Echo Web Framework

After making some tests I have found out that the problem is probably between the oc4j.jar library of the Oracle Application Server and the library of Echo2.
If the oc4j library exists in the classpath of the project the same exception is thrown, even if this library is not used inside the application.
I have found out this when I have tried to call an EJB remotely from the Oracle Application Server.
Is there any solution to this because I am evaluating the Echo2 framework to be used in a project using Oracle Application Server.

This is the complete stacktrace running an Echo application in the Oracle Application
Server after adding the ex.printStackTrace() line in the XMLDocument.java

java.lang.UnsupportedClassVersionError: nextapp/echo2/webcontainer/WebContainerServlet (Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].util.OC4JSecureClassLoader.defineClassEntry(OC4JSecureClassLoader.java:172)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.defineClass(ContextClassLoader.java:1170)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.findClass(ContextClassLoader.java:406)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.loadClass(ContextClassLoader.java:154)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].util.OC4JSecureClassLoader.defineClassEntry(OC4JSecureClassLoader.java:172)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.defineClass(ContextClassLoader.java:1170)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.findClass(ContextClassLoader.java:406)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.loadClass(ContextClassLoader.java:154)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:219)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.loadServlet(HttpApplication.java:2075)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.findServlet(HttpApplication.java:4582)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.getRequestDispatcher(HttpApplication.java:2608)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:640)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.AJPRequestHandler.run(AJPRequestHandler.java:208)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.AJPRequestHandler.run(AJPRequestHandler.java:125)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
at java.lang.Thread.run(Thread.java:534)
Echo2Test: Servlet error
java.lang.UnsupportedClassVersionError: nextapp/echo2/webcontainer/WebContainerServlet (Unsupported major.minor version 49.0)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].util.OC4JSecureClassLoader.defineClassEntry(OC4JSecureClassLoader.java:172)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.defineClass(ContextClassLoader.java:1170)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.findClass(ContextClassLoader.java:406)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.loadClass(ContextClassLoader.java:154)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
at java.lang.ClassLoader.defineClass0(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:537)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:123)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].util.OC4JSecureClassLoader.defineClassEntry(OC4JSecureClassLoader.java:172)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.defineClass(ContextClassLoader.java:1170)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.findClass(ContextClassLoader.java:406)
at java.lang.ClassLoader.loadClass(ClassLoader.java:289)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].naming.ContextClassLoader.loadClass(ContextClassLoader.java:154)
at java.lang.ClassLoader.loadClass(ClassLoader.java:235)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:302)
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:219)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.loadServlet(HttpApplication.java:2075)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.findServlet(HttpApplication.java:4582)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpApplication.getRequestDispatcher(HttpApplication.java:2608)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:640)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.AJPRequestHandler.run(AJPRequestHandler.java:208)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].server.http.AJPRequestHandler.run(AJPRequestHandler.java:125)
at com.evermind[Oracle Application Server Containers for J2EE 10g (10.1.2.0.0)].util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
at java.lang.Thread.run(Thread.java:534)

I have compiled it and I get the same stacktrace as in my first post:
The only think that is added is the last line:
"Caused by: java.lang.NullPointerException"

XML-22900: (Fatal Error) An internal error condition occurred.
05/12/14 11:12:06 Error Message
javax.xml.transform.TransformerException: XML-22900: (Fatal Error) An internal error condition occurred.
at oracle.xml.jaxp.JXTransformer.reportException(JXTransformer.java:737)
at oracle.xml.jaxp.JXTransformer.transform(JXTransformer.java:348)
at nextapp.echo2.webrender.output.XmlDocument.render(XmlDocument.java:107)
at nextapp.echo2.webcontainer.WindowHtmlService.service(WindowHtmlService.java:101)
at nextapp.echo2.webcontainer.NewInstanceService.service(NewInstanceService.java:76)
at nextapp.echo2.webrender.WebRenderServlet.process(WebRenderServlet.java:273)
at nextapp.echo2.webrender.WebRenderServlet.doGet(WebRenderServlet.java:185)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:740)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:853)
at com.evermind.server.http.ServletRequestDispatcher.invoke(ServletRequestDispatcher.java:810)
at com.evermind.server.http.ServletRequestDispatcher.forwardInternal(ServletRequestDispatcher.java:322)
at com.evermind.server.http.HttpRequestHandler.processRequest(HttpRequestHandler.java:790)
at com.evermind.server.http.AJPRequestHandler.run(AJPRequestHandler.java:208)
at com.evermind.server.http.AJPRequestHandler.run(AJPRequestHandler.java:125)
at com.evermind.util.ReleasableResourcePooledExecutor$MyWorker.run(ReleasableResourcePooledExecutor.java:192)
at java.lang.Thread.run(Thread.java:534)
Caused by: java.lang.NullPointerException
---------
java.lang.NullPointerException

I'm not exactly sure what's going on here, but I think I can narrow it down to two possibilites: either something is wrong with Oracle's JAXP implementation or Echo2 is somehow misusing the JAXP API.

The following is pulled from Hashtable.java from the Sun JDK 1.4.2 (src.zip in JDK download):

331    public synchronized Object get(Object key) {
332	Entry tab[] = table;
333	int hash = key.hashCode();

..from that we can conclude that Hashtable.get() was called with a null key. Unfortunately I think that's where my investigation of this stack trace ends, unless Oracle's JAXP implementation has source available?

