Spring Data JPA 实现多表关联查询的示例代码

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 @Override public 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 @Override public 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)@SpringBootTestpublic class UserInfoRepositoryTests { @Autowired  private UserInfoRepository userInfoRepository; @Autowired private AddressRepository addressRepository; @Before  public 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","[email protected]", addr1.getAddressId());    UserInfo user2 = new UserInfo("Ww", 25,"Male","[email protected]", addr2.getAddressId());    userInfoRepository.save(user1);    userInfoRepository.save(user2);  } @After public void deleteAll() {  userInfoRepository.deleteAll();  addressRepository.deleteAll(); } @Test public 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_idHibernate: 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 protected]]
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 protected]]
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;@Entitypublic class Author implements Serializable { private static final long serialVersionUID = 1227555837798655046L; @Id  @GeneratedValue  private Integer id;  private String name; public Author() {  super(); } public Author(String name) {  super();  this.name = name; } // getter, setter @Override  public 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;@Entitypublic class Book implements Serializable { private static final long serialVersionUID = -2470510857424220408L; @Id  @GeneratedValue  private Integer id;  private String name;  public Book() {    super();  }  public Book(String name) {    super();    this.name = name;  } //getter, setter @Override public 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 { @Id private Integer bookId; @Id private 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)@SpringBootTestpublic class BookRepositoryTests { @Autowired private BookRepository bookRepository; @Autowired private AuthorRepository authorRepository; @Autowired private BookAuthorRepository bookAuthorRepository; @Before public 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())); } @After public void deleteAll() {  bookAuthorRepository.deleteAll();  bookRepository.deleteAll();  authorRepository.deleteAll(); } @Test public 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,

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武林网。