JNI的某些数组和字符串类型转换

jbytearray转c++byte数组

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jbyte * arrayBody = env->GetByteArrayElements(data,0);

jsize theArrayLengthJ = env->GetArrayLength(data);

BYTE * starter = (BYTE *)arrayBody;

jbyteArray 转 c++中的BYTE[]

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//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

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//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 *

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

char* 转jstring

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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*

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// jstring str

const char *key = env->GetStringUTFChars(str, 0);

//jboolean isOffer

jsClient->modify(key, isOffer);

env->ReleaseStringUTFChars(str, key);

JNI 返回 jbyteArray

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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*

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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

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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

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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

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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[]

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jfieldID byteData = (env)->GetFieldID(clazz,"bData","[B");

jbyteArray pDataIn = (jbyteArray) (env)->GetObjectField(objDataIn, byteData);

jsize theArrayLeng = env->GetArrayLength(pDataIn);

//byte[]转为BYTE[]

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

BYTE * jDataIn = (BYTE *)arrayBody;

//将BYTE数组转为jarray

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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

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(env)->SetObjectField(objDataIn,byteData,jarray);

(env)->SetIntField(objDataIn,pDataInLen,jDataInLen);

(env)->ReleaseByteArrayElements(pDataIn, arrayBody, 0);