Java Servlets - Can anyone help me!?

hansley

Oct 9 2004, 08:01 AM

Can anyone post here one or some examples of Simple Java Servlets please?
I need more resources to do my assignments.
Searching the web takes up too much time.
So I am using one of the purpose of a forum, sharing ideas....lol

arp

Oct 9 2004, 03:20 PM

Hi;

to show just how easy this is, here is probably the simplest/shortest servlet you can write:

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

public class HelloWorld extends HttpServlet{

public void doGet(HttpServletRequest req, HttpServletResponse res)
throws ServletException, IOException{

res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.println("Hello World");
}
}

I suggest if/when you get the time to go through sun's course:

http://java.sun.com/developer/onlineTraini...s/Fundamentals/

there's obvioulsy so much more you can do with servlets, so you need to be more precise asto what you need to know/achieve. It may even be the case that you should be looking at JSP instead of servlets...

hope this helps

- arp

sanweikui

Oct 10 2004, 03:10 AM

good advice!
But have you got a servlet container for your code? and do you know how to deploy the code?

eldeo

Oct 10 2004, 11:56 AM

very simple servlet:
////////////////////////////////////////////////
import javax.servlet.*;
import javax.servlet.http.*;
import java.io.*;

public class SimpleServlet extends HttpServlet {
int i = 0; // Servlet "persistence"
public void service(HttpServletRequest req,
HttpServletResponse res) throws IOException {
res.setContentType("text/html");
PrintWriter out = res.getWriter();
out.print("<HEAD><TITLE>");
out.print("simple servlet");
out.print("</TITLE></HEAD><BODY>");
out.print("<h1>This is simple servlet " + i++);
out.print("</h1></BODY>");
out.close();
}
}
////////////////////////////////////////////////

eldeo

Oct 10 2004, 12:07 PM

To deploy this code you need
- Sun Application Server
or
- Tomcat

I advise you to download Tomcat from this site

http://jakarta.apache.org/tomcat/

and read tutorial. You need serveral hours to learn about it

--
eldeo

björn

Oct 26 2004, 06:46 PM

deploying on tomcat is actually quite easy. you have to make a so-called web-application (see below) and then zip all the files belonging to the webapp. then rename this to war. Call this file, say... mywebapp.war. Drop this file in your /path-to-tomcat/tomcat/webapps directory.
start the tomcat and if you use a local tomcat installation you can now reach the webapp under
http://localhost:8080/mywebapp/url-pattern (for explanation of url-pattern see my explanation of web-application.

What is a web-application?
Well.. basically it is a bunch of files, which can be JSP, html, java classes, jar files.. etc

a webapp basically has the following directory structure:

./WEB-INF/
./WEB-INF/classes/ (here you put the java classes of your servlet for ex. )
./WEB-INF/lib/ (here you put any non-standard libraries you use in your java classes)
./WEB-INF/web.xml (the so called web-application deployment descriptor... see below)
./some_jsp_page.jsp (here you can put jsp pages...)
./some_web_page.html (... as well as any static content)

What is contained in the web.xml?
It's an xml file where you describe your web-application. It could look like this:

CODE

<?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">

<description>
An examplatory web.xml file
</description>

<servlet>
<servlet-name>helloWorld</servlet-name>
<servlet-class>my.java.package.HelloWorldServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>helloWorld</servlet-name>
<url-pattern>/sayHello</url-pattern>
</servlet-mapping>
</web-app>

If you write a servlet class my.java.package.HelloWorldServlet now, place it under
WEB-INF/classes/my/java/package/HelloWorldServlet.class, make a war file called hello.war of it and then deploy it on your tomcat you have successfully written and deployed your first webapp...
you can reach it under http://localhost:8080/hello/sayHello (if you have a local tomcat running)

For further reading:
There are many many tutorials on the web, but i would also recommend reading the servlet and the jsp specification from sun...
Link to Servlet Spec
Link to JSP specification

have fun...

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