Understanding and Resolving Spring DataBufferLimitException

In the world of Spring Webflux, you may encounter a DataBufferLimitException. This exception can be a bit perplexing if you’re not familiar with how Spring handles data streams. In this blog post, I’ll demystify this exception, explain why it occurs, and provide a solution on how to resolve it.

What is DataBufferLimitException?

When you send a request to an API and receive a response, the data in the request or response body is managed as a stream of DataBuffer chunks. Spring Webflux has a default limit on the number of bytes that can be buffered whenever the input stream needs to be aggregated. This limit is set to 256KB (262,144 bytes) and is defined by the spring.codec.max-in-memory-size property.

If the data sent or received exceeds this limit, Spring throws a DataBufferLimitException. The error message typically looks like this:

Caused by: org.springframework.core.io.buffer.DataBufferLimitException: Exceeded limit on max bytes per JSON object: 262144

This exception is Spring’s way of telling you that the size of the data you’re trying to send or receive has exceeded the maximum in-memory size it can handle.

How to Resolve DataBufferLimitException

The good news is that you can customize this default limit. If you find that the data you’re working with is consistently larger than the default limit, you can increase the maxInMemorySize to a value that better suits your needs.

Here’s an example of how you can do this:

public void init() {
    final int maxInMemorySize = 10 * 1024 * 1024; // 10MB
    final ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder()
            .codecs(configurer -> configurer.defaultCodecs().maxInMemorySize(maxInMemorySize))
            .build();
    webClient = WebClient.builder()
            .exchangeStrategies(exchangeStrategies)
            .baseUrl(BASE_URL)
            .defaultHeader(HttpHeaders.CONTENT_TYPE, MediaType.APPLICATION_JSON_VALUE)
            .defaultHeader(HttpHeaders.ACCEPT, MediaType.APPLICATION_JSON_VALUE)
            .build();
}

In this code snippet, we’re setting the maxInMemorySize to 10MB, which should be sufficient for most use cases. We then build an ExchangeStrategies object with the new limit and use it to configure our WebClient.

Conclusion

Understanding the DataBufferLimitException in Spring Webflux is crucial for managing data streams effectively. By knowing how to adjust the maxInMemorySize, you can ensure that your application can handle the data it needs to process without running into this exception. Always remember to adjust these settings with consideration for your application’s memory usage and performance.