Spring Data JPA 实现多表关联查询的示例代码-eolink官网

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 {

@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SiSWKYw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(userSiSWKYw1);

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 usehttp://r_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 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 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 = authorIdhttp://;

}

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

}

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

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,

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