Spring Data JPA 实现多表关联查询

原文链接：https://blog.csdn.net/johnf_nash/article/details/80587204

多表查询在spring data jpa中有两种实现方式，第一种是利用hibernate的级联查询来实现，第二种是创建一个结果集的接口来接收连表查询后的结果，这里介绍第二种方式。

一、一对一映射

实体 UserInfo ：用户。

实体 Address：家庭住址。

这里通过外键的方式(一个实体通过外键关联到另一个实体的主键)来实现一对一关联。

实体类

1、实体类 UserInfo.java

package com.johnfnash.learn.domain;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="tb_user")
public class UserInfo implements Serializable {private static final long serialVersionUID = 8283950216116626180L;@Id@GeneratedValue(strategy=GenerationType.IDENTITY)private Long userId;private String name;private int age;private String sex;private String email;// 与 Address 的关联  private Long addressId;public UserInfo() {super();}public UserInfo(String name, int age, String sex, String email, Long addressId) {super();this.name = name;this.age = age;this.sex = sex;this.email = email;this.addressId = addressId;}// getter, setter@Overridepublic String toString() {return String.format("UserInfo [userId=%d, name=%s, age=%s, sex=%s, email=%s]", userId, name, age, sex, email);}}

2. 实体类 Address.java

package com.johnfnash.learn.domain;import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.GenerationType;
import javax.persistence.Id;
import javax.persistence.Table;@Entity
@Table(name = "tb_address")
public class Address {@Id@GeneratedValue(strategy = GenerationType.IDENTITY)private Long addressId;private String areaCode;private String country;private String province;private String city;private String area;private String detailAddress;public Address() {super();}public Address(String areaCode, String country, String province, String city, String area,String detailAddress) {super();this.areaCode = areaCode;this.country = country;this.province = province;this.city = city;this.area = area;this.detailAddress = detailAddress;}// getter, setter@Overridepublic String toString() {return "Address [addressId=" + addressId + ", areaCode=" + areaCode + ", country=" + country + ", province="+ province + ", city=" + city + ", area=" + area + ", detailAddress=" + detailAddress + "]";}}

Dao 层

1、UserInfoRepository.java

package com.johnfnash.learn.repository;import java.util.List;import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;import com.johnfnash.learn.domain.UserInfo;
import com.johnfnash.learn.domain.ViewInfo;public interface UserInfoRepository extends JpaRepository<UserInfo, Long> {@Query(value = "SELECT new com.johnfnash.learn.domain.ViewInfo(u, a) FROM UserInfo u, Address a WHERE u.addressId = a.addressId")public List<ViewInfo> findViewInfo();}

注：这里的 ViewInfo 类用来一个用来接收多表查询结果集的类（使用 new + 完整类名构造函数）
代码如下：

package com.johnfnash.learn.domain;import java.io.Serializable;public class ViewInfo implements Serializable {private static final long serialVersionUID = -6347911007178390219L;private UserInfo userInfo;private Address address;public ViewInfo() {}public ViewInfo(UserInfo userInfo) {Address address = new Address();this.userInfo = userInfo;this.address = address;}public ViewInfo(Address address) {UserInfo userInfo = new UserInfo();this.userInfo = userInfo;this.address = address;}public ViewInfo(UserInfo userInfo, Address address) {this.userInfo = userInfo;this.address = address;}// getter, setter}

2. AddressRepository.java

package com.johnfnash.learn.repository;import org.springframework.data.jpa.repository.JpaRepository;import com.johnfnash.learn.domain.Address;public interface AddressRepository extends JpaRepository<Address, Long> {}

测试代码

package com.johnfnash.learn;import java.util.List;import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;import com.johnfnash.learn.domain.Address;
import com.johnfnash.learn.domain.UserInfo;
import com.johnfnash.learn.domain.ViewInfo;
import com.johnfnash.learn.repository.AddressRepository;
import com.johnfnash.learn.repository.UserInfoRepository;@RunWith(SpringRunner.class)
@SpringBootTest
public class UserInfoRepositoryTests {@Autowiredprivate UserInfoRepository userInfoRepository;@Autowiredprivate AddressRepository addressRepository;@Beforepublic void init() {Address addr1 = new Address("027","CN","HuBei", "WuHan","WuChang", "123 street");Address addr2 = new Address("023","CN","ChongQing", "ChongQing","YuBei", "123 road");addressRepository.save(addr1);addressRepository.save(addr2);UserInfo user1 = new UserInfo("ZS", 21,"Male","123@xx.com", addr1.getAddressId());UserInfo user2 = new UserInfo("Ww", 25,"Male","234@xx.com", addr2.getAddressId());userInfoRepository.save(user1);userInfoRepository.save(user2);}@Afterpublic void deleteAll() {userInfoRepository.deleteAll();addressRepository.deleteAll();}@Testpublic void testQuery() {List<ViewInfo> viewInfos = userInfoRepository.findViewInfo();for (ViewInfo viewInfo : viewInfos) {System.out.println(viewInfo.getUserInfo());System.out.println(viewInfo.getAddress());}}}

