# Determine Filter Criteria
source: https://developer.mastercard.com/commercial-event-notifications/documentation/use_cases/determine_fields/index.md

Before creating subscriptions, use the [fieldmappings](https://developer.mastercard.com/commercial-event-notifications/documentation/parameters/fieldmappings/index.md) endpoint to retrieve the list of fields available to define filter criteria for your subscriptions.
The [response](https://developer.mastercard.com/commercial-event-notifications/documentation/parameters/fieldmappings/index.md) to this request lists the different fields that you can use to construct a filter specification for your subscriptions.
Diagram det-filter-criteria

The following call, which requires no parameters, requests the list of fieldmappings that are available for use when specifying filter criteria.

```java
//Calling Get Field Mapping
FieldMappingApi fieldMappingApi = new FieldMappingApi(client); //Passing the initialized API client to FieldMapping API
List<FieldMapping> fieldMappingList = null;
try {
    fieldMappingList = fieldMappingApi.fieldmappingsGet();
} catch (ApiException e) {
    System.err.println("Exception when calling Get FieldMappingAPI");
    e.printStackTrace();
}
System.out.println("Get FieldMappings response:" + fieldMappingList.toString());
```

### Try it Out {#try-it-out}


API Reference: `GET /fieldmappings`

### Additional Information {#additional-information}

Refer to the [Codes and Formats](https://developer.mastercard.com/commercial-event-notifications/documentation/codeandformats/index.md) for more information about error codes.