jaxb 将循环引用映射到 xml-尊龙凯时

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 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 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