Itegrating DWR (Direct Web Remoting) with Spring

Hi Springers, I have used DWR (Direct Web Remoting) in my last project which was pretty interesting and I want to share the simplest way of using DWR with spring application. Download the latest version of dwr.jar from here. And put it in the /WEB-INF/lib folder. I have used DWR 2.0.5.

Add the following lines in your web.xml

<servlet>
  <servlet-name>dwr-invoker</servlet-name>
  <display-name>DWR Servlet</display-name>
  <servlet-class>
    org.directwebremoting.servlet.DwrServlet
  </servlet-class>
  <init-param>
     <param-name>debug</param-name>
     <param-value>true</param-value>
  </init-param>
</servlet>

<servlet-mapping>
  <servlet-name>dwr-invoker</servlet-name>
  <url-pattern>/dwr/*</url-pattern>
</servlet-mapping>

Now create a dwr.xml in the WEB-INF folder alongside web.xml and add the following line in that file.

<!DOCTYPE dwr PUBLIC
    "-//GetAhead Limited//DTD Direct Web Remoting 2.0//EN"
    "http://getahead.org/dwr/dwr20.dtd">

<dwr>
  <allow>
    <create creator="new" javascript="JDate">
      <param name="class" value="java.util.Date"/>
    </create>
    <create creator="new" javascript="Demo">
      <param name="class" value="your.java.Bean"/>
    </create>
  </allow>
</dwr>

To check go to the following URL.

http://localhost:8080/[YOUR-WEBAPP]/dwr/

You should see a page showing you the classes that you’ve selected.

To learn detail about DWR please visit the documentation site of DWR.

Restoring Default Ubuntu Panel

This is for the newbies in the Ubuntu Community. Sometimes we want to configure our panels on Ubuntu to give a nicer look. And the newbies often fail to do that as they want and may want to restore the default panel settings. Restoring the default panel setting on Ubuntu is pretty simple. Just run the following command in the terminal and you will get your default Ubuntu panels back.

sudo debconf gnome-panel

But this is not a permanent solution. To permanently enable your default panel configuration enter the following commands in the terminal sequentially.

gconftool –recursive-unset /apps/panel
rm -rf ~/.gconf/apps/panel
pkill gnome-panel

Enjoy!!

N.B. Don’t worry if any of the command removes all your panel. The next command will restore it to default configuration.

Installing Apache Tomcat 6 on Ubuntu (8.04 / 8.10)

Before we install Tomcat you’ll need to make sure that whether we already have installed Java. Let’s assume that we are trying to install Tomcat we’ve already installed java, but if we aren’t sure we can check with the dpkg command like so:

dpkg –get-selections | grep sun-java

This should give we this output if we already installed java:

sun-java6-bin                                   install
sun-java6-jdk                                   install
sun-java6-jre                                   install

If that command has no results, we’ll want to install the latest version with this command:

sudo apt-get install sun-java6-jdk

Installation

Now we’ll download and extract Tomcat from the apache site. We should check to make sure there’s not another version and adjust accordingly.

wget http://apache.host.com/tomcat/tomcat-6/v6.0.14/bin/apache-tomcat-6.0.14.tar.gz

tar xvzf apache-tomcat-6.0.14.tar.gz

The best thing to do is move the tomcat folder to a permanent location. I chose /usr/local/tomcat.

sudo mv apache-tomcat-6.0.14 /usr/local/tomcat

Tomcat requires setting the JAVA_HOME variable. The best way to do this is to set it in the .bashrc file.

The better method is editing the .bashrc file and adding the bolded line there. We’ll have to logout of the shell for the change to take effect.

vi ~/.bashrc

Add the following line:

export JAVA_HOME=/usr/lib/jvm/java-6-sun

At this point we can start tomcat by just executing the startup.sh script in the tomcat/bin folder.

Automatic Starting

To make tomcat automatically start when we boot up the computer, we can add a script to make it auto-start and shutdown.

sudo vi /etc/init.d/tomcat

Now paste in the following:

# Tomcat auto-start
#
# description: Auto-starts tomcat
# processname: tomcat
# pidfile: /var/run/tomcat.pid

export JAVA_HOME=/usr/lib/jvm/java-6-sun

case $1 in
start)
sh /usr/local/tomcat/bin/startup.sh
;;
stop)
sh /usr/local/tomcat/bin/shutdown.sh
;;
restart)
sh /usr/local/tomcat/bin/shutdown.sh
sh /usr/local/tomcat/bin/startup.sh
;;
esac
exit 0

We’ll need to make the script executable by running the chmod command:

sudo chmod 755 /etc/init.d/tomcat

The last step is actually linking this script to the startup folders with a symbolic link. Execute these two commands and we should be on our way.

sudo ln -s /etc/init.d/tomcat /etc/rc1.d/K99tomcat
sudo ln -s /etc/init.d/tomcat /etc/rc2.d/S99tomcat

Tomcat should now be fully installed and operational. Cheers!

Thanks