Saturday, October 20, 2007

Running Servlets on Windows XP

20/10/2007

In my last blog, I wrote about how to run servlets in Fedora. As most of us use Windows not Fedora, so it forced me to write on running servlets in Windows XP. For my surprise it is more simple and easy than Fedora. So let's start.....


1. We need two things for running servlets in Windows XP: Sun Java SDK of course and tomcat. If you don't have Sun Java SDK, download the latest from http://72.5.124.55/javase/downloads/index.jsp

Download tomcat6 Windows Service Installer package from http://tomcat.apache.org/download-60.cgi



2. Install Java SDK. Now we have to set the environment variables for Java else we have to type the whole path of java compiler and interpreter each time to compile and run any Java Program. For doing that

i. Go to Start -> Control Panel. If its not in Classical view then choose 'switch to Classical View'. Double click on System icon. Now you'll be seeing a System Properties dialog box similar to the following.



ii. Now click on Advanced tab, You will see a button named Environment Variables at the Bottom of it. Click on it and now you'll see a dialog box similar to the following.



iii. On User variables, click on New. Now for Variable name enter 'path' and for Variable value enter the path of your JDK bin files directory. If you didn't change your default installation directory during installation it'll be something like 'C:\Program Files\Java\jdk1.6.0_03\bin\' where jdk1.6.0_03 will be replaced by your version of Java SDK. Click OK.



iv. Check that you correctly set the environment variable. Start -> Run. Type cmd. Now in Command Prompt type

java -version

It should give the output like this.





3. Install tomcat6. Start Tomcat by finding its start program in the Programs Menu (located in the Start menu). Look under Apache tomcat 6.0 and click Monitor Tomcat. In your notification area on taskbar Apache Tomcat icon will come. Double click on it and you'll see a dialog box. Start tomcat If it is not already started.




For more information on installation and setup tomcat visit the following links:

http://tomcat.apache.org/tomcat-6.0-doc/index.html
http://www.yorku.ca/jhuang/examples/tomcat-install.html (A little outdated though)



4. Check the tomcat installation by typing http://localhost:8080/ in your browser.





5. Now for compiling java servlets program you have to set the CLASSPATH environment variable to include the servlet-api.jar package path which will be 'C:\Program Files\Apache Software Foundation\Tomcat 6.0\lib\servlet-api.jar' for default installation directory. Change the path if you changed the installation directory. Now again set it using the same procedure for setting environment variables for Java. Remember to click on New button of User variables
not System variables.




6. Now we'll take a sample servlet program and will name it as MyHelloWorld.java

import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class MyHelloWorld extends HttpServlet {
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body>");
out.println("<head>");
out.println("<title>Hello World!</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Hello World!</h1>");
out.println("</body>");
out.println("</html>");
}
}

Save it using notepad as MyHelloWorld.java. Now compile it using javac command from the command prompt.




7. Now go to the tomcat installation directory. For default installation it would be C:\Program Files\Apache Software Foundation\Tomcat 6.0 here You will find webapp directory. Inside webapp directory make a directory named test. In this directory we will keep our web applications. Inside test, create directory WEB-INF. Inside WEB-INF create directory classes. Now inside classes we'll keep both our source and class files.


8. Copy the MyHelloWorld.java and MyHelloWorld.class files to the directory classes. Now to run our servlet we have to write our own web.xml file in the WEB-INF directory. Tomcat server reads the file web.xml to get information about the servlets. We'll open a file in notepad and copy and paste the following contents in the file. Save the file in the WEB-INF directory with the name web.xml

<web-app xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd"
version="2.5">
<servlet>
<servlet-name>MyHelloWorld</servlet-name>
<servlet-class>MyHelloWorld</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>MyHelloWorld</servlet-name>
<url-pattern>/servlet/MyHelloWorld</url-pattern>
</servlet-mapping>
</web-app>

In the file the tags <servlet-name> and <servlet-class> gives the information about servlet-name and servlet-class and the tag <url-pattern> tells about the URL pattern to run the servlet.

9. Now stop and restart Tomcat from the icon in Taskbar. To run the sevlet type address
http://localhost:8080/test/servlet/MyHelloWorld


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Thursday, October 18, 2007

Running Servlets on Fedora 7

18/10/2007

I was wondering for last two days to compile and run my java servlet programs on Fedora. But I couldn't find any useful information on internet. After much research and trial and errors I finally got to run servlets on Fedora. And this is how I did this, I think this might be useful for another novice like me. I have used the backward approach for this tutorial. It means problems first and then the solutions. Of course I could have used the straight approach like do this this and this and you are done. But I think that wont be much useful as you wouldn't know what thing is needed for what.

