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338 lines (259 loc) · 10.3 KB
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"""
Utility functions for working with and reasoning about Java types.
"""
from typing import Any, Callable, Sequence, Tuple, Union
import jpype
from scyjava._jvm import jimport, jvm_started, start_jvm
from scyjava.config import Mode, mode
class JavaClasses:
"""
Utility class used to make importing frequently-used Java classes
significantly easier and more readable.
Benefits:
* Minimal boilerplate
* Lazy evaluation
* Usable within type hints
Example:
from scyjava import JavaClasses
class MyJavaClasses(JavaClasses):
@JavaClasses.java_import
def String(self): return "java.lang.String"
@JavaClasses.java_import
def Integer(self): return "java.lang.Integer"
# ... and many more ...
jc = MyJavaClasses()
def parse_number_with_java(s: "jc.String") -> "jc.Integer":
return jc.Integer.parseInt(s)
"""
def java_import(func: Callable[[], str]) -> property:
"""
A decorator used to lazily evaluate a java import.
func is a function of a Python class that takes no arguments and
returns a string identifying a Java class by name.
Using that function, this decorator creates a property
that when called, imports the class identified by the function.
"""
@property
def inner(self):
if not jvm_started():
raise Exception()
try:
return jimport(func(self))
except TypeError:
return None
return inner
def jclass(data):
"""
Obtain a Java class object.
Supported types include:
A. Name of a class to look up -- e.g. "java.lang.String" --
which returns the equivalent of Class.forName("java.lang.String").
B. A static-style class reference -- e.g. String --
which returns the equivalent of String.class.
C. A Java object -- e.g. foo --
which returns the equivalent of foo.getClass().
Note that if you pass a java.lang.Class object, you will get back Class.class,
i.e. the Java class for the Class class. :-)
:param data: The object from which to glean the class.
:return: A java.lang.Class object, suitable for use with reflection.
:raise TypeError: if the argument is not one of the aforementioned types.
"""
if isinstance(data, str):
# Name of a class -- case (A) above.
return jclass(jimport(data))
if mode == Mode.JPYPE:
start_jvm()
if isinstance(data, jpype.JClass):
# JPype object representing a static-style class -- case (B) above.
return data.class_
elif mode == Mode.JEP:
if str(type(data.getClass())) == "<class 'jep.PyJClass'>":
# Jep object representing a static-style class -- case (B) above.
raise ValueError(
"Jep does not support Java class objects "
+ "-- see https://github.com/ninia/jep/issues/405"
)
# A Java object -- case (C) above.
if jinstance(data, "java.lang.Object"):
return data.getClass()
raise TypeError("Cannot glean class from data of type: " + str(type(data)))
def jstacktrace(exc) -> str:
"""
Extract the Java-side stack trace from a Java exception.
Example of usage:
from scyjava import jimport, jstacktrace
try:
Integer = jimport('java.lang.Integer')
nan = Integer.parseInt('not a number')
except Exception as exc:
print(jstacktrace(exc))
:param exc: The Java Throwable from which to extract the stack trace.
:return: A multi-line string containing the stack trace, or empty string
if no stack trace could be extracted.
"""
try:
StringWriter = jimport("java.io.StringWriter")
PrintWriter = jimport("java.io.PrintWriter")
sw = StringWriter()
exc.printStackTrace(PrintWriter(sw, True))
return str(sw)
except BaseException:
return ""
def isjava(data) -> bool:
"""Return whether the given data object is a Java object."""
if mode == Mode.JEP:
return jinstance(data, "java.lang.Object")
assert mode == Mode.JPYPE
return isinstance(data, jpype.JClass) or isinstance(data, jpype.JObject)
def is_jbyte(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Byte")
def is_jshort(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Short")
def is_jinteger(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Integer")
def is_jlong(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Long")
def is_jfloat(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Float")
def is_jdouble(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Double")
def is_jboolean(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Boolean")
def is_jcharacter(the_type: type) -> bool:
return _is_jtype(the_type, "java.lang.Character")
def is_jarray(data: Any) -> bool:
"""Return whether the given data object is a Java array."""
if mode == Mode.JEP:
return str(type(data)) == "<class 'jep.PyJArray'>"
assert mode == Mode.JPYPE
return isinstance(data, jpype.JArray)
def jinstance(obj, jtype) -> bool:
"""
Test if the given object is an instance of a particular Java type.
:param obj: The object to check.
:param jtype: The Java type, as either a jimported class or as a string.
:return: True iff the object is an instance of that Java type.