At this point I'm left to really just take guesses at the problem. One idea might be to play around with the render method XMLDocument a bit...perhaps first by checking to see if there's any way that PrintWriter might be null, i.e.:

    public void render(PrintWriter pw)
    throws IOException {
System.err.println("PrintWriter="+pw);
        try {
            TransformerFactory tFactory = TransformerFactory.newInstance();
            Transformer transformer = tFactory.newTransformer();
            if (outputProperties != null) {
                transformer.setOutputProperties(outputProperties);
            }
            DOMSource source = new DOMSource(document);
            StreamResult result = new StreamResult(pw);
            transformer.transform(source, result);
        } catch (TransformerException ex) {
            throw new IOException("Unable to write document to OutputStream: " + ex.toString());
        }
    }

.....and then maybe seeing if commenting out the transformer.setOutputProperties() line has any effect.

I'll try and review the DOM buildup/rendering code and see if I can find anything out of spec. There's a chance suggestions above might help, but I don't have much faith that they will.

Ok, I did some decompiling and debugging, and I've discovered that reportSAXEvents invokes the endElement() method of class XSLSAXPrintDriver with three params: a namespace a localname and a qualifiedname.
It fails looking up a hashtable of emptytags with the localname as key. the hashtable contains the following:

emptyTags = new Hashtable(20);
emptyTags.put("area", "area");
emptyTags.put("base", "base");
emptyTags.put("basefont", "basefont");
emptyTags.put("br", "br");
emptyTags.put("col", "col");
emptyTags.put("frame", "frame");
emptyTags.put("hr", "hr");
emptyTags.put("img", "img");
emptyTags.put("input", "input");
emptyTags.put("isindex", "isindex");
emptyTags.put("link", "link");
emptyTags.put("meta", "meta");
emptyTags.put("param", "param");

This part of the code is only executed if the outMethod (set via the properties of the transformer) is either HTML or XHTML. I'll see if forcing outMethod to XML.

Tristan

erksmaas+Jan 31 2006, 06:59 PM(erksmaas @ Jan 31 2006, 06:59 PM)

The error has gone with the latest JDeveloper Release from Jan 06.

HMH

erksmaas+Mar 1 2006, 12:02 AM(erksmaas @ Mar 1 2006, 12:02 AM)

We are having the same issue on Oracle AS 10.1.2. Anyone made any progress on this issue? It is a show stopper for us as well. We would like to use the framework for our customer, but we must run on Oracle AS.

LKF

Are you confirming that Echo2 works on IE but not on FireFox whe used OAS 10.1.2.

My guess woyuld be that some other issue has come into play because by the time the code gets down to the client browser, Oracles JAXP will have done its work.

As a guess, it could be producing "XML" output which is slightly different to the norm and it MAY make it through Ie but not FireFox but this is an unlikely situation.

I'm confirming that Echo2 does not work in combination with OC4J 10.1.3 (in JDeveloper 10.1.3) and firefox. Same echo2 distribution works in combination with OC4J 10.1.3 and IE.

OC4J is Oracle Container for Java - witch is part of OAS 10.1.3 (not released yet). Same OC4J 10.1.2 is in OAS 10.1.2 (in production) - with this one I cannot confirm above statements. 10.1.3 runs on java 5, 10.1.2 is stil on 1.4.

I will play around with libraries and report back. Thx for advices :D

Same problem here. We plan to use Echo2 in the future (i'm testing it for usability) but we are highly dependent on Oracle AS 10.1.2.0.0, in JDeveloper it runs perfectly but when we deploy it to AS we get:

Unable to write document to OutputStream: javax.xml.transform.TransformerException: XML-22900: (Fatal Error) An internal error condition occurred.

Does anyone have a solution?

<strike>There may actually a problem with mixing DOM1 and DOM2 code in this example that will need to be rectified in Echo2 (will post more info on this later).</strike>
Edit: retracting that statement for the moment. I was thinking it might be illegal to use the DOM Level 2 DOMImplementation.createDocument() method and then use DOM Level 1 methods to work on it....but this appears not to be the case.

However, as far I can tell, Oracle simply refuses to handle DOM1 rendering w/ HTML. The following does NOT work, though if we change the element name from "html" to anything else, e.g. "foo", it works fine. Clearly they're treating html docs as a special case. Changing the code to use entirely DOM2 API calls (Edit: i.e., exclusively using methods that end in "NS") does work, even with an "html" root element.

package mypackage1;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import javax.xml.parsers.ParserConfigurationException;
import javax.xml.transform.Transformer;
import javax.xml.transform.TransformerException;
import javax.xml.transform.TransformerFactory;
import javax.xml.transform.dom.DOMSource;
import javax.xml.transform.stream.StreamResult;

import org.w3c.dom.DOMImplementation;
import org.w3c.dom.Document;
import org.w3c.dom.DocumentType;
import org.w3c.dom.Element;

public class Servlet2 extends HttpServlet 
{
    private static final String CONTENT_TYPE = "text/html; charset=UTF-8";

    public void init(ServletConfig config) throws ServletException {
        super.init(config);
    }

    public void doGet(HttpServletRequest request, HttpServletResponse response) 
    throws ServletException, IOException {
        response.setContentType(CONTENT_TYPE);
        PrintWriter out = response.getWriter();
        try {
            try {
                DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
                DocumentBuilder builder = factory.newDocumentBuilder();
                Document document = builder.newDocument();
                Element htmlElement = document.createElement("html");
                document.appendChild(htmlElement);
                TransformerFactory tFactory = TransformerFactory.newInstance();
                Transformer transformer = tFactory.newTransformer();
                DOMSource source = new DOMSource(document);
                StreamResult result = new StreamResult(out);
                transformer.transform(source, result);
            } catch (TransformerException ex) {
                throw new RuntimeException(ex);
            } catch (ParserConfigurationException ex) {
                throw new RuntimeException(ex);
            }
        } catch (RuntimeException ex2) {
            ex2.printStackTrace();
            throw(ex2);
        }
    }
}

One more update...I've posted an article on Oracle's developer forums here with a really simple test case:
http://forums.oracle.com/forums/thread.jspa?threadID=398110