100 lines
3.6 KiB
Python
100 lines
3.6 KiB
Python
# *****************************************************************************
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# See NOTICE file for details.
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#
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# *****************************************************************************
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"""
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JPype Beans Module
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------------------
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This customizer finds all occurences of methods with get or set and converts
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them into Python properties. This behavior is sometimes useful in programming
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with JPype with interactive shells, but also leads to a lot of confusion.
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Is this class exposing a variable or is this a property added JPype.
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As an unnecessary behavior that violates both the Python principle
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*"There should be one-- and preferably only one --obvious way to do it."* and
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the C++ principle *"You only pay for what you use"*. This misfeature
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was removed from the distribution as a default. However, given that it is
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useful to have methods appear as properties, it was moved to a
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an optional module.
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To use beans as properties:
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.. code-block:: python
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import jpype.beans
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The beans property modification is a global behavior and applies retroactively
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to all classes currently loaded. Once started it can not be undone.
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"""
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import _jpype
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from . import _jcustomizer
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from ._pykeywords import pysafe as _pysafe
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def _extract_accessor_pairs(members):
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"""Extract pairs of corresponding property access methods
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(getter and setter) from a Java class's members (attributes).
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If a public method with a property's name exists no pair for
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that property will be extracted.
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Returns a dictionary with the property name as key and a tuple
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of (getter method, setter method) as value. A tuple element
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value might be `None` if only a getter or only a setter
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exists.
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"""
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accessor_pairs = {}
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for name, member in members.items():
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if not isinstance(member, _jpype._JMethod) or len(name) <= 3:
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continue
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if name == "getClass":
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continue
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if member._isBeanAccessor():
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property_name = name[3].lower() + name[4:]
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try:
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pair = accessor_pairs[property_name]
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pair[0] = member
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except KeyError:
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accessor_pairs[property_name] = [member, None]
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elif member._isBeanMutator():
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property_name = name[3].lower() + name[4:]
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try:
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pair = accessor_pairs[property_name]
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pair[1] = member
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except KeyError:
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accessor_pairs[property_name] = [None, member]
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return accessor_pairs
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@_jcustomizer.JImplementationFor("java.lang.Object")
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class _BeansCustomizer(object):
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""" Add properties for get/set Bean patterns found in classes. """
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def __jclass_init__(self):
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accessor_pairs = _extract_accessor_pairs(self.__dict__)
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for attr_name, (getter, setter) in accessor_pairs.items():
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attr_name = _pysafe(attr_name)
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# Don't mess with an existing member
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if attr_name is None or attr_name in self.__dict__:
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continue
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# Add the property
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self._customize(attr_name, property(getter, setter))
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