Spring Data JPA 實現多表關聯查詢

多表查詢在spring data jpa中有兩種實現方式，第一種是利用hibernate的級聯查詢來實現，第二種是建立一個結果集的介面來接收連表查詢後的結果，這裡介紹第二種方式。

一、一對一對映

實體 UserInfo ：使用者。

實體 Address：家庭住址。

這裡通過外來鍵的方式(一個實體通過外來鍵關聯到另一個實體的主鍵)來實現一對一關聯。

實體類

1、實體類 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 = 8283950216116626180
 
L;

@Id
@GeneratedValue(strategy=GenerationType.IDENTITY)
private Long userId;
private String name;
private int age;
private String sex;
private String email;
// 與 Address 的關聯  
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);

}
}

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2. 實體類 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 + "]";

}
}

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Dao 層

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();
}

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注：這裡的 ViewInfo 類用來一個用來接收多表查詢結果集的類（使用 new + 完整類名建構函式）
程式碼如下：

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
}

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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> {
}

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測試程式碼

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(<span class="hljs-string">"ZS"</span>, <span class="hljs-number">21</span>,<span class="hljs-string">"Male"</span>,<span class="hljs-string">"[email protected]"</span>, addr1<span class="hljs-preprocessor">.getAddressId</span>())<span class="hljs-comment">;</span>
    UserInfo user2 = new UserInfo(<span class="hljs-string">"Ww"</span>, <span class="hljs-number">25</span>,<span class="hljs-string">"Male"</span>,<span class="hljs-string">"[email protected]"</span>, addr2<span class="hljs-preprocessor">.getAddressId</span>())<span class="hljs-comment">;</span>
    userInfoRepository<span class="hljs-preprocessor">.save</span>(user1)<span class="hljs-comment">;</span>
    userInfoRepository<span class="hljs-preprocessor">.save</span>(user2)<span class="hljs-comment">;</span>
}

@After

public void deleteAll() {

userInfoRepository.deleteAll();
addressRepository<span class="hljs-preprocessor">.deleteAll</span>()<span class="hljs-comment">;</span>

}
@Test

public void testQuery() {

List<ViewInfo> viewInfos = userInfoRepository.findViewInfo();

for (ViewInfo viewInfo : viewInfos) {

System.out.println(viewInfo.getUserInfo());

System.out.println(viewInfo.getAddress());

}

}
}

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查詢相關的 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_

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查詢結果如下：

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]

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二、多對多對映

實體 Author ：作者。

實體 Book ：書籍

這裡通過關聯表的方式來實現多對多關聯。

實體類

實體類：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;
<span class="hljs-keyword">private</span> 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);

}
}

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Book.java 實體類

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;
<span class="hljs-keyword">private</span> String name;

<span class="hljs-keyword">public</span> <span class="hljs-title">Book</span>() {
    <span class="hljs-keyword">super</span>();
}

<span class="hljs-keyword">public</span> <span class="hljs-title">Book</span>(String name) {
    <span class="hljs-keyword">super</span>();
    <span class="hljs-keyword">this</span>.name = name;
}

//getter, setter
@Override
public String toString() {
return String.format("Book [id=%s, name=%s]", id, name);

}
}

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實體類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
}

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注：這裡使用 @IdClass 註解指定一個聯合主鍵類來對映實體類的多個屬性。這個聯合主鍵類的程式碼如下：

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;

}
}

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Dao 層

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);
}

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注：
1）這裡使用 nativeQuery = true 指定使用原生 SQL 進行查詢（個人覺得複雜的查詢使用原生SQL更好
2）這裡使用了 mysql 的內建函式 GROUP_CONCAT 進行行轉列, HQL 無法直接識別。可能會出現 Caused by: org.hibernate.QueryException: No data type for node: org.hibernate.hql.internal.ast.tree.MethodNode 的錯誤

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> {
}

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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> {
}

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測試程式碼

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(<span class="hljs-string">"Spring in Action"</span>)<span class="hljs-comment">;</span>
  Book springboot = new Book(<span class="hljs-string">"Spring Boot in Action"</span>)<span class="hljs-comment">;</span>
  bookRepository<span class="hljs-preprocessor">.save</span>(spring)<span class="hljs-comment">;</span>
  bookRepository<span class="hljs-preprocessor">.save</span>(springboot)<span class="hljs-comment">;</span>

  bookAuthorRepository<span class="hljs-preprocessor">.save</span>(new BookAuthor(spring<span class="hljs-preprocessor">.getId</span>(), lewis<span class="hljs-preprocessor">.getId</span>()))<span class="hljs-comment">;</span>
  bookAuthorRepository<span class="hljs-preprocessor">.save</span>(new BookAuthor(spring<span class="hljs-preprocessor">.getId</span>(), mark<span class="hljs-preprocessor">.getId</span>()))<span class="hljs-comment">;</span>
  bookAuthorRepository<span class="hljs-preprocessor">.save</span>(new BookAuthor(springboot<span class="hljs-preprocessor">.getId</span>(), mark<span class="hljs-preprocessor">.getId</span>()))<span class="hljs-comment">;</span>
  bookAuthorRepository<span class="hljs-preprocessor">.save</span>(new BookAuthor(springboot<span class="hljs-preprocessor">.getId</span>(), peter<span class="hljs-preprocessor">.getId</span>()))<span class="hljs-comment">;</span>

}
@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&lt;Object[]&gt; books = bookRepository<span class="hljs-preprocessor">.findByNameContaining</span>(<span class="hljs-string">"Spring%"</span>)<span class="hljs-comment">;</span>
for (Object[] book : books) {
  for (Object object : book) {
    System<span class="hljs-preprocessor">.out</span><span class="hljs-preprocessor">.print</span>(object + <span class="hljs-string">", "</span>)<span class="hljs-comment">;</span>
  }
  System<span class="hljs-preprocessor">.out</span><span class="hljs-preprocessor">.println</span>()<span class="hljs-comment">;</span>
}

}
}

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執行 findAll 方法後，查詢的相關 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

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輸出的結果如下：

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

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參考

(1) Spring Data JPA 實現多表關聯查詢

(2) springboot(五): spring data jpa的使用