CODEWITHSUNDEEP
javaxmlxsltxsdschema
Bc L
Bc L

Reputation: 13

XSD schema changes, XSLT and backwards compatibility

this is more of a high level question about using jaxb and xslt, as I try to gain more of an understanding of what I need to do, and what I need to learn more about.

I have inherited an application that has Java class files generated from an xsd schema (using jaxb), does some stuff, then writes one of these objects to a serialized 'save file'.

I currently need to make changes to the xsd, which of course will mean some of my originally generated classes will be updated. However, I still need to be able to load the old serialized saved files for backwards compatibility - does this mean I need to maintain a copy of the current xsd, and all generated class files in order to load the old serialized save files? Does anyone have a suggested way I can do this, if I must be able to load the old files?

For all future version of the xsd, I intend to output saved files to xml, and use xslt to transform the file before unmarshalling the xml, which I think will work, as mentioned in this thread How should I manage different incompatible formts of Xml based documents. Doesn't help me with the older serialized files though - any ideas?

Thanks.

Upvotes: 1

Views: 519

Answers (1)

Michael Kay
Michael Kay

Reputation: 163360

Probably the main drawback of JAXB, and of data binding in general, is that it makes schema evolution very cumbersome. XML is a technology where people expect to change and extend the schema/data model frequently, whereas in Java it is hard-coded and hard to change. Use of XML-oriented languages like XSLT and XQuery is a big advantage in such situations.

Saving persistent data in the form of serialized Java objects seems completely perverse to me. Before you move to your new schema format, convert it all back to XML. The whole point of XML is that the data is then in a format that is far more durable, and not dependent on the continued existence of the software that created it.

Upvotes: 1

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