Error parsing json to java object: expecting number, got string

Question

I am calling a service which returns responses as json and turn them into a Java object using Gson. In 47 of 50 cases, I get the Java object however in 3 of the cases, I get the following error:

com.google.gson.JsonSyntaxException: Expecting number, got: STRING
    at com.google.gson.internal.bind.TypeAdapters$11.read(TypeAdapters.java:304)
    at com.google.gson.internal.bind.TypeAdapters$11.read(TypeAdapters.java:293)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172)
    at com.google.gson.internal.bind.TypeAdapterRuntimeTypeWrapper.read(TypeAdapterRuntimeTypeWrapper.java:40)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:81)
    at com.google.gson.internal.bind.CollectionTypeAdapterFactory$Adapter.read(CollectionTypeAdapterFactory.java:60)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$1.read(ReflectiveTypeAdapterFactory.java:93)
    at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:172)
    at com.google.gson.Gson.fromJson(Gson.java:795)
    at com.google.gson.Gson.fromJson(Gson.java:761)
    at com.google.gson.Gson.fromJson(Gson.java:710)
    at com.google.gson.Gson.fromJson(Gson.java:682)

One json response which is failing can be seen here: http://ec2-50-112-212-186.us-west-2.compute.amazonaws.com/ske.json. My Java bean is the following:

import java.util.List;

import com.google.gson.annotations.SerializedName;

public class WordSketch{

    @SerializedName("Gramrels")
    private List<Gramrel> gramrels;

    public List<Gramrel> getGramrels(){
        return this.gramrels;
    }
    public void setGramrels(List<Gramrel> gramrels){
        this.gramrels = gramrels;
    }

    public static class Gramrel {

        @SerializedName("Words")
        private List<Word> words;
        private Number count;
        private String name;
        private Number score;
        private Number seek;

        public List<Word> getWords(){
            return this.words;
        }
        public void setWords(List<Word> words){
            this.words = words;
        }
        public Number getCount(){
            return this.count;
        }
        public void setCount(Number count){
            this.count = count;
        }
        public String getName(){
            return this.name;
        }
        public void setName(String name){
            this.name = name;
        }
        public Number getScore(){
            return this.score;
        }
        public void setScore(Number score){
            this.score = score;
        }
        public Number getSeek(){
            return this.seek;
        }
        public void setSeek(Number seek){
            this.seek = seek;
        }
    }

    public static class Word {
        private Number count;
        private Number id;
        private String lempos;
        private Number score;
        private Number seek;
        private String word;

        public Number getCount(){
            return this.count;
        }
        public void setCount(Number count){
            this.count = count;
        }
        public Number getId(){
            return this.id;
        }
        public void setId(Number id){
            this.id = id;
        }
        public String getLempos(){
            return this.lempos;
        }
        public void setLempos(String lempos){
            this.lempos = lempos;
        }
        public Number getScore(){
            return this.score;
        }
        public void setScore(Number score){
            this.score = score;
        }
        public Number getSeek(){
            return this.seek;
        }
        public void setSeek(Number seek){
            this.seek = seek;
        }
        public String getWord(){
            return this.word;
        }
        public void setWord(String word){
            this.word = word;
        }
    }
}

and the actual gson call is gson.fromJson(json, WordSketch.class).

Could anyone point out what is wrong or at least give me some light as to how to debug (quickly) since I don't know in which part of the json, gson is failing?

Thanks a lot,

MikO · Accepted Answer · 2013-04-21 13:16:26Z

4

By observing your JSON, I've realised that some fields that usually have a numeric value, other times they have an empty string as value.

For example, the 3rd gramrel in the response is:

{
    "count": "",
    "colbreak": 1,
    "name": "unary rels",
    "score": "",
    "Words": [
        {
            "count": 6,
            "word": "prp_għaċ-",
            "name": "prp_għaċ-",
            "score": 9.1,
            "Words": [ ],
            "seek": 2231297
        }
    ],
    "seek": 0
},

As in your class you have defined count and score of type Number, GSON complains!

EDIT: I suggest you to have all fields in your classes to be of type String and then you can convert it as you need... I mean, you can use the class you wrote just as a response wrap class, and then create your actual classes from that response class...

WordSketch ws = gson.fromJson(json, WordSketch.class);
for (Gramrel g in ws.getGramrels) {
    Number count = //convert the String into Number...
    //etc...
    MyGrammel myGrammel = new MyGrammel(count, ...);
}

In this example, your Gramrel class is only a temporary class to wrap the response, and MyGramrel is the actual class you'll use (the one with the properties of type Number)....

edited Apr 21, 2013 at 13:16

answered Apr 18, 2013 at 20:38

MikO

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2 Comments

Krt_Malta Over a year ago

hmm ic. 10x! best to change everything to string then I guess and then parse to a number?

MikO Over a year ago

exactly! it's just what I was writing in the EDIT... :)

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