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，小编觉得挺不错的，现在分享给大家，也给大家做个参考。一起跟随小编过来看看吧

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 { @Query(value = "SELECT new com.johnfnash.learn.domain.ViewInfo(u, a) FROM UserInfo u, Address a WHERE u.addressId = a.addressId") public List 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 { }

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 { @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","123@xx.com", addr1.getAddressId()); UserInfo user2 = new UserInfo("Ww", 25,"Male","234@xx.com", addr2.getAddressId()); userInfoRepository.save(user1); userInfoRepository.save(user2); } @After public void deleteAll() { userInfoRepository.deleteAll(); addressRepository.deleteAll(); } @Test public void testQuery() { List 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 @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; @Entity public 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 { @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 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 { }

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 { }

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 { @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 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：