[Update Sept 2020] Although my original answer here, from many years ago, seems to be helpful and is still getting upvotes, I now use the GSON library from Google, which I find to be more intuitive.

I've got the following code:

public void testJackson() throws IOException {  
    ObjectMapper mapper = new ObjectMapper(); 
    File from = new File("albumnList.txt"); 
    TypeReference<HashMap<String,Object>> typeRef 
            = new TypeReference<HashMap<String,Object>>() {};

    HashMap<String,Object> o = mapper.readValue(from, typeRef); 
    System.out.println("Got " + o); 
}   

It's reading from a file, but mapper.readValue() will also accept an InputStream and you can obtain an InputStream from a string by using the following:

new ByteArrayInputStream(astring.getBytes("UTF-8")); 

There's a bit more explanation about the mapper on my blog.

the solution is quite simple:

ObjectMapper jsonMapper = new ObjectMapper();
TypeReference<Map<String, Map<String, DataType>>> typeRef = 
        new TypeReference<Map<String, Map<String, DataType>>>() {};
Map<String, Map<String, DataType>> configMap = jsonMapper.readValue(strJson, typeRef);

I solved it by just using Spring Boot's native json parser:

org.springframework.boot.json.JsonParser springParser = JsonParserFactory.getJsonParser();
Map<String, Object> result = springParser.parseMap(response.getBody());

However the real credit goes to ericbn from this post: How to parse a dynamic JSON key in a Nested JSON result?