FetchType.LAZY在休眠状态下不适用于@ManyToOne映射 [英] FetchType.LAZY not working for @ManyToOne mapping in hibernate
问题描述
简单地说,我在Child类和Parent类之间存在多对一的关系.我想加载所有子级,而不必加载其父级详细信息. 我的孩子班是
Simply put I have a many to one relation on the Child class with the Parent class. I want to load all the children without having to load their parent details. My child class is
@Entity
public class Child implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
@ManyToOne(fetch = FetchType.LAZY)
@JoinColumn(name = "parentId", referencedColumnName = "id")
private Parent parent;
public Child() {
}
// Getters and setters here
}
我的父母班是
@Entity
public class Parent implements Serializable {
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;
private String name;
public Parent() {
}
}
我有一个休息控制器,我想和他一起取所有没有父母的孩子
I have a rest controller with which I want to fetch all the children without their parents
@GetMapping
public List<Child> getChildren() {
return childRepository.findAll();
}
当我运行它时,它会抛出
When i run this it throws
{
"timestamp": "2019-02-22T13:45:31.219+0000",
"status": 500,
"error": "Internal Server Error",
"message": "Type definition error: [simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->com.example.attendance.models.Child[\"parent\"]->com.example.attendance.models.Parent$HibernateProxy$1QzJfFPz[\"hibernateLazyInitializer\"])",
"trace": "org.springframework.http.converter.HttpMessageConversionException: Type definition error: [simple type, class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor]; nested exception is com.fasterxml.jackson.databind.exc.InvalidDefinitionException: No serializer found for class org.hibernate.proxy.pojo.bytebuddy.ByteBuddyInterceptor and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationFeature.FAIL_ON_EMPTY_BEANS) (through reference chain: java.util.ArrayList[0]->com.example.attendance.models.Child[\"parent\"]->com.example.attendance.models.Parent$HibernateProxy$1QzJfFPz[\"hibernateLazyInitializer\"])\n\tat org.springframework.http.converter.json.AbstractJackson2HttpMessageConverter.writeInternal(AbstractJackson2HttpMessageConverter.java:293)\n\tat org.springframework.http.converter.AbstractGenericHttpMessageConverter.write(AbstractGenericHttpMessageConverter.java:103)\n\tat org.springframework.web.servlet.mvc.method.annotation.AbstractMessageConverterMethodProcessor.writeWithMessageConverters(AbstractMessageConverterMethodProcessor.java:290)\n\tat org.springframework.web.servlet.mvc.method.annotation.RequestResponseBodyMethodProcessor.handleReturnValue(RequestResponseBodyMethodProcessor.java:180)
我应该进行哪些更改,以便可以延迟加载父类?
What do I change so that I can lazy load the parent class?
提前谢谢.
推荐答案
您已经延迟加载了父类.发生异常是因为在加载父对象之前序列化了Child对象.要禁用它,您可以使用以下注释您的Child类:
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
You already lazy load the parent class. Exception happens because you serialize Child objects before parents are loaded. To disable it you can annotate your Child class with that:
@JsonIgnoreProperties({"hibernateLazyInitializer", "handler"})
在那之后,Parent在序列化中将被忽略.
After that Parent will be ignored in serialization.
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