JPA 复杂查询 - Querydsl

 添加依赖

    <!--query dsl -->  <dependency>  <groupId>com.querydsl</groupId>  <artifactId>querydsl-jpa</artifactId>  </dependency>  <dependency>  <groupId>com.querydsl</groupId>  <artifactId>querydsl-apt</artifactId>  <scope>provided</scope>  </dependency>  

    <plugin>  <groupId>com.mysema.maven</groupId>  <artifactId>apt-maven-plugin</artifactId>  <version>1.1.3</version>  <executions>  <execution>  <goals>  <goal>process</goal>  </goals>  <configuration>  <outputDirectory>target/generated-sources/java</outputDirectory>  <processor>com.querydsl.apt.jpa.JPAAnnotationProcessor</processor>  </configuration>  </execution>  </executions>  </plugin>  

运行 mvn compile， 将生成Query实体。

单表查询

package com.chhliu.springboot.jpa.repository;import java.util.List;import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;
import javax.persistence.Query;
import javax.transaction.Transactional;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.data.domain.Page;
import org.springframework.data.domain.PageRequest;
import org.springframework.data.domain.Sort;
import org.springframework.stereotype.Component;import com.chhliu.springboot.jpa.entity.QUser;
import com.chhliu.springboot.jpa.entity.User;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQueryFactory;/*** 描述：QueryDSL JPA* @author chhliu*/
@Component
@Transactional
public class UserRepositoryManagerDsl {@Autowiredprivate UserRepositoryDls repository;@Autowired@PersistenceContextprivate EntityManager entityManager;private JPAQueryFactory queryFactory;@PostConstructpublic void init() {queryFactory = new JPAQueryFactory(entityManager);}public User findUserByUserName(final String userName){/*** 该例是使用spring data QueryDSL实现*/QUser quser = QUser.user;Predicate predicate = quser.name.eq(userName);return repository.findOne(predicate);}/*** attention:* Details：查询user表中的所有记录*/public List<User> findAll(){QUser quser = QUser.user;return queryFactory.selectFrom(quser).fetch();}/*** Details：单条件查询*/public User findOneByUserName(final String userName){QUser quser = QUser.user;return queryFactory.selectFrom(quser).where(quser.name.eq(userName)).fetchOne();}/*** Details：单表多条件查询*/public User findOneByUserNameAndAddress(final String userName, final String address){QUser quser = QUser.user;return queryFactory.select(quser).from(quser) // 上面两句代码等价与selectFrom.where(quser.name.eq(userName).and(quser.address.eq(address)))// 这句代码等同于where(quser.name.eq(userName), quser.address.eq(address))
            .fetchOne();}/*** Details：使用join查询*/public List<User> findUsersByJoin(){QUser quser = QUser.user;QUser userName = new QUser("name");return queryFactory.selectFrom(quser).innerJoin(quser).on(quser.id.intValue().eq(userName.id.intValue())).fetch();}/*** Details：将查询结果排序*/public List<User> findUserAndOrder(){QUser quser = QUser.user;return queryFactory.selectFrom(quser).orderBy(quser.id.desc()).fetch();}/*** Details：Group By使用*/public List<String> findUserByGroup(){QUser quser = QUser.user;return queryFactory.select(quser.name).from(quser).groupBy(quser.name).fetch();}/*** Details：删除用户*/public long deleteUser(String userName){QUser quser = QUser.user;return queryFactory.delete(quser).where(quser.name.eq(userName)).execute();}/*** Details：更新记录*/public long updateUser(final User u, final String userName){QUser quser = QUser.user;return queryFactory.update(quser).where(quser.name.eq(userName)).set(quser.name, u.getName()).set(quser.age, u.getAge()).set(quser.address, u.getAddress()).execute();}/*** Details：使用原生Query*/public User findOneUserByOriginalSql(final String userName){QUser quser = QUser.user;Query query = queryFactory.selectFrom(quser).where(quser.name.eq(userName)).createQuery();return (User) query.getSingleResult();}/*** Details：分页查询单表*/public Page<User> findAllAndPager(final int offset, final int pageSize){Predicate predicate = QUser.user.id.lt(10);Sort sort = new Sort(new Sort.Order(Sort.Direction.DESC, "id"));PageRequest pr = new PageRequest(offset, pageSize, sort);return repository.findAll(predicate, pr);}
}

