daniel-shuy

2026

TypeScript

Module Augmentation

Module Augmentation can be used to patch type definitions in modules, e.g. in third-party libraries.

For example, @types/json-schema provides type definitions for JSON Schema, but the JSONSchema7 interface for Draft-07 does not support custom keywords. We cannot simply create a new type that extends JSONSchema7 (e.g. JSONSchema7WithExtensions) because JSONSchema7 recursively references itself. To allow custom keywords that start with x- (to be compatible with future versions of JSON Schema), we can augment the module to add an index signature to the JSONSchema7 interface globally.

daniel-shuy

public List<String> getErrorMessages(BindingResult bindingResult) {
  return bindingResult.getAllErrors()
    .stream()
    .map(error -> {
      var defaultMessage = error.getDefaultMessage();
      if (error instanceof FieldError) {
        var fieldError = (FieldError) error;
        return String.format("%s %s", fieldError.getField(), defaultMessage);
      } else {
        return defaultMessage;

daniel-shuy

@Component
@Slf4j
public class ErrorLoggingInterceptor implements ClientHttpRequestInterceptor {
  @Nonnull
  @Override
  public ClientHttpResponse intercept(@Nonnull HttpRequest request, @Nonnull byte[] body, ClientHttpRequestExecution execution)
      throws IOException {
    var response = execution.execute(request, body);
    
    var statusCode = response.getStatusCode();

daniel-shuy

enum Weekday {
  MONDAY = 'MONDAY',
  TUESDAY = 'TUESDAY',
  WEDNESDAY = 'WEDNESDAY',
  THURSDAY = 'THURSDAY',
  FRIDAY = 'FRIDAY',
}

enum Weekend {
  SATURDAY = 'SATURDAY',

daniel-shuy

A @Constraint annotation is normally mapped to ConstraintValidator(s) using the @Constraint#validatedBy annotation parameter.

This however has the limitation that the @Constraint annotation has to know about the ConstraintValidator(s) during compilation, which may not always be feasible (for example, if the annotation is used at the DTO layer, but a ConstraintValidator depends on the service layer

daniel-shuy

@ControllerAdvice
public class EmptyOptionalResponseBodyControllerAdvice implements ResponseBodyAdvice<Optional<?>> {
    @Override
    public boolean supports(MethodParameter returnType, @Nullable Class<? extends HttpMessageConverter<?>> converterType) {
        return Optional.class.isAssignableFrom(returnType.getParameterType());
    }

    @Override
    public Optional<?> beforeBodyWrite(Optional<?> body, @Nullable MethodParameter returnType, @Nullable MediaType selectedContentType,
                                       @Nullable Class<? extends HttpMessageConverter<?>> selectedConverterType,

daniel-shuy

jib-maven-plugin's default example runs the build goal during the package phase. The build goal will push the docker image to the remote registry, which may be too frequent to run in the package phase for some projects.

This template instead configures the jib-maven-plugin to run the following goals in the following phases:

Phase	Goal	Goal Description
package	buildTar	Build docker image as tar file
install	dockerBuild	Build docker image and install in Docker daemon

daniel-shuy

import akka.actor.ActorSystem
import akka.dispatch.MessageDispatcher
import akka.event.LoggingAdapter
import akka.http.scaladsl.model.headers.{Authorization, OAuth2BearerToken}
import akka.http.scaladsl.server.Directives.{optionalCookie, optionalHeaderValueByType, provide, reject}
import akka.http.scaladsl.server.{AuthorizationFailedRejection, Directive1, Directives}
import org.keycloak.adapters.KeycloakDeployment
import org.keycloak.adapters.rotation.AdapterTokenVerifier
import org.keycloak.representations.AccessToken

daniel-shuy

import com.google.common.collect.Iterables;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
import javax.validation.ConstraintViolation;
import javax.validation.ConstraintViolationException;
import javax.ws.rs.core.MediaType;
import javax.ws.rs.core.Response;
import javax.ws.rs.ext.ExceptionMapper;
import javax.ws.rs.ext.Provider;

daniel-shuy

import javax.enterprise.context.Dependent;
import javax.enterprise.context.RequestScoped;
import javax.enterprise.inject.Produces;
import javax.persistence.EntityManager;
import javax.persistence.PersistenceContext;

@Dependent
public class EntityManagerProducer {
    @PersistenceContext(name = "persistence-unit")  // name is Persistence Unit Name configured in persistence.xml
    private EntityManager entityManager;