Setting path and classpath

[sandy0594]

Hi all,I am lil bit new to Linux platform.Can someone kindly guide me how to set path and classpath in Ubuntu 10.10..

In windows we go to environment variables and create a new variable path for setting path and classpath for classpath

Variable:PATH
Value   :C:/Program Files/Java/Jdk1.6.0/bin

Variable: CLASSPATH
Value   : .;C:/oracle/product/db_1/jdbc/lib/classes12.jar

The above is the format we set path and class-path in windows..so,how do we do the same thing back here in Ubuntu10.10

[r-senior]

You probably don't need to. Assuming you have installed the JDK from the repositories, a simple example will work out of the box:

$ cat Hello.java
public class Hello {
    public static void main(String ... args) {
        System.out.println("hello");
    }
}
$ javac Hello.Java
$ java Hello
hello

The PATH is already set up (via /usr/bin/java and a couple more steps via /etc/alternatives).

If you need to compile or run with additional libraries, you can use the -cp option, e.g.

$ javac -cp <path-to-jar-file>
$ java -cp <path-to-jar-file>

Setting a CLASSPATH variable can just lead to confusion.

If you are using an IDE, it will define its own settings for its Java platforms and libraries (i.e. classpath). Maven will pick up javac and java from the standard path and manage its classpath.

So no need.

[sandy0594]

As u say,for normal java program path will be set by Ubuntu..But,coming to server side programming like servlets and jsp's and jdbc programming we need to set path and classpath for few jar files..

For eg:

import java.sql.*; 
class PureConnection 
{ 
public static void main(String[]args) throws Exception 
{ 
String driver = "oracle.jdbc.driver.OracleDriver"; 
String url = "jdbc:oracle:thin:@localhost:1521:orcl"; 
String user = "scott"; 
String password = "tiger"; 
Class.forName(driver); 
System.out.println("Driver Loaded"); 
Connection con = DriverManager.getConnection(url,user,password); 
System.out.println("connected"); 
con.close(); 
} 
}

sandy@ubuntu:~/Java Programs$ javac PureConnection.java
sandy@ubuntu:~/Java Programs$ java PureConnection.java
Exception in thread "main" java.lang.NoClassDefFoundError: PureConnection/java
Caused by: java.lang.ClassNotFoundException: PureConnection.java
at java.net.URLClassLoader$1.run(URLClassLoader.java: 217)
at java.security.AccessController.doPrivileged(Native Method)
at java.net.URLClassLoader.findClass(URLClassLoader.j ava:205)
at java.lang.ClassLoader.loadClass(ClassLoader.java:3 21)
at sun.misc.Launcher$AppClassLoader.loadClass(Launche r.java:294)
at java.lang.ClassLoader.loadClass(ClassLoader.java:2 66)
Could not find the main class: PureConnection.java. Program will exit.
sandy@ubuntu:~/Java Programs$

For the above program to execute we need to set classpath for classes12.jar available in oracle(C:/oracle/product/db_1/jdbc/lib/classes12.jar).So,how can i set the classpath for that

[r-senior]

As I said above, you can use use the -cp option.

If you must use the CLASSPATH environment variable, and I would advise against it:

export CLASSPATH=".:/home/sandy/Somewhere/classes12.jar"

That will only exist for your current shell session. To make it permanent, add that line to ~/.bashrc or, preferably, a script called from ~/.bashrc

If you are doing server-side programming with JSP and JDBC, consider the attached screenshot. These are the included libraries in a small web application written with Spring and Hibernate. If this is your direction, you could save yourself a lot of time and trouble by spending two hours working through the Maven tutorial.

[sandy0594]

This is how my bash profile looks..where should i add that environment variables for setting the path and classpath in the below bash profile

# ~/.bashrc: executed by bash(1) for non-login shells.
# see /usr/share/doc/bash/examples/startup-files (in the package bash-doc)
# for examples

# If not running interactively, don't do anything
[ -z "$PS1" ] && return

# don't put duplicate lines in the history. See bash(1) for more options
# ... or force ignoredups and ignorespace
HISTCONTROL=ignoredups:ignorespace

# append to the history file, don't overwrite it
shopt -s histappend

# for setting history length see HISTSIZE and HISTFILESIZE in bash(1)
HISTSIZE=1000
HISTFILESIZE=2000

# check the window size after each command and, if necessary,
# update the values of LINES and COLUMNS.
shopt -s checkwinsize

# make less more friendly for non-text input files, see lesspipe(1)
    [ -x /usr/bin/lesspipe ] && eval "$(SHELL=/bin/sh lesspipe)"

# set variable identifying the chroot you work in (used in the prompt below)
if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then
    debian_chroot=$(cat /etc/debian_chroot)
fi

