spring data jpa关联查询（一对一、一对多、多对多）

　　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>



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　　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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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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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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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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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：

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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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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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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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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);
    
}

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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：

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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;">;
}



}

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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;">;
}



}

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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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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。

 

原文地址：https://www.cnblogs.com/hhhshct/p/9492741.html
posted @ 2019-05-22 09:17  星朝  阅读(3052)  评论(0)  编辑  收藏  举报