Passing System Property Resource from JNLP file to Java Webstart

Java have changed the way how system properties are passed from jnlp file to the javaws (Java Webstart).

Since the update of Java to 1.7.0_45, getting the system property using the following code will no longer work:

System.getProperty("myproperty");

There are two solution for this issue:
1. You need to sign the jnlp files

     See this link for instruction:
     http://docs.oracle.com/javase/7/docs/technotes/guides/jweb/signedJNLP.html

2. Update the JNLP files to have additional prefix in the resource string variable

     Example: For log4j.configuration, here is what you need to do:
<resources>
<j2se version="1.7"/>
<jar href="lib/log4j-1.2.16.jar"/>
<property name="jnlp.log4j.configuration" value="file:///C:/log4j.properties "/>
</resources>

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I haven't tried the #1 yet because it is quite complex. Option #2 is the quickest solution. However, you need to update your program to also add a prefix when reading the system property.

System.getProperty("jnlp.myproperty");

For backward compatibility, it is recommended to always check for the old variable before using the new variable.

       String property = System.getProperty("jnlp.myproperty");
       if (property.isEmpty())
       {
             property = System.getProperty("myproperty");
       }

Feel free comment if you still encounter any issue related to this.

Credits to:
https://community.oracle.com/message/11239354

Changing log level in log4j without restarting your application

For instance,  you have an application deployed in production and you need to set the log level to debug to investigate an issue. Normally, you will edit the log4j.properties and restart the application in order to have the changes take effect.

What if there are many users currently logged in to the application and you are not allowed to restart?

Will you wait for every user to logoff? What if there are 24/7 operations running on the application?

In that case, restart is not an option. Reverting the log level back to original will also require another restart.

Solution
Implement Log4j file watchdog

Although you will still need to deploy code changes to implement the watcher, you only do it at first then the succeeding changes on your log4j configuration (log4j.properties) will no longer need application restart to take effect.

Here's how it's done
org.apache.log4j.Logger logger = null;
org.apache.log4j.PropertyConfigurator.configureAndWatch("C:\\log4j.properties");
logger = org.apache.log4j.Logger.getLogger("");
logger.info("Info Message");
logger.error("Error Message");
logger.warn("Warn Message");
logger.trace("Trace Message");



No idea on what is log4j and how to use it?
Visit https://logging.apache.org/log4j/1.2/