Hi, All Here I would like to propose a change to separate the DTM classes (classes under org.apache.xml) from Xalan and XPath. Before going into the details of this change, it is better to review the current status first.
The Xalan classes are organized into three different layers with package names org.apache.xalan, org.apache.xpath and org.apache.xml. The package org.apache.xml is meant to be in the lowest level. It contains the DTM implementation and common xml utility classes. Currently some classes under org.apache.xml have dependencies on classes in org.apache.xalan and org.apache.xpath. As an example, you can find the following line in org.apache.xml.dtm.ref.sax2dtm.SAX2DTM which reads a value from the Xalan TransformerFactoryImpl class: m_useSourceLocationProperty=org.apache.xalan.processor.TransformerFactoryImpl.m_source_location; The DTM separation work is driven by the following requirements: 1. Currently we cannot build a separate dtm.jar which only contains the classes under org.apache.xml, because some classes have dependencies on classes at a higher level. 2. The DTM separation work is a prerequisite for the on-going XPath separation work, which aims at providing a standalone xpath.jar. 3. DTM separation is required when we move to one jar packaging, i.e. put both XSLTC and Xalan classes into one big jar. If we don't do this, we will lose the capability of building the jar with Sun JDK 1.4. 4. The work in the XSLTC_DTM branch also has a requirement on DTM separation, if we want to retain the capability of building a standalone xsltc.jar. 5. The new structure is cleaner and easier to maintained. Changes by the DTM separation work: Three XPath utility classes (DOMHelper, DOM2Helper and DOMOrder) are moved from org.apache.xpath to org.apache.xml.utils. They are used by a few classes in org.apache.xml.utils. They have no dependency on other XPath classes. It is logical to move them to the lower level component. 60 error messages are moved from XSLTErrorResources and XPATHErrorResourcse to a new XMLErrorResources class in org.apache.xml.res. These error messages are only used by the classes in org.apache.xml. The class XSLMessages is separated into three classes: org.apache.xml.res.XMLMessages, org.apache.xpath.res.XPATHMessages and the original org.apache.xalan.res.XSLMessages. XSLMessages extends XPATHMessages, which again extends XMLMessages. In the new architecture, each class only handles error resources at its own level. The common interfaces in the old XSLMessages are moved to XMLMessages, while the createXPATHMessage and createXPATHWarning interfaces are moved to XPATHMessages. Because of the inheritance relation, all interfaces in XSLMessages still work in the same way as before. The inner class ThreadControler in org.apache.xalan.transformer.TransformerImpl is moved to a new class org.apache.xml.utils.ThreadControllerWrapper, so that it can be used by IncrementalSAXSource_Filter. The interface setThreadControler() is also moved to the ThreadControllerWrapper class. Other interfaces like runTransformerThread() and setTransformerThread() are still kept in TransformerImpl. A static field m_source_location is added in SAX2DTM. Its setter method is called by org.apache.xalan.processor.TransformerFactoryImpl whenever the FEATURE_SOURCE_LOCATION attribute is changed. Move some of the constants in org.apache.xalan.templates.Constants to a new class org.apache.xml.utils.Constants, so that they can be used by XPath (probably also by XSLTC in the future). The users do not need to change anything if they do not use the XPath internal (and deprecated) utility classes DOMHelper and DOM2Helper. The main change of the DTM separation work is the restructuring of messages. There is no performance impact for this work. If you have any comments or concerns, please post it on the list. Regards, Morris Kwan XSLT Development IBM Toronto Lab Tel: (905)413-3729 Email: [EMAIL PROTECTED]
