title: CLASSPATH, Java Buld Path (eclipse), and WEB-INF\LIB : what to use, when, and why?
body: <p>I recently switched to J2EE from .NET, and am confused about where to put JAR files.  I know that the CLASSPATH, WEB-INF, and Eclipse's Java Web Path are all places where JARs can be stored, but I'm confused about which folder to use, when, and why.</p>
  
  <p>First off, we have the CLASSPATH.  I usually set this by going into "Environment Variables" inside "My Computer."  I know that this is the default place where the Java compiler looks for JAR files.  When I add a folder or a JAR to my CLASSPATH environment variable, why is it ignored by Eclipse, the Java compiler, and the web server?</p>
  
  <p>Also, I know that WEB-INF\LIB is a place where you can put JAR files that your web app is going to use.  However, I've put JARs in WEB-INF\LIB only to have them be ignored.  In what situations should I put JARs into WEB-INF\LIB folder?  How do I get Eclipse or the web server to notice them?</p>
  
  <p>So far, the only thing that works for me is to actually change the Java Build Path for an Eclipse project.  I'll select the JARs I need and hit "Add External JARs."  Most of the time when I do this, Eclipse will recognize my JARs and read the classes therein.  However, I've run into a bunch of weird random errors while doing this (mostly having to do with dependencies, I think).  For some reason, I just get the feeling that this isn't the right way to do things, and that I'm missing some vital piece of information.  When should I be manually Adding External JARs inside Eclipse, and when should I be doing things differently?  How come Eclipse's Java Build Path doesn't seem to know about the folders in my CLASSPATH environment variable?</p>
  
  <p>Really, I would just like to gain a better understanding of the CLASSPATH, Eclipse's Java Build Path, and the WEB-INF/LIB folder -- the purposes they serve, the relationships between them, and where I should be putting my JARs in various situations.  I would appreciate any advice you could give me, or any articles that you could recommend.</p>
  
  <p>Thank you.</p>