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15

2

Note: All the similar questions are answering this from the perspective of the shell (e.g. Is javac available? java -version or which java). I'm looking explicitly for the perspective of the currently running JVM.

There are programs that require to be run from within a JDK's JRE, not "just" a JRE. I'm wondering if there's a simple way to find out what my currently running program is executed in.

I'm looking for a generic way to figure this out, rather than an analysis of the program in question and duplicating its use of JDK features. That's why I'd prefer not to execute an external process testing if javac is on the path, if possible. I'm rather looking for some code that will run within a JDK, but fail within a JRE.

It could be Class.forName with a class that's only available in a JDK. It could be a system property. Or anything else.

If I have to execute an external process with javac: So be it. But I'd prefer something simpler and generic.

Clarification from deep down in the comments:

From time to time I'm running into this problem with Liferay, which requires to be run from within a JDK's JRE. I was entertaining the thought to just deploy another plugin that provides a userfriendly error message if run without a JDK available. I shy away from analyzing which code is the one failing in a JRE-only environment, and I don't want to modify Liferay's code, rather add my own plugin to do the analysis and warn.

java jvm liferay

share|improve this question

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  It will always be running on a JRE.
  
  – mwarren
  Jul 19 at 14:47
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  The JDK supplies the tools to build a Java application and has a JRE included to run applications on. A JRE installation just has the JRE and no build tools.
  
  – mwarren
  Jul 19 at 14:50
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Consider the keywords: a "kit" is something that you use; an "environment" is something that you live in. You make something in the kit and then run it in the environment.
  
  – zero298
  Jul 19 at 14:53
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  Since Java has become modular, the distinction between JRE and JDK is obsolete. You have to clarify which feature you need and then, check for the presence of that feature. If it is the compiler, you can check for the presence of the compiler API. But if you don’t use that API but require the presence of a command line javac tool, you have to check for precisely that.
  
  – Holger
  Jul 19 at 14:57
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  So you’re saying, the problem is that Liferay has certain requirements on the environment, but doesn’t provide a user friendly error message? Then, you should file a bug report to Liferay’s developers and that’s it.
  
  – Holger
  Jul 19 at 15:03
  

  
  
  
  

 | 
show 12 more comments

15

2

Note: All the similar questions are answering this from the perspective of the shell (e.g. Is javac available? java -version or which java). I'm looking explicitly for the perspective of the currently running JVM.

There are programs that require to be run from within a JDK's JRE, not "just" a JRE. I'm wondering if there's a simple way to find out what my currently running program is executed in.

I'm looking for a generic way to figure this out, rather than an analysis of the program in question and duplicating its use of JDK features. That's why I'd prefer not to execute an external process testing if javac is on the path, if possible. I'm rather looking for some code that will run within a JDK, but fail within a JRE.

It could be Class.forName with a class that's only available in a JDK. It could be a system property. Or anything else.

If I have to execute an external process with javac: So be it. But I'd prefer something simpler and generic.

Clarification from deep down in the comments:

From time to time I'm running into this problem with Liferay, which requires to be run from within a JDK's JRE. I was entertaining the thought to just deploy another plugin that provides a userfriendly error message if run without a JDK available. I shy away from analyzing which code is the one failing in a JRE-only environment, and I don't want to modify Liferay's code, rather add my own plugin to do the analysis and warn.

java jvm liferay

share|improve this question

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  It will always be running on a JRE.
  
  – mwarren
  Jul 19 at 14:47
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  The JDK supplies the tools to build a Java application and has a JRE included to run applications on. A JRE installation just has the JRE and no build tools.
  
  – mwarren
  Jul 19 at 14:50
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  Consider the keywords: a "kit" is something that you use; an "environment" is something that you live in. You make something in the kit and then run it in the environment.
  
  – zero298
  Jul 19 at 14:53
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  Since Java has become modular, the distinction between JRE and JDK is obsolete. You have to clarify which feature you need and then, check for the presence of that feature. If it is the compiler, you can check for the presence of the compiler API. But if you don’t use that API but require the presence of a command line javac tool, you have to check for precisely that.
  
