In Spring Boot, you can’t configure the embedded Tomcat maxSwallowSize via the common application properties, there is no option like server.tomcat.*.maxSwallowSize

Solution

To fix it, you need to declare a TomcatEmbeddedServletContainerFactory bean and configure the maxSwallowSize like this :

//...
import org.apache.coyote.http11.AbstractHttp11Protocol;
import org.springframework.boot.context.embedded.tomcat.TomcatConnectorCustomizer;
import org.springframework.boot.context.embedded.tomcat.TomcatEmbeddedServletContainerFactory;
    private int maxUploadSizeInMb = 10 * 1024 * 1024; // 10 MB
    @Bean
    public TomcatEmbeddedServletContainerFactory tomcatEmbedded() {
        TomcatEmbeddedServletContainerFactory tomcat = new TomcatEmbeddedServletContainerFactory();
        tomcat.addConnectorCustomizers((TomcatConnectorCustomizer) connector -> {
            // connector other settings...
            // configure maxSwallowSize
            if ((connector.getProtocolHandler() instanceof AbstractHttp11Protocol<?>)) {
                // -1 means unlimited, accept bytes
                ((AbstractHttp11Protocol<?>) connector.getProtocolHandler()).setMaxSwallowSize(-1);
        });
        return tomcat;

References

1. Spring file upload and connection reset issue
2. common application properties
3. Spring Boot file upload error handling (Japanase)