How to check JRE version prior to launch?

Question

What\'s the best way to determine if the version of the JRE installed on a machine is high enough for the application which the user wants to run? Is there a way of doing it

Answer 1

Generally, we've approached this with a C or (when unix-only) shell wrapper. Not sure this will really work for you.

We also approach this by embedding the JRE in our product. Takes care of 99.9% of the cases (the other 0.1% of the time is a user explicitly changing our configuration to use a different JVM). Again, not sure that this is a reasonable solution for you.

In our case, there is significant amounts of native code (JNI and otherwise), so tailoring an installable image for each platform we support is required anyway. But if you're dealing with a pure-Java solution, you may simply have to document your minimum and tell people to get with the program (no pun intended) if they're to run your stuff. It's sorta like people complaining that my Mac won't run MSVC, or that my Linux box is having problems running World of Warcraft. That's just not the (virtual) machine the software is targeted for - you need to switch. At least in the Java world, we really can call this an upgrade, though, without hurting anyone's OS-religious feelings. (Try telling the Mac user to "upgrade" to Windows XP to run MSVC - there's a beat-down waiting to happen.)

Answer 2

Have a launching class compiled for Java 1.2 which invokes the real main() in your 1.6 classes. If an unsupported class exception is thrown them catch it and display a nice error message.

Answer 3

System.getProperties() gives you a listing of JVM properties including the different version ids of the JRE, JVM and specification. This implemented for all versions of Java so should work regardless of version compiled in and version run in, or the implementation.

If you write a basic class to test the version, you can call this first in your main() launching class. It must really be basic functionality though or you might risk breaking it.

Answer 4

You might also consider using Commons-Launcher, which allows you to setup various environment settings, or perform pre-checks before calling your application.

http://commons.apache.org/launcher

Answer 5

I find that WinRun4J works quite well for me (but then again I may be biased since I wrote it:-)). This lets you specify a minimum and/or maximum version of java allowed. It will pop up a message box to the user if a suitable JRE version is not found (and the message is customisable).

Answer 6

For the launcher - Check the version in there.

Inside the APP; as above use System.getProperties();

Properties sProp = java.lang.System.getProperties();
String sVersion = sProp.getProperty("java.version");
sVersion = sVersion.substring(0, 3);
Float f = Float.valueOf(sVersion);
if (f.floatValue() < (float) 1.4) {
    System.out.println("Java version too low ....");
    System.exit(1);
}
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