Spring Data JPA 与 MyBatisPlus的比较

前言

JPA（Java Persistence API）和MyBatis Plus是两种不同的持久化框架，它们具有不同的特点和适用场景。

JPA是Java官方的持久化规范，它提供了一种基于对象的编程模型，可以通过注解或XML配置来实现对象与数据库的映射关系。JPA的优点是可以对数据库进行更高级的操作，如查询、更新、删除等，同时也支持事务管理和缓存机制，能够更好地支持复杂的业务逻辑。

MyBatis Plus (MPP) 是在MyBatis基础上进行封装的增强版本，它提供了更简单易用的API和更高效的性能。MyBatis Plus通过XML或注解的方式来配置数据库映射关系，并提供了丰富的查询、更新、删除操作的方法。相对于JPA，MyBatis Plus配置简单、易于上手，同时也灵活性较高，能够更好地满足项目的特定需求。

如果只是针对单表的增删改查，两者十分相似，本质上都算ORM框架，那么到底什么时候适合用JPA，什么时候用MyBatisPlus，下面做下这两者的详细对比。

POM依赖

JPA

<dependency><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-data-jpa</artifactId>
</dependency>

MPP

<dependency><groupId>com.baomidou</groupId><artifactId>mybatis-plus-boot-starter</artifactId>
</dependency>

Entity定义

JPA

import javax.persistence.Column;
import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.Table;
import javax.persistence.GeneratedValue;@Entity
@Table(name = "dept")
public class Dept {@Id@Column(name = "id")@GeneratedValue(strategy = GenerationType.AUTO)private Long id;@Column(name = "code")private String code;@Column(name = "name")private String name;
}

MPP

import com.baomidou.mybatisplus.annotation.TableField;
import com.baomidou.mybatisplus.annotation.TableId;@TableName(value = "dept")
public class Dept {@TableId(value = "id", type = IdType.AUTO)private Long id;@TableField(value = "code")private String code;@TableField(value = "name")private String name;
}

DAO定义

基础CRUD

JPA

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.stereotype.Repository;@Repository
public interface DeptRepository extends JpaRepository<Dept, Long> {
}

MPP

import org.apache.ibatis.annotations.Mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;@Mapper
public interface DeptMapper extends BaseMapper<Dept> {
}

基类主要方法

方法	JpaRepository	BaseMapper
插入一条记录	save(T entity)	insert(T entity)
插入多条记录	saveAll(Iterable entities)	insertBatchSomeColumn(List entityList)
根据 ID 删除	deleteById(ID id)	deleteById(Serializable id)
根据实体(ID)删除	delete(T entity)	deleteById(T entity)
根据条件删除记录	-	delete(Wrapper queryWrapper)
删除（根据ID或实体 批量删除）	deleteAllById(Iterable<? extends ID> ids)	deleteBatchIds(Collection<?> idList)
根据 ID 修改	save(T entity)	updateById(T entity)
根据条件更新记录	-	update(Wrapper updateWrapper)
根据 ID 查询	findById(ID id)	selectById(Serializable id)
查询（根据ID 批量查询）	findAllById(Iterable ids)	selectBatchIds(Collection<? extends Serializable> idList)
根据条件查询一条记录	-	selectOne(Wrapper queryWrapper)
根据条件判断是否存在记录	exists(Example example)	exists(Wrapper queryWrapper)
根据条件查询总记录数	count(Example example)	selectCount(Wrapper queryWrapper)
根据条件查询全部记录	findAll(Example example, Sort sort)	selectList(Wrapper queryWrapper)
根据条件查询分页记录	findAll(Example example, Pageable pageable)	selectPage(P page, Wrapper queryWrapper)

Example、Specification VS Wrapper

JPA使用Example和Specification 类来实现范本数据的查询，而MPP使用QueryWrapper来设置查询条件

JPA Example

Dept dept = new Dept();
dept.setCode("100");
dept.setName("Dept1");// select * from dept where code = '100' and name = 'Dept1';
List<Dept> deptList = deptRepository.findAll(Example.of(dept)); 

默认是生成的条件都是 “=”，如果要设置其他比较符，需要使用ExampleMatcher

Dept dept = new Dept();
dept.setCode("100");
dept.setName("Dept1");// select * from dept where code like '100%' and name like '%Dept1%';
List<Dept> deptList = deptRepository.findAll(Example.of(dept, ExampleMatcher.matching().withMatcher("code", ExampleMatcher.GenericPropertyMatchers.startsWith()).withMatcher("name", ExampleMatcher.GenericPropertyMatchers.contains()))); 

Example仅能实现对字符串类型的匹配模式，如果要设置其他类型的字段，可以实现JpaSpecificationExecutor接口来完成：

import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.JpaSpecificationExecutor;
import org.springframework.stereotype.Repository;@Repository
public interface DeptRepository extends JpaRepository<Dept, Long>, JpaSpecificationExecutor<Dept>  {
}

增加以上接口后，会增加以下查询方法：

• findOne(Specification spec)
• findAll(Specification spec)
• findAll(Specification spec, Pageable pageable)
• count(Specification spec)
• exists(Specification spec)

使用示例：

Dept dept = new Dept();
dept.setCode("100");
dept.setName("Dept1");// select * from dept where code like '100%' and name like '%Dept1%';
Specification<Dept> spec = new Specification<Dept>() {@Overridepublic Predicate toPredicate(Root<Dept> root, CriteriaQuery<?> query, CriteriaBuilder cb) {List<Predicate> predicates = new ArrayList<>();//  模糊查询（前缀匹配）if (dept.getCode() != null && !dept.getCode().isEmpty()) {predicates.add(cb.like(root.get("code"), dept.getCode() + "%"));}//  模糊查询if (dept.getName() != null && !dept.getName().isEmpty()) {predicates.add(cb.like(root.get("code"), '%' + dept.getCode() + "%"));}return query.where(predicates.toArray(new Predicate[predicates.size()])).getRestriction();}
};
List<Dept> deptList = deptRepository.findAll(Example.of(dept)); 

