Command Pattern and Generics in Java - JSON Story (3)

So what I want to do is to put a list of the same objects into List<Map<String,String>>. I created some converters for convert single object into <Map<String,String>>;. When I start to write the list converter, I realize that I only need a generic one and use the command pattern.
Here is the list converter:

public class ConverterToList<T> {



 public List<Map<String,String>> convertToList(Collection<T> collection, ConverterToMap<T> converter){
  
  List<Map<String,String>> list=new ArrayList<Map<String,String>>();
  for (T t:collection){
   list.add(converter.convertToMap(t));
  }
  return list;
 }

}

And the interface for command

public interface ConverterToMap<T> {
 
 public Map<String,String> convertToMap(T t);
 
}

A sample implementation

public class ConverterToMapJob implements ConverterToMap<Job> {

 @Override
 public Map<String, String> convertToMap(Job job) {
  Map<String, String> map = new HashMap<String, String>();

  JsonHelper helper = new JsonHelper(map);

  helper.addCheckNull(job.getId(), "id");

  helper.addCheckNull(job.getSubmitTimestamp(), "submitTimestamp");
  helper.addCheckNull(job.getScheduleTimestamp(), "scheduleTimestamp");
  helper.addCheckNull(job.getEndTimestamp(), "endTimestamp");
  helper.addCheckNull(job.getUpdateTimestamp(), "updateTimestamp");
  helper.addCheckNull(job.getHost(), "host");
  helper.addCheckNull(job.getName(), "name");
  helper.addCheckNull(job.getPort(), "port");
               //now I am free to put any bean. Even not a bean. 
  helper.addCheckNull(job.getJobStatus(), "status");
  return map;
 }

}

I am fairly happy with this. This structure only handles a flat object or an array of it, and not general enough for more complex multi-level objects. But that fits my needs now and in the foreesable future of this project. I probably will hang with it and leave the json problem in my back. It is generally not a good idea to reinvent the wheel, but when the wheel is too complicated for your car, maybe it is better to roll your own.