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spring data jpa关联查询（一对一、一对多、多对多）

本文转载自  查看原文  2019-05-22 09:17  1354    通用实践/ 开发经验/ java经验集锦/ 工作总结/ Spring/ SpringDataJpa/ SQL

　　在实际过往的项目中，常用的查询操作有：1、单表查询，2、一对一查询（主表和详情表）3、一对多查询（一张主表，多张子表）4、多对多查询（如权限控制，用户、角色多对多）。做个总结，所以废话不多说。

　　使用idea构建springboot项目，引入依赖如下：

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dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-jpa</artifactId>
        </dependency>

    &lt;dependency&gt;
        &lt;groupId&gt;com.h2database&lt;/groupId&gt;
        &lt;artifactId&gt;h2&lt;/artifactId&gt;
        &lt;scope&gt;runtime&lt;/scope&gt;
    &lt;/dependency&gt;
    &lt;dependency&gt;
        &lt;groupId&gt;org.projectlombok&lt;/groupId&gt;
        &lt;artifactId&gt;lombok&lt;/artifactId&gt;
        &lt;optional&gt;<span style="color: #0000ff;">true</span>&lt;/optional&gt;
    &lt;/dependency&gt;
    &lt;dependency&gt;
        &lt;groupId&gt;org.springframework.boot&lt;/groupId&gt;
        &lt;artifactId&gt;spring-boot-starter-test&lt;/artifactId&gt;
        &lt;scope&gt;test&lt;/scope&gt;
    &lt;/dependency&gt;
&lt;/dependencies&gt;</pre>



   
   
  
  

    
    
   
   复制代码

　　使用h2数据库做测试用，application.yml配置如下：

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spring:
  jpa:
    generate-ddl: true
    hibernate:
      ddl-auto: update
    properties:
      hibenate:
        format_sql: false
    show-sql: true
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　　首先，一对一有好几种，这里举例的是常用的一对一双向外键关联（改造成单向很简单，在对应的实体类去掉要关联其它实体的属性即可），并且配置了级联删除和添加，相关类如下：

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package io.powerx;

import lombok.*;


import javax.persistence.*;


/**


    
    
   
   
     
    
  •  
    Created by Administrator on 2018/8/15.
     */
     @Getter
     @Setter
     @Entity
         public class Book {
     @Id
     @GeneratedValue
         private Integer id;
     
    private String name;
     
    @OneToOne(cascade = {CascadeType.PERSIST,CascadeType.REMOVE})
     @JoinColumn(name    ="detailId",referencedColumnName = "id")
         private BookDetail bookDetail;
     
    public Book(){
         super();
     }
         public Book(String name){
         super();
         this.name =name;
     }
     
    public Book(String name, BookDetail bookDetail) {
         super();
         this.name = name;
         this.bookDetail = bookDetail;
     }
     @Override
         public String toString() {
         if (null == bookDetail) {
         return String.format("Book [id=%s, name=%s, number of pages=%s]", id, name, "<EMPTY>");
     }
     
     </span><span style="color: #0000ff;">return</span> String.format("Book [id=%s, name=%s, number of pages=%s]"<span style="color: #000000;">, id, name, bookDetail.getNumberOfPages());

     
    }
     }
    •

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复制代码 
package io.powerx;

import lombok.Getter;
 import lombok.Setter;


import javax.persistence.*;


@Getter
 @Setter
 @Entity(name = "BOOK_DETAIL")
 public class BookDetail {


@Id
@GeneratedValue
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Integer id;

@Column(name </span>= "NUMBER_OF_PAGES"<span style="color: #000000;">)
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Integer numberOfPages;

@OneToOne(mappedBy </span>= "bookDetail"<span style="color: #000000;">)
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Book book;

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> BookDetail() {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> BookDetail(Integer numberOfPages) {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
    </span><span style="color: #0000ff;">this</span>.numberOfPages =<span style="color: #000000;"> numberOfPages;
}

@Override
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String toString() {
    </span><span style="color: #0000ff;">if</span> (<span style="color: #0000ff;">null</span> ==<span style="color: #000000;"> book) {
        </span><span style="color: #0000ff;">return</span> String.format("Book [id=%s, name=%s, number of pages=%s]", id, "&lt;EMPTY&gt;"<span style="color: #000000;">);
    }

    </span><span style="color: #0000ff;">return</span> String.format("Book [id=%s, name=%s, number of pages=%s]"<span style="color: #000000;">, id,book.getId(),book.getName());
}



}

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复制代码 
package io.powerx;

import org.springframework.data.jpa.repository.JpaRepository;


/**


    
    
   
   
     
    
  • Created by Administrator on 2018/8/15.
     */
     public interface BookRepository extends JpaRepository<Book,Integer> {
     Book findByName(String name);
     }
    •
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复制代码 
package io.powerx;

import org.springframework.data.jpa.repository.JpaRepository;


/**


    
    
   
   
     
    
