Static resources caching issues with ShallowEtagHeaderFilter and Jetty caching directives #32039
Description
Affects: 6.1.2 on Spring Boot 3.2.0
When the ShallowEtagHeaderFilter is enabled along with the jetty web server, static resources fail to load every second time.
If you fetch a static resource under this configuration, it will work fine for the first call. On the second request, with an ETag attached, the server responds with the following error:
<h2>HTTP ERROR 500 java.io.IOException: written 0 < 4 content-length</h2> URI: | http://localhost:8080/ -- | -- 500 java.io.IOException: written 0 < 4 content-length java.io.IOException: written 0 < 4 content-length <h3>Caused by:</h3><pre>java.io.IOException: written 0 < 4 content-length at org.eclipse.jetty.server.internal.HttpChannelState$ChannelResponse.write(HttpChannelState.java:1182) at org.eclipse.jetty.server.Response$Wrapper.write(Response.java:735) at org.eclipse.jetty.server.handler.ContextResponse.write(ContextResponse.java:56) at org.eclipse.jetty.ee10.servlet.HttpOutput.channelWrite(HttpOutput.java:204) at org.eclipse.jetty.ee10.servlet.HttpOutput.complete(HttpOutput.java:435) at org.eclipse.jetty.ee10.servlet.ServletContextResponse.completeOutput(ServletContextResponse.java:209) at org.eclipse.jetty.ee10.servlet.ServletChannel.handle(ServletChannel.java:553) at org.eclipse.jetty.ee10.servlet.ServletHandler.handle(ServletHandler.java:464) at org.eclipse.jetty.security.SecurityHandler.handle(SecurityHandler.java:571) at org.eclipse.jetty.ee10.servlet.SessionHandler.handle(SessionHandler.java:703) at org.eclipse.jetty.server.handler.ContextHandler.handle(ContextHandler.java:761) at org.eclipse.jetty.server.Server.handle(Server.java:179) at org.eclipse.jetty.server.internal.HttpChannelState$HandlerInvoker.run(HttpChannelState.java:594) at org.eclipse.jetty.server.internal.HttpConnection.onFillable(HttpConnection.java:424) at org.eclipse.jetty.io.AbstractConnection$ReadCallback.succeeded(AbstractConnection.java:322) at org.eclipse.jetty.io.FillInterest.fillable(FillInterest.java:99) at org.eclipse.jetty.io.SelectableChannelEndPoint$1.run(SelectableChannelEndPoint.java:53) at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.runTask(AdaptiveExecutionStrategy.java:478) at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.consumeTask(AdaptiveExecutionStrategy.java:441) at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.tryProduce(AdaptiveExecutionStrategy.java:293) at org.eclipse.jetty.util.thread.strategy.AdaptiveExecutionStrategy.produce(AdaptiveExecutionStrategy.java:195) at org.eclipse.jetty.util.thread.QueuedThreadPool.runJob(QueuedThreadPool.java:971) at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.doRunJob(QueuedThreadPool.java:1201) at org.eclipse.jetty.util.thread.QueuedThreadPool$Runner.run(QueuedThreadPool.java:1156) at java.base/java.lang.Thread.run(Thread.java:1583) </pre> It seems that the response is already marked as "Not Modified" and the body cleared by one caching component, while the other still expects it to be unchanged.
Repository with minimal reproducer: https://github.com/sebastian-steiner/spring-cacheissue