“润物无声”：只做增强不做改变，引入它不会对现有的工程产生影响。
“效率至上”：只需要简单配置，即可CRUD操作
“丰富功能”：热加载，代码生成，分页，性能分析等功能一应俱全
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<dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-test</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.junit.vintage</groupId>
        <artifactId>junit-vintage-engine</artifactId>
    </dependency>
    <!--mybatis-plus 持久层-->
    <dependency>
        <groupId>com.baomidou</groupId>
        <artifactId>mybatis-plus-boot-starter</artifactId>
        <version>3.3.1</version>
    </dependency>
    <dependency>
        <groupId>mysql</groupId>
        <artifactId>mysql-connector-java</artifactId>
    </dependency>
    <!-- lombok用来简化实体类-->
    <dependency>
        <groupId>org.projectlombok</groupId>
        <artifactId>lombok</artifactId>
        <optional>true</optional>
    </dependency>
</dependencies>
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import lombok.Data;
@Data
public class User {
//    在添加lombok插件后，使用data注解，省去get，set
  private Long id;
  private String name;
  private Integer age;
  private String email;
}
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//核心代码，让UserMapper继承内置的BaseMapper (内置CRUD方法)
@Repository
public interface UserMapper extends BaseMapper<User> {
}
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//
// Source code recreated from a .class file by IntelliJ IDEA
// (powered by Fernflower decompiler)
//
package com.baomidou.mybatisplus.core.mapper;
import com.baomidou.mybatisplus.core.conditions.Wrapper;
import com.baomidou.mybatisplus.core.metadata.IPage;
import java.io.Serializable;
import java.util.Collection;
import java.util.List;
import java.util.Map;
import org.apache.ibatis.annotations.Param;
public interface BaseMapper<T> extends Mapper<T> {
    int insert(T entity);
    int deleteById(Serializable id);
    int deleteByMap(@Param("cm") Map<String, Object> columnMap);
    int delete(@Param("ew") Wrapper<T> wrapper);
    int deleteBatchIds(@Param("coll") Collection<? extends Serializable> idList);
    int updateById(@Param("et") T entity);
    int update(@Param("et") T entity, @Param("ew") Wrapper<T> updateWrapper);
    T selectById(Serializable id);
    List<T> selectBatchIds(@Param("coll") Collection<? extends Serializable> idList);
    List<T> selectByMap(@Param("cm") Map<String, Object> columnMap);
    T selectOne(@Param("ew") Wrapper<T> queryWrapper);
    Integer selectCount(@Param("ew") Wrapper<T> queryWrapper);
    List<T> selectList(@Param("ew") Wrapper<T> queryWrapper);
    List<Map<String, Object>> selectMaps(@Param("ew") Wrapper<T> queryWrapper);
    List<Object> selectObjs(@Param("ew") Wrapper<T> queryWrapper);
    <E extends IPage<T>> E selectPage(E page, @Param("ew") Wrapper<T> queryWrapper);
    <E extends IPage<Map<String, Object>>> E selectMapsPage(E page, @Param("ew") Wrapper<T> queryWrapper);
}
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@MapperScan("com.zeus.demomp.mapper")
public class DemompApplication {
    public static void main(String[] args) {
        SpringApplication.run(DemompApplication.class, args);
    }
}
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class DemompApplicationTests {
    @Autowired
    private UserMapper userMapper;
    @Test
    //查找全部
    public void fillAll() {
        List<User> users = userMapper.selectList(null);
        System.out.println(users);
    }
}
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