JAXB - 如果为false则抑制布尔属性

Question

让我们说我有一堂课

@XmlRootElement(name="thing")
public class Thing{
    private String name;
    private boolean awesome;

    @XmlValue public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return this.value;
    }


    @XmlAttribute public void setAwesome(boolean awesome) {
        this.awesome = awesome;
    }
    public boolean isAwesome() {
        return this.awesome;
    }
}

如果我创建了一些东西,然后将它们编组为XML,它看起来像这样:

飞行忍者:

<thing awesome="true">flying ninja</thing>

一个普通的老爆米花球:

<thing awesome="false">popcorn ball</thing>

但是......我想要做的是改变我的布尔属性被编组的方式.我宁愿看到爆米花球看起来像这样,压抑了令人敬畏的属性:

<thing>popcorn ball</thing>

我怎样才能做到这一点？

非常感谢!

Answer 1

注意: 我是EclipseLink JAXB(MOXy)的负责人,也是JAXB 2.X(JSR-222)专家组的成员.

使用MOXy,您可以XmlAdapter按照Hovercraft Full Of Eels的建议进行操作.它看起来像:

BooleanAdapter

import javax.xml.bind.annotation.adapters.XmlAdapter;

public class BooleanAdapter extends XmlAdapter<Boolean, Boolean> {

    @Override
    public Boolean unmarshal(Boolean v) throws Exception {
        return Boolean.TRUE.equals(v);
    }

    @Override
    public Boolean marshal(Boolean v) throws Exception {
        if(v) {
            return v;
        }
        return null;
    }

}

事情

您将属性与XmlAdapter使用@XmlJavaTypeAdapter注释相关联,如下所示:

import javax.xml.bind.annotation.XmlAttribute;
import javax.xml.bind.annotation.XmlRootElement;
import javax.xml.bind.annotation.XmlValue;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlRootElement(name="thing")
public class Thing{
    private String name;
    private boolean awesome;

    @XmlValue public void setName(String name) {
        this.name = name;
    }
    public String getName() {
        return this.name;
    }


    @XmlAttribute
    @XmlJavaTypeAdapter(BooleanAdapter.class)
    public void setAwesome(boolean awesome) {
        this.awesome = awesome;
    }
    public boolean isAwesome() {
        return this.awesome;
    }
}

演示

import javax.xml.bind.JAXBContext;
import javax.xml.bind.Marshaller;

public class Demo {

    public static void main(String[] args) throws Exception {
        JAXBContext jc = JAXBContext.newInstance(Thing.class);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);

        Thing thing = new Thing();
        thing.setName("popcorn ball");

        thing.setAwesome(false);
        marshaller.marshal(thing, System.out);

        thing.setAwesome(true);
        marshaller.marshal(thing, System.out);
    }

}

产量

<?xml version="1.0" encoding="UTF-8"?>
<thing>popcorn ball</thing>
<?xml version="1.0" encoding="UTF-8"?>
<thing awesome="true">popcorn ball</thing>

使用JAXB RI

如果使用JAXB RI运行此示例,则会出现以下异常:

Exception in thread "main" com.sun.xml.bind.v2.runtime.IllegalAnnotationsException: 1 counts of IllegalAnnotationExceptions
Adapter example.BooleanAdapter is not applicable to the field type boolean. 
    this problem is related to the following location:
        at @javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter(type=class javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter$DEFAULT, value=class example.BooleanAdapter)
        at public boolean example.Thing.isAwesome()
        at forum251.Thing

欲获得更多信息

• http://bdoughan.blogspot.com/2011/05/specifying-eclipselink-moxy-as-your.html
• http://bdoughan.blogspot.com/2010/07/xmladapter-jaxbs-secret-weapon.html
• http://bdoughan.blogspot.com/2011/05/jaxb-and-joda-time-dates-and-times.html