假设我有一个类

@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;
    }
}

如果我创建一些东西，然后将它们编码为 XML，它看起来像这样:

飞行忍者:

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

一个普通的旧爆米花球:

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

但是...我想做的是改变我的 boolean 属性的编码方式。我宁愿看到爆米花球是这个样子的，压制awesome属性:

<thing>popcorn ball</thing>

我该怎么做？

非常感谢!

最佳答案

注意:我是 EclipseLink JAXB (MOXy)领导，以及 JAXB 2.X ( JSR-222) 专家组的成员。

使用 MOXy，您可以按照 Hovercraft Full Of Eels 的建议执行 XmlAdapter 方法.它看起来像:

boolean 适配器

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;
    }

}

东西

您使用 @XmlJavaTypeAdapter 注释将您的属性与 XmlAdapter 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);
    }

}

输出

<?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

如果您使用 JAXB RI 运行此示例，您将遇到以下异常:

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

了解更多信息

• 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

关于java - JAXB - 如果为 false，则抑制 boolean 属性，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/6552740/