Head First Servlets and JSP, 2nd Edition

Servlets Demystified (write, deploy, run)

Just so those new to servlets can stop holding their breath, here’s a quick guide to writing, deploying, and running a servlet. This might create more questions than it answers—don’t panic, you don’t have to do this right now. It’s just a quick demonstration for those who can’t wait. The next chapter includes a more thorough tutorial.

1. Build this directory tree (somewhere not under tomcat).

   

2. Write a servlet named Ch1Servlet.java and put it in the src directory (to keep this example simple, we aren’t putting the servlet in a package, but after this, all other servlet examples in the book will be in packages).

   

3. Create a deployment descriptor (DD) named web.xml, put it in the etc directory

   

4. Build this directory tree under the existing tomcat directory...

5. From the project1 directory, compile the servlet...

   

   (the Ch1Servlet.class file will end up in project1/classes)

6. Copy the Ch1Servlet.class file to WEB-INF/classes, and copy the web.xml file to WEB-INF.

   

7. From the tomcat directory, start Tomcat...

   %bin/startup.sh

8. Launch your browser and type in:

   

   it should display:

   

9. For now, every time you update either a servlet class or the deployment descriptor, shutdown Tomcat:

   %bin/shutdown.sh

Actually, trying to format HTML inside a servlet’s out.println() pretty much sucks.

This is one of the worst parts (no, the worst part) of servlets. Stuffing properly formatted HTML tags into the println(), just so that you can insert variables and method calls, is just brutal. Don’t even think about doing anything the least bit sophisticated.

There are no Dumb Questions

Q:

Q: It can’t be that bad... why can’t I just copy a whole page of HTML from my web page editor, like Dreamweaver, and paste it into the println(). It’s not like I have to be able to read the code in there.

A:

A: Obviously, you haven’t tried this yet. It sounds good. Yes. I’ll just make my page in a decent web page editor (or even a simple text file would be easier than in my Java code) and then a quick copy and paste into the println() and voila! Except you get about 1,378 compiler errors. Remember, you can’t have a carriage return (a real one) inside a String literal. And while we’re talking about Strings... what about all your HTML that has double-quote marks in it?

A JSP page looks just like an HTML page, except you can put Java and Java-related things inside the page.

So it really is like inserting a variable into your HTML.