Showing posts with label Redhat. Show all posts

Thursday, 22 February 2018

Using Byteman to Find Out Why the TimeZone Changed on a Java App Server

I found the following article/blog post and I thought it worthy of mentioning it here.

Using Byteman to Find Out Why the TimeZone Changed on a Java App Server

It concerns the injection of a monitor into your application (or application server), to monitor certain method calls, and print a Stacktrace (for instance) if they occur.

Handy if it occurs deep inside a framework or production server or in one of many deployed wars, and you don't know where.

References

Developers Redhat - Using Byteman to Find Out Why the TimeZone Changed on a Java App Server: https://developers.redhat.com/blog/2018/02/21/byteman-timezone-changed/
Jboss - Byteman: http://byteman.jboss.org/

Tuesday, 14 January 2014

Installing JDK in Fedora Core

Seems to work fine. I am writing it down here, because I do not do it often, and I keep forgetting the steps.

Installing java

I have switched over to using openjdk. It seems to be pretty stable and standard in Fedora Core.

The openjdk-7-jre package contains just the Java Runtime Environment

yum install java-1.7.0-openjdk

The actual Java Development Kit can be installed as below.

yum install java-1.8.0-openjdk-devel

Call me weird, but I find it confusing to name both packages "openjdk", but then, that's the name of the thing.

Switching javac

If I try "alternatives --config javac", I get.

There are 2 programs which provide 'javac'.

  Selection    Command
-----------------------------------------------
*  1           /usr/lib/jvm/java-1.7.0-openjdk-1.7.0.75-2.5.4.2.fc20.x86_64/bin/javac
 + 2           /usr/lib/jvm/java-1.8.0-openjdk.x86_64/bin/javac

Enter to keep the current selection[+], or type selection number:

Switching java

If I try "alternatives --config java", I get.

There is 1 program that provides 'java'.

  Selection    Command
-----------------------------------------------
*+ 1           /usr/lib/jvm/jre-1.7.0-openjdk.x86_64/bin/java

Enter to keep the current selection[+], or type selection number:

I need to install the Oracle JDK, that is as simple as downloading the rpm and installing it with "rpm i jdk-7u13-linux-x64.rpm".

Then, I am required to set a symbolic link using the 'alternatives --install' commandline. See [1] for more information on that.

Then, I can set the default using "alternatives --config java" again.

[root@localhost Downloads]#  alternatives --config java

There are 3 programs which provide 'java'.

  Selection    Command
-----------------------------------------------
   1           /usr/lib/jvm/jre-1.6.0-openjdk.x86_64/bin/java
   2           /usr/lib/jvm/jre-1.5.0-gcj/bin/java
*+ 3           /usr/java/jre1.7.0_45/bin/java

Enter to keep the current selection[+], or type selection number:

Updated 22 April 2014: added OpenJDK, removed specifics regarding Oracle

References

[1] Installing Sun Oracle Java JDK on Fedora, Centos, Redhat and RHel: http://www.if-not-true-then-false.com/2010/install-sun-oracle-java-jdk-jre-7-on-fedora-centos-red-hat-rhel/
Java - FedoraProject: http://fedoraproject.org/wiki/Java
OpenJDK: http://openjdk.java.net/install/