Issue when trying to use Jackson in java

Question

I'm trying to use Jackson to convert some JSON data into Java objects ,a list of objects to be precise,but I get this error:

org.codehaus.jackson.map.JsonMappingException: Can not deserialize instance of entitylayer.Detail out of START_ARRAY token

this is the code:

 ObjectMapper mapper = new ObjectMapper(); 
 List<Detail> lcd = (List<Detail>) mapper.readValue(ld, Detail.class);

ld is the list in Json format, this is the part that makes me comfused in the jackson tutorial. what does new File("user.json") represent? I assumed that was the string in json format I wanted to convert, that's why I used ld.

I hope you can help me out with it

Answer 1

From the tutorial you linked (other Collections work the same way):

So if you want to bind data into a Map you will need to use:

Map<String,User> result = mapper.readValue(src, new TypeReference<Map<String,User>>() { });

where TypeReference is only needed to pass generic type definition (via anynomous inner class in this case): the important part is > which defines type to bind to.

If you don't do this (and just pass Map.class), call is equivalent to binding to Map (i.e. "untyped" Map), as explained above.

Edit:

If you insist on being spoon fed:

List<Detail> lcd = mapper.readValue(ld, new TypeReference<List<Detail>>() {});