除了equal、notEqual, 针对日期、数字类型，还有gt、ge、lt、le等常用比较符。

自定义接口

JPA

JPA支持接口规范方法名查询，一般查询方法以 find、findBy、read、readBy、get、getBy为前缀，JPA在进行方法解析的时候会把前缀取掉，然后对剩下部分进行解析。例如：

@Repository
public interface DeptRepository extends JpaRepository<Dept, Long> {// 调用此方法时，会自动生成 where code = ? 的条件Dept getByCode(String code);
}

常用的方法命名有：

关键字	方法命名	sql where字句
Distinct	findDistinctByLastnameAndFirstname	select distinct …​ where x.lastname = ?1 and x.firstname = ?2
And	findByNameAndPwd	where name= ? and pwd =?
Or	findByNameOrSex	where name= ? or sex=?
Is,Equals	findById, findByIdIs, findByIdEquals	where id= ?
Between	findByIdBetween	where id between ? and ?
LessThan	findByIdLessThan	where id < ?
LessThanEquals	findByIdLessThanEquals	where id <= ?
GreaterThan	findByIdGreaterThan	where id > ?
GreaterThanEquals	findByIdGreaterThanEquals	where id > = ?
After	findByIdAfter	where id > ?
Before	findByIdBefore	where id < ?
IsNull	findByNameIsNull	where name is null
isNotNull,NotNull	findByNameNotNull	where name is not null
Like	findByNameLike	where name like ?
NotLike	findByNameNotLike	where name not like ?
StartingWith	findByNameStartingWith	where name like ‘?%’
EndingWith	findByNameEndingWith	where name like ‘%?’
Containing	findByNameContaining	where name like ‘%?%’
OrderBy	findByIdOrderByXDesc	where id=? order by x desc
Not	findByNameNot	where name <> ?
In	findByIdIn(Collection<?> c)	where id in (?)
NotIn	findByIdNotIn(Collection<?> c)	where id not in (?)
True	findByEnabledTue	where enabled = true
False	findByEnabledFalse	where enabled = false
IgnoreCase	findByNameIgnoreCase	where UPPER(name)=UPPER(?)
First,Top	findFirstByOrderByLastnameAsc	order by lastname limit 1
FirstN,TopN	findTop3ByOrderByLastnameAsc	order by lastname limit 3

MPP

MyBatisPlus没有JPA那样可以根据接口的方法名自动组装查询条件，但是可以利用Java8的接口默认实现来达到同样的目的，只不过需要编写少量的代码：

import org.apache.ibatis.annotations.Mapper;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;@Mapper
public interface DeptMapper extends BaseMapper<Dept> {default Dept getByCode(String code) {return selectOne(Wrappers.<Dept>lambdaWrapper().eq(Dept::getCode, code));}
}

自定义SQL

JPA支持通过@Query注解和XML的形式实现自定义SQL，而MyBatis支持通过@Select、@Delete、@Update、@Script注解和XML的形式实现自定义SQL。

JPA

JPA的自定义SQL分为JPQL(Java Persistence Query Language Java 持久化查询语言)和原生SQL两种。
JPQL:

import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;@Repository
public interface DeptRepository extends JpaRepository<Dept, Long> {@Query(value = "select d from Dept d where d.code = ?1")Dept getByCode(String code);@Modifying@Query(value = "delete from Dept d where d.code = :code")int deleteByCode(@Param("code") String code);
}

原生SQL

import org.springframework.data.jpa.repository.Query;
import org.springframework.data.repository.query.Param;@Repository
public interface DeptRepository extends JpaRepository<Dept, Long> {@Query(value = "SELECT * FROM dept WHERE name = ?1", countQuery = "SELECT count(*) FROM dept WHERE name = ?1", nativeQuery = true)Page<Dept> findByName(@Param("name") String name, Pageable pageable);
}

XML形式：
/resource/META-INFO/orm.xml

<named-query name="Dept.getByCode"><query> select d from Dept d where d.code = ?1</query>
</named-query>
<named-native-query name="Dept.deleteByCode"><query> DELETE FROM dept WHERE code = ?1</query>
</named-native-query>

MyBatis

JPA的自定义SQL分为注解形式和XML形式
注解形式:

import org.apache.ibatis.annotations.Mapper;
import org.apache.ibatis.annotations.Param;
import org.apache.ibatis.annotations.Select;
import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.baomidou.mybatisplus.core.metadata.IPage;@Mapper
public interface DeptMapper extends BaseMapper<Dept> {@Select(value = "SELECT * FROM dept WHERE code = #{code}")Dept getByCode(@Param("code") String code);@Delete("DELETE FROM dept WHERE code = #{code}")int deleteByCode(@Param("code") String code);@Select(value = "SELECT * FROM dept WHERE name = #{name}")IPage<Dept> findByName(@Param("name") String name, IPage<Dept> page);
}

XML形式：
/resource/mapper/DeptMapper.xml

<select id = "getByCode", resultType = "Dept">SELECT * FROM dept WHERE code = #{code}
</select>
<delete id = "deleteByCode">DELETE FROM dept WHERE code = #{code}
</select>
<select id = "findByName">SELECT * FROM dept WHERE name = #{name}
</select>