tomcat 8，如何访问外部java jar库文件

Question

I am using tomcat 8 and have an external library directory called /opt/thirdParty. I have the third party library in this directory. (ie. the library directory is outside of tomcat server)

and have context.xml under META-INF configured like this

<?xml version="1.0" encoding="UTF-8"?>
<Context>
    <Resources className="externalPackage.ExteranlJavaClass">
        <PreResources className="externalPackage.ExteranlJavaClass"
            base="/opt/thirdParty/firstWebApp.jar"
            internalPath="/"
            webAppMount="/WEB-INF/lib" />
    </Resources>
</Context>

when I start the tomcat server and get error in the catalina.out file

java.lang.ClassNotFoundException: externalPackage.ExteranlJavaClass

I need help on how to configure the tomcat server so that I can access the external library files at /opt/thirdParty directory.

Thanks.

I also tried following and get the same error message: java.lang.ClassNotFoundException: externalPackage.ExteranlJavaClass thanks for help

<Context> <Loader className="externalPackage.ExteranlJavaClass" 
  virtualClasspath="/opt/thirdParty/firstWebApp.jar"/> <JarScanner     
  scanAllDirectories="true" /> 
</Context>

Answer 1

You have several options:

1. Add your external directory to the server-classpath by changeing the server-startup settings in the start-script
2. add external library to the server-classpath by moving it to common-libs/share-libs directory of your application server
3. Load your class on runtime using an custom classloader
4. move your external library to internal
5. If using webapp specs > 3.0 you can make your library a web-fragment and deploy it to the app-server

Answer 2

Can't you just make a symlink from /opt/3rdParty/lib1.jar to CATALINA_BASE/lib folder?

Note! Don't forget to fix file permission issues

Answer 3

The className attribute in the PreResources element specifies an implementation of org.apache.catalina.WebResourceSet which is used to load the resource. Since you want to load a jar you can use the standard JarResourceSet

<PreResources className="org.apache.catalina.webresources.JarResourceSet" ...