休眠和杰克逊懒惰序列化 [英] Hibernate and Jackson lazy serialization

问题描述

我正在使用Hibernate和Jackson来编写我的对象序列化项目。
我认为我理解它是如何工作的，但我无法设法实现它。

如果我理解的很好，只要一个关系获取模式设置为LAZY，如果你想要这个关系，你必须初始化它。

这是我的课程：

  @Entity 
 @JsonIgnoreProperties（ignoreUnknown = true）
 @Table（schema =MDDI_ADMIN，name =MINIUSINE）
 @ Cache（usage = CacheConcurrencyStrategy.READ_WRITE）
 public class MiniUsine {
 
 @Id 
 @Column（name =MINIUSINEID，nullable = false）
 private int miniUsineID ; 
 
 @Column（name =NAME，length = 40，nullable = false）
私有字符串名称; 
 
 @OneToMany（cascade = CascadeType.ALL）
 @JoinColumn（name =FluxID）
 @JsonInclude（JsonInclude.Include.NON_EMPTY）
 private Set<通量GT; fluxs = new HashSet< Flux>（）; 
  

以及所有getters和setters。

我也试过这个 JsonInclude.Include.NON_EMPTY 作为类的注解。还尝试了NON_NULL。
然而，杰克逊一直向我发送

com.fasterxml.jackson.databind.JsonMappingException：未能延迟初始化一个角色集合： MiniUsine.fluxs，没有会话或会话被关闭（通过引用链：java.util.ArrayList [0] - > MiniUsine [fluxs]）

我将它序列化为： mapper.writeValueAsString（optMU）;

使用Jackson 2.3 .2

感谢您的帮助

解决方案

据我了解，hibernate返回的实体对象是一个派生自实体类的代理。如果尝试访问事务外的惰性字段的getter方法，则会得到LazyInitializationException。
我想说的是将flux设置为空集并不会对您有任何帮助。

  private set< ;助焊剂> fluxs = new HashSet< Flux>（）; 
  

Hibernate会重载getter，如果您尝试在事务之外访问它（这是杰克逊正在做的检查它是否为空），你会得到LazyInit错误。

I'm working on a project using Hibernate and Jackson to serialize my objects. I think I understand how it is suposed to work but I can't manage to make it works.

If I understand well, as soon as a relation fetch mode is set to LAZY, if you want this relation, you have to initialize it.

Here is my class :

@Entity
@JsonIgnoreProperties(ignoreUnknown = true)
@Table(schema="MDDI_ADMIN", name = "MINIUSINE")
@Cache(usage=CacheConcurrencyStrategy.READ_WRITE)
public class MiniUsine {

    @Id
    @Column(name="MINIUSINEID", nullable = false)
    private int miniUsineID;

    @Column(name = "NAME", length = 40, nullable = false)
    private String name;

    @OneToMany(cascade = CascadeType.ALL)
    @JoinColumn(name="FluxID")
    @JsonInclude(JsonInclude.Include.NON_EMPTY)
    private Set<Flux> fluxs = new HashSet<Flux>();

And all getters and setters.

I've also tried this JsonInclude.Include.NON_EMPTY as class annotation. Also tried the NON_NULL. However, jackson keeps sending me

com.fasterxml.jackson.databind.JsonMappingException: failed to lazily initialize a collection of role: MiniUsine.fluxs, no session or session was closed (through reference chain: java.util.ArrayList[0]->MiniUsine["fluxs"])

I'm serializing it with : mapper.writeValueAsString(optMU);

Using Jackson 2.3.2

Thanks for help

解决方案

As far as I understand, the entity object that hibernate returns is a proxy which derives from your entity class. If you try to access getter methods for lazy fields outside of a transaction, you get LazyInitializationException. The point I want to make is setting fluxs to empty set doesn't help you at all.

private Set<Flux> fluxs = new HashSet<Flux>();

Hibernate overloads the getter and if you try to access it outside of a transaction(which jackson is doing to check if it is empty), you get the LazyInit error.

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