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How do I set my CLASSPATH for servlets?

Created May 4, 2012

Alex Chaffee

That depends.

For developing servlets, just make sure that the JAR file containing javax.servlet.* is in your CLASSPATH, and use your normal development tools (javac and so forth).

  • For JSDK: JSDK_HOME/lib/jsdk.jar
  • For Tomcat: TOMCAT_HOME/lib/servlet.jar

For running servlets, you need to set the CLASSPATH for your servlet engine. This varies from engine to engine. Each has different rules for how to set the CLASSPATH, which libraries and directories should be included, and which libraries and directories should be excluded. Note: for engines that do dynamic loading of servlets (e.g. JRun, Apache Jserv, Tomcat), the directory containing your servlet class files shoud not be in your CLASSPATH, but should be set in a config file. Otherwise, the servlets may run, but they won't get dynamically reloaded.

The Servlets 2.2 spec says that the following should automatically be included by the container, so you shouldn't have to add them to your CLASSPATH manually. (Classloader implementations are notoriously buggy, though, so YMMV.)

  • classes in the webapp/WEB-INF/classes directory
  • JAR files in the webapp/WEB-INF/lib directory
This applies to webapps that are present on the filesystem, and to webapps that have been packaged into a WAR file and placed in the container's "webapps" directory. (e.g. TOMCAT_HOME/webapps/myapp.war)

The Complete CLASSPATH Guide for Servlets (http://www.meangene.com/java/classpath.html) by Gene McKenna (mckenna@meangene.com) has detailed instructions on how to set your CLASSPATH for JavaWebServer and JRun.

See also http://www.jguru.com/faq/view.jsp?EID=413601
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