拥有用于 XSD 验证的线程安全缓存

Question

I am working on an application for XSD validation and I want my schemas to be cached.
On the other hand the application uses multiple threads so I am wonder what is the thread-safe approach to load the XSD files.
At the moment I have a new net.sf.saxon.s9api.Processor gets created for every XSD. A SchemaManager is using to validate lots of xmls after that

Processor processor = new Processor(true);

SchemaManager sm = processor.getSchemaManager();
sm.load(new StreamSource(new File(xsdFilename)));

Is it really necessary? Can I instantiate a single Processor and use it for all the XSDs? So would it be safe to get the SMs in multi-thread context in this case?

Additionally, is it correct to store SchemaManager instances in a Map by which the application cache is represented? Or SchemaValidator objects should be use for it?

Answer 1

The Saxon Processor and SchemaManager can be used to store multiple schemas (or rather, one schema that is the union of all the schema components from multiple schema documents), and it's thread safe, so it should work fine so long as all the schemas are compatible. By that I mean you can't have two different schema components with the same name, eg as a result of loading different no-namespace schemas, or as a result of using xs:redefines.

If you want to keep your schemas separate, however, you will need a different Processor and SchemaManager for each one.

The SchemaValidator object isn't thread-safe: you should create a new SchemaValidator for each validation task. Creating this object is cheap.

It's also worth noting that there are corner cases where validating against a "composite" schema may change the validation outcome even if the several parts of the schema are disjoint: for example, when an element wildcard has processContents="strict" or processContents="lax" .