How to Resolve java.net.unknownhostexception in Jboss

This post describes How to Resolve java.net.unknownhostexception in Jboss.
Many times we have seen when we start jboss we are facing one exception in jboss "java.net.UnknownHostException".

1:  java.net.UnknownHostException: localhost.localdomain: localhost.localdomain  
2:  at java.net.InetAddress.getLocalHost(InetAddress.java:1234)  
3:  at org.jboss.system.server.ServerInfo.getHostAddress(ServerInfo.java:233)  

How to resolve this Exception.One Quick solutions to resolve this exception is modify /etc/hosts configuration file in linux.
in this post will discuss how to modify /etc/hosts file and how to change entry in /etc/hosts file.

What is /etc/hosts file

The hosts file contains lines of text containing IP address in the first text field followed by one or more host names. Each field is separated by white space (blanks or seperated by tab).
Comment lines may be included; they are indicated by a hash character (#) in the first position of such lines. Entirely blank lines in the file are ignored.

For example,Hosts contains following details:

1:  # IPAddress Hostname        Alias   
2:  192.168.11.55 chkmmd051.kgnglobal.local chkmmd051   
3:  127.0.0.1 localhost.localdomain localdomain   
4:  ::1  localhost localhost.localdomain localhost6 localhost6.localdomain6   

The left column is the IP address to be resolved. The next column is that host's name and next columns are alias for that host. In the second line, for example, the IP address 192.168.11.55 is for the host chkmmd051.kgnglobal.local Another alias is chkmmd051.

to change this file will require root user permission, After you are finished configuration of your files, don't forget to restart your services and restart your jboss server for the changes to take effect.

References :

1. How do I modify my hosts file? @ http://www.rackspace.com/knowledge_center/article/how-do-i-modify-my-hosts-file
2. How to Modify /etc/hosts @ http://community.linuxmint.com/tutorial/view/159

How To select Oracle Driver Version

This post describes how to use diffrent JDBC drivers with diffrent JDK versions.
whenever we upgrdate our database or JDK we are facing Exceptions like "DriverManager.getConnection gives the Error: "No suitable driver".

Check this link for more information how to select oracle driver version and other database version.

Which JDBC drivers support which versions of Javasoft's JDK?

Below table shows how to use jdk and JDBC drivers.

Driver Compatibility Matrix

JDBC drivers Version	Driver Type	JDK Version
Oracle pre-8i	OCI THIN Drivers	JDK 1.0.x and JDK 1.1.x
Oracle 8.1.5	OCI and THIN Drivers	JDK 1.0.x and JDK 1.1.x
Oracle 8.1.6 SDK	THIN Driver	JDK 1.1.x and JDK 1.2.x (aka Java2)
8.1.6 SDK	OCI Driver	JDK 1.1.x
8.1.6	OCI and THIN Driver	JDK 1.1.x and JDK 1.2.x
8.1.7	OCI and THIN Driver	JDK 1.1.x and JDK 1.2.x
9.0.1	OCI and THIN Driver	JDK 1.1.x, JDK 1.2.x and JDK 1.3.x
9.0.2	OCI and THIN Driver	JDK 1.1.x, JDK 1.2.x, JDK 1.3.x, and JDK 1.4.x
10.1.0	OCI and THIN Driver	JDK 1.1.x, JDK 1.2.x, JDK 1.3.x, and JDK 1.4.x
10.2.0	OCI and THIN Driver	JDK 1.2.x, JDK 1.3.x, JDK 1.4.x, and JDK 5.0.x

What are the jar files and supported JDK Installation.

Supported JDK Installation for Oracle Drivers.

Supported Jar File	Java Version	Remarks
ojdbc5.jar	JDK1.5
ojdbc5_g.jar	JDK1.5	compiled with option -g
ojdbc5dms.jar	JDK1.5	includes code to support Oracle Dynamic Monitoring Service
ojdbc5dms_g.jar	JDK1.5	includes code to support Oracle Dynamic Monitoring Service
ojdbc6.jar	JDK1.6	support basic functionality for the Thin and OCI drivers
ojdbc6_g.jar	JDK1.6
ojdbc6dms.jar	JDK1.6	Oracle Dynamic Monitoring Service (DMS)
ojdbc6dms_g.jar	JDK1.6	full JDBC logging support

In future whenever you upgrade Database version you have to conside appropriate JDK version.

References :

1. Oracle Driver Version @ http://www.oracle.com/technetwork/java/hotspotfaq-138619.html
2. Feature Matrix for Oracle Server JDBC drivers @ https://www.inetsoftware.de/products/jdbc-driver/oracle/features