JImport

Module for dynamically loading Java Classes using the import system.

This is a replacement for the jpype.JPackage(“com”).fuzzy.Main type syntax. It features better safety as the objects produced are checked for class existence.

Setup

To enable Java imports, you must first start the JVM and then import the jpype.imports module:

import jpype
import jpype.imports  # Enable Java imports

# Start the JVM
jpype.startJVM()

# Now you can import Java classes
import java.lang
from java.util import ArrayList

Once jpype.imports is imported, Python’s import system will automatically load Java classes and packages as if they were Python modules.

Import Styles

This module supports three different styles of importing java classes.

1) Import of the package path

import <java_package_path>

Importing a series of package creates a path to all classes contained in that package. The root package is added to the global scope. Imported packages are added to the directory of the base module.

import java

mystr = java.lang.String('hello')
mylist = java.util.LinkedList()
path = java.nio.files.Paths.get()

2) Import of the package path as a module

import <java_package> as <var>

A package can be imported as a local variable. This provides access to all Java classes in that package including contained packages.

Example:

import java.nio as nio
bb = nio.ByteBuffer()
path = nio.file.Path()

3) Import a class from an object

from <java_package> import <class>[,<class>*] [as <var>]

An individual class can be imported from a java package. This supports inner classes as well.

Example:

# Import one class
from java.lang import String
mystr = String('hello')

# Import multiple classes
from java.lang import Number,Integer,Double
# Import java inner class java.lang.ProcessBuilder.Redirect
from java.lang.ProcessBuilder import Redirect

This method can also be used to import a static variable or method from a class. Wildcards import all packages and public classes into the global scope.

Import caveats

Keyword naming

Occasionally a java class may contain a python keyword. Python keywords as automatically remapped using trailing underscore.

Example:

from org.raise_ import Object  => imports "org.raise.Object"

Limitations

• Non-static members can be imported but can not be called without an instance. JPype does not provide an easy way to determine which functions objects can be called without an object.