Exception when using an OIF Business Process Plug-in

If you write a Business Processing plug-in for Oracle Identity Federation (OIF) and follow the installation instructions in the documentation you may encounter NoClassDefFoundError looking for org.apache.commons.codec.DecoderException. Here's what that exception looks like:

java.lang.RuntimeException: javax.servlet.ServletException: java.lang.NoClassDefFoundError: org/apache/commons/codec/DecoderException
        at oracle.security.fed.controller.ApplicationController.processServletRequest(Unknown Source)
        at oracle.security.fed.controller.web.servlet.FederationServlet.doGet(Unknown Source)
        at oracle.security.fed.controller.web.servlet.FederationServlet.doPost(Unknown Source)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:820)
        Truncated. see log file for complete stacktrace
Caused By: javax.servlet.ServletException: java.lang.NoClassDefFoundError: org/apache/commons/codec/DecoderException
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:341)
        at weblogic.servlet.internal.ServletStubImpl.execute(ServletStubImpl.java:183)
        at weblogic.servlet.internal.RequestDispatcherImpl.invokeServlet(RequestDispatcherImpl.java:523)
        at weblogic.servlet.internal.RequestDispatcherImpl.forward(RequestDispatcherImpl.java:253)
        at oracle.security.fed.controller.web.flow.URLContextTarget.perform(Unknown Source)
        Truncated. see log file for complete stacktrace
Caused By: java.lang.NoClassDefFoundError: org/apache/commons/codec/DecoderException

This is easily fixed - just copy Oracle/Middleware/user_projects/domains/IDMDomain/servers/wls_oif1/tmp/_WL_user/oif-libs/i78h77/APP-INF/lib/commons-codec-1.2.jar to the same lib directory as your plug-in and other jars listed in the docs. PS: don't forget to copy the updated files in when you apply a patch!