Introduce a CopyUtils class that makes copies of OM trees
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Key: WSCOMMONS-236
URL: https://issues.apache.org/jira/browse/WSCOMMONS-236
Project: WS-Commons
Issue Type: Improvement
Components: AXIOM
Reporter: Rich Scheuerle
Assignee: Rich Scheuerle
Problem Summary:
Some consumers of Axiom need to make copies of the OM tree.
Providing a CopyUtils utility in Axiom would allow them to delegate this
work to Axiom.
It would also allow the Axiom project to more tightly control this critical
function.
Goals of CopyUtils
1) The Source tree should be minimally affected by the copy. For example,
copying an OM SOAPEnvelope
should not cause unnecessary expansion of descendent OMDataSource
elements.
2) Retain class identity for nodes in the tree. For example, a SOAPFault
object in the source tree
will cause a SOAPFault object to be created in the target tree.
3) Handle all of the nuances. For example, SOAPHeaderBlocks have processed
flags. The state of these
flags should be copied to the target tree.
4) If Axiom controls the CopyUtils code, then Axiom is in a better position
to fix the utility as Axiom is
improved/upgraded.
Example Usage:
An example is the Sandesha project. Here is the code in SandeshaUtils that
makes a copy of a tree
be writing and reparsing the data.
public static MessageContext cloneMessageContext (MessageContext oldMsg)
throws AxisFault {
MessageContext newMsg = new MessageContext ();
newMsg.setOptions(new Options (oldMsg.getOptions()));
//TODO hd to use following hack since a 'clone' method was not
available for SOAPEnvelopes.
//Do it the correct way when that becomes available.
OMElement newElement = oldMsg.getEnvelope().cloneOMElement();
String elementString = newElement.toString();
try {
ByteArrayInputStream stream = new ByteArrayInputStream(
elementString.getBytes("UTF8"));
StAXSOAPModelBuilder builder = new StAXSOAPModelBuilder(
XMLInputFactory.newInstance().createXMLStreamReader(stream),
null);
SOAPEnvelope envelope = builder.getSOAPEnvelope();
newMsg.setEnvelope(envelope);
} catch (XMLStreamException e) {
throw AxisFault.makeFault(e);
} catch (UnsupportedEncodingException e) {
throw AxisFault.makeFault(e);
}
newMsg.setConfigurationContext(oldMsg.getConfigurationContext());
newMsg.setAxisService(oldMsg.getAxisService());
newMsg.setTransportOut(oldMsg.getTransportOut());
newMsg.setTransportIn(oldMsg.getTransportIn());
return newMsg;
}
This code will be changed to:
/**
* Clone the MessageContext
* @param oldMsg
* @return
* @throws AxisFault
*/
public static MessageContext cloneMessageContext (MessageContext
oldMsg) throws AxisFault {
MessageContext newMsg = new MessageContext ();
newMsg.setOptions(new Options (oldMsg.getOptions()));
// Create a copy of the envelope
SOAPEnvelope oldEnvelope = oldMsg.getEnvelope();
if (oldEnvelope != null) {
SOAPEnvelope newEnvelope =
CopyUtils.copy(oldMsg.getEnvelope());
newMsg.setEnvelope(newEnvelope);
}
newMsg.setConfigurationContext(oldMsg.getConfigurationContext());
newMsg.setAxisService(oldMsg.getAxisService());
newMsg.setTransportOut(oldMsg.getTransportOut());
newMsg.setTransportIn(oldMsg.getTransportIn());
return newMsg;
}
Full Disclosure:
I understand that Axiom provides a clone() method on its interfaces.
Currently the implementation of clone() is
inadequate and/or broken. For example, invoking clone() on a SOAP11BodyImpl
will return a OMElement (not a SOAP11BodyImpl).
Using a separate static utility to control the copying of a tree is an easy
and effective way to fix the existing clone()
inadequacies. If the clone() methods are fixed, then it will be easy to
incorporate those changes into the CopyUtils code.
In addition, an external copy utility allows us to provide more
sophisticated copy support (e.g. copyAndFlatten).
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