Solved

Problem with System.setProperty(key,  value)

Posted on 2000-04-03
6
240 Views
Last Modified: 2006-11-17
Instead of "System.getEnv()", which is deprecated since java 1.2,  we use the method "System.getProperty(Key ) for the reading of environment- variables.
With the method "System.setProperty(key, value)" we set a selfdefined environment-variable.

When we start another Programm which read the selfdefined environment-variable with the method "System.getProperty(Key )" we get returnvalue "null".

Which Lifetime has a Property set by the "System.setProperty(key, value)" method?

Ziab
0
Comment
Question by:ziab
6 Comments
 
LVL 7

Expert Comment

by:Sasha_Mapa
ID: 2679502
The System class has a static object named props where all the properties are kept. On initialization, System has a native method initProperties which it calls to fill in the properties in props. The setProperty method adds a property to the props object.
All this means that the properties will be shared between applications that run on the same instance of a JVM. Programs running on different instaces will not share properties (because the setProperty method does nothing to change any external objects in any way).
I am not 100% sure about this, as I never worked with properties, just looked at the docs and source code for System so if other experts can correct/confirm my answer, please do :-)
0
 
LVL 3

Expert Comment

by:falter
ID: 2679578
If you wanna make the new defined key available to an other process (second JVM), try to save your properties in the first process and load them in the second one.

Have a look at java.utils.Properties class and something like

....
Properties myProps = System.getProperties();
myProps.put(key,value);
myProps.save("myPropertyFile");
....


In second program do something like
....
Properties myProps = Properties.load("myPropertyFileName);
System.setProperties(myProps);
....
0
 

Expert Comment

by:erlingd
ID: 2679652
I think the only way to change env variables for an "upcomming" program is to change the env array you use in "java.lang.Runtime.exec".
As far as I can remember env. variables are static they are parameters when you start the program up. And can only be changed within a batch/command script.
Pls. correct me if I'm wrong!

0
Free Tool: SSL Checker

Scans your site and returns information about your SSL implementation and certificate. Helpful for debugging and validating your SSL configuration.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

 

Author Comment

by:ziab
ID: 2679842
Thanks for the comments,

but we are seaching for a possibility to set, save and hold a selfdefined env-var in the env only with Java.

Ziab
0
 
LVL 1

Accepted Solution

by:
sankars98 earned 100 total points
ID: 2680487


 You can use the following class to get & set the environment variable to the OS level..
 This is windows specific..

 import java.io.*;
 import java.util.*;
 public class EnvironmentVariables extends Hashtable{
   public EnvironmentVariables() {
     String[] cmd = {"cmd", "/c", "SET"};
     try {
         Process proc = Runtime.getRuntime().exec(cmd);
         BufferedReader inp = new BufferedReader(new InputStreamReader(proc.getInputStream()));
         String LINE = inp.readLine();
         while (LINE != null) {
             int eqPos = LINE.indexOf("=");
             if (eqPos >= 0) {
               String name = LINE.substring(0, eqPos);
               String value = LINE.substring(eqPos + 1);
               super.put(name.toUpperCase(), value);
             }
             LINE = inp.readLine();
         }
         inp.close();
       } catch (IOException e) {
         System.out.println("Weird I/O error");
     }
   }
   public synchronized String get(Object name) {
     String theName = name.toString().toUpperCase();
     return (String)super.get(theName);
   }
   public synchronized Object put(Object name, Object value) {
       String theName = name.toString().toUpperCase();
       String theValue = value.toString();
       Object result = super.get(theName);
       // this is windows specific
       String[] cmd = {"cmd", "/c", "SET " + theName + "=" + theValue};
       try {
         Process proc = Runtime.getRuntime().exec(cmd);
         BufferedReader inp = new BufferedReader(new InputStreamReader(proc.getInputStream()));
         String LINE = inp.readLine();
         while (LINE != null) {}
           super.put(name.toString().toUpperCase(), value.toString());
           return result;
       } catch (IOException e) {
         System.out.println("Weird I/O error");
         return null;
       }
   }
 }



 Usage :

 EnvironmentVariables eVariables = new EnvironmentVariables();
 String value = eVariables.get("MYENVIRONMENTVARIABLE");


Sankar S.
0
 

Author Comment

by:ziab
ID: 2689872
Thanks Sankar S.
0

Featured Post

Free Tool: Site Down Detector

Helpful to verify reports of your own downtime, or to double check a downed website you are trying to access.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
difference of if loops 23 62
varialbe initialization 11 37
jboss 7.1 start up error 1 33
restrict decimal places for double datatype 10 19
By the end of 1980s, object oriented programming using languages like C++, Simula69 and ObjectPascal gained momentum. It looked like programmers finally found the perfect language. C++ successfully combined the object oriented principles of Simula w…
Go is an acronym of golang, is a programming language developed Google in 2007. Go is a new language that is mostly in the C family, with significant input from Pascal/Modula/Oberon family. Hence Go arisen as low-level language with fast compilation…
Viewers learn about the “while” loop and how to utilize it correctly in Java. Additionally, viewers begin exploring how to include conditional statements within a while loop and avoid an endless loop. Define While Loop: Basic Example: Explanatio…
Viewers will learn one way to get user input in Java. Introduce the Scanner object: Declare the variable that stores the user input: An example prompting the user for input: Methods you need to invoke in order to properly get  user input:

856 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question