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Java and XML

Java and XML. Philip Johnson Collaborative Software Development Laboratory Information and Computer Sciences University of Hawaii Honolulu HI 96822. Why do we care?. XML is a standard representation for data. We want an efficient and effective way to:

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Java and XML

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  1. Java and XML Philip Johnson Collaborative Software Development Laboratory Information and Computer Sciences University of Hawaii Honolulu HI 96822

  2. Why do we care? • XML is a standard representation for data. • We want an efficient and effective way to: • Read in XML data and process it using Java. • Write out XML data • Oh, and you will be required to read in XML as part of the DueDates 2.0 assignment. :)

  3. Ways to do this • Read in or write out the XML file as text. • Ridiculous. Don’t even think about it. • Use SAX or DOM or JDOM packages. • OK in some circumstances. • Use JAXB 2.0. • The preferred and easiest approach.

  4. The Approach in a Nutshell • (1) Create an XML “example” file(s) illustrating what your XML data looks like. • (2) Create an XML “schema” that describes the structure of your XML data. • (3) Check your work: Validate the data files against the schema. • (4) Run the JAXB compiler to autogenerate Java classes that represent your XML schema. • (5) Use the JAXB library to read XML data and produce Java instances, or take a Java instance and write it out as XML.

  5. Example: Stack!!!! • Say you have a Stack system and you want to read in a “configuration file” that contains a default stack. • We need to: • Figure out what the XML data looks like. • Figure out the XML schema for this data. • Make sure data is consistent with schema. • Autogenerate the Java classes using JAXB. • Write code to read in the default stack.

  6. Stack XML data example

  7. Stack XML Schema example

  8. Validating the schema to data

  9. Generating the Java files

  10. Generating Java files (cont)

  11. Writing the code

  12. Testing the code

  13. Of course, we must verify

  14. Note there are 2 Stacks!

  15. Miscellaneous Details • You must download JAXB and define JAXB_HOME • Required so that Ant tasks work. • You do not need an Eclipse classpath var. Why? • Our approach requires two new build files: • validateXml.build.xml • jaxb.build.xml • You will want to exclude JAXB-generated files from Checkstyle, PMD, and FindBugs • Those files are “black boxes” and you do not touch them. • Sample Stack system shows only reading XML. • Writing XML is similarly easy.

  16. Get the source code • Available in stack-johnson/branches/jaxb-example • You can either SVN checkout: • http://stack-johnson.googlecode.com/svn/branches/jaxb-example • Or try the SVN “switch” command to move back and forth between trunk and jaxb-example. • Real SVN Hackers Use Switch. • Use validateXml.build.xml and jaxb.build.xml • You must edit these files slightly to suit your needs!

  17. How to install JAXB • Go to https://jaxb.dev.net/ • Download JAXB RI 2.1.9 (jaxb-2_1_9.zip) • Extract to get jaxb-ri. Rename to jaxb-2.1.9. • Those guys at Sun just don’t get it. • Define JAXB_HOME to point to this directory.

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