Re: [xsl] how to make a log file in XSLT?

["David Birnbaum djbpitt@xxxxxxxxx" <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>]

Update the XML log files in an XML database with XQuery update?

On Sun, Mar 12, 2023 at 5:42b/PM Dimitre Novatchev dnovatchev@xxxxxxxxx <
xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx> wrote:

> The requirement that the "log file" must be an XML document is
> too-restricting in this problem.
>
> This is why people generally don't write their log records as elements of
> an XML file.
>
> There are logging systems that write the log records in a database table
> (thus the log records from a farm of web servers is collected just in one
> place instead of N and also writing a log record within a transaction
> solves the concurrency problem).
>
> And having as a field the log-timestamp frees us from any ordering
> requirement, too. Furthermore such records can be grouped on the values of
> other fields, such as LogLevel, EventId, ApplicationName, Category, ...,
> etc.
>
> Taking all this into account, if I needed logging from an XSLT
> transformation, I would just send requests to a web-service, and let it do
> the writing.
>
> Even this could be a little-bit tricky, because the doc() and document()
> function are required (I think) to use the GET Http Verb, and this could
> have unexpected results if caching were enabled. To explicitly disable
> caching for GET, one must be able to create a specific header, something
> that is again not (yet) possible in pure XSLT/XPath. Ideally we should be
> able to use the POST or PUT verb for such service-endpoints.
>
> I also understand that one may want to get the log represented as an XML
> document, but again, let us leave this serialization to the respective
> service endpoint -- it should be none of our business how the data is
> actually organized behind the curtains.
>
> Thanks,
> Dimitre
>
> On Sun, Mar 12, 2023 at 1:11b/PM Jean-Luc Chevillard
> jeanluc.chevillard@xxxxxxxxx <xsl-list-service@xxxxxxxxxxxxxxxxxxxxxx>
> wrote:
>
>> Dear list members,
>>
>> I have been wondering for a long time whether there was a method for
>> automatically recording some elements of information every time I run
>> a given script.
>>
>> As a minimum example, I would start with an empty file
>> +++++++++++++++
>> <?xml version="1.0" encoding="UTF-8"?>
>> <log>
>> </log>
>> +++++++++++++++++++++++
>>
>> After running the script once, the file would become
>> +++++++++++++++
>> <?xml version="1.0" encoding="UTF-8"?>
>> <log>
>>    <entry>[2023-03-12 (19:53)]</entry>
>> </log>
>> +++++++++++++++++++++++
>>
>> After running the script a second time, one hour later, the file would
>> become
>> +++++++++++++++
>> <?xml version="1.0" encoding="UTF-8"?>
>> <log>
>>    <entry>[2023-03-12 (20:53)]</entry>
>>   <entry>[2023-03-12 (19:53)]</entry>
>> </log>
>> +++++++++++++++++++++++
>>
>> I have just tried doing this by applying the script at the bottom of
>> this message (in which "copy.xslt" is the identity transform) to a
>> base file, but as I expected, I obtained an error message stating:
>>
>> System ID: C:\JLC\XML_tests\cEnAvaraiyam\log_book_experiment.xslt
>> Scenario: 4a_log_experiment
>> XML file: C:\JLC\XML_tests\cEnAvaraiyam\cEnA_MSS_rectangles_chart.xml
>> XSL file: C:\JLC\XML_tests\cEnAvaraiyam\log_book_experiment.xslt
>> Engine name: Saxon-PE 11.4
>> Severity: fatal
>> Problem ID: XTRE1500
>> Description: Cannot read a document that was written during the same
>> transformation:
>> file:/C:/JLC/XML_tests/cEnAvaraiyam/experimental_log_book.xml
>> Start location: 17:63
>> Length: 1
>> URL: http://www.w3.org/TR/xslt20/#err-XTRE1500
>>
>> Is there a method for obtaining the desired result by using XSLT?
>>
>> Thanks for your answers
>>
>> -- Jean-Luc
>>
>> ++++++++++++++++++++++++++++
>> log_book_experiment.xslt
>> ++++++++++++++++++++++++++++
>> <?xml version="1.0" encoding="UTF-8"?>
>> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform";
>>     xmlns:xs="http://www.w3.org/2001/XMLSchema";
>>     exclude-result-prefixes="xs"
>>     version="2.0">
>>
>>     <xsl:import href="copy.xslt"/>
>>
>>     <xsl:output method="xml" encoding="UTF-8" indent="yes"/>
>>
>>     <xsl:variable name="TIME_STAMP"
>> select="concat('[',format-date(current-date(), '[Y]-[M02]-[D02]'), '
>> (', format-time(current-time(), '[H]:[m]'), ')]')"/>
>>
>>     <xsl:variable name="Log_file_name"
>> select="'experimental_log_book.xml'"/>
>>
>>     <xsl:variable name="current_log_content"
>> select="document($Log_file_name)"/>
>>
>>     <xsl:variable name="new_log_content">
>>         <log>
>>             <entry><xsl:value-of select="$TIME_STAMP"/></entry>
>>             <xsl:for-each select="$current_log_content//entry">
>>                 <xsl:copy-of select="."/>
>>             </xsl:for-each>
>>         </log>
>>     </xsl:variable>
>>
>>     <xsl:template match="/">
>>         <xsl:result-document href="{$Log_file_name}">
>>             <xsl:copy-of select="$new_log_content"></xsl:copy-of>
>>         </xsl:result-document>
>>         <xsl:apply-templates select="root"/>
>>     </xsl:template>
>>
>>
>> </xsl:stylesheet>
>> +++++++++++++++++++++++++++++++++
>>
>>
>>
>
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