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Setting a property for System.getProperty()

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  Setting a property for System.getProperty() RVic <rvince99@hotmail.com> - 2013-05-09 07:53 -0700
    Re: Setting a property for System.getProperty() lipska the kat <"nospam at neversurrender dot co dot uk"> - 2013-05-09 16:22 +0100
    Re: Setting a property for System.getProperty() Eric Sosman <esosman@comcast-dot-net.invalid> - 2013-05-09 11:33 -0400
    Re: Setting a property for System.getProperty() RVic <rvince99@hotmail.com> - 2013-05-09 09:01 -0700
      Re: Setting a property for System.getProperty() Arne Vajhøj <arne@vajhoej.dk> - 2013-05-09 21:51 -0400
    Re: Setting a property for System.getProperty() RVic <rvince99@hotmail.com> - 2013-05-09 09:14 -0700
      Re: Setting a property for System.getProperty() markspace <markspace@nospam.nospam> - 2013-05-09 09:48 -0700
        Re: Setting a property for System.getProperty() Arne Vajhøj <arne@vajhoej.dk> - 2013-05-09 21:57 -0400

#23962 — Setting a property for System.getProperty()

I inherited someones mountain of code wherein they use different idioms and ways of doing things than I typically do.

In one instance, there is a line of code:

System.getProperty("cn.env");

which, depending on what machine it is run on, has properties like "production" or "mirror"

Yet, I think this call, System.getProperty(), calls properties from the actual system, like (System.getProperty("user.home") or System.getProperty("file.separator").

So how can I set this on a particular machine (Ubuntu 12 in this case) for a value for cn.env? 

Thanks in advance, RVic

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#23963

On 09/05/13 15:53, RVic wrote:
> I inherited someones mountain of code wherein they use different idioms and ways of doing things than I typically do.
>
> In one instance, there is a line of code:
>
> System.getProperty("cn.env");
>
> which, depending on what machine it is run on, has properties like "production" or "mirror"
>
> Yet, I think this call, System.getProperty(), calls properties from the actual system, like (System.getProperty("user.home") or System.getProperty("file.separator").
>
> So how can I set this on a particular machine (Ubuntu 12 in this case) for a value for cn.env?
>
> Thanks in advance, RVic

Well of course you can use System.setProperty("myprop", "myval");

Or ...

You can set properties when you start your application using the -D 
command line switch.

something like

javac Foo.java
java -Dmyprop=myval Foo

in you code you can access these properties like so
System.getProperty("myprop");

This would return the String "myval"

HTH

lipska

-- 
Lipska the Kat©: Troll hunter, sandbox destroyer
and farscape dreamer of Aeryn Sun

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#23964

On 5/9/2013 10:53 AM, RVic wrote:
> I inherited someones mountain of code wherein they use different idioms and ways of doing things than I typically do.
>
> In one instance, there is a line of code:
>
> System.getProperty("cn.env");
>
> which, depending on what machine it is run on, has properties like "production" or "mirror"
>
> Yet, I think this call, System.getProperty(), calls properties from the actual system, like (System.getProperty("user.home") or System.getProperty("file.separator").
>
> So how can I set this on a particular machine (Ubuntu 12 in this case) for a value for cn.env?

     java -Dcn.env=ZaphodBeeblebrox MyClass

... is one way.  See also System.setProperty(), which you could
use in a "launcher" class like

	public class Launcher {
	    public static void main(String[] args) {
	        // Get a value -- this takes one from the
	        // environment, but you could get as fancy
	        // as you like here.
	        String value = System.getenv("CN_ENV");

	        // Set the property.
	        System.setProperty("cn.env", value);

	        // Run the "real" main() method.
	        MyClass.main(args);
	    }
	}

-- 
Eric Sosman
esosman@comcast-dot-net.invalid

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#23965

I need to set it outside of of the running application, so the -D option is what I need to invoke. However, THis is a war archive running under tomcat, started (in script) with:

sudo service tomcat-$SITE start

How would you invoke the -Dcn.env="mirror" in this?

Thanks for your help here guys! RVic

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#23975

On 5/9/2013 12:01 PM, RVic wrote:
> I need to set it outside of of the running application, so the -D option is what I need to invoke. However, THis is a war archive running under tomcat, started (in script) with:
>
> sudo service tomcat-$SITE start
>
> How would you invoke the -Dcn.env="mirror" in this?

Typical you would set it in env variable JAVA_OPTS and
then catalina.sh would pick it up.

Arne

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#23966

Well, apparently it IS being set, in /etc/init.d for that file I see:
---------------------------------
JVM_PARAM='-verbose:gc -XX:+PrintGCDetails -Dcn.instance=router -Dcn.env=mirror'

export JVM_PARAM

# Call the common script
/home/cnadmin/scripts/tomcat/tomcat.sh $1
----------------------------------------------------

So I guess it is being set here. I shall go back to the drawing board, apparetnyl what I believed to be the problem may not be the problem. Thanks for your help guys. RVic

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#23967

On 5/9/2013 9:14 AM, RVic wrote:
> Well, apparently it IS being set, in /etc/init.d for that file I
> see: --------------------------------- JVM_PARAM='-verbose:gc
> -XX:+PrintGCDetails -Dcn.instance=router -Dcn.env=mirror'
>
> export JVM_PARAM
>
> # Call the common script /home/cnadmin/scripts/tomcat/tomcat.sh $1
> ----------------------------------------------------
>
> So I guess it is being set here. I shall go back to the drawing
> board, apparetnyl what I believed to be the problem may not be the
> problem. Thanks for your help guys. RVic
>

Does this actually do anything?  I don't think the jvm will treat the 
JVM_PARAM variable in a special way.  Google at least didn't seem to 
come up with anything.  So unless the JVM_PARAM is on the invocation 
line to tomcat.sh, I don't think anyone is going to see these values.

You might try modifying the tomcat.sh script to dump its parameters to a 
file where you can see them, just to verify what's being passed in to 
the tomcat instance.  There might be a better way too; maybe the ps 
command can be induced to dump the command line of a running process.

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#23976

On 5/9/2013 12:48 PM, markspace wrote:
> On 5/9/2013 9:14 AM, RVic wrote:
>> Well, apparently it IS being set, in /etc/init.d for that file I
>> see: --------------------------------- JVM_PARAM='-verbose:gc
>> -XX:+PrintGCDetails -Dcn.instance=router -Dcn.env=mirror'
>>
>> export JVM_PARAM
>>
>> # Call the common script /home/cnadmin/scripts/tomcat/tomcat.sh $1
>> ----------------------------------------------------
>>
>> So I guess it is being set here. I shall go back to the drawing
>> board, apparetnyl what I believed to be the problem may not be the
>> problem. Thanks for your help guys. RVic
>>
>
> Does this actually do anything?  I don't think the jvm will treat the
> JVM_PARAM variable in a special way.  Google at least didn't seem to
> come up with anything.  So unless the JVM_PARAM is on the invocation
> line to tomcat.sh, I don't think anyone is going to see these values.
>
> You might try modifying the tomcat.sh script to dump its parameters to a
> file where you can see them, just to verify what's being passed in to
> the tomcat instance.  There might be a better way too; maybe the ps
> command can be induced to dump the command line of a running process.

The JVM does certainly not do anything itself.

But that tomcat.sh may very well include JVM_PARAM in the
java command line.

For a standard Tomcat download from Apache the env var is
JAVA_OPTS and the script is catalina.sh (called from startup.sh).

Arne

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