Read part of a JSON String using Jackson

Question

The JSON string is as follows

{    "rank":"-text_relevance",    "match-expr":"(label 'star wars')",    "hits":{       "found":7,       "start":0,       "hit":[          {"id":"tt1185834",              "data":{                 "actor":["Abercrombie, Ian","Baker, Dee","Burton, Corey"],                 "title":["Star Wars: The Clone Wars"]              }          },          .          .          .          {"id":"tt0121766",              "data":{                 "actor":["Bai, Ling","Bryant, Gene","Castle-Hughes, Keisha"],                 "title":["Star Wars: Episode III - Revenge of the Sith"]              }          }        ]     },     "info":{        "rid":"b7c167f6c2da6d93531b9a7b314ad030b3a74803b4b7797edb905ba5a6a08",        "time-ms":2,        "cpu-time-ms":0     }     }  

It has many fields, but I just have want the Data field. This won't work:

mapper.readvalue(jsonString,Data.class);  

How do I make Jackson read just the "Data" field?

Answer 1

Jackson 2.3 now has a JsonPointer class you can use. There's a simple example in their quick overview for the release.

Usage is simple: for JSON like

{     "address" : { "street" : "2940 5th Ave", "zip" : 980021 },        "dimensions" : [ 10.0, 20.0, 15.0 ]  } 

you could use expressions like:

  JsonNode root = mapper.readTree(src);    int zip =root.at("/address/zip").asIntValue();    double height = root.add("/dimensions/1").asDoubleValue();// assuming it's the second number in there