JAXB 将循环引用映射到 XML

JAXB Mapping cyclic references to XML(JAXB 将循环引用映射到 XML)

问题描述

我有一个包含循环的对象图.如何让 JAXB 处理这个问题?我尝试在子类中使用 @XmlTransient 注释，但 JAXB 编组器仍然检测到循环.

I have an object graph that contains a cycle. How do I get JAXB to handle this? I tried using the @XmlTransient annotation in the child class but the JAXB marshaller still detects the cycle.

@Entity
@XmlRootElement
public class Contact {

    @Id
    private Long contactId;

    @OneToMany(mappedBy = "contact")
    private List<ContactAddress> addresses;

...

}

@Entity
@XmlRootElement
public class ContactAddress {

    @Id
    private Long contactAddressId;

    @ManyToOne
    @JoinColumn(name = "contact_id")
    private Contact contact;

    private String address;

...

}

推荐答案

使用 JAXB 的好处是它是一个具有多种实现的标准运行时(就像 JPA 一样).

The good thing about using JAXB is that it is a standard runtime with multiple implementations (just like JPA).

如果您使用 EclipseLink JAXB (MOXy)，那么您可以使用许多扩展来处理 JPA 实体，包括双向关系.这是使用 MOXy @XmlInverseReference 注释完成的.它的作用类似于 marshal 上的 @XmlTransient 并在 unmarshal 上填充目标到源的关系.

If you use EclipseLink JAXB (MOXy) then you have many extensions available to you for handling JPA entities including bi-directional relationships. This is done using the MOXy @XmlInverseReference annotation. It acts similar to @XmlTransient on the marshal and populates the target-to-source relationship on the unmarshal.

http://wiki.eclipse.org/EclipseLink/Examples/MOXy/JPA/关系

@Entity 
@XmlRootElement 
public class Contact { 

    @Id 
    private Long contactId; 

    @OneToMany(mappedBy = "contact") 
    private List<ContactAddress> addresses; 

... 

} 

@Entity 
@XmlRootElement 
public class ContactAddress { 

    @Id 
    private Long contactAddressId; 

    @ManyToOne 
    @JoinColumn(name = "contact_id") 
    @XmlInverseReference(mappedBy="addresses")
    private Contact contact; 

    private String address; 

... 

} 

其他扩展可用，包括支持复合键和嵌入式键类.

Other extensions are available including support for composite keys & embedded key classes.

要指定 EcliseLink MOXy JAXB 实现，您需要在模型类(即合同)中包含一个 jaxb.properties 文件，其中包含以下条目:

To specify the EcliseLink MOXy JAXB implementation you need to include a jaxb.properties file in with your model classes (i.e. Contract) with the following entry:

javax.xml.bind.context.factory=org.eclipse.persistence.jaxb.JAXBContextFactory

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