Normally, when we write software in Java, when we hover over a class/method, a pop-up window opens with the javadoc text, so we immediately know, what it does, details about parameters it accepts and so on. I was suprised to see, that this is completely missing when we develop Java actions for Mendix. It would be good to just take the existing javadocs for Mendix API/SDK and make it available as .jar with the needed configuration, so it can be seen in IDEs.
Moreover, if we use a package in the Java action (let us say poi-5.3.0.jar) how can we add the needed javadoc? We can place to userlib the package with javadoc, e.g. poi-5.3.0-javadoc.jar. In Mendix 10.3.0 we can not place it in vendorlib because the package management system does not allow to add a javadoc file unfortunately. Now, in Eclipse, we can pair a package and a javadoc (package > Properties > Javadoc location). This will write down the pairing (package-javadoc) in .classpath. But whenever we do "Deploy for Eclipse" (F6) in Mendix, it will delete these changes in .classpath, so we have to put these back every time. The parings should stay there, not be deleted.