[ http://issues.apache.org/jira/browse/AXIS2-919?page=comments#action_12429161 ] Derek Foster commented on AXIS2-919: ------------------------------------
One further note on the AXIOM classes: The common use of Iterators rather than Collections in interfaces (as method return values, etc.) is frustrating to use, and contrary to the design goals of the Java collections classes. Note what the JDK collections design FAQ says about this practice (http://java.sun.com/j2se/1.4.2/docs/guide/collections/designfaq.html#8). I would much prefer that these AXIOM methods return a Collection or List interface rather than an Iterator interface, as per the suggestions in the design FAQ. This can be done fairly simply like so: Collection getTheWidgets() { Iterator myIterator = getTheIterator(); return new AbstractCollection() { public Iterator iterator() { return myIterator; } } } In general, using Iterators as return values and method parameter values the way AXIOM does is much more awkward than using Collection interfaces. I think this is a significant weak point in the AXIOM design. It means, for instance, that I can only iterate over the returned values once without calling the 'get' method again. Also I cannot, for instance, simply add everything that an iterator references to another collection with a single method call, as I could if a Collection was provided, nor can I use other useful methods like those from the java.util.Collections package on the contents of an iterator. I found it fairly frustrating when working with the header objects from an operation context, for instance. In JDK 1.5, for instance, I would like to be able to write for (Header header : (Collection<Header>)getHeaders()) doSomethingWith(header); or: Set headerSet = new HashSet(headers); but cannot because the interface uses Iterators instead of collections. Anyway, I would file this as a separate "request for enhancement" directly against the AXIOM classes, but I'm not sure where to do that. > Unable to print out entire SOAP message: bug in OMElement.serialize() > --------------------------------------------------------------------- > > Key: AXIS2-919 > URL: http://issues.apache.org/jira/browse/AXIS2-919 > Project: Apache Axis 2.0 (Axis2) > Issue Type: Bug > Components: core, om > Affects Versions: 1.0 > Reporter: Derek Foster > Assigned To: Eran Chinthaka > Priority: Blocker > > I was attempting, inside an XMLBeans-generated service method, to print out > the entire SOAP message to a log file. Towards that end, I tried to execute > the following code: > final StringWriter writer = new StringWriter(); > messageContext.getEnvelope().serialize(writer); > System.out.println(writer.toString()); > However, I was surprised to get the following exception resulting from this: > org.apache.axiom.om.OMException > at > org.apache.axiom.om.impl.llom.OMElementImpl.getNextOMSibling(OMElementImpl.java:266) > at > org.apache.axiom.om.impl.traverse.OMChildrenIterator.next(OMChildrenIterator.java:111) > at > org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:771) > at > org.apache.axiom.soap.impl.llom.SOAPEnvelopeImpl.internalSerialize(SOAPEnvelopeImpl.java:177) > at > org.apache.axiom.om.impl.llom.OMElementImpl.internalSerialize(OMElementImpl.java:756) > at > org.apache.axiom.om.impl.llom.OMNodeImpl.serialize(OMNodeImpl.java:310) > at > org.apache.axiom.om.impl.llom.OMNodeImpl.serialize(OMNodeImpl.java:352) > ... > The cause of the problem appears to be the fact that the SOAP envelope is a > top-level XML object. Thus, the item immediately following it is a > DOCUMENT_END. The OMElementImpl.internalSerialize(XMLStreamWriter, boolean > cache) method contains the following code: > Iterator children = this.getChildren(); > while (children.hasNext()) { > ((OMNodeEx) children.next()).internalSerialize(writer); > which seems plausible. However, the iterator that is returned is of type > OMChildrenIterator. Its hasNext method looks like this: > /** > * Returns <tt>true</tt> if the iteration has more elements. (In other > * words, returns <tt>true</tt> if <tt>next</tt> would return an element > * rather than throwing an exception.) > * > * @return Returns <tt>true</tt> if the iterator has more elements. > */ > public boolean hasNext() { > return (currentChild != null); > } > but its next() method looks like this: > /** > * Returns the next element in the iteration. > * > * @return Returns the next element in the iteration. > * @throws java.util.NoSuchElementException > * iteration has no more elements. > */ > public Object next() { > nextCalled = true; > removeCalled = false; > if (hasNext()) { > lastChild = currentChild; > currentChild = currentChild.getNextOMSibling(); > return lastChild; > } > return null; > } > which is a problem, because currentChild.getNextOMSibling() looks like this: > /** > * Gets the next sibling. This can be an OMAttribute or OMText or > * OMELement for others. > * > * @throws OMException > */ > public OMNode getNextOMSibling() throws OMException { > while (!done) { > int token = builder.next(); > if (token == XMLStreamConstants.END_DOCUMENT) { > throw new OMException(); > } > } > return super.getNextOMSibling(); > } > which will under some circumstances throw an OMException, which is not in the > contract of the iterator's next() method to throw. > Thus, iterator.hasNext() is returning true, implying that there is a next > element, but when next() is actually called, the iterator discovers that it > has reached the end of the document, and that therefore there really is no > next element. It therefore throws an OMException. > Firstly, if the next() method is going to be implemented this way, then > hasNext() should perform enough lookahead on the document to detect that the > next item in the input stream is indeed a END_DOCUMENT, and should therefore > return false, since under these circumstances there truly isn't a next > element (and calling next() would therefore always throw an OMException). > That way, when the end of the document is hit, the serialize method will > simply stop and return its results rather than trying to advance past the end > of the document as it does now. > Secondly, this OMException really should have some meaningful error text in > it, such as "Can't call 'next()' on an iterator which is positioned at > element 'foo' which is the last element in the document" or even better, > "Can't call next() when hasNext() returns false" (see below). I can't think > of any cases in typical library code where it is desirable to throw > exceptions that don't have any message text. This is really unpleasant for > anybody that is trying to debug a problem. I would encourage someone to do a > search through the source code for "throw new OMException()" and add an > explanatory error message wherever one is found. -- This message is automatically generated by JIRA. - If you think it was sent incorrectly contact one of the administrators: http://issues.apache.org/jira/secure/Administrators.jspa - For more information on JIRA, see: http://www.atlassian.com/software/jira --------------------------------------------------------------------- To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
