YAML custom object

Question

I have simple YAML document:

object:
  a: 1
  b: 2
  c: 3

Could I read this properties to custom object, which contains a constructor only with 1 argument. For example

public class CustomObject {
        private String value;

        public CustomObject(String value) {
            ....
        }

        getValue ...
        setValue ...
    }

where value is result of properties concatenation a,b,c with mask (as result 1:2/3)?

Answer 1

This is possible with custom constructors and representers:

class CustomObjectConstructor extends Constructor {
    public CustomObjectConstructor() {
        this.yamlConstructors.put(new Tag("!customObject"), new ConstructCustomObject());
    }

    private class ConstructCustomObject extends AbstractConstruct {
        public Object construct(Node node) {
            final Map<Object, Object> values = constructMapping(node);
            final String a = (String) values.get("a");
            final String b = (String) values.get("b");
            final String c = (String) values.get("c");
            return new CustomObject(a + ":" + b + "/" + c);
        }
    }
}

You can use it like this:

Yaml yaml = new Yaml(new CustomObjectConstructor());
CustomObject myObject =
    (CustomObject) yaml.load("!customObject\na: 1\nb: 2\nc: 3");

Of course, this needs refinement for handling error cases, but it shows the general idea. To dump the object as a mapping, you can define a representer similarly to the code here. See the documentation for more information.