public static DynamicMessage buildJsonMessage(final String jsonParam) {
        // build Descriptor and set request param
        Descriptors.Descriptor jsonDescriptor = buildJsonMarshallerDescriptor();
        DynamicMessage.Builder jsonDynamicMessage = DynamicMessage.newBuilder(jsonDescriptor);
        jsonDynamicMessage.setField(jsonDescriptor.findFieldByName(GrpcConstants.JSON_DESCRIPTOR_PROTO_FIELD_NAME), jsonParam);
        return jsonDynamicMessage.build();
    }
@Test
    public void testBuildJsonMessage() {
        DynamicMessage jsonMessage = JsonMessage.buildJsonMessage();

        assertEquals(GrpcConstants.JSON_DESCRIPTOR_PROTO_NAME, jsonMessage.getDescriptorForType().getFullName());
    }