  – Holger
  Jul 19 at 14:57
  

  
  
  
  


• 
  
  
  

  
  2
  

  
  
  
  
  
  

  
  
  So you’re saying, the problem is that Liferay has certain requirements on the environment, but doesn’t provide a user friendly error message? Then, you should file a bug report to Liferay’s developers and that’s it.
  
  – Holger
  Jul 19 at 15:03
  

  
  
  
  

 | 
show 12 more comments

Note: All the similar questions are answering this from the perspective of the shell (e.g. Is javac available? java -version or which java). I'm looking explicitly for the perspective of the currently running JVM.

There are programs that require to be run from within a JDK's JRE, not "just" a JRE. I'm wondering if there's a simple way to find out what my currently running program is executed in.

I'm looking for a generic way to figure this out, rather than an analysis of the program in question and duplicating its use of JDK features. That's why I'd prefer not to execute an external process testing if javac is on the path, if possible. I'm rather looking for some code that will run within a JDK, but fail within a JRE.

It could be Class.forName with a class that's only available in a JDK. It could be a system property. Or anything else.

If I have to execute an external process with javac: So be it. But I'd prefer something simpler and generic.

Clarification from deep down in the comments:

From time to time I'm running into this problem with Liferay, which requires to be run from within a JDK's JRE. I was entertaining the thought to just deploy another plugin that provides a userfriendly error message if run without a JDK available. I shy away from analyzing which code is the one failing in a JRE-only environment, and I don't want to modify Liferay's code, rather add my own plugin to do the analysis and warn.

java jvm liferay

share|improve this question

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

share|improve this question

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

share|improve this question

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

edited Jul 22 at 17:34

Mikhail Kholodkov

6,94788 gold badges3333 silver badges5959 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

asked Jul 19 at 14:46

Olaf KockOlaf Kock

38.1k77 gold badges4646 silver badges7979 bronze badges

2 Answers
2

active

oldest

votes

20

javax.tools.ToolProvider.getSystemJavaCompiler() will return null if no compiler is available, and a JavaCompiler if it is.

Technically it just tells you if the compiler is available of course, but that in most scenarios will imply the existence of the JDK.

share|improve this answer

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Ah, that might be even better than my answer.
  
  – Stefan Reich
  Jul 19 at 15:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Awesome, thanks. That looks like it's also working in OpenJDKs, as they might not necessarily duplicate com.sun.*
  
  – Olaf Kock
  Jul 19 at 15:09
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Of course, that won’t tell you whether a command line javac command exists nor whether a software, naively assuming to run in a jre directy inside a jdk installation (which is not the case since Java 9), will work with the current environment.
  
  – Holger
  Jul 19 at 15:13
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Holger: Good enough for a quickfix to the current pain. In the long run, your comment is right: Bring a friendlier message into the core product. But that's the long run, and I'm rather impatient.
  
  – Olaf Kock
  Jul 19 at 15:15
  

  
  
  
  

add a comment | 

4

Class.forName("com.sun.tools.javac.Main");

If there is no exception, it is a JDK.

It works with current JDKs, but it's probably not part of any official spec.

share|improve this answer

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks - as you write in Michael's answer, and see in my comment there, I'll probably rather go with his, assuming it's working in any JDK, not just Oracle's.
  
  – Olaf Kock
  Jul 19 at 15:10
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  @OlafKock No problem. I will cry only shortly. :-)
  
  – Stefan Reich
  Jul 19 at 15:12
  

  
  
  
  

add a comment | 

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20

javax.tools.ToolProvider.getSystemJavaCompiler() will return null if no compiler is available, and a JavaCompiler if it is.

Technically it just tells you if the compiler is available of course, but that in most scenarios will imply the existence of the JDK.

share|improve this answer

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Ah, that might be even better than my answer.
  
