Why to fail to creat .dll

Question

Hi dear all,
I have a existing c++ class such as HelloWorld, and a method hello() is contained in it. I want to call it from a java class.
JNIEXPORT void JNICALL Java_JBlindSignature_hello(JNIEnv * env, jobject obj)
HelloWorld hw;
hw.hello();
But it fail to create a dll file: error LNK2001: unresolved external symbol "public: void __
thiscall Namespace::HelloWorld::hello(void)" (?hello@HelloWorld@ETI@@QAEXXZ)
***.dll : fatal error LNK1120: 1 unresolved externals     
It will succeed if I don't call the hello method. What is the problem?
Would you like to tell me the reason as soon as possible?
Best regards,
Johnson

Answer 1

How to import? Is it to "#include HelloWorld.h"?
But it is ok if I wirte off the line "hw.hello()".
I use the command line to create the dll:
cl -Ig:\jdk1.3.1\include -Ig:\jdk1.3.1\include\win32 -MD -LD **.cpp -Fe**.dll