Failed to execute COM class: com4j.ComException: 8

Question

I'm trying for some days to execute a ".dll" file from an JAVA application. If you are interested you can read my first question: Call a .dll function using command line

I used "com4j" to create the COM classes for my DLL. The generated classes looks good and I tried to execute the code, more exactly a method called "getUnitInfo" located in a class called "_Tester":

@DISPID(1610809376) //= 0x60030020. The runtime will prefer the VTID if present
  @VTID(8)
  int getUnitInfo(
    java.lang.String strRequest,
    Holder<java.lang.String> strUnitInfo,
    @Optional @DefaultValue("") java.lang.String strStationName,
    @Optional @DefaultValue("") java.lang.String strUserID);

The instance:

Holder<String> holder = new Holder<String>("test");
        _Tester instance =  ClassFactory.createTester();
        instance.getUnitInfo("", holder, "", "");  

But it throws this exception:

Exception in thread "main" com4j.ExecutionException: com4j.ComException: 80040154 CoCreateInstance failed : Class not registered : .\com4j.cpp:153
    at com4j.ComThread.execute(ComThread.java:203)
    at com4j.Task.execute(Task.java:25)
    at com4j.COM4J.createInstance(COM4J.java:97)
    at com4j.COM4J.createInstance(COM4J.java:72)
    at DLL.ClassFactory.createTester(ClassFactory.java:21)
    at proiect.DllTest.run(DllTest.java:17)
    at proiect.DllTest.main(DllTest.java:11)

I have read a lot of posts regarding this problem on the internet but nothing helped. Using "PE deconstruct" tool to find out that the .dll file that I need to execute is 32 bit based. I have a 64 bit Windows OS but I installed a 32 bit JAVA and Eclipse.

If I execute "java -version" o the command line:

java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) Client VM (build 25.171-b11, mixed mode)

The com4j documentation is lacking information, I think the new generated JAva code still need to communicate with the old DLL but I don't know how it has to be referenced.

Can anybody help?

EDIT The instance is create using this UUID:

 public static DLL._Tester createTester() {
    return COM4J.createInstance( DLL._Tester.class, "{4B7CF2DB-F936-4BA3-9DC6-5E99E5220270}" );
  }

And I found this in the Windows registry:

Answer 1

Hi i have faced the same issue one month back and the final resolution i have founded which has resolved my issue is changing my java 64bit to 32 bit, and it started working. note- only add com4j.jar in build path and do not register any .dll files.

Hope this will work for you

Answer 2

CoCreateInstance failed : Class not registered means the GUID you provided does not match any COM item in your Windows registry.

You can try loading a COM object with a different GUID- go into system registry and find any valid GUID, maybe the one associated with Microsoft Excel (in my case, the entry is located under Computer\HKEY_CLASSES_ROOT\Excel.Application\CLSID).

To register your DLL, maybe How do I register a DLL file on Windows 7 64-bit? helps.

EDIT Check your registry under Computer\HKEY_LOCAL_MACHINE\SOFTWARE\Classes\CLSID. Is you GUID listed under Classes?