Best way to detect whether code is running in an application server java

问题

For a J2EE bean I am reusing code that was developed for a java swing application. JOptionPane.showMessageDialog() is unfortunately commonly used. Most occurences luckily in code sections that are not reused by the J2EE application, but in some cases lower levels of the code has instances of JOptionPane.showMessageDialog(). Obviously this it results in dialog boxes popping up on the server, which is what I want to avoid.

As a first step I'd like to somehow assure that no dialog boxes will ever occur on the server.

Someone suggested peeking in some event or paint queue (I do not recall which one): That would be:

// old code: JOptionPane.showMessageDialog(msg);
if ( someEventQueue.size() == 0 ) // <== consider this pseudo-code
  Log.log(msg); // I am running on a server. Tell the log.
else
  JOptionPane.showMessageDialog(msg); // I have a user made of meat. Tell him!

I never really got that working. What would you do?

回答1:

Make sure the server is started with

java -Djava.awt.headless=true

Most servers should be started that way by default. Then you can check:

boolean headless_check = GraphicsEnvironment.isHeadless();

More details on headless available here:

回答2:

I just tested this with OpenJDK Runtime Environment (IcedTea 2.4.3) (Gentoo build 1.7.0_45-b31) on Linux, and I find that unset DISPLAY was also sufficient to make isHeadless() (and isHeadlessInstance()) return true.

So, this method doesn't just tell you whether AWT was forced to ignore the system's graphics capabilities, but rather whether your process has access to graphics capabilities at all.

Example:
The code is running on some box that has no display card (that's probably what you want to know) so you can always check the system property if for some reason you want to know whether headless mode was forced.

来源：https://stackoverflow.com/questions/1014620/best-way-to-detect-whether-code-is-running-in-an-application-server-java

标签

java

joptionpane