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JAXB generic @XmlValue

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暖寄归人
暖寄归人 2021-02-06 06:00

The goal is to produce the following XML with JAXB


   string data
   binary data
4条回答
  • 无人共我
    无人共我 (楼主)
    2021-02-06 06:58

    You could leverage an XmlAdapter for this use case instead of @XmlValue:

    BarAdapter

    package forum8807296;

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

public class BarAdapter extends XmlAdapter> {

    @Override
    public Bar unmarshal(Object v) throws Exception {
        if(null == v) {
            return null;
        }
        Bar bar = new Bar();
        bar.setValue(v);
        return bar;
    }

    @Override
    public Object marshal(Bar v) throws Exception {
        if(null == v) {
            return null;
        }
        return v.getValue();
    }

}



    Foo
    


    The XmlAdapter is associated with the bars property using the @XmlJavaTypeAdapter annotation:
    


    package forum8807296;

import java.util.List;
import javax.xml.bind.annotation.*;
import javax.xml.bind.annotation.adapters.XmlJavaTypeAdapter;

@XmlRootElement
public class Foo {
    private List bars;

    @XmlElement(name="bar")
    @XmlJavaTypeAdapter(BarAdapter.class)
    public List getBars() {
        return bars;
    }

    public void setBars(List bars) {
        this.bars = bars;
    }

}

    


    Bar
    


    package forum8807296;

public class Bar {
    private T value;

    public T getValue() {
        return value;
    }

    public void setValue(T value) {
        this.value = value;
    }
}

    


    Demo
    


    You can test this example using the following demo code:
    


    package forum8807296;

import java.util.ArrayList;
import java.util.List;

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(Foo.class);

        Foo foo = new Foo();
        List bars = new ArrayList();
        foo.setBars(bars);

        Bar stringBar = new Bar();
        stringBar.setValue("string data");
        bars.add(stringBar);

        Bar binaryBar = new Bar();
        binaryBar.setValue("binary data".getBytes());
        bars.add(binaryBar);

        Marshaller marshaller = jc.createMarshaller();
        marshaller.setProperty(Marshaller.JAXB_FORMATTED_OUTPUT, true);
        marshaller.marshal(foo, System.out);
    }

}

    


    Output
    


    Note how the output includes the xsi:type attributes to preserve the type of the value.  You can eliminate the the xsi:type attribute by having your XmlAdapter return String instead of Object, if you do this you will need handle the conversion from String to the appropriate type yourself for the unmarshal operation:
    


    

    string data
    YmluYXJ5IGRhdGE=


    
    
    
             
    
                                                        
    
            
            
    
              
                
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