Using "." in CLASSPATH

Question

I am following the Tomcat/servlet tutorial at http://www.moreservlets.com/Using-Tomcat-4.html
It's all been going great, until "Test 3: A Servlet That Uses Packages and Utilities". When I try to compile the servlet, I get an error because it can't find the class needed. They are both in the same folder. The tutorial says to include "." in my CLASSPATH variable. I have done that, but it still doesn't work. Here is what my CLASSPATH looks like...
.;C:\ServletDevel;C:\j2sdk1.4.0_01\jre\lib\ext\servlet.jar
How do I get the servlet to compile with the class in the same folder?

Answer 1

first, if you're using the java compiler installed under C:\j2sdk1.4.0_01 you don't need to include C:\j2sdk1.4.0_01\jre\lib\ext\servlet.jar in your class path.
second, some things to look out for:
are you using package names in your source? if you are, you should use the -d switch to javac to make it put the compiled classes in some directory. you should also make this directory part of you class path instead of ".". -d makes javac put the compiled file into a sub-directory with the same name as the package, which is where the java command will later look for it.
are you compiling your java files one by one, or are you using a wild card? by using a wild card, like "javac *.java", the compiler will compile all the files at once, taking care of dependencies as well.
when you're saying the "missing" class is in the same directory, do you mean the .class file or the .java file? if you're using package names in the source code, the .class file will not be searched for in the same directory, even if it's in the class path. the java command tries to find the .class file by going through the class path, and for each directory found it will append the package name of the class to the directory name, then look for the class file in the subdirectory so named.
here's an example:
java Foo.java Bar.javawhere both Foo and Bar are specified to be in the package foo.bar, will create the files Foo.class and Bar.class in the directory where you did the compile. If you set the class path to "." and try to run foo using
java Foohowever, it won't work, for several reasons.
first of all, the command should actually be
java foo.bar.Foobecause java needs the full class name of the class it's going to run, as input.
second, that command wont work either, because, with the class path set to ".", java will look for the class foo.bar.Foo in the directory "./foo/bar". so you need to either put your .class files into this directory, or run javac with the -d option.
here's how you would make it all work:
- set CLASSPATH to an existing directory, eg. "classes"
CLASSPATH=classes- compile using wildcards and -d
javac -d classes *.java- verify that your class files were put in a sub directory under "classes"
- run the class "Foo" (or copy everything to where the servlet engine wants it)
java foo.bar.Foo