Question

I am using Gson class to convert JSON string data to Intent object. But I am getting exception.

JSON string of Intent:

{
   "targetIntent":{
      "mAction":"android.intent.action.VIEW",
      "mData":{
         "authority":{
            "decoded":"com.android.contacts",
            "encoded":"com.android.contacts"
         },
         "fragment":{

         },
         "path":{
            "decoded":"NOT CACHED",
            "encoded":"/contacts/lookup/1471i541ce89b89ad6a59"
         },
         "query":{

         },
         "scheme":"content",
         "uriString":"NOT CACHED",
         "host":"NOT CACHED",
         "port":-2
      },
      "mFlags":0
   }
}

Conversion code:

Intent targetIntent =
    gson.fromJson(histroyDataObject.getString("targetIntent"), Intent.class);

This gives exception:

Cause: Instantiation Exception
Detail Message: Failed to invoke private android.net.Uri() with no args

Stack trace:

08-31 01:08:19.045: W/System.err(290): Caused by: java.lang.InstantiationException: android.net.Uri
08-31 01:08:19.065: W/System.err(290):  at java.lang.reflect.Constructor.constructNative(Native Method)
08-31 01:08:19.065: W/System.err(290):  at java.lang.reflect.Constructor.newInstance(Constructor.java:446)
08-31 01:08:19.065: W/System.err(290):  at com.google.gson.internal.ConstructorConstructor$2.construct(ConstructorConstructor.java:91)
08-31 01:08:19.076: W/System.err(290):  ... 24 more

Thanks for your help.

Answer 1

My bet is Intent#uriString is of type android.net.Uri which has no no-arg public constructor. I means you have to write JsonDeserializer<Uri> like this:

public class UriDeserializer implements JsonDeserializer<Uri> {
  @Override
  public Uri deserialize(final JsonElement src, final Type srcType,
      final JsonDeserializationContext context) throws JsonParseException {
    return Uri.parse(src.getAsString());
  }
}

and then register it via GsonBuilder:

Gson gson = new GsonBuilder()
    .registerTypeAdapter(Uri.class, new UriDeserializer())
    .create();

EDIT:

You have to register custom adapters in case any property doesn’t define public no-arg constructor. You may read more in Gson docs – Custom Serialization and Deserialization.