查询相关的 sql 如下：

Hibernate: select userinfo0_.user_id as col_0_0_, address1_.address_id as col_1_0_ from tb_user userinfo0_ cross join tb_address address1_ where userinfo0_.address_id=address1_.address_id
Hibernate: select userinfo0_.user_id as user_id1_4_0_, userinfo0_.address_id as address_2_4_0_, userinfo0_.age as age3_4_0_, userinfo0_.email as email4_4_0_, userinfo0_.name as name5_4_0_, userinfo0_.sex as sex6_4_0_ from tb_user userinfo0_ where userinfo0_.user_id=?
Hibernate: select address0_.address_id as address_1_3_0_, address0_.area as area2_3_0_, address0_.area_code as area_cod3_3_0_, address0_.city as city4_3_0_, address0_.country as country5_3_0_, address0_.detail_address as detail_a6_3_0_, address0_.province as province7_3_0_ from tb_address address0_ where address0_.address_id=?
Hibernate: select userinfo0_.user_id as user_id1_4_0_, userinfo0_.address_id as address_2_4_0_, userinfo0_.age as age3_4_0_, userinfo0_.email as email4_4_0_, userinfo0_.name as name5_4_0_, userinfo0_.sex as sex6_4_0_ from tb_user userinfo0_ where userinfo0_.user_id=?
Hibernate: select address0_.address_id as address_1_3_0_, address0_.area as area2_3_0_, address0_.area_code as area_cod3_3_0_, address0_.city as city4_3_0_, address0_.country as country5_3_0_, address0_.detail_address as detail_a6_3_0_, address0_.province as province7_3_0_ from tb_address address0_ where address0_.address_id=?
Hibernate: select userinfo0_.user_id as user_id1_4_, userinfo0_.address_id as address_2_4_, userinfo0_.age as age3_4_, userinfo0_.email as email4_4_, userinfo0_.name as name5_4_, userinfo0_.sex as sex6_4_ from tb_user userinfo0_
Hibernate: select address0_.address_id as address_1_3_, address0_.area as area2_3_, address0_.area_code as area_cod3_3_, address0_.city as city4_3_, address0_.country as country5_3_, address0_.detail_address as detail_a6_3_, address0_.province as province7_3_ from tb_address address0_

查询结果如下：

UserInfo [userId=1, name=ZS, age=21, sex=Male, email=123@xx.com]
Address [addressId=1, areaCode=027, country=CN, province=HuBei, city=WuHan, area=WuChang, detailAddress=123 street]
UserInfo [userId=2, name=Ww, age=25, sex=Male, email=234@xx.com]
Address [addressId=2, areaCode=023, country=CN, province=ChongQing, city=ChongQing, area=YuBei, detailAddress=123 road]

二、多对多映射

实体 Author ：作者。

实体 Book ：书籍

这里通过关联表的方式来实现多对多关联。

实体类

实体类：Author.java

package com.johnfnash.learn.domain;import java.io.Serializable;import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;@Entity
public class Author implements Serializable {private static final long serialVersionUID = 1227555837798655046L;@Id@GeneratedValueprivate Integer id;private String name;public Author() {super();}public Author(String name) {super();this.name = name;}// getter, setter@Overridepublic String toString() {return String.format("Author [id=%s, name=%s]", id, name);}}

Book.java 实体类

package com.johnfnash.learn.domain;import java.io.Serializable;import javax.persistence.Entity;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;@Entity
public class Book implements Serializable {private static final long serialVersionUID = -2470510857424220408L;@Id@GeneratedValueprivate Integer id;private String name;public Book() {super();}public Book(String name) {super();this.name = name;}//getter, setter@Overridepublic String toString() {return String.format("Book [id=%s, name=%s]", id, name);}}

实体类BookAuthor.java

package com.johnfnash.learn.domain;import javax.persistence.Entity;
import javax.persistence.Id;
import javax.persistence.IdClass;
import javax.persistence.Table;@Entity
@IdClass(BookAuthorPK.class)
@Table(name = "book_author")
public class BookAuthor {@Idprivate Integer bookId;@Idprivate Integer authorId;public BookAuthor() {super();}public BookAuthor(Integer bookId, Integer authorId) {super();this.bookId = bookId;this.authorId = authorId;}// getter, setter}

