Parsing a YAML document with a map at the root using snakeYaml

Question

I want to read a YAML document to a map of custom objects (instead of maps, which snakeYaml does by default). So this:

19:
  typeID: 2
  limit: 300
20:
  typ         


        

Answer 1

You need to add a custom Constructor. However, in your case you don't want register an "item" or "item-list" tag.

In effect, you want to apply Duck Typing to your Yaml. It's not super efficient, but there is a relatively easy way to do this.

class YamlConstructor extends Constructor {
  @Override
  protected Object constructObject(Node node) {

    if (node.getTag() == Tag.MAP) {
        LinkedHashMap map = (LinkedHashMap) super
                .constructObject(node);
        // If the map has the typeId and limit attributes
        // return a new Item object using the values from the map
        ...
    }
     // In all other cases, use the default constructObject.
    return super.constructObject(node);