Molindo Techblog

<build>
  <plugins>
    <plugin>
      <groupId>org.apache.maven.plugins</groupId>
      <artifactId>maven-surefire-plugin</artifactId>
      <version>2.4.3</version>
      <configuration>
        <systemProperties>
          <property>
            <name>java.io.tmpdir</name>
            <value>${java.io.tmpdir}${file.separator}surefire-${user.name}-${project.artifactId}</value>
          </property>
        </systemProperties>
      </configuration>
    </plugin>
  </plugins>
</build>

// existing
File tmp = new File(System.getProperty("java.io.tmpdir"), "output.txt");
 
// new
File tmpDir = new File(System.getProperty("java.io.tmpdir"));
tmpDir.mkdirs();
File tmp = new File(tmpDir, "output.txt");

public static File getTmpDir() {
  File tmpDir = new File(System.getProperty("java.io.tmpdir"));
  tmpDir.mkdirs();
  return tmpDir;
}

// Use toString() to get values:
// "/tmp/output.txt"
System.out.println(new File(SystemProperty.JAVA_IO_TMPDIR + "output.txt"));
// "You are running Linux, version 2.6.24-25-generic"
System.out.println(String.format("You are running %s, version %s", SystemProperty.OS_NAME, SystemProperty.OS_VERSION));
 
// get and set values
SystemProperty.JAVA_IO_TMPDIR.set("/dev/null");
 
// avoid setting of properties that shouldn't be changed
// throws UnsupportedOperationException
SystemProperty.JAVA_CLASS_PATH.set(newClassPath);

Responses

1. john says:
   

   November 28th, 2009 at 8:11 am (#)

   ### PLEASE POST THIS AT http://j.mp/props0 or http://j.mp/props1
   /**
   * Windows XP only: known values:
   */
   USER_VARIANT(“user.variant”),

2. Christopher Deckers says:
   

   November 28th, 2009 at 12:33 pm (#)

   Here is a list of settable properties (some have to be set very early to have an effect):

   “sun.awt.disableMixing” (for Sun VM on Java 6u14+)
   “sun.awt.noerasebackground”
   “sun.awt.xembedserver”

   By-the-way, I love this idea of an enum for all properties, and I will probably create a similar enum for my application-specific properties!

   Keep up the good work.
   -Christopher

3. Christopher Deckers says:
   

   November 28th, 2009 at 9:54 pm (#)

   I have added the following method:
   public String get(String defaultValue);

   It allows to specify the default value to return when the value of the property is null. It calls:
   System.getProperty(getName(), defaultValue);

   -Christopher

4. Steve Chaloner says:
   

   December 1st, 2009 at 12:53 pm (#)

   You might also be interested in objectify-led : http://www.objectify.be/objectify-led/

   It handles assignment of properties using, amoung other things, system properties, properties files or arbitrary data sources. Type conversion is also handled.

   public class Foo
   {
   @Property(“blah.value”);
   private static String BLAH = “default-value”;

   @Property(“mystring.value”);
   private String myString;

   @Property(“myint.value”);
   private int myInt = -1;

   public static void main(String[] args)
   {
   Foo foo = new Foo();
   new PropertySetter().process(foo);
   }
   …
   }

5. Stefan Fußenegger says:
   

   December 1st, 2009 at 7:54 pm (#)

   Hi Christopher,

   thanks for your input. I’ve added the get(String) method. Additionally, I’ve added some convenience methods that convert the String: getInteger(String), getLong(String), getBoolean(String), getFloat(String), getDouble(String), getFile(String) (all with a no-argument alternative and a corresponding setter).

   I’m also thinking about uploading the result as a Maven artifact as soon as my work is done. This way, it can easily be included in any project.

6. Stefan Fußenegger says:
   

   December 2nd, 2009 at 9:08 am (#)

   Hi Steve,

   First, sorry that I’ve forgotten to approve your comment yesterday. Personally, I’m not interested as I’m normally using Spring for what you describe. And if not, compared to

   @Property(“user.country”);
   private String country = “US”;

   using

   private String country = SystemProperty.USER_COUNTRY.get(“US”);

   looks far less … frightening

   How do you process the annotations? I couldn’t find that information on your site.

7. Steve Chaloner says:
   

   December 11th, 2009 at 12:01 pm (#)

   Hi Stefan,

   take a look at http://objectify-led.googlecode.com/svn/trunk/src/main/java/be/objectify/led/PropertySetter.java and you’ll see how the annotations are processed.

   I like your approach for well-known properties, but for arbitrary properties it would require either the developer to update the class manually and then have to merge in your future updates, or for you to add properties from potentially proprietary projects to the enum.

   Personally, I would (and will) use your SystemProperty enum for well-known props (don’t re-invent the wheel!) and objectify-led for project-specific properties.

8. Stefan Fußenegger says:
   

   December 11th, 2009 at 12:13 pm (#)

   Hi Steve,

   there’s nothing too spectacular in this class. But when and how is PropertySetter#process(..) invoked? But don’t get me wrong. Your project looks nice. However, it’s mostly a subset of Spring’s functionality – and Spring is what I’m already using on a daily basis.

   I know that my enum isn’t suited for project-specific properties. That never was it’s intention. I’m not even sure about using an enum. But the “how” is not important anyway. My main objective was documentation on the one hand and getting rid of string constants on the other hand. Both in order to leverage IDE capabilities such as autocompletion and inline Javadoc.

9. Steve Chaloner says:
   

   December 11th, 2009 at 12:24 pm (#)

   Hi Stefan,

   PropertySetter#process(..) is the entry point to traverse the variables of an object/class – see my original post for an example.

   Most of my projects involve Spring, but a few small ones don’t and I don’t want to have to a) use Spring or b) set the properties and do the type conversion by hand – that’s where objectify-led (need to find a shorter name…) comes in handy.

   One other advantage (which I haven’t written yet) is automatic help generation on the command line. Since all properties which can be set are annotated, they can automatically be discovered and printed out. Hope to get around to implementing this at the weekend.

10. Stefan Fußenegger says:
    

    December 11th, 2009 at 12:29 pm (#)

    Okay, so now it all comes together. Actually, it sound nice. I could have used it for some groovy scripts

11. Steve Chaloner says:
    

    December 11th, 2009 at 12:32 pm (#)

    I think I need to collate what I’ve written here and update the project site. Thanks for the discussion

12. Iain says:
    

    February 18th, 2011 at 2:02 pm (#)

    ### PLEASE POST THIS AT http://j.mp/props0 or http://j.mp/props1

    /**
    * Windows 7 only; known values:
    */
    USER_VARIANT(“user.variant”),
    name mismatch: SUN_AWT_DISABLEMIXING: sun.awt.disableMixing=null (expected SUN_AWT_DISABLE_MIXING)

13. Stathis Alexopoulos says:
    

    April 26th, 2013 at 9:13 am (#)

    Hi Stefan,

    I don’t know if you still maintaining that code, but finally i discovered what is the mystery

    /**
    * Windows only: known values: “” (empty string)
    */
    USER_VARIANT(“user.variant”),

    the user.variant property is part of the triplet

    user.language
    user.country
    user.variant

    needed to define a Locale instance. Could you please update your source code?

14. Stefan Fußenegger says:
    

    April 26th, 2013 at 5:59 pm (#)

    Stathis,

    what do you want me to update? Remove the “Windows ONLY” comment only?

    Note that I’ve updated the post with a link to our GitHub project.

    Cheers

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