How to avoid the java.lang.IncompatibleClassChangeError

Question

Hi all!
I have problem to make my client Java application to work under Oracle JVM. This application works fine as standalone java class. In this mode it communicates fine with a web server.
I have loaded all needed jar files into my user (sample) using the following command:
Loadjava -thin -r -v -f -user sample/sample@<my_url>:1521:usr10se <jar files and classes>
When I call my public method from a PL/SQL function I receive the following error:
ERROR at line 1:
ORA-29532: Java call terminated by uncaught Java exception:
java.lang.IncompatibleClassChangeError
The following is a trace context:
*** 2006-11-29 17:28:10.134
*** ACTION NAME:() 2006-11-29 17:28:10.134
*** MODULE NAME:(SQL*Plus) 2006-11-29 17:28:10.134
*** SERVICE NAME:(…) 2006-11-29 17:28:10.134
*** SESSION ID:(49.5) 2006-11-29 17:28:10.134
java.lang.IncompatibleClassChangeError
     at org.apache.axis.encoding.SerializationContext.startElement(SerializationContext.java:1122)
     at org.apache.axis.message.MessageElement.outputImpl(MessageElement.java:1253)
     at org.apache.axis.message.MessageElement.output(MessageElement.java:1208)
     at org.apache.axis.message.SOAPBody.outputImpl(SOAPBody.java:139)
     at org.apache.axis.message.SOAPEnvelope.outputImpl(SOAPEnvelope.java:478)
     at org.apache.axis.message.MessageElement.output(MessageElement.java:1208)
     at org.apache.axis.SOAPPart.writeTo(SOAPPart.java:315)
     at org.apache.axis.SOAPPart.writeTo(SOAPPart.java:269)
     at org.apache.axis.SOAPPart.saveChanges(SOAPPart.java:530)
     at org.apache.axis.attachments.AttachmentsImpl.getAttachmentCount(AttachmentsImpl.java:554)
     at org.apache.axis.Message.getContentType(Message.java:486)
     at org.apache.axis.transport.http.HTTPSender.writeToSocket(HTTPSender.java:343)
     at org.apache.axis.transport.http.HTTPSender.invoke(HTTPSender.java:138)
     at org.apache.axis.strategies.InvocationStrategy.visit(InvocationStrategy.java:32)
     at org.apache.axis.SimpleChain.doVisiting(SimpleChain.java:118)
     at org.apache.axis.SimpleChain.invoke(SimpleChain.java:83)
     at org.apache.axis.client.AxisClient.invoke(AxisClient.java:165)
     at org.apache.axis.client.Call.invokeEngine(Call.java:2784)
     at org.apache.axis.client.Call.invoke(Call.java:2767)
     at org.apache.axis.client.Call.invoke(Call.java:1792)
     at org.uddi4j.transport.ApacheAxisTransport.send(ApacheAxisTransport.java:87)
     at org.uddi4j.transport.TransportBase.send(TransportBase.java:53)
     at org.uddi4j.client.UDDIProxy.send(UDDIProxy.java:1778)
     at org.uddi4j.client.UDDIProxy.find_tModel(UDDIProxy.java:823)
     at …. Call from my class
I suspected multiple definitions of the SerializationContext.class in my jar files but was wrong: there is only one definition in the axis.jar file. For some reasons this jar file contained SerializationContext.class and SerializationContext.java modules, but I resolved this problem earlier: loadjava does not allow loading the both.
What can be cause of the java.lang.IncompatibleClassChangeError problem?
What I have to do to make my class work from Oracle JVM?
Thanks,
Roman

Answer 1

Avi,
You right, at the beginning I had problems with jar files compiled using Java 1.5. But I discovered this problem earlier, when tried to test standalone client application. Since then a whole web services tool kit, provided by my company, was recompiled with Java 1.4 and now I have no problem with standalone classes, running under Oracle JDK 1.4 environment. It means that I’m pretty sure that all Java classes that I’m loading to Oracle are compiled with JDK 1.4.
You also right with your second guess: not all Java objects in the user_objects table of the SAMPLE user are VALID. I started from a scratch (again): dropped all Java objects from user schema and followed Kuassi Mensah instructions from the “Virtualize Your Oracle Database with Web Services” (http://www.oracle.com/technology/pub/articles/mensah_dws.html): I downloaded and then loaded to my schema the Web Service Call-out Utility jar files using the following command: loadjava -u sample/sample@usr10se -r -v -f -genmissing C:\oracle\ora10_DB\sqlj\lib\dbwsclientws.jar C:\oracle\ora10_DB\sqlj\lib\dbwsclientdb102.jar.
This command loaded about 5000 java objects, but 400+ of them were INVALID and I saw a lot of “ORA-29534: referenced object … could not be resolved” errors.
The tool kit provided by the group in my company only increased number of invalid objects.
What is a strategy in this situation?
Do all the objects have to be VALID?
I can try to resolve the “ORA-29521: referenced name ... could not be found” errors by finding corresponding classes in some jar files and loading these jar files, but it does not guarantee that all ORA-29534 errors will go away. What else can I do to cleanup my java objects?
Thank you very mach,
Roman