"""
if isinstance(jtype, str):
jtype = jimport(jtype)
if mode == Mode.JEP:
return isinstance(obj, jtype.__pytype__)
assert mode == Mode.JPYPE
return isinstance(obj, jtype)
def jarray(kind, lengths: Sequence):
"""
Create a new n-dimensional Java array.
:param kind: The type of array to create. This can either be a particular
type of object as obtained from jimport, or else a special code for one of
the eight primitive array types:
* 'b' for byte
* 'c' for char
* 'd' for double
* 'f' for float
* 'i' for int
* 'j' for long
* 's' for short
* 'z' for boolean
:param lengths: List of lengths for the array. For example:
`jarray('z', [3, 7])` is the equivalent of `new boolean[3][7]` in Java.
You can pass a single integer to make a 1-dimensional array of that length.
:return: The newly allocated array
"""
if isinstance(kind, str):
kind = kind.lower()
if isinstance(lengths, int):
lengths = [lengths]
arraytype = kind
if mode == Mode.JEP:
import jep # noqa: F401
if len(lengths) == 1:
# Fast case: 1-d array (we can use primitives)
arr = jep.jarray(lengths[0], arraytype)
else:
# Slow case: n-d array (we cannot use primitives)
# See https://github.com/ninia/jep/issues/439
kinds = {
"b": jimport("java.lang.Byte"),
"c": jimport("java.lang.Character"),
"d": jimport("java.lang.Double"),
"f": jimport("java.lang.Float"),
"i": jimport("java.lang.Integer"),
"j": jimport("java.lang.Long"),
"s": jimport("java.lang.Short"),
"z": jimport("java.lang.Boolean"),
}
if arraytype in kinds:
arraytype = kinds[arraytype]
kind = arraytype
# build up the array type
for _ in range(len(lengths) - 1):
arraytype = jep.jarray(0, arraytype)
# instantiate the n-dimensional array
arr = jep.jarray(lengths[0], arraytype)
elif mode == Mode.JPYPE:
start_jvm()
# build up the array type
kinds = {
"b": jpype.JByte,
"c": jpype.JChar,
"d": jpype.JDouble,
"f": jpype.JFloat,
"i": jpype.JInt,
"j": jpype.JLong,
"s": jpype.JShort,
"z": jpype.JBoolean,
}
if arraytype in kinds:
arraytype = kinds[arraytype]
for _ in range(len(lengths)):
arraytype = jpype.JArray(arraytype)
# instantiate the n-dimensional array
arr = arraytype(lengths[0])
else:
raise RuntimeError(f"Invalid mode: {mode}")
if len(lengths) > 1:
for i in range(len(arr)):
arr[i] = jarray(kind, lengths[1:])
return arr
def numeric_bounds(
the_type: type,
) -> Union[Tuple[int, int], Tuple[float, float], Tuple[None, None]]:
"""
Get the minimum and maximum values for the given numeric type.
For example, a Java long returns (int(Long.MIN_VALUE), int(Long.MAX_VALUE)),
whereas a Java double returns (float(-Double.MAX_VALUE), float(Double.MAX_VALUE)).
:param the_type: The type whose minimum and maximum values are needed.
:return:
The minimum and maximum values as a two-element tuple of int or float,
or a two-element tuple of None if no known bounds.
"""
if is_jbyte(the_type):
Byte = jimport("java.lang.Byte")
return int(Byte.MIN_VALUE), int(Byte.MAX_VALUE)
if is_jshort(the_type):
Short = jimport("java.lang.Short")
return int(Short.MIN_VALUE), int(Short.MAX_VALUE)
if is_jinteger(the_type):
Integer = jimport("java.lang.Integer")
return int(Integer.MIN_VALUE), int(Integer.MAX_VALUE)
if is_jlong(the_type):
Long = jimport("java.lang.Long")
return int(Long.MIN_VALUE), int(Long.MAX_VALUE)
if is_jfloat(the_type):
Float = jimport("java.lang.Float")
return float(-Float.MAX_VALUE), float(Float.MAX_VALUE)
if is_jdouble(the_type):
Double = jimport("java.lang.Double")
return float(-Double.MAX_VALUE), float(Double.MAX_VALUE)
return None, None
def _is_jtype(the_type: type, class_name: str) -> bool:
"""
Test if the given type object is *exactly* the specified Java type.
:param the_type: The type object to check.
:param class_name: The fully qualified Java class name in string form.
:return: True iff the type is exactly that Java type.
"""
# NB: Stringify the type to support both bridge modes. Ex:
# * JPype: <java class 'java.lang.Integer'>
# * Jep: <class 'java.lang.Integer'>
return f"class '{class_name}'" in str(the_type)
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