Baeldung Pro comes with both absolutely No-Ads as well as finally with Dark Mode, for a clean learning experience:
Once the early-adopter seats are all used, the price will go up and stay at $33/year.
Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, visit the documentation page.
You can also ask questions and leave feedback on the Azure Container Apps GitHub page.
Azure Container Apps is a fully managed serverless container service that enables you to build and deploy modern, cloud-native Java applications and microservices at scale. It offers a simplified developer experience while providing the flexibility and portability of containers.
Of course, Azure Container Apps has really solid support for our ecosystem, from a number of build options, managed Java components, native metrics, dynamic logger, and quite a bit more.
To learn more about Java features on Azure Container Apps, you can get started over on the documentation page.
And, you can also ask questions and leave feedback on the Azure Container Apps GitHub page.
Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.
Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.
With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.
Try a 14-Day Free Trial of Orkes Conductor today.
Modern software architecture is often broken. Slow delivery leads to missed opportunities, innovation is stalled due to architectural complexities, and engineering resources are exceedingly expensive.
Orkes is the leading workflow orchestration platform built to enable teams to transform the way they develop, connect, and deploy applications, microservices, AI agents, and more.
With Orkes Conductor managed through Orkes Cloud, developers can focus on building mission critical applications without worrying about infrastructure maintenance to meet goals and, simply put, taking new products live faster and reducing total cost of ownership.
Try a 14-Day Free Trial of Orkes Conductor today.
Mocking is an essential part of unit testing, and the Mockito library makes it easy to write clean and intuitive unit tests for your Java code.
Get started with mocking and improve your application tests using our Mockito guide:
Handling concurrency in an application can be a tricky process with many potential pitfalls. A solid grasp of the fundamentals will go a long way to help minimize these issues.
Get started with understanding multi-threaded applications with our Java Concurrency guide:
Spring 5 added support for reactive programming with the Spring WebFlux module, which has been improved upon ever since. Get started with the Reactor project basics and reactive programming in Spring Boot:
Since its introduction in Java 8, the Stream API has become a staple of Java development. The basic operations like iterating, filtering, mapping sequences of elements are deceptively simple to use.
But these can also be overused and fall into some common pitfalls.
To get a better understanding on how Streams work and how to combine them with other language features, check out our guide to Java Streams:
Explore Spring Boot 3 and Spring 6 in-depth through building a full REST API with the framework:
Yes, Spring Security can be complex, from the more advanced functionality within the Core to the deep OAuth support in the framework.
I built the security material as two full courses - Core and OAuth, to get practical with these more complex scenarios. We explore when and how to use each feature and code through it on the backing project.
You can explore the course here:
All Access is finally out, with all of my Spring courses. Learn JUnit is out as well, and Learn Maven is coming fast. And, of course, quite a bit more affordable. Finally.
>> GET THE COURSE
Spring Data JPA is a great way to handle the complexity of JPA with the powerful simplicity of Spring Boot.
Get started with Spring Data JPA through the guided reference course:
End-to-end testing is a very useful method to make sure that your application works as intended. This highlights issues in the overall functionality of the software, that the unit and integration test stages may miss.
Playwright is an easy-to-use, but powerful tool that automates end-to-end testing, and supports all modern browsers and platforms.
When coupled with LambdaTest (an AI-powered cloud-based test execution platform) it can be further scaled to run the Playwright scripts in parallel across 3000+ browser and device combinations:
Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
Yes, we're now running our Spring Sale. All Courses are 25% off until 26th May, 2025:
The Apache HTTP Client is a very robust library, suitable for both simple and advanced use cases when testing HTTP endpoints. Check out our guide covering basic request and response handling, as well as security, cookies, timeouts, and more:
1. Overview
In this short tutorial, we’ll discuss how to implement and inject the ResponseErrorHandler interface in a RestTemplate instance to gracefully handle the HTTP errors returned by remote APIs.
2. Default Error Handling
By default, the RestTemplate will throw one of these exceptions in the case of an HTTP error:
- HttpClientErrorException – in the case of HTTP status 4xx
- HttpServerErrorException – in the case of HTTP status 5xx
- UnknownHttpStatusCodeException – in the case of an unknown HTTP status
All of these exceptions are extensions of RestClientResponseException.
Obviously, the simplest strategy to add custom error handling is to wrap the call in a try/catch block. Then we can process the caught exception as we see fit.
However, this simple strategy doesn’t scale well as the number of remote APIs or calls increases. It would be more efficient if we could implement a reusable error handler for all of our remote calls.
3. Implementing a ResponseErrorHandler
A class that implements ResponseErrorHandler will read the HTTP status from the response and either:
- Throw an exception that is meaningful to our application
- Simply ignore the HTTP status and let the response flow continue without interruption
We need to inject the ResponseErrorHandler implementation into the RestTemplate instance.
Thus, we can use the RestTemplateBuilder to build the template, and replace the DefaultResponseErrorHandler in the response flow.
So let’s first implement our RestTemplateResponseErrorHandler:
@Component
public class RestTemplateResponseErrorHandler implements ResponseErrorHandler {
@Override
public boolean hasError(ClientHttpResponse httpResponse) throws IOException {
return httpResponse.getStatusCode().is5xxServerError() ||
httpResponse.getStatusCode().is4xxClientError();
}
@Override
public void handleError(ClientHttpResponse httpResponse) throws IOException {
if (httpResponse.getStatusCode().is5xxServerError()) {
//Handle SERVER_ERROR
throw new HttpClientErrorException(httpResponse.getStatusCode());
} else if (httpResponse.getStatusCode().is4xxClientError()) {
//Handle CLIENT_ERROR
if (httpResponse.getStatusCode() == HttpStatus.NOT_FOUND) {
throw new NotFoundException();
}
}
}
}Then we can build the RestTemplate instance using the RestTemplateBuilder to introduce our RestTemplateResponseErrorHandler:
@Service
public class BarConsumerService {
private RestTemplate restTemplate;
@Autowired
public BarConsumerService(RestTemplateBuilder restTemplateBuilder) {
RestTemplate restTemplate = restTemplateBuilder
.errorHandler(new RestTemplateResponseErrorHandler())
.build();
}
public Bar fetchBarById(String barId) {
return restTemplate.getForObject("/bars/4242", Bar.class);
}
}4. Testing Our Implementation
Finally, we’ll test this handler by mocking a server and returning a NOT_FOUND status:
@ExtendWith(SpringExtension.class)
@ContextConfiguration(classes = { NotFoundException.class, Bar.class })
@RestClientTest
public class RestTemplateResponseErrorHandlerIntegrationTest {
@Autowired
private MockRestServiceServer server;
@Autowired
private RestTemplateBuilder builder;
@Test
public void givenRemoteApiCall_when404Error_thenThrowNotFound() {
Assertions.assertNotNull(this.builder);
Assertions.assertNotNull(this.server);
RestTemplate restTemplate = this.builder
.errorHandler(new RestTemplateResponseErrorHandler())
.build();
this.server
.expect(ExpectedCount.once(), requestTo("/bars/4242"))
.andExpect(method(HttpMethod.GET))
.andRespond(withStatus(HttpStatus.NOT_FOUND));
Assertions.assertThrows(NotFoundException.class, () -> {
Bar response = restTemplate.getForObject("/bars/4242", Bar.class);
});
}
}5. Conclusion
In this article, we presented a solution to implement and test a custom error handler for a RestTemplate that converts HTTP errors into meaningful exceptions.
The code backing this article is available on GitHub. Once you're logged in as a Baeldung Pro Member, start learning and coding on the project.
