Is There a Java Library to Access the Native Windows API

Is there a Java library to access the native Windows API?

You could try these two, I have seen success with both.

http://jawinproject.sourceforge.net

The Java/Win32 integration project
(Jawin) is a free, open source
architecture for interoperation
between Java and components exposed
through Microsoft's Component Object
Model (COM) or through Win32 Dynamic
Link Libraries (DLLs).

https://github.com/twall/jna/

JNA provides Java programs easy access
to native shared libraries (DLLs on
Windows) without writing anything but
Java code—no JNI or native code is
required. This functionality is
comparable to Windows' Platform/Invoke
and Python's ctypes. Access is dynamic
at runtime without code generation.

JNA allows you to call directly into
native functions using natural Java
method invocation. The Java call looks
just like it does in native code. Most
calls require no special handling or
configuration; no boilerplate or
generated code is required.

Also read up here:

http://en.wikipedia.org/wiki/Java_Native_Interface

The Java Native Interface (JNI) is a
programming framework that allows Java
code running in a Java Virtual Machine
(JVM) to call and to be called1 by
native applications (programs specific
to a hardware and operating system
platform) and libraries written in
other languages, such as C, C++ and
assembly.

http://en.wikipedia.org/wiki/Java_Native_Access

Java Native Access provides Java
programs easy access to native shared
libraries without using the Java
Native Interface. JNA's design aims to
provide native access in a natural way
with a minimum of effort. No
boilerplate or generated glue code is
required.

Is there a Java library for access external windows?

it depends, here is what I found so far.

you can access process names listed on the Task Manager via the Runtime object found here

an explanation on how to use it is on stackoverflow already here.
but you need to know the name of the app you want to find, such as mspaint.exe, msword.exe, myprogram.exe, and so on...

now if you know the executable name, and the application happens to be running, you can use Java's Robot library to get a 'screenshot'. the java API library for Robot is found here and an example of how to use it can be found here. The stackoverflow answer goes into details about using Robot vs another custom tailored approach to just getting a screenshot.

Also note that the pages i linked to are for Java 7, there is also a Java 8 library found here which would be the more current version.

I usually just google "java api X" and whatever I'm looking for.

hope that helps.

Accessing Windows API from a Java application - JNI or JNA?

For general-purpose invocation of native code, JNA tends to be much easier, because you don't have to write a C/C++ stub.

However, it's not always possible to do what you need via JNA. Let me explain why:

I think that for what you want to do, JNI is going to be required.
The issue is that SetWindowsHookEx takes parameters including a pointer to the hook procedure and a handle to the DLL that contains the hook procedure. Windows will be using that info to invoke the hook procedure. As you might imagine, Windows is not going to be able call directly into a method of an object in the JVM.

So, I believe that you're going to have to use JNI to write a dll that will sit between your java app and the Windows API. That dll will contain the actual hook process, and will invoke SetWindowsHookEx for you. The dll's hook process can then use JNI to invoke your java object.

Calling Win32 API method from Java

1. JNA seems the industry standard of what you want, "provides Java programs easy access to native shared libraries (DLLs on Windows) without writing anything but Java code—no JNI or native code is required"

2. There is also Java Foreign Function Interface -
   example usage
   
   If is ok for you, you could embed the JRuby interpreter and call winapi via jruby-ffi wich is a lot easier, see here, here, and here

Using winapi in java application

You need to create a wrapper that will call those functions in the User32 library. Don't call them directly. Take a look at this tutorial http://www.ibm.com/developerworks/java/tutorials/j-jni/.

There are more steps involved then simply loading the library and called the function. Also must note that if you do this, you remove one of the best things of Java. Being able to write once run anywhere. You will be tethered to Windows. If this isnt a problem for you, then no big deal. Are you sure this isnt something you can't do from Java directly. JNI should really be a last resort.

Also, from my experience with JNI, it can lead to unstable applications if not used carefully.

Do you know of a Java library to access the native linux api?

Have a look at JNA.

Here is the summary of JNA from their home page.

JNA provides Java programs easy access to native shared libraries (DLLs on Windows) without writing anything but Java code—no JNI or native code is required. This functionality is comparable to Windows' Platform/Invoke and Python's ctypes. Access is dynamic at runtime without code generation.

See their getting started page for some samples. Like calling native printf.

How can I listen to Windows events from a Java app?

Technolgies which might be useful:

• Java Native Access (JNA) provides Java programs easy access to native shared libraries (DLLs on Windows) without writing anything but Java code—no JNI or native code is required.

• Message oriented Middleware which includes C/C++ drivers, for example Apache ActiveMQ, OpenMQ or xmlBlaster

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