溫馨提示×
您好，登錄后才能下訂單哦！
點擊 登錄注冊 即表示同意《億速云用戶服務條款》
您好，登錄后才能下訂單哦！
小編給大家分享一下spring boot jpa如何整合QueryDSL來簡化復雜操作，相信大部分人都還不怎么了解，因此分享這篇文章給大家參考一下，希望大家閱讀完這篇文章后大有收獲，下面讓我們一起去了解一下吧！
前言
使用過spring data jpa的同學，都很清楚，對于復雜的sql查詢，處理起來還是比較復雜的，而本文中的QueryDSL就是用來簡化JPA操作的。
Querydsl定義了一種常用的靜態類型語法，用于在持久域模型數據之上進行查詢。JDO和JPA是Querydsl的主要集成技術。本文旨在介紹如何使用Querydsl與JPA組合使用。JPA的Querydsl是JPQL和Criteria查詢的替代方法。QueryDSL僅僅是一個通用的查詢框架，專注于通過Java API構建類型安全的SQL查詢。
要想使用QueryDSL，需要做兩個前提操作：
1、pom文件中，加入依賴
<!--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，加入編譯插件
<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>
該插件會查找使用javax.persistence.Entity注解的域類型，并為它們生成對應的查詢類型。下面以User實體類來說明，生成的查詢類型如下：
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);
}
}我們建立好實體類之后，然后運行mvn clean complie命令，就會在
<outputDirectory>target/generated-sources/java</outputDirectory>
目錄下生成對應的查詢類型。然后將生成的類都拷貝到項目中，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：方便查看測試結果
* @author chhliu
*/
@Override
public String toString() {
return "User [id=" + id + ", name=" + name + ", address=" + address + ", age=" + age + "]";
}
}上面的這個實體類，主要用于單表操作。
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 + "]";
}
}上面兩個Entity主要用于一對一關系的示例操作
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實體類
* @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實體類
* @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…………
}上面兩個Entity用于展示一對多關系的示例操作。
首先，我們來看單表操作
1、使用spring data jpa
要想使用spring data jpa提供的QueryDSL功能，很簡單，直接繼承接口即可。Spring Data JPA中提供了QueryDslPredicateExecutor接口,用于支持QueryDSL的查詢操作接口，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>{
// 繼承接口
}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類似，詳情請參考：https://www.jb51.net/article/137757.htm
測試如下：
public User findUserByUserName(final String userName){
/**
* 該例是使用spring data QueryDSL實現
*/
QUser quser = QUser.user;
Predicate predicate = quser.name.eq(userName);// 根據用戶名，查詢user表
return repository.findOne(predicate);
}對應的sql如下：
復制代碼 代碼如下:
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=?
單表操作示例代碼如下：
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){
/**
* 該例是使用spring data QueryDSL實現
*/
QUser quser = QUser.user;
Predicate predicate = quser.name.eq(userName);
return repository.findOne(predicate);
}
/**
* attention:
* Details：查詢user表中的所有記錄
*/
public List<User> findAll(){
QUser quser = QUser.user;
return queryFactory.selectFrom(quser)
.fetch();
}
/**
* Details：單條件查詢
*/
public User findOneByUserName(final String userName){
QUser quser = QUser.user;
return queryFactory.selectFrom(quser)
.where(quser.name.eq(userName))
.fetchOne();
}
/**
* Details：單表多條件查詢
*/
public User findOneByUserNameAndAddress(final String userName, final String address){
QUser quser = QUser.user;
return queryFactory.select(quser)
.from(quser) // 上面兩句代碼等價與selectFrom
.where(quser.name.eq(userName).and(quser.address.eq(address)))// 這句代碼等同于where(quser.name.eq(userName), quser.address.eq(address))
.fetchOne();
}
/**
* Details：使用join查詢
*/
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：將查詢結果排序
*/
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：刪除用戶
*/
public long deleteUser(String userName){
QUser quser = QUser.user;
return queryFactory.delete(quser).where(quser.name.eq(userName)).execute();
}
/**
* Details：更新記錄
*/
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：分頁查詢單表
*/
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(一對一)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：多表動態查詢
*/
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：將查詢結果以DTO的方式輸出
*/
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：多表動態查詢，并分頁
*/
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();
}
}上面將查詢結果以DTO的方式輸出的示例中，在查詢結束后，將查詢結果手動的轉換成了DTO對象，這種方式其實不太優雅，QueryDSL給我們提供了更好的方式，見下面的示例：
/**
* 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來代替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：使用構造方法，注意構造方法中屬性的順序必須和構造器中的順序一致
*/
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();
}上面只是提供了幾種思路，當然，還可以使用@QueryProjection來實現，非常靈活。
一對多示例：
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：一對多，條件查詢
*/
public List<Tuple> findOrderAndOrderItemByOrderName(String orderName){
//添加查詢條件
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);
//拿到結果
return jpaQuery.fetch();
}
/**
* Details：多表連接查詢
*/
public List<Tuple> findAllByOrderName(String orderName){
//添加查詢條件
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);
//拿到結果
return jpaQuery.fetch();
}
}從上面的示例中，我們可以看出，QueryDSL大大的簡化了我們的操作
以上是“spring boot jpa如何整合QueryDSL來簡化復雜操作”這篇文章的所有內容，感謝各位的閱讀！相信大家都有了一定的了解，希望分享的內容對大家有所幫助，如果還想學習更多知識，歡迎關注億速云行業資訊頻道！
免責聲明：本站發布的內容（圖片、視頻和文字）以原創、轉載和分享為主，文章觀點不代表本網站立場，如果涉及侵權請聯系站長郵箱：is@yisu.com進行舉報，并提供相關證據，一經查實，將立刻刪除涉嫌侵權內容。
