解析GSON Google Places API

Question

I'm trying to parse a json to my java object, but I'm getting error from gson.

The error is:

com.google.gson.JsonParseException: Expecting object found: "{   \"debug_info\" : [],   \"html_attributions\" : [],   \"results\" : [      {         \"geometry\" : {            \"location\" : {               \"lat\" : 53.330661,               \"lng\" : -6.265253            }         },         \"icon\" : \"http://maps.gstatic.com/mapfiles/place_api/icons/bar-71.png\",         \"id\" : \"b50995ee5107706386c43d562fc614dc9db57937\",         \"name\" : \"Lower Deck\",         \"rating\" : 3.5,         \"reference\" : \"CnRoAAAATUQrAt8LAzje_32Uzm5jklTmhsYA_orKtp9DIO_-kmCTU7DsHkNBae3aY9dLusdqJaSGwdj6G_-LpqbKWIi5r0RjcJWHljxCex8wI9UMO93uqSpr63S6qyNjJdw01nGEl1LLtbtz4VRGuKdEAl6sShIQEeM3-QnEjeoO7lEWZBYQQBoU0TOKwurVvTs565wKYPLQNmkLF5w\",         \"types\" : [ \"bar\", \"establishment\" ],         \"vicinity\" : \"1 Portobello Harbour, Dublin\"      },      {         \"geometry\" : {            \"location\" : {               \"lat\" : 53.332361,               \"lng\" : -6.275473            }         },         \"icon\" : \"http://maps.gstatic.com/mapfiles/place_api/icons/bar-71.png\",         \"id\" : \"8e8f338164d20d4ad7d943db980ce62d0325c2b5\",         \"name\" : \"The Headline Bar\",         \"rating\" : 3.6,         \"reference\" : \"CnRvAAAAvlARk-Q-08T9kuvY_mp90vn10jf84TDNKymDtVyEYvt1wg7TEJyaqGF_R6zDGkXBoKSOEfovqm-A8w42OlOa1yAE-nMdGVgR_EKJKu5HHdzUmKlkFoPqcJxbJpFAblqCMz_ClpbwMEMtFNLA_hZidRIQVCg4_6vqhJuSDSqtbIG2zxoUeEGHiUYqFk2e_aB18dqFSKx_E5Y\",         \"types\" : [ \"bar\", \"establishment\" ],         \"vicinity\" : \"118 S Circular Rd, Crumlin, Dublin\"      }   ],   \"status\" : \"OK\"}"

Then my classes are the following:

GoogleMapper

    @SerializedName("debug_info")
    private List<String> debug_info;

    @SerializedName("html_attributions")
    private List<String> html_attributions;

    @SerializedName("next_page_token")
    private String next_page_token;

    @SerializedName("results")
    private List<Results> results;

    @SerializedName("status")
    private String status;

Results

@SerializedName("geometry")
private Geometry geometry;

@SerializedName("icon")
private String icon;

@SerializedName("id")
private String id;

@SerializedName("name")
private String name;

@SerializedName("photos")
private Photos photos;

@SerializedName("rating")
private Double rating;

@SerializedName("reference")
private String reference;

@SerializedName("types")
private List<String> types;

@SerializedName("vicinity")
private String vicinity;

Geometry

@SerializedName("location")
private Location location;

Location

@SerializedName("lat")
private Double lat;

@SerializedName("lng")
private Double lng;

Photos

    @SerializedName("height")
    private int height;

    @SerializedName("width")
    private int width;

    @SerializedName("html_attributions")
    private List<String> html_attributions;

    @SerializedName("photo_reference")
    private String photo_reference;

And finally, I'm trying to do the following code:

    Gson gson = new GsonBuilder().serializeNulls().create();
    String json = gson.toJson(retorno.toString());

    GoogleMapper mapper = gson.fromJson(json, GoogleMapper.class);

Please, anyone can help me? Thanks

Answer 1

You are using your Gson instance wrong. It should be

gson.toJson(ritorno);

you do NOT need to call ritorno.toString()

Gson can directly serialize from an object.

toString() has actually nothing to do with json, or serialization.

Additional information about good practices:

You should implement your own toString() method for your classes to have better readability for debugging. It has nothing to do with serializing your object to a String.

Gson is extremely to use and if you are not worried about performances then it is a good choice. Otherwise there is (really) faster (but slightly less obvious to use or configure) libraries like : Jackson-Json