多表操作示例(一对一)

package com.chhliu.springboot.jpa.repository;import java.util.ArrayList;
import java.util.List;import javax.annotation.PostConstruct;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;import com.chhliu.springboot.jpa.dto.PersonIDCardDto;
import com.chhliu.springboot.jpa.entity.QIDCard;
import com.chhliu.springboot.jpa.entity.QPerson;
import com.querydsl.core.QueryResults;
import com.querydsl.core.Tuple;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQuery;
import com.querydsl.jpa.impl.JPAQueryFactory;@Component
public class PersonAndIDCardManager {@Autowired@PersistenceContextprivate EntityManager entityManager;private JPAQueryFactory queryFactory;@PostConstructpublic void init() {queryFactory = new JPAQueryFactory(entityManager);}/*** Details：多表动态查询*/public List<Tuple> findAllPersonAndIdCard(){Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());JPAQuery<Tuple> jpaQuery = queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name).from(QIDCard.iDCard, QPerson.person).where(predicate);return jpaQuery.fetch();}/*** Details：将查询结果以DTO的方式输出*/public List<PersonIDCardDto> findByDTO(){Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());JPAQuery<Tuple> jpaQuery = queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name).from(QIDCard.iDCard, QPerson.person).where(predicate);List<Tuple> tuples = jpaQuery.fetch();List<PersonIDCardDto> dtos = new ArrayList<PersonIDCardDto>();if(null != tuples && !tuples.isEmpty()){for(Tuple tuple:tuples){String address = tuple.get(QPerson.person.address);String name = tuple.get(QPerson.person.name);String idCard = tuple.get(QIDCard.iDCard.idNo);PersonIDCardDto dto = new PersonIDCardDto();dto.setAddress(address);dto.setIdNo(idCard);dto.setName(name);dtos.add(dto);}}return dtos;}/*** Details：多表动态查询，并分页*/public QueryResults<Tuple> findByDtoAndPager(int offset, int pageSize){Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());return queryFactory.select(QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name).from(QIDCard.iDCard, QPerson.person).where(predicate).offset(offset).limit(pageSize).fetchResults();}
}

上面将查询结果以DTO的方式输出的示例中，在查询结束后，将查询结果手动的转换成了DTO对象，这种方式其实不太优雅，QueryDSL给我们提供了更好的方式，见下面的示例：

/*** Details：方式一：使用Bean投影*/public List<PersonIDCardDto> findByDTOUseBean(){Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());return queryFactory.select(Projections.bean(PersonIDCardDto.class, QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name)).from(QIDCard.iDCard, QPerson.person).where(predicate).fetch();}/*** Details：方式二：使用fields来代替setter*/public List<PersonIDCardDto> findByDTOUseFields(){Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());return queryFactory.select(Projections.fields(PersonIDCardDto.class, QIDCard.iDCard.idNo, QPerson.person.address, QPerson.person.name)).from(QIDCard.iDCard, QPerson.person).where(predicate).fetch();}/*** Details：方式三：使用构造方法，注意构造方法中属性的顺序必须和构造器中的顺序一致*/public List<PersonIDCardDto> findByDTOUseConstructor(){Predicate predicate = (QPerson.person.id.intValue()).eq(QIDCard.iDCard.person.id.intValue());return queryFactory.select(Projections.constructor(PersonIDCardDto.class, QPerson.person.name, QPerson.person.address, QIDCard.iDCard.idNo)).from(QIDCard.iDCard, QPerson.person).where(predicate).fetch();}

上面只是提供了几种思路，当然，还可以使用@QueryProjection来实现，非常灵活。
一对多示例：

package com.chhliu.springboot.jpa.repository;import java.util.List;import javax.annotation.PostConstruct;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;import com.chhliu.springboot.jpa.entity.QOrder;
import com.chhliu.springboot.jpa.entity.QOrderItem;
import com.querydsl.core.Tuple;
import com.querydsl.core.types.Predicate;
import com.querydsl.jpa.impl.JPAQuery;
import com.querydsl.jpa.impl.JPAQueryFactory;@Component
public class OrderAndOrderItemManager {@Autowired@PersistenceContextprivate EntityManager entityManager;private JPAQueryFactory queryFactory;@PostConstructpublic void init() {queryFactory = new JPAQueryFactory(entityManager);}/*** Details：一对多，条件查询*/public List<Tuple> findOrderAndOrderItemByOrderName(String orderName){//添加查询条件Predicate predicate = QOrder.order.orderName.eq(orderName);JPAQuery<Tuple> jpaQuery = queryFactory.select(QOrder.order, QOrderItem.orderItem).from(QOrder.order, QOrderItem.orderItem).where(QOrderItem.orderItem.order.id.intValue().eq(QOrder.order.id.intValue()), predicate);//拿到结果return jpaQuery.fetch();}/*** Details：多表连接查询*/public List<Tuple> findAllByOrderName(String orderName){//添加查询条件Predicate predicate = QOrder.order.orderName.eq(orderName);JPAQuery<Tuple> jpaQuery = queryFactory.select(QOrder.order, QOrderItem.orderItem).from(QOrder.order, QOrderItem.orderItem).rightJoin(QOrder.order).on(QOrderItem.orderItem.order.id.intValue().eq(QOrder.order.id.intValue()));jpaQuery.where(predicate);//拿到结果return jpaQuery.fetch();}
}

链接

Querydsl Reference Guide

使用QueryDSL

复杂查询的封装

spring boot-jpa整合QueryDSL来简化复杂操作

Spring Boot JPA - 使用 Querydsl 处理复杂的操作