Jax-WS - To Remove Empty Tags from Request XML

jax-ws, jaxb, moxy, web-services, xml

Solution

Note: I'm the EclipseLink JAXB (MOXy) lead and a member of the JAXB (JSR-222) expert group.

By default MOXy like other JAXB implementations will not marshal an element for null values:

- http://blog.bdoughan.com/2012/04/binding-to-json-xml-handling-null.html

POSSIBLE PROBLEM

I believe the `strIpAddress` property is not null, but contains a value of empty String (""). This would cause the empty element to be written out.

Root

package forum11215485;

import javax.xml.bind.annotation.*;

@XmlRootElement
@XmlAccessorType(XmlAccessType.FIELD)
public class Root {

    String nullValue;
    String emptyStringValue;
    String stringValue;

}

Demo

package forum11215485;

import javax.xml.bind.*;

public class Demo {

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

        Root root = new Root();
        root.nullValue = null;
        root.emptyStringValue = "";
        root.stringValue = "Hello World";

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

}

Output

Note how there is no element marshalled out for the `nullValue` field, and the `emptyStringValue` field is marshalled as an empty element.

<?xml version="1.0" encoding="UTF-8"?>
<root>
   <emptyStringValue></emptyStringValue>
   <stringValue>Hello World</stringValue>
</root>

SOLUTION #1 - Ensure the property is set to null and not ""

SOLUTION #2 - Write an XmlAdapter that converts "" to null

An `XmlAdapter` is a JAXB mechanism that allows an object to be marshalled as another object.

StringAdapter

The following `XmlAdapter` will marshal empty strings as null. This will cause them not to appear in the XML representation.

package forum11215485;

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

public class StringAdapter extends XmlAdapter<String, String> {

    @Override
    public String unmarshal(String v) throws Exception {
        return v;
    }

    @Override
    public String marshal(String v) throws Exception {
        if(null == v || v.length() == 0) {
            return null;
        }
        return v;
    }

}

package-info

The `XmlAdapter` is hooked in using the `@XmlJavaTypeAdapter` annotation. Below is an example of hooking it in at the package level so that it applies to a fields/properties of type String within the package. For more information see: http://blog.bdoughan.com/2012/02/jaxb-and-package-level-xmladapters.html

@XmlJavaTypeAdapter(value=StringAdapter.class, type=String.class)
package forum11215485;

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

Output

Now the output from running the demo code is the following:

<?xml version="1.0" encoding="UTF-8"?>
<root>
   <stringValue>Hello World</stringValue>
</root>

Problem

Original source

Related problems

• Transforming empty element into null when unmarshalling with JAXB