Py4J - A Bridge between Python and Java

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# 8. Changelog

The changelog describes in plain English the changes that occurred between Py4J releases.

## 8.1. Py4J 0.9

- Python side: constructor parameters have been deprecated in favor of GatewayParameters and CallbackServerParameters. This was necessary because the number of configuration options is growing fast. Old parameters will be supported until Py4J 1.0 (at least two more minor versions).
- Python side: IDEs and interactive interpreters such as IPython can now get help text/autocompletion for Java classes, objects, and members. This makes Py4J an ideal tool to explore complex Java APIs (e.g., the Eclipse API). Thanks to @jonahkichwacoders
- Python side: the callback gateway server (necessary for Java to call back Python functions) can be daemonized and can be started after the main JavaGateway is started.
- Python side: py4j.java_gateway.launch_gateway has now a cleaner implementation that discards stdout and stderr output by default. It is also possible to redirect the output from these channels to separate files, deques, or queues. Thanks to @davidcsterratt for finding the root cause and work on the fix.
- It is now possible to install Py4J from git with pip: pip install git+https://github.com/bartdag/py4j.git
- The Eclipse components of Py4J have been moved to another repository. Existing forks and pull requests can still use the @before-eclipse-split branch until Py4J reaches 1.0. Fixes won’t be backported to this branch, but pull requests will be merged by the main maintainer to @master if requested.
- Major cleanup of Python source code to make it fully flake8 (pep8 + pyflakes) compliant. This should be easier to contribute now.
- Major test cleanup effort to make Python tests more reliable. Testing Py4J is difficult because there are many versions of Python and Java to test and Python 2.6 lacks many interesting test features. Effort to make tests even more robust will continue in the next milestone.
- We introduced a contributing guide and an implicit contributor license agreement that indicates that anyone contributing to Py4J keeps the copyright of the contribution but gives a non-revokable right to license the code using Py4J’s license (3-clause BSD). The copyright statement has been changed to “Copyright (c) 2009-2015, Barthelemy Dagenais and individual contributors. All rights reserved.” to make it clear that individual contributors retain copyrights of their contributions. An AUTHORS.txt file has been added to the repository to keep track of contributors: if your name is not in the file and you have contributed to Py4J, do not hesitate to write on the mailing list or open a pull request.
- Cleaned up the doc that was referring to broken links or refactored classes. Long-time users may want to review the advanced topics page.
- Added support for Python Wheels.
- We have a new website: https://www.py4j.org
- We have a new blog: https://blog.py4j.org
- Eclipse features have moved to: http://eclipse.py4j.org
- We have a new mailing list.
- github 0.9 milestone

## 8.2. Py4J 0.8.2.1

- Fixed a test that used an assert method that does not exist in Python 2.6

## 8.3. Py4J 0.8.2

- Fixed constructors not being able to pass proxy (python classes implementing Java interfaces)
- Java 6 compatibility was restored in compiled jar file.
- Fixed unit tests for JDK 8
- Added a few extra paths to find_jar_path
- github 0.8.2 milestone

## 8.4. Py4J 0.8.1

- Fixed a bug in type inference when interface hierarchy is deeper than abstract class hierarchy.
- Added a utility method `is_instance_of` in py4j.java_gateway to determine if a JavaObject is an instance of a class.
- Released Py4J in central Maven repository.
- github 0.8.1 milestone

## 8.5. Py4J 0.8

- Major fix to the Java byte[] support. Thanks to @agronholm for spotting this subtle but major issue and thanks to @fdinto from The Atlantic for providing a patch!
- Ability to fail early if the py4j.java_gateway.JavaGateway cannot connect to the JVM.
- Added support for long primitives, BigDecimal, enum types, and inner classes on the Java side.
- Set saner log levels
- Many small bug fixes and API enhancements (backward compatible).
- Wrote a section in the FAQ about security concerns and precautions with Py4J.
- Added support of Travis-CI and cleaned up the test suite to remove hardcoded paths.
- github 0.8 milestone

## 8.6. Py4J 0.7

- Major refactoring to support Python 3. Thanks to Alex Grönholm for his patch.
- The build and setup files have been totally changed. Py4J no longer requires Paver to build and everything is done through ant. The setup.py file only uses distutils.
- Added support for Java byte[]: byte array are passed by value and converted to bytearray or bytes.
- Py4J package name changed from Py4J to py4j.
- Bug fixes in the Python callback server and unicode support.
- github 0.7 milestone

## 8.7. Py4J 0.6

- Added new exception `Py4JJavaError` that enables Python client programs to access instance of Java exception thrown in the Java client code.
- Improved Py4J setup: no more warnings displayed when installing Py4J.
- Bug fixes and API additions.
- github 0.6 milestone

## 8.8. Py4J 0.5

- Added the ability to import packages (e.g., `java_import(gateway.jvm, 'java.io.*')`)
- Added support for pattern filtering in `JavaGateway.help()` (e.g., `gateway.help(obj,'get*Foo*Bar')`)
- Added support for automatic conversion of Python collections (list, set, dictionary) to Java collections. User `JavaGateway(auto_convert=True)` or an explicit convertor.
- Created two Eclipse features: one embeds the Py4J Java library. The other provides a default GatewayServer that is started when Eclipse starts. Both features are available on the new Py4J Eclipse update site: `http://www.py4j.org/py4j_eclipse`
- Redesigned the module decomposition of Py4J: there are no more mandatory circular dependencies among modules.
- github 0.5 milestone

## 8.9. Py4J 0.4

- Polishing of existing features: fields can be set (not just read), None is accepted as a method parameter, methods are sorted alhabetically in gateway.help(), etc.
- Java Exception Stack Trace are now propagated to Python side.
- Changed interfaces member in Callback classes to implements.
- Internal refactoring to adopt clearer terminology and make Py4J protocol extensible.
- Many bug fixes: most are related to the callback feature.
- github 0.4 milestone

## 8.10. Py4J 0.3

- Added support for Java arrays and set.
- Added support for callbacks: Java objects can now call back Python objects.
- Completely redesigned threading and connection model of Py4J to allow multiple threads and callbacks on both side.
- Refactored the memory management to ensure best effort garbage collection.
- github 0.3 milestone

## 8.11. Py4J 0.2

- It is now possible to call constructors and reference static members: use the jvm member of a JavaGateway object.
- Java Map is converted to a Python Dictionary.
- Field access is supported through the `get_field` function or the `auto_field=True` member of JavaGateway.
- Obtain an interactive help page with `JavaGateway.help(object)`.
- Set is only accessible through the Java Set interface for now.
- Arrays can be referenced, but individual items can only be accessed with this workaround: `gateway.jvm.java.lang.reflect.Array.get(object,index)`.
- Complete rewrite of the reflection engine on the Java side for more flexibility.
- Improved memory model: no more memory leak caused by Py4J.
- New concurrency model: Py4J is now thread-safe.
- github 0.2 milestone

## 8.12. Py4J 0.1

- This is the first release.
- Basic features like connecting to a JVM and calling methods are implemented.
- Java List is converted to a Python List.
- Field access, constructors, and static classes are NOT accessible yet.
- Dictionary and Set are only accessible through the Java Map and Set interface for now.
- Arrays can be referenced, but individual items cannot be accessed yet.
- github 0.1 milestone

### Questions/Feedback?

- Try the FAQ -- It answers many questions.
- Search for information in the archives of the py4j-users mailing list, or post a question.
- If you notice errors with this documentation, open a ticket and let us know. Please, only open a ticket for feedback or improvements on the docs. To get help, use the links above!

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