jni object的使用

痛定思痛。 2022-09-23 04:52 365阅读 0赞

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 );  
  
..elided...  
  
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);

[Java]: http://lib.csdn.net/base/17