Read a JSON file using JACKSON

Question

I want to read a JSON file received.

That's the form of the JSON file:

{
    "name": "list_name"
    "items": [
        {
            "id": 4
        },
        {
            "id": 3
        },
        {
            "id": 2
        },
    ]
} 

I want to parse that JSON that represents a movie list, and the id's of the movies. I want to extract the ids and the name.

@PUT
@Path("/")
@Consumes(MediaType.APPLICATION_JSON)
public Response deleteMoviesFromList2(@Context HttpServletRequest req) Long movieListId) {
    Long userId = getLoggedUser(req);
    getLoggedUser(req);

    final String json = "some JSON string";
    final ObjectMapper mapper = new ObjectMapper();


    return buildResponse(listMovieService.remove(¿?));
}

I want to extract the ids but I have no clue how to do it.

Solution 1

You can convert json string using ObjectMapper class like this.

ObjectMapper objectMapper = new ObjectMapper();

String carJson =
    "{ \"brand\" : \"Mercedes\", \"doors\" : 5 }";

try {
    Car car = objectMapper.readValue(carJson, Car.class);

    System.out.println("car brand = " + car.getBrand());
    System.out.println("car doors = " + car.getDoors());
} catch (IOException e) {
    e.printStackTrace();
}

Here you can replace Car class with your custom Movie class and you are done.

Solution 2

If you have a movie class defined, such as:

class Movie {
    String id;
    //getters
    //setters
}

and a Movie list class:

class MovieList {
    String name;
    List<Movie> items;
    //getters
    //setters
}

Then you can use an object mapper with an inputStream:

try(InputStream fileStream = new FileInputStream("movielist.json")) {
    MovieList list = mapper.readValue(fileStream, MovieList.class);
}

ObjectMapper's readValue has an overloaded version that takes an input stream, and that's the one used above.

Comments

[niceman]

related stackoverflow.com/questions/7693669/…

[niceman]

if I recall you only need to add jackson jars to the classpath and jersey will use them to convert any json to any class you want and vice versa

[niceman]

ofcourse your class needs to be a (pseudo) JavaBean

[Arnau Van Boschken ArnauB]

But I don't have the carJson var. I received a JSON from a PUT call.

[DeepInJava]

You can take your json string in some string variable and then convert to equivalent object using Object mapper.