注：这里使用 @IdClass 注解指定一个联合主键类来映射实体类的多个属性。这个联合主键类的代码如下：

package com.johnfnash.learn.domain;import java.io.Serializable;public class BookAuthorPK implements Serializable {private static final long serialVersionUID = -1158141803682305656L;private Integer bookId;private Integer authorId;public Integer getBookId() {return bookId;}public void setBookId(Integer bookId) {this.bookId = bookId;}public Integer getAuthorId() {return authorId;}public void setAuthorId(Integer authorId) {this.authorId = authorId;}}

Dao 层

BookRepository.java

package com.johnfnash.learn.repository;import java.util.List;import org.springframework.data.jpa.repository.JpaRepository;
import org.springframework.data.jpa.repository.Query;import com.johnfnash.learn.domain.Book;public interface BookRepository extends JpaRepository<Book, Integer> {@Query(nativeQuery = true, value = "SELECT b.id, b.name, GROUP_CONCAT(a.name) as authorName from book b, author a, book_author ba"+ " where b.id = ba.book_id and a.id = ba.author_id and b.name like ?1 group by b.id, b.name")List<Object[]> findByNameContaining(String name);}

注：
1）这里使用 nativeQuery = true 指定使用原生 SQL 进行查询（个人觉得复杂的查询使用原生SQL更好
2）这里使用了 mysql 的内置函数 GROUP_CONCAT 进行行转列, HQL 无法直接识别。可能会出现 Caused by: org.hibernate.QueryException: No data type for node: org.hibernate.hql.internal.ast.tree.MethodNode 的错误

JpaRepository.java

package com.johnfnash.learn.repository;import org.springframework.data.jpa.repository.JpaRepository;import com.johnfnash.learn.domain.Author;public interface AuthorRepository extends JpaRepository<Author, Integer> {}

BookAuthorRepository.java

package com.johnfnash.learn.repository;import org.springframework.data.jpa.repository.JpaRepository;import com.johnfnash.learn.domain.BookAuthor;public interface BookAuthorRepository extends JpaRepository<BookAuthor, Integer> {}

测试代码

package com.johnfnash.learn;import static org.junit.Assert.assertEquals;import java.util.List;import org.junit.After;
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.junit4.SpringRunner;import com.johnfnash.learn.domain.Author;
import com.johnfnash.learn.domain.Book;
import com.johnfnash.learn.domain.BookAuthor;
import com.johnfnash.learn.repository.AuthorRepository;
import com.johnfnash.learn.repository.BookAuthorRepository;
import com.johnfnash.learn.repository.BookRepository;@RunWith(SpringRunner.class)
@SpringBootTest
public class BookRepositoryTests {@Autowiredprivate BookRepository bookRepository;@Autowiredprivate AuthorRepository authorRepository;@Autowiredprivate BookAuthorRepository bookAuthorRepository;@Beforepublic void init() {Author lewis = new Author("Lewis");Author mark = new Author("Mark");Author peter = new Author("Peter");authorRepository.save(lewis);authorRepository.save(mark);authorRepository.save(peter);Book spring = new Book("Spring in Action");Book springboot = new Book("Spring Boot in Action");bookRepository.save(spring);bookRepository.save(springboot);bookAuthorRepository.save(new BookAuthor(spring.getId(), lewis.getId()));bookAuthorRepository.save(new BookAuthor(spring.getId(), mark.getId()));bookAuthorRepository.save(new BookAuthor(springboot.getId(), mark.getId()));bookAuthorRepository.save(new BookAuthor(springboot.getId(), peter.getId()));}@Afterpublic void deleteAll() {bookAuthorRepository.deleteAll();bookRepository.deleteAll();authorRepository.deleteAll();}@Testpublic void findAll() {assertEquals(bookRepository.findAll().size(), 2);assertEquals(authorRepository.findAll().size(), 3);List<Object[]> books = bookRepository.findByNameContaining("Spring%");for (Object[] book : books) {for (Object object : book) {System.out.print(object + ", ");}System.out.println();}}}

执行 findAll 方法后，查询的相关 SQL 如下：

Hibernate: SELECT b.id, b.name, GROUP_CONCAT(a.name) as authorName from book b, author a, book_author ba where b.id = ba.book_id and a.id = ba.author_id and b.name like ? group by b.id, b.name

输出的结果如下：

3652, Spring in Action, Lewis,Mark,
3653, Spring Boot in Action, Mark,Peter,

参考

(1) Spring Data JPA 实现多表关联查询

(2) springboot(五): spring data jpa的使用

(3) Spring Data JPA 实现多表关联查询