Question

I have the following code with a simple class and a method for writing and then reading:

ObjectMapper mapper = new ObjectMapper();
  try{
      DataStore testOut = new DataStore();
      DataStore.Checklist ch1 = testOut.addChecklist();
      ch1.SetTitle("Checklist1");

      String output = mapper.writeValueAsString(testOut);
      JsonNode rootNode = mapper.readValue(output, JsonNode.class);
      Map<String,Object> userData = mapper.readValue(output, Map.class);
    }


public class DataStore {
public static class Checklist
{
    public Checklist()
    {

    }
    private String _title;
    public String GetTitle()
    {
        return _title;
    }
    public void SetTitle(String title)
    {
        _title = title;
    }

}
//Checklists
private Vector<Checklist> _checklists = new Vector<Checklist>();
public Checklist addChecklist()
{
    Checklist ch = new Checklist();
    ch.SetTitle("New Checklist");
    _checklists.add(ch);
    return ch;
}
public Vector<Checklist> getChecklists()
{
    return _checklists;
}
public void setChecklists(Vector<Checklist> checklists)
{
    _checklists = checklists;
}
}

The line:
String output = mapper.writeValueAsString(testOut);
causes an exception that has had me baffled for hours and about to abandon using this at all.
Any hints are appreciated.

Here is the exception:
No serializer found for class DataStore$Checklist and no properties discovered to create BeanSerializer (to avoid exception, disable SerializationConfig.Feature.FAIL_ON_EMPTY_BEANS) ) (through reference chain: DataStore[“checklists”]->java.util.Vector[0])

Answer 1

There are multiple ways to do it, but I will start with what you are doing wrong: your naming of getter and setter method is wrong — in Java one uses “camel-case”, so you should be using “getTitle”. Because of this, properties are not found.

Besides renaming methods to use Java-style names, there are alternatives:

• You can use annotation JsonProperty("title") for GetTitle(), so that property is recognized
• If you don’t want the wrapper object, you could alternatively just add @JsonValue for GetTitle(), in which case value used for the whole object would be return value of that method.