Question: Attribute "empty" not working as expected with SimpleFramework


Attribute "empty" not working as expected with SimpleFramework

Answers 1
Added at 2017-01-02 12:01

So I was trying to set an empty attribute when an element has no value.

So my class looks like this:

@Order(attributes = { "name" })
public class TypeNumber {
    @Attribute(required = false)
    protected String name;

    @Element(required = false)
    @Attribute(empty = "xsi:nil=\"true\"")
    protected BigDecimal value;

    //getter setter methods goes here  

In case of empty value I was expecting output:

<field name="some_name">
    <value xsi:nil="true"/>

While the actual output is:

<field name="some_name"/>

Any idea why the empty attribute is not working as expected? Or am I doing it wrong ?

Note: I am using SimpleFramework XML with VisitorStrategy. So, can't use AnnotationStrategy. Also I have custom Visitor to read and write nodes.

Answers to

Attribute &quot;empty&quot; not working as expected with SimpleFramework

nr: #1 dodano: 2017-01-02 21:01

You will need a custom Converter...

Right now your outputs are:
<typeNumber name="original" value="10"/>
<typeNumber name="original_empty" value="xsi:nil=&quot;true&quot;"/>

So let's get started!

First thing you got to do is pass AnnotationStrategy to the constructor of your Persister:

Serializer serializer = new Persister(new AnnotationStrategy());

.. then create a custom Converter in your model:

@Root(name = "TypeNumberFixed")
@Order(attributes = {"name"})
class TypeNumberFixed {
    @Attribute(required = false)
    protected String name;

    @Element(required = false, name = "value")
    protected BigDecimal value;

    public static class FixConverter implements Converter<TypeNumberFixed> {

        public TypeNumberFixed read(InputNode inputNode) throws Exception {
            //Implement your own deConverter
            return null;

        public void write(OutputNode node, TypeNumberFixed value) throws Exception {
            OutputNode valueNode = node.getChild("value");
            if (value.value != null) {
            } else {
                valueNode.setAttribute("xsi:nil", "true");

This will generate following output for empty/nonempty values respectively:

typeNumberFixed.value = null:

<TypeNumberFixed name="new_empty">
   <value xsi:nil="true"/>

typeNumberFixed.value = 30:

<TypeNumberFixed name="new">

Here's the repo if you're interested.

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