OSB: Custom XPath vs Java Callout classloader difference

the Custom Xpath classloader doesn't access the jars in the domain lib folder (like /opt/oracle/domains/osbpl1do/lib folder), while the java callout does. So a function might work when invoked by JavaCallout, but give a nasty error from a customxpath:

 java.lang.ClassNotFoundException: org.apache.commons.codec.binary.Hex
 at weblogic.utils.classloaders.GenericClassLoader.findLocalClass(GenericClassLoader.java:297)
 at weblogic.utils.classloaders.GenericClassLoader.findClass(GenericClassLoader.java:270)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:306)
 at java.lang.ClassLoader.loadClass(ClassLoader.java:247)
 at weblogic.utils.classloaders.GenericClassLoader.loadClass(GenericClassLoader.java:179)

If you need some common libraries in a Custom Xpath, you better add the jar explicitly to the JVM classpath

vi /opt/oracle/domains/osbpl1do/bin/setDomainEnv.sh

EXT_POST_CLASSPATH=/opt/oracle/domains/osbpl1do/lib/commons-codec-1.4.jar

restart your managed server
Check the JVM classpath:

pid="the managed server pid"
jinfo -sysprops ${pid} | grep java.class.path | awk -F'=' '{print $2}'

this gives me this new classpath:

....many more
/opt/oracle/fmw11_1_1_5/wlserver_10.3/server/lib/xqrl.jar
/opt/oracle/domains/osbpl1dom/lib/commons-codec-1.4.jar
/opt/oracle/fmw11_1_1_5/patch_wls1035/profiles/default/sys_manifest_classpath/weblogic_patch.jar
....many more

For more on WebLogic classloader, see here