Tackling WebClientRequestException in Spring: An Exhaustive Guide
Unexpected errors can be a nightmare for developers and can happen anytime during development, especially when using reactive programming in Spring. One such stumbling block that has become a common sight in the logs is the “
WebClientRequestException”. In this article, we delve deep into the internals of this exception, exploited by many an exception, and provide proven methods and practices to deal with this monstrous hurdle.
Before proceeding with the detailed explanation, it’s essential to have considerable knowledge of Spring, Spring-Boot framework, and reactive programming.
Understanding WebClientRequestException
WebClientRequestException is a subclass of Spring’s WebClientResponseException. It signifies an HTTP client error.
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public class WebClientRequestException extends WebClientResponseException
Mostly it occurs when Spring’s WebClient is unable to establish a connection with the server, resulting in “Connection Refused” errors.
Why WebClientRequestException?
WebClient is a non-blocking, reactive web client introduced with Spring 5. It’s part of Spring WebFlux module that offers significantly more robust features compared to RestTemplate. However, it becomes problematic when the client can’t connect to the server or when the request times out.
Best Practices to handle WebClientRequestException
1. Explicit Handling
The simplest technique to handle WebClientRequestException is to perform an explicit handling. The powerful onErrorReturn operator can be leveraged to handle the exception in a meaningful way.
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WebClient.builder()
.get()
.uri(uri)
.retrieve()
.bodyToMono(String.class)
.onErrorReturn(WebClientRequestException.class, "Connection Error Occurred")
.block();
In this snippet, when WebClient encounters WebClientRequestException, we simply return a custom error message.
2. Custom Error Decoder
Another way to handle it is to implement a custom Error Decoder. In this method, you can catch the exception and map it to your custom Exception class.
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public class CustomErrorDecoder implements ErrorDecoder {
@Override
public Throwable decode(String methodKey, Response response) {
if(response.status() == 500) {
return new WebClientRequestException("Server Error");
}
// Handle other status codes...
return default.decode(methodKey, response);
}
}
3. Retry Mechanism
WebClient offers a retry mechanism. If your application encounters a WebClientRequestException, it can retry the connection request a specified number of times.
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WebClient.builder()
.get()
.uri(uri)
.retrieve()
.bodyToMono(String.class)
.retry(3)
.block();
Here, if WebClient encounters WebClientRequestException, it retries the request three times before giving up.
4. Use Circuit Breaker
Consider using a Circuit Breaker pattern. With a Circuit Breaker in place, your service will fail fast which can improve the application’s overall latency. Spring Cloud provides an implementation of the Circuit Breaker pattern with the Spring Cloud Circuit Breaker project.
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@CircuitBreaker(name = "backendA", fallbackMethod = "fallback")
public String sampleMethod() {
// WebClient call here
}
public String fallback(Throwable throwable) {
return "Fallback response";
}
In this specific example, if the method sampleMethod fails, Spring Cloud Circuit Breaker calls the fallback method.
Conclusion
WebClientRequestException in Spring is a common and crucial error during application development. It is always imperative to scrutinize the application response and handle the probable exceptions. We hope these practices will guide you smoothly on your Java journey.
Happy coding!