Make GsonGraphQLResponseFactory.buildResponse throw on empty string

aws-amplify · Jan 4, 2023 · 8e88676 · 8e88676
1 parent e40b03c
commit 8e88676
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diff --git a/aws-api/src/main/java/com/amplifyframework/api/aws/GsonGraphQLResponseFactory.java b/aws-api/src/main/java/com/amplifyframework/api/aws/GsonGraphQLResponseFactory.java
@@ -22,6 +22,7 @@
 import com.amplifyframework.api.graphql.GraphQLRequest;
 import com.amplifyframework.api.graphql.GraphQLResponse;
 import com.amplifyframework.api.graphql.PaginatedResult;
+import com.amplifyframework.util.Empty;
 import com.amplifyframework.util.GsonFactory;
 import com.amplifyframework.util.TypeMaker;
 
@@ -56,6 +57,18 @@ final class GsonGraphQLResponseFactory implements GraphQLResponse.Factory {
     @Override
     public <T> GraphQLResponse<T> buildResponse(GraphQLRequest<T> request, String responseJson)
             throws ApiException {
+
+        // On empty strings, Gson returns null instead of throwing JsonSyntaxException. See:
+        // https://github.com/google/gson/issues/457
+        // https://github.com/google/gson/issues/1697
+        if (Empty.check(responseJson)) {
+            throw new ApiException(
+                "Amplify encountered an error while deserializing an object.",
+                new JsonParseException("Empty response."),
+                AmplifyException.TODO_RECOVERY_SUGGESTION
+            );
+        }
+
         Type responseType = TypeMaker.getParameterizedType(GraphQLResponse.class, request.getResponseType());
         try {
             Gson responseGson = gson.newBuilder()

diff --git a/aws-api/src/test/java/com/amplifyframework/api/aws/GsonGraphQLResponseFactoryTest.java b/aws-api/src/test/java/com/amplifyframework/api/aws/GsonGraphQLResponseFactoryTest.java
@@ -114,6 +114,26 @@ public void nonJsonResponseThrowsApiException() throws ApiException {
         });
     }
 
+    /**
+     * Validates that an empty response throws an
+     * ApiException instead of returning a null reference.
+     * @throws ApiException From API configuration
+     */
+    @Test
+    public void emptyResponseThrowsApiException() throws ApiException {
+        // Arrange some empty string from a "server"
+        final String emptyResponse = "";
+
+        // Act! Parse it into a model.
+        Type responseType = TypeMaker.getParameterizedType(PaginatedResult.class, Todo.class);
+        GraphQLRequest<PaginatedResult<Todo>> request = buildDummyRequest(responseType);
+
+        // Assert that the appropriate exception is thrown
+        assertThrows(ApiException.class, () -> {
+            responseFactory.buildResponse(request, emptyResponse);
+        });
+    }
+
     /**
      * Validates that the converter is able to parse a partial GraphQL
      * response into a result. In this case, the result contains some