Handling a ReadTimeoutException with Spring's WebClient

Question

I'm making a call to a REST service using the Spring WebClient, and I am trying to handle an io.netty.handler.timeout.ReadTimeoutException which might happen from time to time:

            try {
                List<Asset> assets = client.searchAssets("some-type", assetCode);
                // do sometihng
            } catch (ReadTimeoutException ex) {
                log.error("TimeoutException, can't wait no more :)");
            }

However, when there is a Timeout Exception, this seems to be the exception I'm getting: WebClientRequestException

My question is, should I catch this WebClientRequestException instead? How will I ever know if this was due to a ReadTimeoutException?

Answer 1

In Spring's WebClient, exceptions from the underlying netty library (like io.netty.handler.timeout.ReadTimeoutException) are often wrapped in a WebClientRequestException. This is why you're seeing the WebClientRequestException instead of the TimeoutException.

When you catch a WebClientRequestException, you can check its cause to see if it is a TimeoutException. Here's an example of how to do that:

try {
    // do something
} catch (WebClientRequestException ex) {
    if (ex.getCause() instanceof TimeoutException) {
        // timeout
    } else {
        // else
    }
}

Please be aware that the timeout exception you may encounter is not the standard java.util.concurrent.TimeoutException but rather the io.netty.handler.timeout.TimeoutException. It's important to note that handling this exception will create a dependency (coupling) on the Netty library. If you modify the Spring WebClient configuration and switch the underlying library from Netty to another option, you must also update your code accordingly.