详解spring boot jpa整合QueryDSL来简化复杂操作

2024-07-13 10:17:33

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前言

使用过spring data jpa的同学，都很清楚，对于复杂的sql查询，处理起来还是比较复杂的，而本文中的QueryDSL就是用来简化JPA操作的。

Querydsl定义了一种常用的静态类型语法，用于在持久域模型数据之上进行查询。JDO和JPA是Querydsl的主要集成技术。本文旨在介绍如何使用Querydsl与JPA组合使用。JPA的Querydsl是JPQL和Criteria查询的替代方法。QueryDSL仅仅是一个通用的查询框架，专注于通过Java API构建类型安全的SQL查询。

要想使用QueryDSL，需要做两个前提操作：

1、pom文件中，加入依赖

<!--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>

2、pom文件中，加入编译插件

<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>

该插件会查找使用javax.persistence.Entity注解的域类型，并为它们生成对应的查询类型。下面以User实体类来说明，生成的查询类型如下：

package com.chhliu.springboot.jpa.entity; import static com.querydsl.core.types.PathMetadataFactory.*; import com.querydsl.core.types.dsl.*; import com.querydsl.core.types.PathMetadata; import javax.annotation.Generated; import com.querydsl.core.types.Path; /**  * QUser is a Querydsl query type for User  */ @Generated("com.querydsl.codegen.EntitySerializer") public class QUser extends EntityPathBase<User> {  private static final long serialVersionUID = 1153899872L;  public static final QUser user = new QUser("user");  public final StringPath address = createString("address");  public final NumberPath<Integer> age = createNumber("age", Integer.class);  public final NumberPath<Integer> id = createNumber("id", Integer.class);  public final StringPath name = createString("name");  public QUser(String variable) {   super(User.class, forVariable(variable));  }   public QUser(Path<? extends User> path) {   super(path.getType(), path.getMetadata());  }   public QUser(PathMetadata metadata) {   super(User.class, metadata);  } }

我们建立好实体类之后，然后运行mvn clean complie命令，就会在

<outputDirectory>target/generated-sources/java</outputDirectory>

目录下生成对应的查询类型。然后将生成的类都拷贝到项目中，即可。

本文涉及到的Entity如下：

package com.chhliu.springboot.jpa.entity; import java.io.Serializable; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.GenerationType; import javax.persistence.Id; import javax.persistence.Table; @Entity @Table(name="t_user") public class User implements Serializable{   /**   *   */  private static final long serialVersionUID = 1L;   @Id()  @GeneratedValue(strategy = GenerationType.AUTO)  private int id;  private String name;  private String address;  private int age;  …………省略getter，setter方法…………  /**   * attention:   * Details：方便查看测试结果   * @author chhliu   */  @Override  public String toString() {   return "User [id=" + id + ", name=" + name + ", address=" + address + ", age=" + age + "]";  } }

上面的这个实体类，主要用于单表操作。

package com.chhliu.springboot.jpa.entity; import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToOne; import javax.persistence.Table; /**  * 描述：TODO  * @author chhliu  */ @Entity @Table(name="PERSON") public class Person {  @Id  @GeneratedValue  private Integer id;  private String name;  private String address;    @OneToOne(mappedBy="person", cascade={CascadeType.PERSIST, CascadeType.REMOVE, CascadeType.MERGE})  private IDCard idCard;     …………省略getter，setter方法…………  @Override  public String toString() {   return "Person [id=" + id + ", name=" + name + ", address=" + address + ", idCard=" + idCard + "]";  } }

package com.chhliu.springboot.jpa.entity; import javax.persistence.CascadeType; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToOne; import javax.persistence.Table; /**  * 描述：  * @author chhliu  */ @Entity @Table(name="IDCARD") public class IDCard {  @Id  @GeneratedValue  private Integer id;  private String idNo;  @OneToOne(cascade={CascadeType.MERGE, CascadeType.REMOVE, CascadeType.PERSIST}, fetch=FetchType.EAGER)  private Person person;    …………省略getter，setter方法…………  @Override  public String toString() {   return "IDCard [id=" + id + ", idNo=" + idNo + ", person=" + person + "]";  } }

