I provide this for you
to hopefully save you some time and pain.
As part of my expereince in getting
to know NB Development v7 on my Windows 64-bit workstation I found another frustrating adventure in trying
to get
the JNI (Java Native Interface) abilities up and working in my project. As such, I am including a brief summary of steps required (as all
the documentation I found was completely incorrect for these versions of Windows and NetBeans on how
to do JNI). It took a couple of days of experimentation and reviewing every webpage I could find that included these technologies as keyword searches. Yuk!! Not fun.
To begin, as NetBeans Development is "all about modules" if you are reading this you probably have a need for one, or more, of your modules
to perform JNI calls. Most of what is available on this site or
the Internet in general (not
to mention
the help file in NB7) is either completely wrong for these versions, or so sparse as
to be essentially unuseful
to anyone other than a JNI expert.
Here is what you are looking for ...
the "cut
to the chase" - "how
to guide"
to get a JNI call up and working on your NB7 / Windows 64-bit box.
1) From within your NetBeans Module (not
the host appliation) declair your native method(s) and make sure you can compile
the Java source without errors.
Example:
package org.mycompanyname.nativelogic;
public class NativeInterfaceTest
{
static
{
try
{
if (System.getProperty( "os.arch" ).toLowerCase().equals( "amd64" ) )
System.loadLibrary( <64-bit_folder_name_on_file_system>/<file_name.dll> );
else
System.loadLibrary( <32-bit_folder_name_on_file_system>/<file_name.dll> );
}
catch (SecurityException se) {}
catch (UnsatisfieldLinkError ule) {}
catch (NullPointerException npe) {}
}
public NativeInterfaceTest() {}
native String echoString(String s);
}
Take notice
to the fact that we only load
the Assembly once (as it's in a static block), because othersise you will throw exceptions if attempting
to load it again. Also take note of our single (in this example) native method titled "echoString". This is
the method that our C / C++ application is going
to implement, then via
the majic of JNI we'll call from our Java code.
2) If using a 64-bit version of Windows (which we are here) we need
to open a 64-bit Visual Studio Command Prompt (versus
the standard 32-bit version), and execute
the "vcvarsall" BAT file, along with an "amd64" command line argument,
to set
the environment up for 64-bit tools.
Example:
<path_to_Microsoft_Visual_Studio_10.0>/VC/vcvarsall.bat amd64
Take note that you can use any version of
the C / C++ compiler from Microsoft you wish. I happen
to have Visual Studio 2005, 2008, and 2010 installed on my box so I chose
to use "v10.0" but any that support 64-bit development will work fine.
The other important aspect here is
the "amd64" param.
3) In
the Command Prompt change drives \ directories on your computer so that you are at
the root of
the fully qualified Class location on
the file system that contains your native method declairation.
Example:
The fully qualified class name for my natively declair method is "org.mycompanyname.nativelogic.NativeInterfaceTest". As we successfully compiled our Java in Step 1 above, we should find it contained in our NetBeans Module something similar
to the following:
"/build/classes/org/mycompanyname/nativelogic/NativeInterfaceTest.class"
We need
to make sure our Command Prompt sets, as
the current directly, "/build/classes" because of our next step.
4) In this step we'll create our C / C++ Header file that contains
the JNI required statments. Type
the following in
the Command Prompt:
javah -jni org.mycompanyname.nativelogic.NativeInterfaceTest and hit enter. If you receive any kind of error that states this is an unrecognized command that simply means your Windows computer does not know
the PATH
to that command (it's in your /bin folder). Either run
the command from there, or include
the fully qualified path name when invoking this application, or set your computer's PATH environmental variable
to include that path in its search.
This should produce a file called "org_mycompanyname_nativelogic_NativeInterfaceTest.h" ... a C Header file. I'd make a copy of this in case you need a backup later.
5) Edit
the NativeInterfaceTest.h header file and include an implementation for
the echoString() method.
Example:
JNIEXPORT jstring JNICALL Java_org_mycompanyname_nativelogic_NativeInterfaceTest_echoString
(JNIEnv *env, jobject jobj, jstring js)
{
return((*env)->NewStringUTF(env, "My JNI is up and working after lots of research"));
}
Notice how you can't simply return a normal Java String (because you're in C at
the moment). You have
to tell
the passed in JVM variable
to create a Java String for you that will be returned back. Check out
the following Oracle web page for other data types and how
to create them for JNI purposes.
6) Close and Save your changes
to the Header file. Now that you've added an implementation
to the Header change
the file extention from ".h"
to ".c" as it's now a C source code file that properly implements
the JNI required interface.
Example:
NativeInterfaceTest.c
7) We need
to compile
the newly created source code file and Link it too. From within
the Command Prompt type
the following:
cl /I"path_to_my_jdks_include_folder" /I"path_to_my_jdks_include_win32_folder" /D:AMD64=1 /LD NativeInterfaceTest.c /FeNativeInterfaceTest.dll /link /machine:x64
Example:
cl /I"D:/Program Files/Java/jdk1.6.0_21/include" /I"D:/Program Files/java/jdk1.6.0_21/include/win32" /D:AMD64=1 /LD NativeInterfaceTest.c /FeNativeInterfaceTest.dll /link /machine:x64
Notice
the quotes around
the paths
to the 'include" and 'include/win32' folders is required because I have spaces in my folder names ... 'Program Files'. You can include them if you have no spaces without problems, but they are mandatory if you have spaces when using a command prompt.
This will generate serveral files, but it's
the DLL we're interested in. This is what
the System.loadLirbary() java method is looking for.
8) Congratuations! You're at
the last step. Simply take
the DLL Assembly and paste it at
the following location:
<path_of_NetBeansProjects_folder>/<project_name>/<module_name>/build/cluster/modules/lib/x64
Note that you'll probably have
to create
the "lib" and "x64" folders.
Example:
C:\Users\<user_name>\Documents\NetBeansProjects\<application_name>\<module_name>\build\cluster\modules\lib\x64\NativeInterfaceTest.dll
Java code ... notice how we don't inlude
the ".dll" file extension in
the loadLibrary() call?
System.loadLibrary( "/x64/NativeInterfaceTest" );
Now, in your Java code you can create a NativeInterfaceTest object and call
the echoString() method and it will return
the String value you typed in
the NativeInterfaceTest.c source code file.
Hopefully this will save you
the brain damage I endured trying
to figure all this out on my own. Good luck and happy coding!