  – Stefan Reich
  Jul 19 at 15:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Awesome, thanks. That looks like it's also working in OpenJDKs, as they might not necessarily duplicate com.sun.*
  
  – Olaf Kock
  Jul 19 at 15:09
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Of course, that won’t tell you whether a command line javac command exists nor whether a software, naively assuming to run in a jre directy inside a jdk installation (which is not the case since Java 9), will work with the current environment.
  
  – Holger
  Jul 19 at 15:13
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Holger: Good enough for a quickfix to the current pain. In the long run, your comment is right: Bring a friendlier message into the core product. But that's the long run, and I'm rather impatient.
  
  – Olaf Kock
  Jul 19 at 15:15
  

  
  
  
  

add a comment | 

20

javax.tools.ToolProvider.getSystemJavaCompiler() will return null if no compiler is available, and a JavaCompiler if it is.

Technically it just tells you if the compiler is available of course, but that in most scenarios will imply the existence of the JDK.

share|improve this answer

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Ah, that might be even better than my answer.
  
  – Stefan Reich
  Jul 19 at 15:09
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  Awesome, thanks. That looks like it's also working in OpenJDKs, as they might not necessarily duplicate com.sun.*
  
  – Olaf Kock
  Jul 19 at 15:09
  

  
  
  
  


• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  
  Of course, that won’t tell you whether a command line javac command exists nor whether a software, naively assuming to run in a jre directy inside a jdk installation (which is not the case since Java 9), will work with the current environment.
  
  – Holger
  Jul 19 at 15:13
  

  
  
  
  


• 
  
  
  

  
  1
  

  
  
  
  
  
  

  
  
  @Holger: Good enough for a quickfix to the current pain. In the long run, your comment is right: Bring a friendlier message into the core product. But that's the long run, and I'm rather impatient.
  
  – Olaf Kock
  Jul 19 at 15:15
  

  
  
  
  

add a comment | 

javax.tools.ToolProvider.getSystemJavaCompiler() will return null if no compiler is available, and a JavaCompiler if it is.

Technically it just tells you if the compiler is available of course, but that in most scenarios will imply the existence of the JDK.

share|improve this answer

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

share|improve this answer

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

answered Jul 19 at 15:07

Michael BerryMichael Berry

46.2k1717 gold badges116116 silver badges173173 bronze badges

4

Class.forName("com.sun.tools.javac.Main");

If there is no exception, it is a JDK.

It works with current JDKs, but it's probably not part of any official spec.

share|improve this answer

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks - as you write in Michael's answer, and see in my comment there, I'll probably rather go with his, assuming it's working in any JDK, not just Oracle's.
  
  – Olaf Kock
  Jul 19 at 15:10
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  @OlafKock No problem. I will cry only shortly. :-)
  
  – Stefan Reich
  Jul 19 at 15:12
  

  
  
  
  

add a comment | 

4

Class.forName("com.sun.tools.javac.Main");

If there is no exception, it is a JDK.

It works with current JDKs, but it's probably not part of any official spec.

share|improve this answer

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges

• 
  
  
  

  
  

  
  
  
  
  
  

  
  
  Thanks - as you write in Michael's answer, and see in my comment there, I'll probably rather go with his, assuming it's working in any JDK, not just Oracle's.
  
  – Olaf Kock
  Jul 19 at 15:10
  

  
  
  
  


• 
  
  
  

  
  4
  

  
  
  
  
  
  

  
  
  @OlafKock No problem. I will cry only shortly. :-)
  
  – Stefan Reich
  Jul 19 at 15:12
  

  
  
  
  

add a comment | 

Class.forName("com.sun.tools.javac.Main");

If there is no exception, it is a JDK.

It works with current JDKs, but it's probably not part of any official spec.

share|improve this answer

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges

share|improve this answer

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges

answered Jul 19 at 15:07

Stefan ReichStefan Reich

58644 silver badges1212 bronze badges