6.4.3. JAX-RS Response Handler¶

6.4.3.6.1. Configure a message in response to an error¶

In some cases, such as a validation error, etc., the error message may have to be configured in the response body and returned. For such cases, support by creating an inherited class of ErrorResponseBuilder.

An implementation example where a JSON format error message is configured in the response is shown below.

public class SampleErrorResponseBuilder extends ErrorResponseBuilder {

    private final ObjectMapper objectMapper = new ObjectMapper();

    @Override
    public HttpResponse build(final HttpRequest request,
            final ExecutionContext context, final Throwable throwable) {
        if (throwable instanceof ApplicationException) {
            return createResponseBody((ApplicationException) throwable);
        } else {
            return super.build(request, context, throwable);
        }
    }

    private HttpResponse createResponseBody(final ApplicationException ae) {
        final HttpResponse response = new HttpResponse(400);
        response.setContentType(MediaType.APPLICATION_JSON);

        // Generation process of error message is omitted

        try {
            response.write(objectMapper.writeValueAsString(errorMessages));
        } catch (JsonProcessingException ignored) {
            return new HttpResponse(500);
        }
        return response;
    }
}

6.4.3.6.2. Return individually defined error response for specific errors¶

For errors that occur in the subsequent process after this handler, error response defined with a particular status code or body may have to be returned.

In such cases, create an inherited class from ErrorResponseBuilder and implement the response generation process individually corresponding to the exception thrown.

An implementation example is shown below.

public class SampleErrorResponseBuilder extends ErrorResponseBuilder {

    @Override
    public HttpResponse build(final HttpRequest request,
            final ExecutionContext context, final Throwable throwable) {
        if (throwable instanceof NoDataException) {
            return new HttpResponse(404);
        } else {
            return super.build(request, context, throwable);
        }
    }
}

6.4.3.6.3. Add common processing to the response returned to the client¶

At any time, such as during normal times or when an error occurs, there are cases when the response returned to the client may want to specify a common response header to support CORS or security for the response.

To handle such cases, the framework provides the ResponseFinisher interface to finish the response. If it is necessary to add common processing to the response,　simply create a class that implements the ResponseFinisher interface and specify it in the responseFinishers property of this handler.

Implementation and configuration examples are shown below.

public class CustomResponseFinisher implements ResponseFinisher {
    @Override
    public void finish(HttpRequest request, HttpResponse response, ExecutionContext context) {
        // Common processing, such as setting the response header.
    }
}

<component class="nablarch.fw.jaxrs.JaxRsResponseHandler">
  <property name="responseFinishers">
    <list>
      <!-- Specify a class that implements ResponseFinisher -->
      <component class="sample.CustomResponseFinisher" />
    </list>
  </property>
</component>

In some cases, an existing handler such as Secure Handler, which sets security-related response headers, may be used as a ResponseFinisher. To handle such cases, the framework provides the AdoptHandlerResponseFinisher class that applies the handler to ResponseFinisher.

The handlers that can be used with AdoptHandlerResponseFinisher are limited to handlers that do not create their own responses and change the responses returned by subsequent handlers.

An example of the use of AdoptHandlerResponseFinisher is shown below.

<component class="nablarch.fw.jaxrs.JaxRsResponseHandler">
  <property name="responseFinishers">
    <list>
      <!-- AdoptHandlerResponseFinisher -->
      <component class="nablarch.fw.jaxrs.AdoptHandlerResponseFinisher">
        <!-- Specify the handler for the handler property -->
        <property name="handler" ref="secureHandler" />
      </component>
    </list>
  </property>
</component>