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介绍

让 MybatisPlus 拥有像 Jpa 一样的直接在 mapper 接口中定义方法名（如 findByUserNameOrderByCreatedAsc ）查询的能力（无需配置xml）

适用场景

假设有一个简单的场景，根据姓名查询用户并按照创建时间排序，如果用 mybatisplus 来写的话，需要用下面的代码来完成：

LambdaQueryWrapper<SysUser> lambdaQueryWrapper = new LambdaQueryWrapper<>();
lambdaQueryWrapper.orderByAsc(SysUser::getCreated);
lambdaQueryWrapper.like(SysUser::getUserName, "赵");
mapper.selectList(lambdaQueryWrapper);

但是如果用 Jpa 来实现，代码就很简单了，只需要在 Repository接口 定义下面的方法，在 service 里直接就可以调用：

List<SysUser> findByUserNameOrderByCreatedAsc(String userName);

所以说，在某些场景下， Jpa 确实是比 MybatisPlus 更简单实用的。为了让 Mybatisplus 拥有 Jpa 的能力，你的项目中非常需要 mybatis-plus-jpa-support !!!

Maven 引入

项目地址：mybatis-plus-jpa-support

<!--基于jdk21，想要低版本的自行下载源码打包-->
<dependency><groupId>com.xiaoyudeguang</groupId><artifactId>mybatis-plus-jpa-support</artifactId><version>1.0.2-SNAPSHOT</version>
</dependency>

使用教程

1. 启动类声明 @EnableMybatisJpaSupport 注解

import com.xiaoyudeguang.mybatis.jpa.annotation.EnableMybatisJpaSupport;
import org.mybatis.spring.annotation.MapperScan;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;@MapperScan(basePackages = {"com.**.mapper"})
@EnableMybatisJpaSupport(basePackages = {"com.**.mapper"})
@SpringBootApplication
public class StartApp {public static void main(String[] args) {SpringApplication.run(StartApp.class, args);}
}

2. 所有 mapper 接口的 @Mapper 注解都要替换为 @com.xiaoyudeguang.mybatis.jpa.support.annotation.Mapper 注解

import com.baomidou.mybatisplus.core.mapper.BaseMapper;
import com.xiaoyudeguang.mybatis.jpa.annotation.Mapper;import java.util.List;@Mapper
public interface SysUserMapper extends BaseMapper<SysUser> {List<SysUser> findByUserNoAndUserNameLike(String userNo, String userName);List<SysUser> findAllOrderByUserNoDesc(String userName);List<SysUser> findByUserNameLikeOrderByUserNoDesc(String userName);long countByUserName(String userName);List<SysUser> findByUserNameLike(String userName);List<SysUser> findByUserNameStartingWith(String userName);List<SysUser> findByUserNameContaining(String userName);void deleteByUserName(String userName);
}

3. 在 Service 中使用

import com.example.mapper.SysUserMapper;
import com.example.model.SysUser;
import jakarta.annotation.Resource;
import org.apache.commons.lang3.StringUtils;
import org.springframework.stereotype.Service;import java.util.List;@Service
public class UserServiceImpl {//注意，这里如果使用@Autowired注解，必须用@Qualifier("sysUserRepository")显示声明@Resourceprivate SysUserMapper sysUserRepository;@Overridepublic List<SysUser> testJpa(String userNo, String userName) {sysUserRepository.findByUserNoAndUserNameLike(userNo, userName);sysUserRepository.findByUserNameLike("findByUserNameLike");sysUserRepository.findAllOrderByUserNoDesc("findAllOrderByUserNoDesc");sysUserRepository.findByUserNameLikeOrderByUserNoDesc("findByUserNameLikeOrderByUserNoDesc");sysUserRepository.findByUserNameStartingWith("findByUserNameStartingWith");sysUserRepository.findByUserNameContaining("findByUserNameContaining");sysUserRepository.countByUserName("countByUserName");sysUserRepository.deleteByUserName("deleteByUserName");return List.of();}
}

4. 通过继承抽象层 AbstractServiceImpl 类的来简化注入过程

import com.baomidou.mybatisplus.extension.service.impl.ServiceImpl;
import com.xiaoyudeguang.mybatis.jpa.annotation.Mapper;
import com.xiaoyudeguang.mybatis.jpa.web.mapper.AbstractMapper;
import com.xiaoyudeguang.mybatis.jpa.web.service.AbstractService;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.util.StringUtils;/*** AbstractServiceImpl类可以直接复制到项目中当做Service层的抽象类*/
public abstract class AbstractServiceImpl<M extends BaseMapper<T>, T> extends ServiceImpl<M, T> implements AbstractService<M, T>, InitializingBean {@Autowiredprivate M baseMapper;protected M mapper;@Autowiredprotected ApplicationContext context;@Override@SuppressWarnings("unchecked")public void afterPropertiesSet() throws Exception {mapper = baseMapper;Class<?> mapperClass = baseMapper.getClass().getInterfaces()[0];String repositoryName = StringUtils.uncapitalize(mapperClass.getSimpleName().replace("Mapper", "Repository"));if (context.containsBean(repositoryName) && mapperClass.getDeclaredAnnotation(Mapper.class) != null) {mapper = (M) context.getBean(repositoryName);}}
}@Service
public class UserServiceImpl extends AbstractServiceImpl<SysUserMapper, SysUser> implements UserService {@Overridepublic List<SysUser> testJpa(String userNo, String userName) {//mapper接口中的自定义方法mapper.findByUserNoAndUserNameLike(userNo, userName);mapper.findByUserNameLike("findByUserNameLike");mapper.findAllOrderByUserNoDesc("findAllOrderByUserNoDesc");mapper.findByUserNameLikeOrderByUserNoDesc("findByUserNameLikeOrderByUserNoDesc");mapper.findByUserNameStartingWith("findByUserNameStartingWith");mapper.findByUserNameContaining("findByUserNameContaining");mapper.countByUserName("countByUserName");mapper.deleteByUserName("deleteByUserName");return List.of();}}