_time FROM users uLEFT JOIN dept d ON u.dept_id = d.id</select> </mapper>
List<User> selectAdultUsers(@Param("status") String status); List<User> selectUserDetail();