JNI的某些数组和字符串类型转换（转）

 JNICC++C#Windows

jbytearray转c++byte数组

C代码  

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

jbyteArray 转 c++中的BYTE[]

C代码  

//jbytearray strInjbyte * 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

C代码  

//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 *

C代码  

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

char* 转jstring

C代码  

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*

C代码  

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

JNI 返回 jbyteArray

C代码  

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*

C代码  

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

C代码  

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

C代码  

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

C代码  

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[]

C代码  

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

//byte[]转为BYTE[]

C代码  

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

//将BYTE数组转为jarray

C代码  

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

C代码  

(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