如何链接用于Java类路径的库？

Question

In Eclipse (Windows 7) I created a dynamic web project. My classes use many external libraries. These were copied into the directory WebContent/WEB-INF/lib/ manually and will be included in the resulting WAR file on building (right-click/Export/...). The WAR file will be deployed on a Tomcat 6 running on a Ubuntu server.

My question is if it's possible to "to tell" the WAR file which packages to use at runtime. Maybe with running the build command manually with parameters added? Or is this the wrong directory the files copied in?

I tried out the following: All external JARs were copied into $JAVA_HOME/jre/lib/ext , so they should appear automatically in classpath. Before exporting and deploying the WAR file I deleted all JARs in WebContent/WEB-INF/lib/ . But that results in a ClassNotFound exception on server-side.

Answer 1

When working with wars, the general idea is to create a war that can be deployed to any instance of Tomcat without having to modify the host environment, which you can't always do due to permissions, access, desired up time, etc.

That said, any libraries your app depends on should appear in the war, in WEB-INF/lib .

As you've noticed, maintaining the jars can be a pain. Look into using a build tool such as Maven or at least Ant.

Also, jars in the Java environment and jars accessible to apps running on Tomcat are two different sets. Tomcat doesn't give access to the underlying Java system for apps running under itself. You could put the jars you need in TOMCAT_HOME\\lib, but that's not really recommended for previously stated reasons.

Answer 2

For exclude the libs you can use war task

I can image you can right click your eclipse project then export -> select ant Buildfiles

add the code from above link, an example, like this, case by case please specify your html, images, output classes folder, and so on.

<war destfile="myapp.war" webxml="src/metadata/myapp.xml">
  <fileset dir="src/html/myapp"/> 
  <fileset dir="src/jsp/myapp"/>
  <lib dir="thirdparty/libs">
    <exclude name="jdbc1.jar"/> // add more lib in your case
  </lib>
  <classes dir="build/main"/> // the class path would be ./build/classes
  <zipfileset dir="src/graphics/images/gifs"
              prefix="images"/>
</war>