I am currently working on project called Enso. We are making heavy use of Apache POI to parse Excel documents our users are processing.

We are also using GraalVM Native Image to compile our application to native executable. Recently we realized in enso-org/enso#12843 that it is necessary to avoid dependency on java.desktop module.

Why Avoiding java.desktop Dependency?

Since Java9 the JDK offers tool called jlink. It can be used to create a smaller JDK ready for execution in the cloud and other restricted environments:

• one can specify set of JDK modules to include
• often it is useful to exclude java.desktop
• in Handle --jvm flag in process with JNI instantiated JVM enso-org/enso#12843 exclusion of java.desktop was necessary
• as GraalVM was crashing when java.desktop was included

Excluding java.desktop is a good practice anyway - reduces bloat of the final application by tens of megabytes.

Patching HSSFColor

• to resolve all the needs of Handle --jvm flag in process with JNI instantiated JVM enso-org/enso#12843
• I had to copy the code of HSSFColor into our repository
• and modify it to avoid instantiating java.awt.Color

Such a solution was good short-term workaround, but I don't want to maintain a fork of POI! Hence my goal is to find a way to include the necessary fixes in your project in the long term. Hence the creation of this PR. Can you please consider its acceptance?

Technicalities

• this PR replaces the RGB handling code in HSSFColor
• originally this code relied on java.awt.Color
  • however that creates unnecessary dependency on java.desktop
• the PR proposes direct manipulation with RGB int compatible with handling in java.awt.Color
• the behavior remains the same
• dependency of HSSFColor on java.desktop is removed

Other Fixes

• there are other places in POI where dependency on java.desktop deserves to be removed
• however that's a long term direction
• I am starting with this simple HSSFColor proposal
• if it is accepted, I create subsequent PRs addressing other java.desktop dependencies