Customizing

Adding and changing functionality of Springwolf is easy. The configuration page mentions the existing ones.

When you feel that Springwolf is missing a feature, you are able to add it yourself. To learn more about how Springwolf works, look behind the scenes.

note

Please let us know on GitHub or Discord, so that other people can benefit from it as well. Contributions are welcome, here are some basic tips.

Springwolf uses interfaces to allow to inject functionality at integration points. Springwolf provides default implementation, but those can be replaced. All default implementations are Spring managed beans, which can be overridden.

AsyncApiCustomizer - Full AsyncAPI document

By implementing the AsyncApiCustomizer interface, the AsyncAPI document can be modified after Springwolf has done all the scanning and has built the document. It's the final interception point before the document is available to the user.

For example, the title can be adjusted - although this should be done through the configuration:

@Component
public class AsyncApiTitleCustomizer implements AsyncApiCustomizer {
    @Override
    public void customize(AsyncAPI asyncAPI) {
         asyncAPI.getInfo().setTitle("Title set through customizer");
    }
}

OperationCustomizer - Operation object

By implementing the OperationCustomizer interface, the Operation object can be modified after Springwolf has scanned an annotated method and extracted the data.

It's possible to create multiple implementations of OperationCustomizer. The order of execution can be controlled by the @Order annotation of Spring.

An example to conditionally add a custom AsyncAPI tag for Kafka batch listeners is shown below:

@Component
public class TagCustomizer implements OperationCustomizer {

    @Override
    public void customize(Operation operation, Method method) {
        KafkaListener annotation = AnnotationScannerUtil.findAnnotation(KafkaListener.class, method);
        if (annotation != null && "true".equals(annotation.batch())) {
            Tag tag = new Tag();
            tag.setName("batch");

            operation.getTags().add(tag);
        }
    }
}

ObjectMapper in DefaultAsyncApiSerializerService

The DefaultAsyncApiSerializerService is responsible for serializing the AsyncAPI document into a String for the Controller.

Use DefaultAsyncApiSerializerService#getJsonObjectMapper() and DefaultAsyncApiSerializerService#getYamlObjectMapper() to customize the ObjectMapper.

ChannelScanners - Channel detection

All ChannelScanner beans are called to scan for channels. This interface is helpful when a protocol currently unsupported by Springwolf is used. Remember to register all payloads in the ComponentsService.

Customize internal behavior

note

Replacing Springwolf beans with custom implementations is for experts only. No support is offered for using internal API.

Custom implementations may break during updates without notice.

Springwolf uses @ConditionalOnMissingBean annotations for most internal Spring beans. If you have a special use-case that requires custom logic, you can replace almost every Springwolf bean by adding your custom implementation as a bean to the Spring context.