Problem with Jackson Parser

[Shashank Sharma]

Hello
I am using following code for parsing a HashMap<string,Object>

HashMap<string,Object> hm=new HashMap<string,Object>();
hm.put("FirstObj",JDO);
JsonString=convertObjectToJson(hm);


//Method for conversion
public String convertObjectToJson( Object historyObject ) throws JsonGenerationException , JsonMappingException , IOException
			{
				
				Writer writer = new StringWriter();
				String JsonString = "";
				mapper.writeValue( writer , historyObject );
				JsonString = writer.toString();
				return JsonString;
			}

but on deserializing it as

HashMap<String,Object> jMap = mapper.readValue(JsonString,new TypeReference<HashMap<String,Object>>() {})
jMap.get("FirstObj");//----->returns a LinkedHashMap  instead of a JDO

Has any tried something like this?

Please help

Thanks In advance