通过JNI实现java调用C代码和C代码调用java的代码

public class HelloWorld { public native void displayHelloWorld(); static {
System.loadLibrary("hello");
} public static void main(String[] args) { new HelloWorld().displayHelloWorld(); } }

/* DO NOT EDIT THIS FILE - it is machine generated */
#include <jni.h>
/* Header for class HelloWorld */#ifndef _Included_HelloWorld
#define _Included_HelloWorld
#ifdef __cplusplus
extern "C" {
#endif
/*
* Class: HelloWorld
* Method: displayHelloWorld
* Signature: ()V
*/
JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld
(JNIEnv *, jobject);#ifdef __cplusplus
}
#endif
#endif

#include <jni.h>
#include "HelloWorld.h"
#include <stdio.h>JNIEXPORT void JNICALL Java_HelloWorld_displayHelloWorld(JNIEnv *env, jobject object)
{
printf("Hello world!\n");
return;
}

public class HelloTest {public static int COUNT = 8;private String msg;
private int[] counts;public HelloTest() {
this("Constructor!!");
}public HelloTest(String msg) {
this.msg = msg;
this.counts = null;
}public String getMessage() {
return msg;
}public static String getHelloWorld() {
return "Hello world!";
}public String append(String str, int i) {
return str + i;
}public int[] getCounts() {
return counts;
}/**
* @param counts
*/
public void setCounts(int[] counts) {
this.counts = counts;
}/**
* @throws IllegalAccessException
*/
public void throwExcp() throws IllegalAccessException {
throw new IllegalAccessException("exception occur.");
}/**
* @param args
*/}

#include <stdio.h>
#include <jni.h>
#include <Windows.h>
#include <iostream>
#include <string.h>
using namespace std;typedef jint (WINAPI *JNICreateJavaVM)(JavaVM **,void **,void *);jstring NewJString(JNIEnv *env, LPCTSTR str);
char* JStringToCString (JNIEnv *env, jstring str);int main()
{
JavaVMInitArgs vm_args;
JavaVMOption options[3];
JavaVM *jvm;
JNIEnv *env;
HINSTANCE hInstance=NULL;
JNICreateJavaVM jniCreateJavaVM;
int res = 0;
const char szTest[] = "hello";/*initial parameter is set*/
options[0].optionString = "-Djava.compiler=NONE";
//classpath is set，if jar is need to use,this jar is also included.options[1].optionString = "-Djava.class.path=.;c:\\";
//the type of message is set,the value of this are gc,class and jni. for example:-verbose:gc,class
options[1].optionString = "-Djava.class.path=.;c:\\"; options[2].optionString = "-verbose:NONE";//version is set,the version are JNI_VERSION_1_1,JNI_VERSION_1_2 and JNI_VERSION_1_4
//installed version you can select is set,but the version of JRE must be not higher than the specified version
vm_args.version = JNI_VERSION_1_4;
vm_args.nOptions = 3;
vm_args.options = options;
//this parameter is specified whether it ignored no standard parameter.If JNI_FLASE is set，when it meets no standard parameter ，JNI_CreateJavaVM will return JNI_ERR
vm_args.ignoreUnrecognized = JNI_TRUE;
//load the jvm.dll
hInstance= LoadLibrary("C:\\Program Files (x86)\\Java\\jre1.5.0_17\\bin\\client\\jvm.dll");
if (hInstance == NULL)
{
return false;
}jniCreateJavaVM = (JNICreateJavaVM)GetProcAddress(hInstance, "JNI_CreateJavaVM");
//JNI_CreateJavaVM create virtual jvm
res = (*jniCreateJavaVM)(&jvm, (void**)&env, &vm_args);
if (res < 0)
{
return -1;
}jclass cls = env->FindClass("HelloTest");jobject obj = env->AllocObject(cls);jmethodID mid = env->GetMethodID(cls, "append","(Ljava/lang/String;I)Ljava/lang/String;");jstring arg = NewJString(env, szTest);
jstring msg = (jstring) env->CallObjectMethod(obj, mid, arg, 12);
char *strh= JStringToCString(env, msg);
std::cout<<strh;
//printf("hhhh%s\n",JStringToCString(env, msg));jvm->DestroyJavaVM();
FreeLibrary(hInstance);
return 0;
}char* JStringToCString (JNIEnv *env, jstring str)// (jstring str, LPTSTR desc, int desc_len)
{
if(str==NULL)
{
return "";
}
//In VC, wide data type is stored by the wchar_t
int len = env->GetStringLength(str);
char *w_buffer = new char[len+1];
char *c_buffer = new char[2*len+1];
ZeroMemory(w_buffer,(len+1)*sizeof(char));const char * charString = env->GetStringUTFChars(str, 0);
strcpy(w_buffer,charString);
env->ReleaseStringUTFChars(str,charString);
//ZeroMemory(c_buffer,(2*len+1)*sizeof(char));char* cstr = w_buffer;
//delete[] w_buffer;
//delete[] c_buffer;return cstr;
}jstring NewJString(JNIEnv *env, LPCTSTR str)
{
if(!env || !str)
{
return 0;
}
int slen = strlen(str);
jchar* buffer = new jchar[slen];
int len = MultiByteToWideChar(CP_ACP,0,str,strlen(str),buffer,slen);
if(len>0 && len < slen)
{
buffer[len]=0;
}
jstring js = env->NewString(buffer,len);
delete [] buffer;
return js;
}