jbytearray转c++byte数组

jbyte * arrayBody = env->GetByteArrayElements(data,0); 
jsize theArrayLengthJ = env->GetArrayLength(data); 
BYTE * starter = (BYTE *)arrayBody; 

这个BYTE在VC里面定义的就是无符号的char类型，typedef unsigned char byte;
C++中的BYTE[]转jbyteArray

//nOutSize是BYTE数组的长度 BYTE pData[]
jbyte *by = (jbyte*)pData;
jbyteArray jarray = env->NewByteArray(nOutSize);
env->SetByteArrayRegin(jarray, 0, nOutSize, by);

在jni的jbyte定义是这样的，有符号的char类型。typedef signed charjbyte;/* signed 8 bits */
下面是windows的DLL库的转换

char* jstringToWindows( JNIEnv *env, jstring jstr )
{
int length = (env)->GetStringLength(jstr );
const jchar* jcstr = (env)->GetStringChars(jstr, 0 );
char* rtn = (char*)malloc( length*2+1 );
int size = 0;
size = WideCharToMultiByte( CP_ACP, 0, (LPCWSTR)jcstr, length, rtn,(length*2+1), NULL, NULL );
if( size <= 0 )
return NULL;
(env)->ReleaseStringChars(jstr, jcstr );
rtn[size] = 0;
return rtn;
}
jstring WindowsTojstring( JNIEnv* env, char* str )
{
jstring rtn = 0;
int slen = strlen(str);
unsigned short * buffer = 0;
if( slen == 0 )
rtn = (env)->NewStringUTF(str );
else
{
int length = MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, NULL, 0 );
buffer = (unsigned short *)malloc( length*2 + 1 );
if( MultiByteToWideChar( CP_ACP, 0, (LPCSTR)str, slen, (LPWSTR)buffer, length ) >0 )
rtn = (env)->NewString( (jchar*)buffer, length );
}
if( buffer )
free( buffer );
return rtn;
}

下面是JNI调用系统API转换的字符串，再转成char指针类型

char* jstringTostring(JNIEnv* env, jstring jstr)
{        
  char* rtn = NULL;
  jclass clsstring = env->FindClass("java/lang/String");
  jstring strencode = env->NewStringUTF("utf-8");
  jmethodID mid = env->GetMethodID(clsstring, "getBytes", "(Ljava/lang/String;)[B");
  jbyteArray barr= (jbyteArray)env->CallObjectMethod(jstr, mid, strencode);
  jsize alen = env->GetArrayLength(barr);
  jbyte* ba = env->GetByteArrayElements(barr, JNI_FALSE);
  if (alen > 0)
  {
    rtn = (char*)malloc(alen + 1);
    memcpy(rtn, ba, alen);
    rtn[alen] = 0;
  }
  env->ReleaseByteArrayElements(barr, ba, 0);
  return rtn;
}

同上相反

jstring stoJstring(JNIEnv* env, const char* pat)
{
jclass strClass = env->FindClass("Ljava/lang/String;");
jmethodID ctorID = env->GetMethodID(strClass, "", "([BLjava/lang/String;)V");
jbyteArray bytes = env->NewByteArray(strlen(pat));
env->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);
jstring encoding = env->NewStringUTF("utf-8");
return (jstring)env->NewObject(strClass, ctorID, bytes, encoding);
} 

常用的。可以通过以上方法对编码进行转换。

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