Ubuntu Use JNI Development example detailed _java

1. Write a Java file in which to declare the native method and load the dynamic link library with a static statement block, the example Prompt.java code is as follows:

Class Prompt {
  private native string Getline (string Prompt);

  public static void Main (String args[]) {
    Prompt p = new Prompt ();
    String input = P.getline ("Type a Line:");
    System.out.println ("User typed:" + input);
  }

  static {
    system.loadlibrary ("Prompt");
  }
}

2. Invoke the Javac command to generate the Prompt.class file;

Javac Prompt.java

3. Invoke Javah command to generate Prompt.h header file for C program reference:

Javah-jni Prompt

The automatically generated header files are as follows:

/* Do isn't EDIT this file-it is machine generated/*
#include <jni.h>/
* Header for Class Prompt * * *

#if Ndef _included_prompt
#define _INCLUDED_PROMPT
#ifdef __cplusplus
extern "C" {
#endif
 * * Class:   Prompt
 * method:  getline
 * Signature: (ljava/lang/string;) ljava/lang/string;
 * *
jniexport jstring jnicall java_prompt_getline
 (jnienv *, Jobject, jstring);

#ifdef __cplusplus
}
#endif
#endif

4. Write prompt.c files to achieve specific functions:

#include <jni.h>
#include <stdio.h>
#include "Prompt.h"

jniexport void Jnicall
Java_ Prompt_getline (jnienv *env, Jobject obj, jstring Prompt) 
{
  char buf[128];
  Const Jbyte *STR;
  str = (*env)->getstringutfchars (env, prompt, NULL);
  if (str = null) {return
    null;    
  }
  printf ("%s", str);
  (*env)->releasestringutfchars (env, prompt, str);
  scanf ("%s", buf);
  Return (*ENV)->newstringutf (env, BUF);
}

5. Compile dynamic library libprompt.so;

Gcc-shared-fpic-i/usr/lib/jvm/java-6-sun-1.6.0.26/include-i/usr/lib/jvm/java-6-sun-1.6.0.26/include/linux Prompt.c-o libprompt.so

6. Run.

Java Prompt

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