上面两个Entity主要用于一对一关系的示例操作

package com.chhliu.springboot.jpa.entity; import java.util.List; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.OneToMany; import javax.persistence.Table; /**  * 描述：Order实体类  * @author chhliu  */ @Entity @Table(name="ORDER_C") public class Order {  @Id  @GeneratedValue  @Column(name="ID")  private Integer id;    @Column(length=20, name="ORDER_NAME")  private String orderName;    @Column(name="COUNT")  private Integer count;    @OneToMany(mappedBy = "order",cascade={CascadeType.PERSIST,CascadeType.REMOVE},fetch = FetchType.EAGER)  private List<OrderItem> orderItems;      …………省略getter，setter方法………… }

package com.chhliu.springboot.jpa.entity; import javax.persistence.CascadeType; import javax.persistence.Column; import javax.persistence.Entity; import javax.persistence.FetchType; import javax.persistence.GeneratedValue; import javax.persistence.Id; import javax.persistence.JoinColumn; import javax.persistence.ManyToOne; import javax.persistence.Table;  /**  * 描述：OrderItem实体类  * @author chhliu  */ @Entity @Table(name="ORDER_ITEM") public class OrderItem {  @Id  @GeneratedValue  @Column(name="ID", nullable=false)  private Integer id;    @Column(name="ITEM_NAME", length=20)  private String itemName;    @Column(name="PRICE")  private Integer price;    @ManyToOne(cascade={CascadeType.PERSIST,CascadeType.REMOVE, CascadeType.MERGE}, fetch=FetchType.EAGER)  @JoinColumn(name = "ORDER_ID")  private Order order;    …………省略getter，setter方法………… }

上面两个Entity用于展示一对多关系的示例操作。

首先，我们来看单表操作

1、使用spring data jpa

要想使用spring data jpa提供的QueryDSL功能，很简单，直接继承接口即可。Spring Data JPA中提供了QueryDslPredicateExecutor接口,用于支持QueryDSL的查询操作接口，如下：

package com.chhliu.springboot.jpa.repository; import org.springframework.data.jpa.repository.JpaRepository; import org.springframework.data.querydsl.QueryDslPredicateExecutor; import com.chhliu.springboot.jpa.entity.User; public interface UserRepositoryDls extends JpaRepository<User, Integer>, QueryDslPredicateExecutor<User>{// 继承接口 }

QueryDslPredicateExecutor接口提供了如下方法：

public interface QueryDslPredicateExecutor<T> {  T findOne(Predicate predicate);  Iterable<T> findAll(Predicate predicate);  Iterable<T> findAll(Predicate predicate, Sort sort);  Iterable<T> findAll(Predicate predicate, OrderSpecifier<?>... orders);  Iterable<T> findAll(OrderSpecifier<?>... orders);  Page<T> findAll(Predicate predicate, Pageable pageable);  long count(Predicate predicate);  boolean exists(Predicate predicate); }

以上方法的使用和spring data jpa中的其他接口使用方法类似，详情请参考：http://www.vevb.com/article/137757.htm

测试如下：

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);// 根据用户名，查询user表   return repository.findOne(predicate);  }

对应的sql如下：

复制代码代码如下:

	select user0_.id as id1_5_, user0_.address as address2_5_, user0_.age as age3_5_, user0_.name as name4_5_ from t_user user0_ where  user0_.name=?

单表操作示例代码如下：

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 {  @Autowired  private UserRepositoryDls repository;    @Autowired  @PersistenceContext  private EntityManager entityManager;    private JPAQueryFactory queryFactory;     @PostConstruct   public 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)如下：

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  @PersistenceContext  private EntityManager entityManager;    private JPAQueryFactory queryFactory;    @PostConstruct  public 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  @PersistenceContext  private EntityManager entityManager;    private JPAQueryFactory queryFactory;    @PostConstruct  public 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();  } }

从上面的示例中，我们可以看出，QueryDSL大大的简化了我们的操作

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持VeVb武林网。

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