diff --git a/README.md b/README.md
index e3ebe8f4709d16506ad11c84fb3a5eba3740ae2c..64ec977e9bfafd41206c5c2655b2be03d90d321b 100644
--- a/README.md
+++ b/README.md
@@ -13,23 +13,39 @@ Please refer to:
## Supported Options
-| Key | Data Type | Default value | Description |
-| ------------------------- | ------------------ | ------------------------------------- | ----------- |
-| graphqlSchemaPaths | List(String) | None | GraphQL schema locations. You can supply multiple paths to GraphQL schemas. |
-| packageName | String | Empty | Java package for generated classes. |
-| outputDir | String | None | The output target directory into which code will be generated. |
-| apiPackage | String | Empty | Java package for generated api classes (Query, Mutation, Subscription). |
-| modelPackage | String | Empty | Java package for generated model classes (type, input, interface, enum, union). |
-| generateApis | Boolean | True | Specifies whether api classes should be generated as well as model classes. |
-| customTypesMapping | Map(String,String) | Empty | Can be used to supply custom mappings for scalars.
Supports:
* Map of (GraphqlObjectName.fieldName) to (JavaType)
* Map of (GraphqlType) to (JavaType) |
-| customAnnotationsMapping | Map(String,String) | Empty | Can be used to supply custom annotations (serializers) for scalars.
Supports:
* Map of (GraphqlObjectName.fieldName) to (JavaType)
* Map of (GraphqlType) to (JavaType) |
+| Key | Data Type | Default value | Description |
+| ------------------------- | ------------------ | ----------------------------------------- | ----------- |
+| graphqlSchemaPaths | List(String) | None | GraphQL schema locations. You can supply multiple paths to GraphQL schemas. |
+| packageName | String | Empty | Java package for generated classes. |
+| outputDir | String | None | The output target directory into which code will be generated. |
+| apiPackage | String | Empty | Java package for generated api classes (Query, Mutation, Subscription). |
+| modelPackage | String | Empty | Java package for generated model classes (type, input, interface, enum, union). |
+| generateApis | Boolean | True | Specifies whether api classes should be generated as well as model classes. |
+| customTypesMapping | Map(String,String) | Empty | Can be used to supply custom mappings for scalars.
Supports:
* Map of (GraphqlObjectName.fieldName) to (JavaType)
* Map of (GraphqlType) to (JavaType) |
+| customAnnotationsMapping | Map(String,String) | Empty | Can be used to supply custom annotations (serializers) for scalars.
Supports:
* Map of (GraphqlObjectName.fieldName) to (JavaType)
* Map of (GraphqlType) to (JavaType) |
| modelValidationAnnotation | String | @javax.validation.
constraints.NotNull | Annotation for mandatory (NonNull) fields. Can be null/empty. |
-| modelNamePrefix | String | Empty | Sets the prefix for GraphQL model classes (type, input, interface, enum, union). |
-| modelNameSuffix | String | Empty | Sets the suffix for GraphQL model classes (type, input, interface, enum, union). |
-| subscriptionReturnType | String | Empty | Return type for subscription methods. For example: `org.reactivestreams.Publisher`, `io.reactivex.Observable`, etc. |
-| generateEqualsAndHashCode | Boolean | False | Specifies whether generated model classes should have equals and hashCode methods defined. |
-| generateToString | Boolean | False | Specifies whether generated model classes should have toString method defined. |
-
-### Inspired by
+| modelNamePrefix | String | Empty | Sets the prefix for GraphQL model classes (type, input, interface, enum, union). |
+| modelNameSuffix | String | Empty | Sets the suffix for GraphQL model classes (type, input, interface, enum, union). |
+| subscriptionReturnType | String | Empty | Return type for subscription methods. For example: `org.reactivestreams.Publisher`, `io.reactivex.Observable`, etc. |
+| generateEqualsAndHashCode | Boolean | False | Specifies whether generated model classes should have equals and hashCode methods defined. |
+| generateToString | Boolean | False | Specifies whether generated model classes should have toString method defined. |
+| jsonConfigurationFile | String | Empty | Path to an external mapping configuration. |
+
+### External mapping configuration
+
+Provide a path to external file via property `jsonConfigurationFile`
+Sample content of the file:
+
+```json
+{
+ "generateApis": true,
+ "packageName": "com.kobylynskyi.graphql.testconfigjson",
+ "customTypesMapping": {
+ "Price.amount": "java.math.BigDecimal"
+ }
+}
+```
+
+## Inspired by
[swagger-codegen](https://github.com/swagger-api/swagger-codegen)