Root Cause

Spring WebClient includes a default codec memory buffer limit to prevent application memory exhaustion. This limit is set to 256KB by default. DataBufferLimitException occurs when the response payload exceeds this threshold.

Reference: [Korean Translation of Web on Reactive Stack] 2. WebClient: 2.1. Configuration

Resolution

To resolve DataBufferLimitException, increase the codec memory buffer limit using the maxInMemorySize parameter during WebClient configuration.

ExchangeStrategies exchangeStrategies = ExchangeStrategies.builder()
    .codecs(configurer -> configurer.defaultCodecs().maxInMemorySize(10 * 1024 * 1024)) // 10MB
    .build();

WebClient webClient = WebClient.builder()
    .exchangeStrategies(exchangeStrategies)
    .build();

As documented in CodecConfigurer#maxInMemorySize, you can also remove the limit by passing -1.

Also note that the exchangeStrategies method that accepts a Consumer parameter is deprecated, as shown below. Use the approach above that passes an ExchangeStrategies instance directly.

WebClient webClient = WebClient.builder()
    .exchangeStrategies(builder ->    // Deprecated approach
        builder.codecs(codecs ->
            codecs.defaultCodecs().maxInMemorySize(10 * 1024 * 1024)
        )
    ).build();