jsaxonpy 0.7.2

Java Saxon XSLT transformations in your python applications

JSaxonPy

jsaxonpy - the python package to be used for your Java Saxon XSLT transformations in your python applications.

Installation

pip install jsaxonpy

Quick overview

>>> from jsaxonpy import Xslt
>>> t = Xslt()
>>> xml = "<root><child>text</child></root>"
>>> xsl = """
<xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
  <xsl:template match="/">
    <xsl:copy-of select="."/>
  </xsl:template>
</xsl:stylesheet>
"""
>>> t.transform(xml, xsl)
'<?xml version="1.0" encoding="UTF-8"?><root><child>text</child></root>'

You can supply params if you needed as python dictioary with keys & values as strings (str type).

>>> params = {"param1": "value1", "param2": "value2"}
>>> out = t.transform(xml, xsl, params)

xml and xsl arguments could be either string documents (str type) or files names wrapped into pathlib.Path(...) class, before being passed.

Also you can run transformations using threads or multiple processes using concurrent.futures or multiprocessing modules. The only known limitation is not to run transformations (using Xslt class) using multi-processing in parent process, you can successfully run it in children. If you try to run in parent process and in children processes, then you application would hang. With threading instantiation of Xslt class works both in main thread and in children threads.

Examples

Plain

from pathlib import Path

from jsaxonpy import Xslt


t = Xslt()
xml = Path("file.xml")
xsl = Path("file.xsl")
print(t.transform(xml, xsl))

would produce:

<?xml version="1.0" encoding="UTF-8"?><root><child>text</child></root>

Threads

from concurrent.futures import ThreadPoolExecutor
from pathlib import Path

from jsaxonpy import Xslt

def func(args):
    xml, xsl = args
    t = Xslt()
    out = t.transform(xml, xsl)
    return out

xsl_path = Path('file.xsl')
worker_args = []

with ThreadPoolExecutor(max_workers=3) as executor:
  for xml_path in map(lambda f: Path(f), ["file1.xml", ..., "fileN.xml"]):
    worker_args.append((xml_path, xsl_path))
    for out in executor.map(func, worker_args):
      assert out == xml

Processes

from concurrent.futures import ProcessPoolExecutor
from pathlib import Path

from jsaxonpy import Xslt

def func(args):
    xml, xsl = args
    t = Xslt()
    out = t.transform(xml, xsl)
    return out

xsl_path = Path('file.xsl')
worker_args = []

with ProcessPoolExecutor(max_workers=3) as executor:
  for xml_path in map(lambda f: Path(f), ["file1.xml", ..., "fileN.xml"]):
    worker_args.append((xml_path, xsl_path))
    for out in executor.map(func, worker_args):
      assert out == xml

GCP Functions

import os, threading
from timeit import default_timer as timer

import functions_framework

from jdk4py import JAVA, JAVA_HOME, JAVA_VERSION
from saxonhe4py import SAXON_HE_JAR
from jsaxonpy import Xslt

# following env variable must be defined, otherwise pyjnius would fail
os.environ["JAVA_HOME"] = str(JAVA_HOME)
os.environ["JDK_HOME"] = str(JAVA_HOME)

# to find the location of Saxon HE
os.environ["CLASSPATH"] = str(SAXON_HE_JAR)

# setup JVM options
os.environ["JVM_OPTIONS"] = "-Xmx64m"


@functions_framework.http
def transform(request):
    #
    thread_id = threading.get_native_id()
    process_id = os.getpid()

    #
    timer_xslt_started = timer()
    t = Xslt() # do not move this from function.
    timer_xslt_ended = timer()

    #
    xml = "<p>Paragraph text</p>"
    xsl = """
    <xsl:stylesheet version="1.0" xmlns:xsl="http://www.w3.org/1999/XSL/Transform">
    <xsl:template match="/">
      <xsl:copy-of select="."/>
    </xsl:template>
    </xsl:stylesheet>
    """

    #
    timer_transform_started = timer()
    output=t.transform(xml, xsl)
    timer_transform_ended = timer()

    return (
      f"{output}\n"
      f"timer(Xslt)      = {timer_xslt_ended - timer_xslt_started:.6f}\n"
      f"timer(transform) = {timer_transform_ended - timer_transform_started:.6f}\n"
      f"thread_id={thread_id} process_id={process_id}\n"
    )

Notes

The following versions of Saxon were tested 9, 10, 11.

