CODEWITHSUNDEEP
javaandroidjsongsondeserialization
Valentin Yuryev
Valentin Yuryev

Reputation: 814

Google Gson issue with deserializing

I have a Java class:

public class Object1 {
    private int field1;
    private String field2;
    private Object2 object2;
    private boolean field3;
}

I've saved some Object1 instance as JSON string using Gson:

    String jsonString = new Gson().toJson(object1, Object1.class);

And then I added new String field to Object1 class:

public class Object1 {
    private int field1;
    private String field2;
    private String field4;
    private Object2 object2;
    private boolean field3;
}

And now I can't to deserialize json string to Object1 instance using method:

Object1 obj1 = new Gson().fromJson(jsonString, Object1.class);

Because of Gson throws exception:

System.err: com.google.gson.JsonSyntaxException: java.lang.IllegalStateException: Expected a string but was BEGIN_OBJECT at line 1 column 444 path $.c at com.google.gson.internal.bind.ReflectiveTypeAdapterFactory$Adapter.read(ReflectiveTypeAdapterFactory.java:224) at com.google.gson.Gson.fromJson(Gson.java:887) at com.google.gson.Gson.fromJson(Gson.java:852) at com.google.gson.Gson.fromJson(Gson.java:801) at com.google.gson.Gson.fromJson(Gson.java:773)

But why? I have JSON string without one field and it can't to be a problem. Why I can't deserialize it?

Upvotes: 0

Views: 1695

Answers (2)

Valentin Yuryev
Valentin Yuryev

Reputation: 814

As it turned out problem was in obfuscation.

If you're not use @SerializedName annotation result JSON can be like that:

{"a":3436213,"b":"some string","c":{.............},"d":true}

We didn't use it because of it isn't DTO. In this case we using JSON just to store some unimportant internal data. But it was very funny lesson for me.

Upvotes: 0

Zun
Zun

Reputation: 1690

Expected a string but was BEGIN_OBJECT

field4 in your json string is not of type String, use a Json to POJO generator to create a proper object.

I like to use http://www.jsonschema2pojo.org/

Upvotes: 0

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