Call DLL file without source code

When using jni perhaps jna call dll When , If dll If it is encrypted , And there is no source file , either .h Header file and do not know the definition of the method, it is difficult to call directly , Need to pass through c Language generates an intermediate Library , Called in the intermediate Library dll

 

The first thing you need to do is java Define the method to be called , And compile it into class, And then through javah Generate a .h The header file , Generally as follows

 

 

The red part is corresponding to us java Method

 

 

Then according to the generated .h Header file writing method body

 

 

The content of the method body depends on the business , Here, it is mainly to call the third party dll, And then through c Get the return value after the language call , Then go back through our method , Then we can call in our code

 

Or through a third party dll Generate lib Call statically in the intermediate Library

1. function dumpbin Order to obtain dll List of all exported functions of :

dumpbin /exports C:\yourpath\yourlib.dll

 

 

2. establish .def file

Now copy all these function names ( Only name!) And paste it into a new text file . name yourlib.def, And will “EXPORTS” Line on top of it . my yourlib.def The documents are as follows :

EXPORTS
_magic_func
_PG_init
exec_get_datum_type
exec_get_datum_type_info
pg_finfo_plpgsql_call_handler
pg_finfo_plpgsql_inline_handler
pg_finfo_plpgsql_validator
plpgsql_DumpExecTree
plpgsql_HashTableInit
plpgsql_IdentifierLookup
plpgsql_add_initdatums
plpgsql_adddatum

Now? , From this definition file , You can create .lib The file . So , We use “lib” command

lib /def:C:\mypath\mylib.def /OUT:C:\mypath\mylib.lib /machine:x86

 

stay VS Add lib Three methods of Library ：

Be careful ：

1、 Each method should also copy the corresponding DLL File to the corresponding directory , Or set DLL Directory location , The specific method is ："Properties" -> "Configuration Properties" -> "Debugging", stay "Working Directory" Set up dll That's the way

2、 Whether it's setting DLL Catalog , Or is it Lib Catalog , Or the directory of the header file , There are release Version and debug Version differentiation , The settings for each version are independent , To set separately .

 

Method 1:   Add by setting the project configuration lib library .

A、 Add the header file directory of the project ： engineering --- attribute --- Configuration properties ---c/c++--- routine --- Attach include directory ： Add the directory where the header files are stored .

B、 Add a file reference to lib Static library path ： engineering --- attribute --- Configuration properties --- The linker --- routine --- Additional Library Directory ： add lib File storage directory .

C   Then add the project reference lib file name ： engineering --- attribute --- Configuration properties --- The linker --- Input --- Additional dependency ： add lib file name .

This method is complicated , And not intuitive , And you may have to fight against debug Version and release Versions are configured differently , Because the two versions of the libraries we generated may be placed in different directories .

I use vs6.0 Compilation of , Yes c The language is unfamiliar , That's how it works

 

Method 2: Use compiled statements :

#ifdef _DEBUG

#pragma comment(lib,"..\\debug\\LedCtrlBoard.lib")

#else

#pragma comment(lib,"..\\release\\LedCtrlBoard.lib")

#endif

This method is intuitive , convenient , And can be directly distinguished according to the above Debug Version and Release Different directories of versions . Of course , Through macro , More versions can also be distinguished .

But when specifying a directory , Careless mistakes are easy to make .

 

Method 3: Add library files directly to the project .

Add like you .h and .cpp file , hold lib Add the file to the project file list .

VC in , Switch to " Solution view ",---> Check to add lib The engineering of --> Click on the right -->" add to "-->" Existing items "--> choice lib file --> determine .

It's that simple , Get it done .

This method is applicable in my project debug Version and Release The same... Is used in all versions lib Library file . This saves you 1 Method to configure the environment , It also eliminates the method 2 The possibility of a statement error .

 

Then introduce a third party into the intermediate Library lib, Then write the business code

Then compile It's like this

java2dll>cl -I J:\java\jkd1.7_32\include -I J:\java\jkd1.7_32\include\win32 -LD java2dll.cpp Dogskin.lib -Fepasencode.dll

Then through the generated dll Go through java call