某些数组和字符串类型转换（转）

jbytearray转c++byte数组 

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

jbyteArray 转 c++中的BYTE[] 

//jbytearray strIn  
jbyte * olddata = (jbyte*)env->GetByteArrayElements(strIn, 0);  
jsize  oldsize = env->GetArrayLength(strIn);  
BYTE* bytearr = (BYTE*)olddata;  
int len = (int)oldsize;  

 

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);  

jbyteArray 转 char * 

char* data = (char*)env->GetByteArrayElements(strIn, 0);  

 

char* 转jstring 

jstring WindowsTojstring(JNIEnv* env, char* str_tmp)  
{  
 jstring rtn=0;  
 int slen = (int)strlen(str_tmp);  
 unsigned short* buffer=0;  
 if(slen == 0)  
 {  
  rtn = env->NewStringUTF(str_tmp);  
 }  
 else  
 {  
  int length = MultiByteToWideChar(CP_ACP, 0, (LPCSTR)str_tmp, slen, NULL, 0);  
  buffer = (unsigned short*)malloc(length*2+1);  
  if(MultiByteToWideChar(CP_ACP, 0, (LPCSTR)str_tmp, slen, (LPWSTR)buffer, length) > 0)  
  {  
   rtn = env->NewString((jchar*)buffer, length);  
  }  
 }  
 if(buffer)  
 {  
  free(buffer);  
 }  
 return rtn;  
}

下面这个没有用过，刚看到，也写进来，以后如果遇到可以验证下看。 

jstring 转 char* 或者 const char* 

// jstring str  
const char *key = env->GetStringUTFChars(str, 0);  
//jboolean isOffer  
jsClient->modify(key, isOffer);  
env->ReleaseStringUTFChars(str, key);  

JNI 返回 jbyteArray 

JNIEXPORT jbyteArray JNICALL Java_Test_getByteArray(JNIEnv *env, jobject obj)  
{  
    jbyteArray firstMacArray = env->NewByteArray( 6 );  
    ......  
    jbyte *bytes = env->GetByteArrayElements( firstMacArray, 0);  
    for ( int i = 0; i < sizeof( pAdapterInfo->Address ); i++ )  
    {  
       bytes[ i ] = pAdapterInfo->Address[ i ];  
    }  
  
    env->SetByteArrayRegion(firstMacArray, 0, 6, bytes );  
    return firstMacArray;  
}  

 

//jstring to char* 

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;  
}  

//char* to jstring 

jstring stoJstring(JNIEnv* env, const char* pat)  
{  
jclass strClass = env->FindClass("Ljava/lang/String;");  
jmethodID ctorID = env->GetMethodID(strClass, "<init>", "([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);  
}   

 

//将jstring类型转换成windows类型 

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;  
}  

 

//将windows类型转换成jstring类型 

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;  
}  
/*JNIEXPORT jstring JNICALL Java_test_cs_web_SWIFTAlianceCASmfTest_strcal 
(JNIEnv *env, jclass obj, jstring jstr1, jstring jstr2) 
{ 
jbyteArray bytes = 0; 
jthrowable exc; 
char *pszResult = NULL;     
char *pszSTR1 = NULL; 
char *pszSTR2 = NULL; 
 
pszSTR1 = jstringTostring(env, jstr1); 
pszSTR2 = jstringTostring(env, jstr2); 
 
 
int nlen = sizeof(char)*(strlen(pszSTR1)+strlen(pszSTR2)); 
pszResult = (char*)malloc(nlen); 
strcpy(pszResult, pszSTR1); 
strcat(pszResult, pszSTR2); 
 
jstring jstrRe = stoJstring(env, pszResult); 
free(pszSTR1); 
free(pszSTR2); 
free(pszResult); 
return(jstrRe); 
} 
*/  

 

jni object的使用 

每一个jni格式的dll中的object对应该java里面的一个类。 
如下例有一个 ObjData类，类中有成员bData ,Len 
public class ObjData { 
  public byte[]  bData; 
  public int Len;        
} 
//------------------------jni获得传过来的Object类型的变量objDataIn-------- 

jclass clazz =(env)->FindClass("ObjData"); 

//从传进来的对象中取出byte[] 

jfieldID byteData = (env)->GetFieldID(clazz,"bData","[B");  
jbyteArray pDataIn = (jbyteArray) (env)->GetObjectField(objDataIn, byteData);  
jsize theArrayLeng = env->GetArrayLength(pDataIn);  

 

//byte[]转为BYTE[] 

jbyte * arrayBody = env->GetByteArrayElements(pDataIn,0);   
BYTE * jDataIn = (BYTE *)arrayBody;   

//将BYTE数组转为jarray 

jbyte* byte = (jbyte*)jDataOut;      
jbyteArray jarray = env->NewByteArray(theArrayLeng);  
env->SetByteArrayRegion(jarray, 0, theArrayLeng, byte);  

 

//给每一个实例的变量付值 

(env)->SetObjectField(objDataIn,byteData,jarray);  
(env)->SetIntField(objDataIn,pDataInLen,jDataInLen);  
(env)->ReleaseByteArrayElements(pDataIn, arrayBody, 0);   

 

其他参考： 
Java 通过JNI调用C或者CPP代码 
http://blog.csdn.net/kenera/archive/2009/02/16/3895343.aspx 
http://apps.hi.baidu.com/share/detail/15732549 
http://dniit.blog.163.com/blog/static/28012894200842810332491/ 
http://hi.baidu.com/liangwind/blog/item/7dcce2c9729d1d1e7f3e6f49.html