MultiPart files should be written to disk by default

[essobedo]

Description

In Jakarta EE 10, the expected behavior when fileSizeThreshold is set to 0 aka the default value has been clearly specified as you can see in the Javadoc.

I quote:

A value of zero means files must always be written to disk.

The current behavior of Jetty is not compliant since only strictly positive values are taken into account.

[essobedo]

A potential fix for it #10937

[joakime]

The first version of Jetty that supports EE10 / Servlet 6.0 specs (where this language about fileSizeThreshold value of 0) is Jetty 12 on the ee10 environment.

[joakime]

Jetty 12 has support for fileSizeThreshold value of 0 in the EE10 environment already.

See EE10 handling ...

jetty.project/jetty-ee10/jetty-ee10-servlet/src/main/java/org/eclipse/jetty/ee10/servlet/ServletMultiPartFormData.java

Line 129 in d1da726

parser.setMaxMemoryFileSize(config.getFileSizeThreshold());

Which uses jetty-core handling ...

jetty.project/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/MultiPartFormData.java

Lines 344 to 355 in d1da726

	/**
	* <p>Sets the maximum memory file size in bytes, after which files will be saved
	* in the directory specified by {@link #setFilesDirectory(Path)}.</p>
	* <p>Use value {@code 0} to always save the files in the directory.</p>
	* <p>Use value {@code -1} to never save the files in the directory.</p>
	*
	* @param maxMemoryFileSize the maximum memory file size in bytes, or -1 for unlimited memory file size
	*/
	public void setMaxMemoryFileSize(long maxMemoryFileSize)
	{
	this.maxMemoryFileSize = maxMemoryFileSize;
	}

Which is implemented here ...

jetty.project/jetty-core/jetty-http/src/main/java/org/eclipse/jetty/http/MultiPartFormData.java

Lines 421 to 432 in d1da726

	long maxMemoryFileSize = getMaxMemoryFileSize();
	if (maxMemoryFileSize >= 0)
	{
	memoryFileSize += buffer.remaining();
	if (memoryFileSize > maxMemoryFileSize)
	{
	try
	{
	// Must save to disk.
	if (ensureFileChannel())
	{
	// Write existing memory chunks.

[essobedo]

Yeah I've just realized that, thx for the quick feedback