XML Catalog resolution is available for Saxon 11.

Before executing you application it is expected you set your java related environment variables, including the CLASSPATH to point to your Java Saxon installation.

You can use JVM_OPTIONS environment variable to set java virtual environment, see example below.

export JVM_OPTIONS="-Xrs -Xmx4096m -XX:ActiveProcessorCount=24";
export CLASSPATH=/usr/local/Saxon-J/saxon-he-11.4.jar;
your_python_app.py

When you pass the same xsl path it is actually being compiled once for the time of the life of the process/thread, which means you do not need to do any special steps to compile those to speed up transformations.

Development note

Based on github issue Passing PythonJavaClass object to Java method/class does not increase Python ref counter to avoid undefined values passed to Saxon code (JVM) it is suggested to assign Python's autoclass or cast derivatives PythonJavaClass to python variables. An example:

instead of:

transformer.setParameter(QName(name), XdmAtomicValue(value))

write:

qname= QName(name)
xdm_atomic_value = XdmAtomicValue(value)
transformer.setParameter(qname, xdm_atomic_value)

API

class JVM

 1 Help on class JVM in module jsaxonpy.jvm:
 2
 3 class JVM(builtins.object)
 4  |  JVM(*args, **kwargs)
 5  |
 6  |  Methods defined here:
 7  |
 8  |  __init__(self)
 9  |      Initialize self.  See help(type(self)) for accurate signature.
10  |

class Xslt

 1 Help on class Xslt in module jsaxonpy.xslt:
 2
 3 class Xslt(InterfaceXslt)
 4  |  Xslt(catalog: Optional[pathlib.Path] = None, jvm: Optional[jsaxonpy.jvm.JVM] = None, licensed_edition: bool = False)
 5  |
 6  |  Xslt class exposes transformations based on Java Saxon transform() method of
 7  |  net.sf.saxon.s9api.XsltTransformer class.
 8  |
 9  |  Notes:
10  |      If you plan to use multiprocessing, then do not instantiate Xslt class
11  |      in parent process because saxon compiler hangs if parent process has jnius
12  |      JVM machine running already.
13  |
14  |  Method resolution order:
15  |      Xslt
16  |      InterfaceXslt
17  |      abc.ABC
18  |      builtins.object
19  |
20  |  Methods defined here:
21  |
22  |  __init__(self, catalog: Optional[pathlib.Path] = None, jvm: Optional[jsaxonpy.jvm.JVM] = None, licensed_edition: bool = False)
23  |      Initializer for Xslt class.
24  |
25  |      Args:
26  |          @catalog (Optional[Path], optional):
27  |              Path to catalog file, optional. Defaults to None.
28  |          @jvm (Optional[JVM], optional):
29  |              optional instance of `JVM` class. Defaults to None.
30  |          @licensed_edition (bool, optional):
31  |              Indicate if you run on Licensed edition. Defaults to False.
32  |
33  |  transform(self, xml: Union[pathlib.Path, str], xsl: Union[pathlib.Path, str], params: Dict[str, str] = {}, pretty: bool = False) -> str
34  |      `transform` method executes the transformation of the input XML string
35  |      or file with provided XSL code and optional XSL parameters.
36  |      You can pass Stylesheet Export File (SEF) in place of `xsl` argument instead
37  |      of regular XSL file path.
38  |
39  |      Args:
40  |          @xml (InputSource):
41  |              XML markup (string) or file pathlib.Path("path/to/file.xml")
42  |          @xsl (InputSource):
43  |              XSL code (string) or file pathlib.Path("path/to/file.xsl")
44  |          @params (XsltParams, optional):
45  |              XSL parameters. Defaults to {}.
46  |          @pretty (bool, optional):
47  |              Format output pretty. Defaults to False.
48  |
49  |      Returns:
50  |          str: The output of the transformation
51  |
52  |      Notes:
53  |          The following types `InputSource`, `XsltParams` are defined as following:
54  |
55  |          InputSource = Union[Path, str]
56  |          XsltParams = Dict[str, str]
57  |
58  |  ----------------------------------------------------------------------
59  |  Readonly properties defined here:
60  |
61  |  is_catalog_supported
62  |
63  |  saxon_major_version
64  |
65  |  saxon_version
66  |