获取类型LAZY仍然会导致Eager加载Hibernate Spring数据 [英] Fetch Type LAZY still causes Eager loading Hibernate Spring data

问题描述

我有一个TagGroup Entity，它与Tags有一对多关系。

  @Entity 
 @Table（name =TAG_GROUP）
公共类TagGroup {
 
 @ OneToMany（fetch = FetchType.LAZY，mappedBy =tagGroup）
 private Set< Tag>标记列表; 
 
 
  

标签实体如下

  @Entity 
 @Table（name =TAGS）
 public class Tag {
 
 @ ManyToOne（可选= false，fetch = FetchType.LAZY）
 @JoinColumn（name =TAG_GROUP_ID）
私有TagGroup tagGroup; 
 
} 
  

我使用Spring数据扩展JPArepository并使用它的findAll方法。

这个问题，Lazy fetch不起作用，但事实上它加载标签列表时也没有显式调用tagList，因为如果它是EAGER ...

任何人都可以告诉我我在做什么错吗？

解决方案

这是因为属性 spring.jpa.open-in-view = true 。

根据< a href =https://docs.spring.io/spring-boot/docs/current/reference/html/common-application-properties.html =nofollow> spring-boot-configuration Spring启动应用程序使用 spring.jpa.open-in-view = true 。

使用此属性

注册OpenEntityManagerInViewInterceptor。将JPA EntityManager绑定到线程以处理请求的整个处理。

所以在你的情况下，随后当你调用 getTagList（）即检索 tagList ，它随后触发另一个查询来获取 tagList > EntityManager 仍然打开。

如果已加载父项的 entityManager 仍处于打开状态，则永远不会抛出LazyInitializationException 。

为了覆盖这个，你可以在 application.properties / application.yml中添加 spring.jpa.open-in-view = false / code>，然后你应该看到 LazyInitializationException 。

I have created a simple Spring boot project with Spring data.

I have a TagGroup Entity which has one to many relation with Tags.

 @Entity
 @Table(name = "TAG_GROUP")
 public class TagGroup{

  @OneToMany(fetch=FetchType.LAZY,mappedBy = "tagGroup")
  private Set<Tag> tagList;

 }

The Tag Entity is as below

  @Entity
  @Table(name = "TAGS")
  public class Tag {

      @ManyToOne(optional = false,fetch=FetchType.LAZY)
       @JoinColumn(name = "TAG_GROUP_ID")
       private TagGroup tagGroup;

  }

I am using Spring data extending the JPArepository and using its findAll method.

The problem , the Lazy fetch doesn't work BUT Infact it is loading the tag list also without calling the tagList explicitly as If it is EAGER...

Can anybody please tell me what I am doing wrong here ?

解决方案

This is because of property spring.jpa.open-in-view=true.

As per the spring-boot-configuration Spring boot applications use spring.jpa.open-in-view=true.

With this property it

Register OpenEntityManagerInViewInterceptor. Binds a JPA EntityManager to the thread for the entire processing of the request.

So in your case, subsequently when you call the getTagList() i.e., retrieve the tagList, it subsequently fires another query to fetch the tagList as the the EntityManager is still open.

As you might know, LazyInitializationException is never thrown if the entityManager that has loaded the parent is still open.

To override this, you can add spring.jpa.open-in-view=false in your application.properties/application.yml and then you should see LazyInitializationException.

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