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;
}