转：JNI jstring与c++字符串类型转换函数

jstring str2jstring(JNIEnv* env,const char* pat)
{
//定义java String类 strClass
jclass strClass = (env)->FindClass("Ljava/lang/String;");
//获取String(byte[],String)的构造器,用于将本地byte[]数组转换为一个新String
jmethodID ctorID = (env)->GetMethodID(strClass, "<init>", "([BLjava/lang/String;)V");
//建立byte数组
jbyteArray bytes = (env)->NewByteArray(strlen(pat));
//将char* 转换为byte数组
(env)->SetByteArrayRegion(bytes, 0, strlen(pat), (jbyte*)pat);
// 设置String, 保存语言类型,用于byte数组转换至String时的参数
jstring encoding = (env)->NewStringUTF("GB2312");
//将byte数组转换为java String,并输出
return (jstring)(env)->NewObject(strClass, ctorID, bytes, encoding);
}

std::string jstring2str(JNIEnv* env, jstring jstr)
{
char*   rtn   =   NULL;
jclass   clsstring   =   env->FindClass("java/lang/String");
jstring   strencode   =   env->NewStringUTF("GB2312");
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);
std::string stemp(rtn);
free(rtn);
return   stemp;
}