The Java Boutique: Introduction to Java - Q and A Package javax.servlet not found in import

Articles : JavaBoutique's Introduction to Java : Q and A :

Package javax.servlet not found in import

Q

What should I do if I get this error:

MyFirstServlet.java:4: Package javax.servlet not found in import.
import javax.servlet.*;
MyFirstServlet.java:5: Package javax.servlet.http not found in import.
import javax.servlet.http.*;
MyFirstServlet.java:7: Superclass HttpServlet of class MyFirstServlet not found

How can make the compiler recognise the javax.servlet directory?

A

Hmmm, let's take a look at the error message you are getting...

Package javax.servlet not found in import. import javax.servlet.*;

This error message is actually pretty complete and useful as far as error messages go. In fact, I think it gives you everything you need to know to solve your problem...if you don't let it scare you that is!

I say it like this because I have found that most beginning developers are quite capable of solving problems like this on their own; Java programming is often quite simple. For the most part, if you feel stuck it is not because you "can't" figure it out but that you have let the code intimidate or scare you. So don't let it!!!! Error messages in particular are your bestest buddies, not your dreaded foes.

For one, it tells you that you are trying to import a package. The package is named "javax.servlet" and you have referenced it in your .java file as:
import javax.servlet.*;

Well, you probably know that packages in Java usually correlate to actual directory structures on your hard drive or in an archived JAR or ZIP file (such as classes.zip).

Let's look at a more familiar case: java.awt.Button.

Hopefully you have installed your Java utilities something like:

C
    Java
        Microsoft
            SDK1.0
        Sun
	    JDK1.0.2/
            JDK1.1.8/
                bin
                docs
                lib
                src

Take a look in the "src" directory and you'll find something like:

C
    Java
        Microsoft
            SDK1.0
        Sun
	    JDK1.0.2/
            JDK1.1.8/
                bin
                docs
                lib
                src
                     java
                         applet
                         awt
                             ...
                             Button.java
                             ...
                         ...
                     ...

Okay, so now you see where the java.awt.Button came from.

It is just like a path that you are fluent in!
java.awt.Button = java/awt/Button.java

NOTE: Packages do not need to officially represent directory structures... but they often do and it is a good way to conceptualize it in the beginning.

Now when Sun compiled the java classes, they compiled them in this package/directory hierarchy and then zipped them all up for use in the classes.zip file which should be in your "lib" directory.

Okay, so let's get back to the error message....

When the error message says that it cannot find the package it can mean one of two things:

1. You have not installed the package anywhere in your set of java classes. You get the regular java classes because you use the classes.zip file. But that file does not necessarily come with all versions of JDK by default.

2. Your CLASSPATH variable does not point to the directory containing the javax classes. The CLASSPATH variable specifies where the java compiler should look for java class file resources. If it does not know to look in the javax directory, then it will never find the file(s) you are after.

Selena Sol contributes to the JavaBoutique's Introduction to Java. Selena curently works for Barclays Capital in London, one of the leading global investment banks in Europe and has worked as a software developer for the National Center for Human Genome research, Microline Software, Neuron Data, and Electric Eye in Singapore. Selena is perhaps best-known for creating the Public Domain Web Script Archive (Extropia) and writing several books on Web Programming (Perl, CGI, Java).
Email: selena@extropia.com

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