1. First thing first, before running servlets you need to compile them. And for that you need Sun Java SDK installed on your system. I'm assuming that you have it already on your system. If not you can go through this blog to find how to install it in Fedora.
http://mann-linuxproject.blogspot.com/2007/07/finally-jdk-is-installed.html


2. For compiling and running you also need tomcat installed on your system. You can choose Tomcat alone or with Apache. I preferred the second one. Install Apache by the command

yum install httpd

and install Tomcat on Fedora by the command

yum install tomcat5 tomcat5-webapps tomcat5-admin-webapps

here tomcat5 is the latest version for fedora.


3. Here is one sample program that I copied and pasted from a tutorial site. We'll use this sample program for our part of tutorial.

import java.io.*;
import java.text.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class DemoServlet extends HttpServlet {

public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws IOException, ServletException
{
response.setContentType("text/html");
PrintWriter out = response.getWriter();
out.println("<html>");
out.println("<body>");
out.println("<head>");
out.println("<title>Hello World!</title>");
out.println("</head>");
out.println("<body>");
out.println("<h1>Hello World!</h1>");
out.println("</body>");
out.println("</html>");
}
}


Type the program in a text editor and save the file as DemoServlet.java.

So like every java program, we'll use javac to compile the program.

javac DemoServlet.java

Even if you didn't did any typing mistakes, you are more likely to get the errors

DemoServlet.java:4: package javax.servlet does not exist
import javax.servlet.*;
^
DemoServlet.java:5: package javax.servlet.http does not exist
import javax.servlet.http.*;
^

If this is the case it means that our CLASSPATH environment is not set. Workaround for this problem is to
append the line
export CLASSPATH=/usr/share/java/servletapi5.jar
to your .bash_profile or .bashrc file. These files will be in your home directory and will be hidden.
Or one can alternatively type the above command each time he logins to compile servlet programs.

After adding the line you have to do a logout and login to reset the environment variables. Now again compile the program. Now it should not give the above errors and if you have typed the program correctly it'll compile successfully.


4. So we have compiled the program now how to run it. We can't just type java DemoSevlet to run the program here. Now we need Tomcat. login as root and make a directory in the tomcat web-application directory by the command

mkdir /var/lib/tomcat5/webapps/test

In this directory make another directory WEB-INF

mkdir /var/lib/tomcat5/webapps/test/WEB-INF

Inside this directory make directory classes

mkdir /var/lib/tomcat5/webapps/test/WEB-INF/classes

Inside classes directory we'll keep our servlet source and corresponding compiled class files. So copy the DemoServlet.java and DemoServlet.class files to this directory.

cp /path/to/DemoServlet.java /var/lib/tomcat5/webapps/test/WEB-INF/classes/
cp /path/to/DemoServlet.class /var/lib/tomcat5/webapps/test/WEB-INF/classes/

Replace /path/to with your own paths to DemoServlet.java and DemoServlet.class
Now in WEB-INF directory we'll create web.xml file which will give information about our servlets to Tomcat server.

While you are still logged as root go to the directory

cd /var/lib/tomcat5/webapps/test/WEB-INF/

Create the file web.xml using gedit

gedit web.xml

Now you should enter the following contents in the file and then save and quit.

<?xml version="1.0" encoding="ISO-8859-1"?>
<web-app xmlns="http://java.sun.com/xml/ns/j2ee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd"
version="2.4">
<servlet>
<servlet-name>DemoServlet</servlet-name>
<servlet-class>DemoServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>DemoServlet</servlet-name>
<url-pattern>/servlet/DemoServlet</url-pattern>
</servlet-mapping>
</web-app>

In the file the tags <servlet-name> and <servlet-class> gives the information about servlet-name and servlet-class and the tag <url-pattern> tells about the URL pattern to run the servlet.

5. Start the Apache server by command

service httpd start

Now test Apache Server by typing address http://localhost/ in your browser.



Start the Tomcat server

service tomcat5 start

Test Tomcat server by typing address http://localhost:8080/ in your browser


Run your servlet by typing address http://localhost:8080/test/servlet/DemoServlet in your browser.
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