Set attribute to empty xml tag using jackson-dataformat-xml library-CodePudding

I have HashMap<String, Object> that is serialized into xml. When Object is null

HashMap<String, Object> h1 = new HashMap<>();
h1.put("test", null);
System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(h1));

Jackson generates something like these

<HashMap>
   <test/>
</HashMap>

So I need somehow add attributes to this empty tag

<HashMap>
   <test attribute = "something"/>
</HashMap>

Is it possible?

CodePudding user response：

You can do it like this ...

Instead of a null you need to use something like a thin wrapper around it, which will instruct XmlMapper to print this attribute information.

Here's a working test which solves the problem.

public class TestXml {
    
    class NullWrapper {
        @JacksonXmlProperty(isAttribute = true)
        private String attribute = "something";
    }

    @Test
    void test() throws JsonProcessingException {
        var mapper = new XmlMapper();
        var h1 = new HashMap<>();
        h1.put("test", new NullWrapper());
        System.out.println(mapper.writerWithDefaultPrettyPrinter().writeValueAsString(h1));
    }
}

Output is ...

<HashMap>
  <test attribute="something"/>
</HashMap>

Does this solve your problem ? Tell me in the comments.