spring jpa中基于实体从多个表中获取数据答案

【问题标题】：Get data from multiple tables based on entities in spring jpaspring jpa中基于实体从多个表中获取数据
【发布时间】：2017-02-04 06:25:34
【问题描述】：

我有如下三个实体：

评论：

@Entity
@Table(name = "comments")
public class CommentBean implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "commentId")
    private long commentId;

    @Column(name = "topicId")
    private String topicId;
}

主题：

@Entity
@Table(name = "topics")
public class TopicBean implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "topicId")
    private String topicId;
    @Column(name = "title")
    private String title;
    @Column(name = "details")
    private String details;
    @Column(name = "username")
    private String username;
    @Column(name = "userImage")
    private String userImage;
    @Column(name = "dayPosted")
    private String dayPosted;
}

喜欢：

@Entity
@Table(name = "comment_likes")
public class CommentLikes implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "commentLikes")
    private String commentLikes;

    @Column(name = "commentId")
    private long commentId;
}

我想根据请求从三个表/实体中获取所有数据：

@RequestMapping(path = "/get_data_on_login", method = RequestMethod.GET)
public ResponseEntity get_data_on_login()) throws Exception {

}

我如何实现这一目标？我见过使用@query 的示例和一些使用searchByAnd... 的示例，但更令人困惑的是要遵循哪种方法。

更新：

尝试使用@JoinColumn 映射表以使用bean.findAll() 获取数据但是，我收到此错误：

org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1589) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:554) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1081) ~[spring-context-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:856) ~[spring-context-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542) ~[spring-context-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:761) [spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:371) [spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) [spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1186) [spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1175) [spring-boot-1.4.3.RELEASE.jar:1.4.3.RELEASE]
    at seconds47.Application.main(Application.java:24) [classes/:?]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:954) ~[hibernate-entitymanager-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:882) ~[hibernate-entitymanager-5.0.11.Final.jar:5.0.11.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:353) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:373) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:362) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1648) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1585) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    ... 16 more
Caused by: org.hibernate.MappingException: Repeated column in mapping for entity: seconds47.beans.CommentBean column: topicId (should be mapped with insert="false" update="false")
    at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:830) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.mapping.PersistentClass.checkPropertyColumnDuplication(PersistentClass.java:848) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.mapping.PersistentClass.checkColumnDuplication(PersistentClass.java:870) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.mapping.PersistentClass.validate(PersistentClass.java:605) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.mapping.RootClass.validate(RootClass.java:265) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.boot.internal.MetadataImpl.validate(MetadataImpl.java:329) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:443) ~[hibernate-core-5.0.11.Final.jar:5.0.11.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:879) ~[hibernate-entitymanager-5.0.11.Final.jar:5.0.11.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:353) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:373) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:362) ~[spring-orm-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1648) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1585) ~[spring-beans-4.3.5.RELEASE.jar:4.3.5.RELEASE]
    ... 16 more

更新代码：

主题豆：

@Entity
@Table(name = "topics")
public class TopicBean implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "topicId")
    private String topicId;
    @Column(name = "title")
    private String title;
    @Column(name = "details")
    private String details;
    @Column(name = "username")
    private String username;
    @Column(name = "userImage")
    private String userImage;
    @Column(name = "dayPosted")
    private String dayPosted;

    @OneToMany(mappedBy="topicBean")
    private List<CommentBean> commentBeans;
}

commentBean：

@Entity
@Table(name = "comments")
public class CommentBean implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Long id;

    @Column(name = "commentId")
    private long commentId;

    @Column(name = "topicId")
    private String topicId;

    @Column(name = "comments")
    private String comments;

    @Column(name = "commentDate")
    private String commentDate;

    @Column(name = "userImage")
    private String userImage;

    @Column(name = "username")
    private String username;

    @ManyToOne
    @JoinColumn(name="topicId")
    private TopicBean topicBean;
}

存储库：

评论点赞回购：

@Repository
public interface CommentLikeRepository extends JpaRepository<CommentLikes, Long>{

    CommentLikes findByCommentId(long commentId);
}

评论回复回购：

@Repository
public interface CommentReplyRepository extends JpaRepository<CommentReply, Long> {

    CommentReply findByReplyId(String replyId);

    @Transactional
    Long deleteByReplyId(String replyId);

}

评论回购：

@Repository
public interface CommentRepository extends JpaRepository<CommentBean, Long>{
    List<CommentBean> findByTopicId(String topicId);
    CommentBean findByCommentId(long commentId);

    @Transactional
    Long deleteByCommentId(long deleteId);
}

主题回购：

@Repository
public interface TopicRepository extends JpaRepository<TopicBean, Long> {
    TopicBean findByTopicId(String topicId);

    @Transactional
    Long deleteByTopicId(String topicId);

    List<TopicBean> findByUsername(String username);
}

用户信息回购：

@Repository
public interface UserInfoRepository extends JpaRepository<UserInfo, Long>{

    UserInfo findByUsername(String username);

    UserInfo findRoleByUsername(String username);
}

【问题讨论】：

标签： java spring spring-boot jpa spring-data-jpa

【解决方案1】：

因为您的标签包括 spring-boot 和 spring-jpa。
我假设您可以使用 spring 数据存储库

发布的实体不以任何方式关联。因此，必须关联实体才能使用一个存储库检索所有数据实体的修改版本如下所示：

cmets 表

@Entity
@Table(name = "comments")
public class CommentBean implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "commentId")
    private long commentId;

    @ManyToOne
    @JoinColumn(name="topicId")
    private TopicBean topicBean;

    @OneToMany(mappedBy="commentBean")
    private List<CommentLikes> commentLikesList;
}

主题表

@Entity
@Table(name = "topics")
public class TopicBean implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "topicId")
    private String topicId;
    @Column(name = "title")
    private String title;
    @Column(name = "details")
    private String details;
    @Column(name = "username")
    private String username;
    @Column(name = "userImage")
    private String userImage;
    @Column(name = "dayPosted")
    private String dayPosted;

    @OneToMany(mappedBy="topicBean")
    private List<CommentBean> commentBeans;
}

comment_likes 表

@Entity
@Table(name = "comment_likes")
public class CommentLikes implements Serializable {

    @Id
    @Column(name = "id")
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "commentLikes")
    private String commentLikes;

    @ManyToOne
    @JoinColumn(name="commentId")
    private CommentBean commentBean;
}

请注意，上面的重写是基于我可以根据原始实体做出的最明智的猜测。

现在这三个实体已正确关联。您可以只使用 TopicBean 存储库来检索所有 TopicBean，其他两个也会被检索到。
topicBeanRepo.findAll()

【讨论】：

这只是一种可能的解决方案。您的问题并没有说只需要一个存储库并且没有发布您的存储库，所以我想您需要一个工作示例。从您发布的表格来看，只有一个存储库无法做到这一点，因为这些表格没有以任何方式关联。
topicBeanRepo.findAll() 在这种情况下会返回一个列表吗？
@kittu 和我之前的回答一样，CommentBean 实体不需要topicId 字段。 @JoinColumn(name="topicId") private TopicBean topicBean 已经关联他们。我发布的实体类是基于我对您的意图的猜测。在我看来，您甚至不需要TopicBean field unless your business logic really requires a second identity column other than the @ID id. You can make the foriegn key directly refer to the primary key id 中的topicId。我强烈建议您阅读 JPA 书籍并学习基础知识。我就是这么学的，而且效果很好。