VTD-XML: The Future of XML ProcessingPresentation Transcript
VTD-XML: The Future of XML Processing Albert Guo firstname.lastname@example.org
VTD-XML Motivations Behind VTD-XML Why VTD-XML? When to Use VTD-XML? Known Limitations Basic Concept Essential Classes Shortcomings Typical Programming Flows Demo Reference Agenda 2
*Numerous*, well-known issues of old XML processing models, below summarizes a few: Comparison with DOM, SAX and PULL http://vtd-xml.sourceforge.net/userGuide/5.html Motivations Behind VTD-XML 3
The next generation XML processing model that is simultaneously:
The world's most memory-efficient random-access XML parser.
The world's fastest XML parser
The world's fastest XPath 1.0 implementation.
The world's most efficient XML indexer that seamlessly integrates with your XML applications.
The world's only incremental-update capable XML parser capable of cutting, pasting, splitting and assembling XML documents with max efficiency.
The world's only XML parser that allows you to use XPath to process 256 GB XML documents.
Why VTD-XML? 4
The scenarios that you may consider using VTD-XML Large XML files that DOM can’t handle Performance-critical transactional Web- Services/SOA applications Native XML database applications Network-based XML content switching/routing/security applications When to Use VTD-XML? 5
Not yet support external entities (those declared within DTD)
Not yet process DTD (return as a single VTD record)
Schema validation feature is planned for a future release.
Extreme long (>=512 chars) element/attribute names or ultra deep document (>= 255 levels) will cause parse exception
Known Limitations 6
Non-extractive tokenization based on Virtual Token Descriptor (VTD): use 64-bit integers to encode offsets, lengths, token types, depths
The XML document is kept intact and un-decoded.
Basic Concept – cont.
In other words, in vast majority of the cases string allocation is *unnecessary*, and nothing but a waste of CPU and memory
VTD-XML performs many string operations directly on VTD records
String to VTD record comparison (both boolean and lexicographically)
Direct conversions from VTD records to ints, longs, floats and doubles
VTD record to String conversion also provided, but avoid them whenever possible for performance reasons
Basic Concept – cont.
VTD-XML’s document hierarchy consists *exclusively* of elements
Move a single, global cursor to different locations in the document tree
Many VTDNav’s methods identify a VTD record with its index value
-1 corresponds to “no such record”
Essential Classes 10
Essential Classes – cont. 11
Poor exception handling Shortcomings 12 If this method does not execute properly, it will just return false from parseFile method, and does not report any exception message.
Add BufferedInput Stream in parseFile method to avoid running out of read buffer max size in UNIX platform Shortcomings – cont. 13 You need to modify the build.bat to rebuild VTD-XML jar file, then set it into class path. //add commons-io jar file into the first line javac-classpath .;D:libcommons-io-1.4commons-io-1.4.jar comximpleware*.java javac comximplewarexpath*.java javac comximplewareparser*.java … Finally, you just need to execute build.bat file. Then it will generate the brand-new jar file for you.
Typical Programming Flows Call VTDGen’s parseFile(…) Start with a byte buffer containing the content of XML, call set_doc() of VTDGen Call VTDGen’s loadIndex(…) Call VTDGen’s parse() Obtain an instance VTDNav from VTDGen Move VTDNav’s cursor manually to various locations and perform corresponding application logic Instantiate autoPilot for node iteration and XPath to perform Corresponding application logic 14
1. Add <age> tag after <geneder> 16
1. Add <age> tag after <geneder> – cont. 17 Compiled XPath expression Binded with NTDNav Assigned age value Moved to gender cursor, and added <age> tag after <gender> tag Outputted to new xml file
2. Remove <age> tag 18
2. Remove <age> tag – cont. 19 Compiled XPath expression Binded with NTDNav Remove <age> Outputted to new xml file
3. Add Contact info after <age> tag 20
3. Add Contact info after <age> tag – cont. 21 Compiled XPath expression Binded with NTDNav Assigned age value Inserted new value after <gender> tag Outputted to new xml file
4. Visit XML file – cont. 23 Compiled XPath expression Binded with NTDNav
4. Visit XML file – cont. 24
Official site http://vtd-xml.sourceforge.net/ Jar files, source code, sample code http://sourceforge.net/projects/vtd-xml/files/ JavaDoc http://vtd-xml.sourceforge.net/javadoc/ Accelerate WSS applications with VTD-XML http://www.javaworld.com/javaworld/jw-01-2007/jw-01-vtd.html Reference 25
Process SOAP with VTD-XML http://jimmyzhang.sys-con.com/node/48764/mobile XPathTutorial: http://www.w3schools.com/XPath/default.asp Sample code http://sites.google.com/site/junyuo/Home/code 26 Reference – cont.