#3 Exception when file mismatches schema

[Tim Booth]

If I start Pedro with one model loaded and try to load
a document created with a different schema I get a big
SAXException.

Pedro should ideally load the correct schema and show
the file, but at least there should be an error message
displayed - the only feedback right now is the
exception trace - ie:

org.xml.sax.SAXException: Experiment file uses schema
"/home/user4/pedro1-3/dist/models/metadata/model/Metadata.xsd"
but the application is using schema
"/home/tbooth/tings/pedro17/dist/models/pedro/model/PEDRoSchema.xsd"
at
pedro.io.PedroDataFileReader.verifySchemaInformation(PedroDataFileReader.java:345)
at
pedro.io.PedroDataFileReader.startElement(PedroDataFileReader.java:428)
at
com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.startElement(AbstractSAXParser.java:533)
at
com.sun.org.apache.xerces.internal.impl.dtd.XMLDTDValidator.startElement(XMLDTDValidator.java:798)
at
com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanStartElement(XMLDocumentFragmentScannerImpl.java:878)
at
com.sun.org.apache.xerces.internal.impl.XMLDocumentScannerImpl$ContentDispatcher.scanRootElementHook(XMLDocumentScannerImpl.java:1157)
at
com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl$FragmentContentDispatcher.dispatch(XMLDocumentFragmentScannerImpl.java:1794)
at
com.sun.org.apache.xerces.internal.impl.XMLDocumentFragmentScannerImpl.scanDocument(XMLDocumentFragmentScannerImpl.java:368)
at
com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:834)
at
com.sun.org.apache.xerces.internal.parsers.XML11Configuration.parse(XML11Configuration.java:764)
at
com.sun.org.apache.xerces.internal.parsers.XMLParser.parse(XMLParser.java:148)
at
com.sun.org.apache.xerces.internal.parsers.AbstractSAXParser.parse(AbstractSAXParser.java:1242)
at
javax.xml.parsers.SAXParser.parse(SAXParser.java:375)
at
javax.xml.parsers.SAXParser.parse(SAXParser.java:176)
at
pedro.io.NativeFileFormatReader.parseNativeFormatFile(NativeFileFormatReader.java:146)
at
pedro.io.NativeFileFormatReader.readFile(NativeFileFormatReader.java:105)
at pedro.FileMenu.openFile(FileMenu.java:608)
at pedro.FileMenu.open(FileMenu.java:408)
at
pedro.FileMenu.actionPerformed(FileMenu.java:1333)

...etc...

[Tim Booth]

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user_id=1164653

This from tim_changelog.txt

25/4/05:
In response to Kev:

> the main pedro io readers use SAX -- and I'm having trouble
> getting exceptions I throw in the code to show up in the
error dialog
> box. For example, if I try loading data files with an
incompatible
> model name stamp, I just get a blank Error dialog. I
don't want to call
> the error dialog from within the io routines because they
may have to be
> used in a setting that doesn't use a UI. Thoughts?

I did some tracing and found the following:

A) Loading a file with the wrong model yields an error message.
B) Having the wrong document element dumps an exception but
there is no error.

A) The error actually comes from
MetaDataReader.fileUsesCurrentSchema
This calls addError directly even though it is not UI code

The trap at FileMenu.openFile is a good place to handle
all the errors, so
all exceptions should end up here.

The original error is trapped at
PedroDataFileReader.verifySchemaInformation
and a SAX exception is thrown. SAX catches this and
cleans up, but then re-throws
the exception so that it turns up in
NativeFileFormatReader.parseNativeFormatFile.
At this point a stack trace is printed and code continues.

Changes made:

Modified the handler in
NativeFileFormatReader.parseNativeFormatFile to re-throw
the exception (converted to a PedroException). Small change.

Modified MetaDataReader.fileUsesCurrentSchema and made
MetaDataReader.checkFileUsesCurrentSchema which throws
PedroExceptions rather than returning
false on error. These exceptions also end up in the
FileMenu.openFile trap. Bigger change.

Kev will check on Wednesday - there may be more to do.