  •  
    Created by Administrator on 2018/8/15.
     */
     public interface BookDetailRepository extends JpaRepository<BookDetail, Integer>{
     
    BookDetail findByNumberOfPages(Integer numberOfPages);
     }
    •

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复制代码 
package io.powerx;

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 java.util.Arrays;


import static org.junit.Assert.assertThat;


@RunWith(SpringRunner.class)
 @SpringBootTest
 public class OnetooneApplicationTests {


@Autowired
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> BookRepository bookRepository;

@Autowired
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> BookDetailRepository bookDetailRepository;

@Before
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> init() {
    Book bookA </span>= <span style="color: #0000ff;">new</span> Book("Spring in Action", <span style="color: #0000ff;">new</span> BookDetail(208<span style="color: #000000;">));
    Book bookB </span>= <span style="color: #0000ff;">new</span> Book("Spring Data in Action", <span style="color: #0000ff;">new</span> BookDetail(235<span style="color: #000000;">));
    Book bookC </span>= <span style="color: #0000ff;">new</span> Book("Spring Boot in Action"<span style="color: #000000;">);
    bookRepository.saveAll(Arrays.asList(bookA, bookB, bookC));
}

@After
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> clear() {
    bookRepository.deleteAll();
}

@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> find() {
    Book book </span>= bookRepository.findByName("Spring in Action"<span style="color: #000000;">);
    System.err.println(book.toString());
}

@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> save() {
    Book book </span>= <span style="color: #0000ff;">new</span> Book("springboot"<span style="color: #000000;">);
    BookDetail bookDetail </span>= <span style="color: #0000ff;">new</span> BookDetail(124<span style="color: #000000;">);
    book.setBookDetail(bookDetail);
    bookRepository.save(book);
}

@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> delete() {

    bookRepository.deleteById(</span>31<span style="color: #000000;">);
}
@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> findbook(){
    BookDetail bd </span>= bookDetailRepository.findByNumberOfPages(235<span style="color: #000000;">);
    System.err.println(bd.toString());

}



}

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　　一对多双向，相关类如下：

复制代码 
package io.powerx;

import lombok.Data;
 import lombok.Getter;
 import lombok.Setter;


import javax.persistence.*;


@Getter
 @Setter
 @Entity
 public class Book {
 @Id
 @GeneratedValue
 private Integer id;


</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String name;

@ManyToOne
@JoinColumn(name</span>="publishId"<span style="color: #000000;">)
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Publisher publisher;

@Override
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String toString() {
    </span><span style="color: #0000ff;">return</span> "Book{" +
            "id=" + id +
            ", name='" + name + '\'' +
            ", publisher=" + publisher.getName() +
            '}'<span style="color: #000000;">;
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Book(String name) {
    </span><span style="color: #0000ff;">this</span>.name =<span style="color: #000000;"> name;
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Book() {
}



}

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复制代码 
package io.powerx;

import lombok.Data;
 import lombok.Getter;
 import lombok.Setter;


import javax.persistence.*;
 import java.util.HashSet;
 import java.util.Set;


/**


    
    
   
   
     
    
  •  
    Created by Administrator on 2018/8/16.
     */
     @Getter
     @Setter
     @Entity
         public class Publisher {
     @Id
     @GeneratedValue
         private Integer id;
     
    private String name;
     
    @OneToMany(cascade = CascadeType.ALL,fetch = FetchType.EAGER)
     @JoinColumn(name    ="publishId",referencedColumnName = "id")
         private Set<Book> books;
     
    public Publisher() {
         super();
     }
     
    public Publisher(String name) {
         super();
         this.name = name;
     }
     
    @Override
     public String toString() {
         return "Publisher{" +
     "id=" + id +
     ", name='" + name + ''' +
     ", books=" + books.size() +
     '}';
     }
     
    •  
   


}

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复制代码 
package io.powerx;

import org.springframework.data.jpa.repository.JpaRepository;


/**


    
    
   
   
     
    
  •  
    Created by Administrator on 2018/8/16.
     */
     public interface BookRepository extends JpaRepository<Book,Integer>{
     
    Book findByName(String name);
     
    •  
   


}

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复制代码 
package io.powerx;

import org.springframework.data.jpa.repository.JpaRepository;


/**


    
    
   
   
     
    
  •  
    Created by Administrator on 2018/8/16.
     */
     public interface PublisherRepository extends JpaRepository<Publisher,Integer> {
     
    Publisher findByName(String name);
     }
    •

复制代码
复制代码 
package io.powerx;

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 java.util.HashSet;
 import java.util.Set;


@RunWith(SpringRunner.class)
 @SpringBootTest
 public class OnetomanyApplicationTests {


@Autowired
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> PublisherRepository publisherRepository;

@Autowired
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> BookRepository bookRepository;

