Exception in thread “main” com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: empty String

Question

I am trying to deserialize a json string to java object as follows

String json="A valid json";
Job job = new Gson().fromJson(json, Job.class);

the above statement is throwing the following exception

Exception in thread "main" com.google.gson.JsonSyntaxException: java.lang.NumberFormatException: empty String
    at com.google.gson.internal.bind.TypeAdapters$7.read(TypeAdapters.java:241)
    at com.google.gson.internal.bind.TypeAdapters$7.read(TypeAdapters.java:231)
    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.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.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:803)
    at com.google.gson.Gson.fromJson(Gson.java:768)
    at com.google.gson.Gson.fromJson(Gson.java:717)
    at com.google.gson.Gson.fromJson(Gson.java:689)
    at com.test.JobValidator.validate(JobValidator.java:10)
    at com.test.Test.main(Test.java:25)
Caused by: java.lang.NumberFormatException: empty String
    at sun.misc.FloatingDecimal.readJavaFormatString(FloatingDecimal.java:1011)
    at java.lang.Double.parseDouble(Double.java:540)
    at com.google.gson.stream.JsonReader.nextInt(JsonReader.java:1178)
    at com.google.gson.internal.bind.TypeAdapters$7.read(TypeAdapters.java:239)
    ... 24 more

here Job is a pojo I defined for this json structure. Why am I getting this exception ? how to fix it?

Answer 1

You are getting this exception because a value in your json string must be a numeric value.

ex: Your Pojo class.

public class Job {

private int id;

public int getId() {
    return id;
}

public void setId(int id) {
    this.id = id;
}

Your json string :

{"id":""}

id must be a numeric value (ex: 0)

More information here : How to handle a NumberFormatException with Gson in deserialization a JSON response