If you’re using the springfox-swagger2 library, you might come across a problem when it comes to generic types (such as Pet<T>). In cases where diamond brackets are used, Swagger will generate an invalid specification, resulting in a validation error in the Swagger Editor (“”$ref values must be RFC3986-compliant percent-encoded URIs”).

The error you get might look like this:

In the above case, Swagger generated a model named Kennel«Pet» from a Kennel<Pet> field. Due to the non-alphanumeric characters, a name like this is invalid for an OpenAPI Specification.

The solution to this problem lies in the Springfox documentation:

By default, types with generics will be labeled with ‘\u00ab'(<<), ‘\u00bb'(>>), and commas. This can be problematic with things like swagger-codegen. You can override this behavior by implementing your own GenericTypeNamingStrategy. For example, if you wanted List<String> to be encoded as ‘ListOfString’ and Map<String, Object> to be encoded as ‘MapOfStringAndObject’ you could set the forCodeGeneration customization option to true during plugin customization:

docket.forCodeGeneration(true|false);

Springfox Documentation

To paraphrase, all we need to do is add forCodeGeneration(true) to the Docket configuration and the model will be generated correctly. Here’s an example Docket configuration with the added change:

@Configuration
@EnableSwagger2
public class SwaggerConfig {

    @Bean
    public Docket api() {
        return new Docket(DocumentationType.SWAGGER_2)
                .select()
                .apis(RequestHandlerSelectors.any())
                .paths(PathSelectors.any())
                .build()
                .forCodeGeneration(true);
    }
}

The generated model name is now KennelOfPet.