November | 2013 | Digital Vortex A-Go-Go

November 21, 2013

Remote Debugging of Java Applications

At work I tried to debug the Java application that we provide to our customers. A nasty performance problem had developed in the course of time. To analyze this, I can recommend using VisualVM. It’s part of Oracle’s JDK (version 6 and up) but is also available as a stand alone download.

VisualVM also allows for remote debugging an application. To this end you can use the “jstatd” application, also part of Oracle’s JDK. When I used this app for some testing, I encountered the following exception at start up:

Could not create remote object
access denied (java.util.PropertyPermission java.rmi.server.ignoreSubClasses write)
java.security.AccessControlException: access denied (java.util.PropertyPermission java.rmi.server.ignoreSubClasses write)
at java.security.AccessControlContext.checkPermission(AccessControlContext.java:264)
at java.security.AccessController.checkPermission(AccessController.java:427)
at java.lang.SecurityManager.checkPermission(SecurityManager.java:536)
at java.lang.System.setProperty(System.java:699)
at sun.tools.jstatd.Jstatd.main(Jstatd.java:122)

Vinay Singla has the answer on his blog. He explains that to run the application requires some permissions before it can run:

Cause :- The “access denied” error is expected, because “jstatd” requires a security policy file specified with the “java.security.policy” system property, if there is no security manager running on the machine.

His solution (as ‘translated to a Windows environment’, by me):

Inside a DOS-box/Console, change to the bin directory, inside the JDK directory. (e.g. c:\program files\java\jdk7\bin)
Check if a file exists with the name “jstatd.all.policy”. If not, create it with Notepad. If so, edit it with Notepad.
Add this information to the file:
grant codebase “file:${java.home}/../lib/tools.jar” {
permission java.security.AllPermission;
};
Run this command: jstatd -J-Djava.security.policy=jstatd.all.policy
Now you can connect to this machine via VisualVM.

Via http://dbafusion.blogspot.nl/2010/05/jstad-error-could-not-create-remote.html

Posted in Development by hAcK

November 16, 2013

How to Downgrade from Google Plus

Chris McLeod has an interesting story regarding canceling your Google+ account, either with or without canceling your entire Google account. Here’s the (essential) text of his article:

Step 1.

Log-in to the Google Account you want to downgrade. If you have multiple accounts, make sure you have switched to the correct one. Click the dropdown menu in the upper-right corner of most Google applications (where your user picture is), and click the Account link circled in red below:

Step 2.

Click the Google+ link in the sidebar menu:

Step 3.

The Downgrade link is at the very bottom of the page:

Step 4.

You will be given the choice to disable your Google+ account, or to delete it, along with any social integrations (Google Buzz, YouTube, etc). Personally, as I know I don’t have any integrations I use with my old account, I went for the delete option. Pick which ever is right for you, then tick the “I Understand/Accept” box at the bottom of the page.

Step 5.

Click the button at the bottom of the page. Your account will be immediately disabled or downgraded from Google Plus. If all goes well, you will see a box asking for comments about why you did this. Feedback is always good for product teams, so leave a little message for them: