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How can a Java program find out if it is running in debug mode?

The application should behave a bit different in regular “full speed” mode than in “debug mode” (when a debugger is attached, when running in debug mode). The application communicates over TCP with either another computer, another process, or within itself. My co-worker wants us to use Socket.setSoTimeout(1000) by default, so that reads from the socket can block for at most 1 second. When debugging, this is not enough of course, and the application stops working as it should. So a solution would be to set the SO_TIMEOUT higher, but just in debug mode (for example: unlimited). Now, I don't always set breakpoints or don't want use a debug build where I could set the “debug” property myself. Sometimes I attach the debugger (remote debugging). I'm mainly using Eclipse so a solution that just works there is OK.

Possible answers include:

  1. To find out if run in debug mode, use the following method in java.lang.management.* or javax.management.* ...

  2. Your co-worker is wrong for reason X, you shouldn't set SO_TIMEOUT to 1 second by default.

Update

I know about the system property approach, but I leave the question open to solve my original question.

David Foerster
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Thomas Mueller
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  • @will Your definition of "debug mode" does not match my definition, and you have a very different use case. In your case, I assume using a configuration setting (system property or other) is just fine. For my use case, it's not. – Thomas Mueller Oct 27 '16 at 04:24
  • Since you are obviously not a beginner in programming I just wanted to know why you try to avoid the system property approach, since you surely know that it will be the most future proof and flexible solution? – the hand of NOD Jul 01 '20 at 07:16
  • @thehandofNOD the system property approach is fine for some use cases, but it's not as convenient. I was looking for a way to automate this. As you can see from the votes on the answers, many others are also interested in having an automated way. – Thomas Mueller Jul 02 '20 at 08:17

3 Answers3

76

I found it out myself now:

boolean isDebug = java.lang.management.ManagementFactory.getRuntimeMXBean().
    getInputArguments().toString().indexOf("jdwp") >= 0;

This will check if the Java Debug Wire Protocol agent is used.

Thomas Mueller
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13

Make the timeout configurable. The simplest way is to just use a system property and read it with Integer.getInteger:

private final static int SOCKET_TIMEOUT =
  Integer.getInteger("com.yourapp.module.socketTimeout", 1000); // default 1 sec

Then, when starting your app for debugging, just set the property from the command line (or an appropriate config file, depending on the environment your app runs in):

java -Dcom.yourapp.module.socketTimeout=1000000 MainClass

This is good because it does not magically alter the behavior when you fire the app up in a debugger, and you can change the timeout when not debugging (for example, if you need to run it somewhere with a slow connection, some day).

(Of course, if your system already uses a config file, it may be appropriate to add this value as an entry there instead.)

As to whether one second is an appropriate timeout... that depends completely on the app. Sometimes it's better to give a correct answer eventually, other times failing quickly is better than waiting for success.

gustafc
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    `Integer.getInteger(..)`? Darn, I didn't know that one. Cool (+1) – Sean Patrick Floyd Sep 23 '10 at 07:41
  • This is a valid solution of course, but it requires a manual step: setting the system property at startup. I wanted to avoid that. – Thomas Mueller Sep 25 '10 at 07:55
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    @ThomasMueller Just set a `com.yourapp.debug=true` system property if running in debug mode and have your application check it. If it's the default value, then you're not running in debug mode. This can be done in the Eclipse Debug configurations, which means you don't need to type it in every time you want to debug the program. – ThePyroEagle Jun 11 '15 at 17:39
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    @ThomasMueller However you only need to do it once, no matter how many times you may want to debug your application. – ThePyroEagle Jun 11 '15 at 20:07
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    *Once per machine. If you have multiple devs, with multiple IDEs, it's still very much worth not having a manual step here, imo. – LadyCailin Feb 01 '19 at 13:02
  • @LadyCailin: Disagree. Just because you have multiple devs and IDEs it's not a good idea to fill your application code with environment settings since you would clutter your code. Might be that for now it's only 1 setting which needs adapted, but with time there will be more and more. So it's a good idea to keep your code "platform"/"environment" independent. Which is what makes JAVA so cool – the hand of NOD Jul 01 '20 at 07:12
5

You're solving the wrong problem. Your program doesn't need to know this unless it's dealing with eclipse or jvm internals.

Solution

Use a system property with a default value:

int timeout = Integer.parseInt( 
    System.getProperty("socket.timeout", "1000"));
socket.setSoTimeout(timeout);

And in the debug launch configuration, just add

-Dsocket.timeout=20000

to the call parameters

(If you don't specify the system property, the default value will be used)

References

Sean Patrick Floyd
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