@Before
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> init() {

    Book book1 </span>= <span style="color: #0000ff;">new</span> Book("spring"<span style="color: #000000;">);
    Book book2 </span>= <span style="color: #0000ff;">new</span> Book("mvc"<span style="color: #000000;">);
    Book book3 </span>= <span style="color: #0000ff;">new</span> Book("mybatis"<span style="color: #000000;">);
    Publisher publisher </span>= <span style="color: #0000ff;">new</span> Publisher("zhonghua"<span style="color: #000000;">);
    Set</span>&lt;Book&gt; set = <span style="color: #0000ff;">new</span> HashSet&lt;Book&gt;<span style="color: #000000;">();
    set.add(book1);
    set.add(book2);
    set.add(book3);
    publisher.setBooks(set);
    publisherRepository.save(publisher);

}

@After
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> clear() {
    publisherRepository.deleteAll();
}

@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> find() {
    Publisher publisher </span>= publisherRepository.findByName("zhonghua"<span style="color: #000000;">);
    System.out.println(publisher);
}

@Test
</span><span style="color: #0000ff;">public</span> <span style="color: #0000ff;">void</span><span style="color: #000000;"> find2() {
    Book book </span>= bookRepository.findByName("mvc"<span style="color: #000000;">);
    System.out.println(book);
}



}

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　　多对多双向，相关代码如下：

复制代码 
package io.powerx;

import lombok.Getter;
 import lombok.Setter;
 import lombok.ToString;


import javax.persistence.*;
 import java.util.Set;


@Getter
 @Setter
 @Entity
 public class Author {


@Id
@GeneratedValue
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Integer id;

</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String name;

@ManyToMany(mappedBy </span>= "authors",fetch =<span style="color: #000000;"> FetchType.EAGER)
</span><span style="color: #0000ff;">private</span> Set&lt;Book&gt;<span style="color: #000000;"> books;

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Author() {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Author(String name) {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
    </span><span style="color: #0000ff;">this</span>.name =<span style="color: #000000;"> name;
}

@Override
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String toString() {
    </span><span style="color: #0000ff;">return</span> "Author{" +
            "id=" + id +
            ", name='" + name + '\'' +
            ", books=" + books.size() +
            '}'<span style="color: #000000;">;
}



}

复制代码
复制代码 
package io.powerx;

import lombok.Getter;
 import lombok.Setter;
 import lombok.ToString;


import javax.persistence.*;
 import java.util.HashSet;
 import java.util.Set;


@Getter
 @Setter
 @Entity
 public class Book {


@Id
@GeneratedValue
</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> Integer id;

</span><span style="color: #0000ff;">private</span><span style="color: #000000;"> String name;

@ManyToMany(cascade </span>= CascadeType.ALL,fetch =<span style="color: #000000;"> FetchType.EAGER)
@JoinTable(name </span>= "BOOK_AUTHOR", joinColumns =<span style="color: #000000;"> {
        @JoinColumn(name </span>= "BOOK_ID", referencedColumnName = "ID")}, inverseJoinColumns =<span style="color: #000000;"> {
        @JoinColumn(name </span>= "AUTHOR_ID", referencedColumnName = "ID"<span style="color: #000000;">)})
</span><span style="color: #0000ff;">private</span> Set&lt;Author&gt;<span style="color: #000000;"> authors;

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Book() {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
}

</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> Book(String name) {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
    </span><span style="color: #0000ff;">this</span>.name =<span style="color: #000000;"> name;
    </span><span style="color: #0000ff;">this</span>.authors = <span style="color: #0000ff;">new</span> HashSet&lt;&gt;<span style="color: #000000;">();
}

</span><span style="color: #0000ff;">public</span> Book(String name, Set&lt;Author&gt;<span style="color: #000000;"> authors) {
    </span><span style="color: #0000ff;">super</span><span style="color: #000000;">();
    </span><span style="color: #0000ff;">this</span>.name =<span style="color: #000000;"> name;
    </span><span style="color: #0000ff;">this</span>.authors =<span style="color: #000000;"> authors;
}

@Override
</span><span style="color: #0000ff;">public</span><span style="color: #000000;"> String toString() {
    </span><span style="color: #0000ff;">return</span> "Book{" +
            "id=" + id +
            ", name='" + name + '\'' +
            ", authors=" + authors.size() +
            '}'<span style="color: #000000;">;
}



}

复制代码
复制代码 
package io.powerx;

import org.springframework.data.jpa.repository.JpaRepository;


import java.util.List;


public interface AuthorRepository extends JpaRepository<Author, Integer> {


Author findByName(String name);

List</span>&lt;Author&gt;<span style="color: #000000;"> findByNameContaining(String name);



}

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复制代码 
package io.powerx;

import org.springframework.data.jpa.repository.JpaRepository;


import java.util.List;


public interface BookRepository extends JpaRepository<Book, Integer> {


Book findByName(String name);

List</span>&lt;Book&gt;<span style="color: #000000;"> findByNameContaining(String name);



}

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　　在调试过程中，注意实体类的tostring方法的重写，避免相互引用；此外如果超过两张表的关联查询，建议使用自定义sql，建立相应的pojo来接收查询结果。

 


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