jaxb-如何从多态类创建XML [英] jaxb - how to create XML from polymorphic classes

问题描述

我刚刚开始使用JAXB从Java对象生成XML输出.我的java类中存在一种多态性，这在JAXB中似乎不起作用.

I've just started using JAXB to make XML output from java objects. A polymorphism exists in my java classes, which seems to not working in JAXB.

下面是我尝试处理它的方式，但是在输出中我没有期望的字段:fieldA或fieldB.

Below is the way how I tried to deal with it, but in the output I haven't expected field: fieldA or fieldB.

@XmlRootElement(name = "root")
public class Root {
    @XmlElement(name = "fieldInRoot")
    private String fieldInRoot;
    @XmlElement(name = "child")
    private BodyResponse child;
    // + getters and setters
}

public abstract class BodyResponse {
}

@XmlRootElement(name = "ResponseA")
public class ResponseA extends BodyResponse {
    @XmlElement(name = "fieldA")
    String fieldB;
    // + getters and setters
}

@XmlRootElement(name = "ResponseB")
public class ResponseB extends BodyResponse {
    @XmlElement(name = "fieldB")
    String fieldB;  
    // + getters and setters  
}

在我开始发明一些复杂的继承之前，有什么好的方法可以做到这一点?

Before I start invent some intricate inheritances, is there any good approach to do this?

推荐答案

对于您的用例，您可能想利用@XmlElementRefs，它对应于XML Schema中的替换组的概念:

For your use case you will probably want to leverage @XmlElementRefs, this corresponds to the concept of substitution groups in XML Schema:

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {
    @XmlElement
    private String fieldInRoot;
    @XmlElementRef
    private BodyResponse child;
    // + getters and setters
}

• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-substitution.html
• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-substitution.html

您还可以将xsi:type属性用作继承指标:

You can also leverage the xsi:type attribute as the inheritance indicator:

• http://blog.bdoughan.com/2010/11/jaxb-and-inheritance-using-xsitype.html

EclipseLink JAXB(MOXy)也具有@XmlDescriminatorNode/@XmlDescriminatorValue扩展名:

EclipseLink JAXB (MOXy) also has the @XmlDescriminatorNode/@XmlDescriminatorValue extension:

• http://bdoughan.blogspot.com/2010/11/jaxb-and-inheritance-moxy-extension.html

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