# set a fancy prompt (non-color, unless we know we "want" color)
case "$TERM" in
    xterm-color) color_prompt=yes;;
esac

# uncomment for a colored prompt, if the terminal has the capability; turned
# off by default to not distract the user: the focus in a terminal window
# should be on the output of commands, not on the prompt
#force_color_prompt=yes

if [ -n "$force_color_prompt" ]; then
    if [ -x /usr/bin/tput ] && tput setaf 1 >&/dev/null; then
        # We have color support; assume it's compliant with Ecma-48
        # (ISO/IEC-6429). (Lack of such support is extremely rare, and such  # a case would tend to support setf rather than setaf.)
        color_prompt=yes
    else
        color_prompt=
    fi
fi

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w\$ '
fi
unset color_prompt force_color_prompt

# If this is an xterm set the title to user@host:dir
case "$TERM" in
xterm*|rxvt*)
    PS1="\[\e]0;${debian_chroot:+($debian_chroot)}\u@\h: \w\a\]$PS1"
    ;;
*)
   ;;
esac

# enable color support of ls and also add handy aliases
if [ -x /usr/bin/dircolors ]; then
    test -r ~/.dircolors && eval "$(dircolors -b ~/.dircolors)" || eval "$(dircolors -b)"
    alias ls='ls --color=auto'
    #alias dir='dir --color=auto'
    #alias vdir='vdir --color=auto'

    alias grep='grep --color=auto'
    alias fgrep='fgrep --color=auto'
    alias egrep='egrep --color=auto'
fi

# some more ls aliases
alias ll='ls -alF'
alias la='ls -A'
alias l='ls -CF'

# Add an "alert" alias for long running commands.  Use like so:
 #   sleep 10; alert
alias alert='notify-send --urgency=low -i "$([ $? = 0 ] && echo terminal || echo error)" "$(history|tail -n1|sed -e '\''s/^\s*[0-9]\+\s*//;s/[;&|]\s*alert$//'\'')"'

# Alias definitions.
# You may want to put all your additions into a separate file like
# ~/.bash_aliases, instead of adding them here directly.
# See /usr/share/doc/bash-doc/examples in the bash-doc package.

if [ -f ~/.bash_aliases ]; then
    . ~/.bash_aliases
fi

# enable programmable completion features (you don't need to enable
# this, if it's already enabled in /etc/bash.bashrc and /etc/profile
# sources /etc/bash.bashrc).
if [ -f /etc/bash_completion ] && ! shopt -oq posix; then
    . /etc/bash_completion
fi

[r-senior]

This is how my bash profile looks..where should i add that environment variables for setting the path and classpath in the below bash profile

Ah well, I tried.

Anywhere (but not inside an 'if' block, obviously). At the bottom is probably easiest to find later on. You'll need to log out and back in again to see them appearing in new terminal windows.

[Blackbug]

well rightly said above if you have installed JDK it will set the PATH by itself
and its better not to create ambiguity with CLASSPATH

To see everythin is installed fine..check

$>which java
$>echo $PATH

if /usr/bin/java is not in your path( and you are sure its installed ), just export the path using:
export PATH=$PATH;/usr/bin/java

[sandy0594]

I set the classpath and my java program is executing..But,i do have a small problem that needs to be addressed.I have 2 users in Ubuntu..One is sandy and oracle..In oracle user,oracle is installed and when i set the classpath in oracle user,the program executes.But,back in sandy user the program fails in execution phase.

export CLASSPATH=".:/opt/oracle/oracle/product/10.2.0/db_2/jdbc/lib/classes12.jar"

In user sandy

sandy@ubuntu:~/Java Programs$ javac PureConnection.java
sandy@ubuntu:~/Java Programs$ java PureConnection
Exception in thread "main" java.lang.ClassNotFoundException: oracle.jdbc.driver.OracleDriver
    at java.net.URLClassLoader$1.run(URLClassLoader.java:217)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(URLClassLoader.java:205)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:321)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:294)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:266)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:186)
    at PureConnection.main(PureConnection.java:10)

In user oracle

oracle@ubuntu:/media/SANDY$ javac PureConnection.java 
oracle@ubuntu:/media/SANDY$ java PureConnection 
Driver Loaded 
connected

So,any hunch on how to solve this issue

[Blackbug]

looks like your user has some priviledge issue.
the user 'oracle' has those priviledges.
not very sure, but try to check it and see the link below

http://download.oracle.com/javase/1....ontroller.html

[sandy0594]

As per my programming knowledge,the problem is regarding the environment variables..Its just that the environment variable specified in user oracle should be used by user sandy.How to use the environment variable specified in one user could be used in other user is the point