Eclipse calls JNI

Http://blog.chinaunix.net/uid-27003388-id-3235189.html

1. Create a Java project (jni_test) in eclipse;

Create a package in SRC, named Jni;

Then create a Java class (Helloworld.java) with the native declaration method in the JNI, with the following file details:

Package JNI;

public class HelloWorld {

Static {

System. loadLibrary ("HelloWorld");

}

public native void disphelloworld ();

/**

* @param args

*/

public static void main (string[] args) {

// TODO auto-generated method stub

//system.getproperty ("Java.library.path");

new HelloWorld (). Disphelloworld ();

}

}

The Eclipse Engineering Tree chart looks like this:

2. Generating JNI header files

On the command line, CD to the SRC directory of the Java Project (jni_test), for example:

CD E:\WORKSPACE\JNI_TEST\SRC

Then execute the JAVAH-JNI Jni.helloworld (package does not miss out)

The resulting jni_helloworld.h file is as follows

/* Don't EDIT this file-it are machine generated */

#include <jni.h>

/* Header for class Jni_helloworld */

#ifndef _included_jni_helloworld

#define _included_jni_helloworld

#ifdef __cplusplus

extern "C" {

#endif

/*

* Class:jni_helloworld

* Method:disphelloworld

* Signature: () V

*/

jniexport void Jnicall Java_jni_helloworld_disphelloworld

(JNIENV *, jobject);

#ifdef __cplusplus

}

#endif

#endif

The Eclipse Engineering Tree chart is updated as follows:

3. Create jni_helloworldimp.cpp in the SRC directory of the Java Project (jni_test), implement functions in jni_helloworld.h, note the function name, the function name in CPP is consistent with the function name of h file.

Jni_helloworldimp.cpp content is as follows:

#include <jni.h>

#include "Jni_helloworld.h"

#include <stdio.h>

jniexport void Jnicall Java_jni_helloworld_disphelloworld

(jnienv *env, Jobject obj)

{

printf ("Hello world!");

Return

}

The Eclipse Engineering Tree chart is updated as follows:

4. In the Java Engineering (jni_test) SRC directory compilation jni_helloworldimp.cpp produce the DLL,

Under the console >cl-ld Jni_helloworldimp.cpp-fehelloworld.dll,
In the parameters of the above command,-LD represents the name that produces the DLL after Dll,-fe, and the specific parameters can be viewed with the cl-help command.
If compiled successfully, it will produce Helloworld.dll, Helloworld.lib, Helloworld.exp,

And a jni_helloworldimp.obj of four files.

The Eclipse Engineering Tree chart is updated as follows:

The following issues may be encountered in this process:

<1>. CL is not an internal command, the workaround:

Add the Vc-bin path to the system environment variable path,

C:\Program Files\Microsoft Visual Studio\vc98\bin

C:\Program Files\Microsoft Visual Studio\common\msdev98\bin

<2>. Fatal error C1083:cannot open include file: ' jni.h ': No such file or directory

Workaround:

Copy%java_home%\include\jni.h

%java_home%\include\win32\jawt_md.h

%java_home%\include\win32\jni_md.h

To the Vc-include directory (C:\Program Files\Microsoft Visual Studio\vc98\include),

Note: Java_home refers to your JDK directory.

Add the Vc-include directory to the System environment variable, adding an include variable,

The variable value is: C:\Program Files\Microsoft Visual Studio\vc98\include

<3>. Link:fatal Error Lnk1104:cannot Open file "LIBCMT.lib"

Workaround:

Add the Vc-lib directory to the System environment variable, adding a Lib variable,

The variable value is: C:\Program Files\Microsoft Visual Studio\vc98\lib

5. Set the Lib path of the Jni_test project, that is, add the Helloworld.dll path to the project's Lib path;

The specific methods are:

Right-click the project name à select attribute properties à select "Java Build Path" in the list on the left and select "+" on the Right tab by selecting "Source" à click the "+" number in front of the project name, choose "Native Library Location "," Edit "to select the path. (Of course, if you copy the DLL to workspace, you can also use a relative path.) You can also right-click "src" to set its properties within the native library item. )

6. Running Jni_test project, run as Java application,console output Hello world!

Eclipse calls JNI