Calling Java library (JAR) from VBA/VBScript/Visual Basic Classic

Question

I'm working with a JAR library, but a native C++ port (as a DLL) isn't available yet.

I need to access this functionality from VBA, and I'm considering three options:

1. Wait for the native port to be completed.
2. Access the JAR library from VBA through a bridge (requiring an installed JRE).
3. Compile the JAR into a native DLL using GCJ, then call it from VBA (although I think this is practically unfeasible).

I believe option 1 would be the easiest, though it requires waiting. Option 3 seems impractical.

Could you provide any insights or suggestions regarding option 2? Specifically, I'm interested in setting up a reliable bridge between VBA and the JAR library.

Thanks for your assistance!

Answer 1

There are couple approaches to be used when you require 2 different technologies to speak, go for Objects/Methods publications using:

• Corba & (or RMI or JMS)
• SOAP
• RESTful API
• WebServices
• File Data exchange.
• IPC Pipeline

Depending on the complexity you will take your solution.

Calling 'java.exe' runs the library in a VM, you can produce an output using a external resource but only the 3 first are meant to exchange objects in a heterogen solution.

Answer 2

This can be performed via a VBA macro using Obba. (Disclaimer: I am working on Obba).

Answer 3

It depends on whether you wish to return values from the JAR file or not. If you do not, and just wish to execute a method then you can use a "Shell" (or ShellExecute) from VB as follows:

Shell("java.exe -jar " & <yourJARFile>)

If you do need to return a value then you will more than likely need a bridge - similar discussion here (for VB.NET, but principle is the same): Can you use Java libraries in a VB.net program?

Based on that most bridges that people have created are for .NET and not for VBA/6 so you would maybe need to create your own somehow, or perhaps create a .NET DLL that is then consumed by your VBA code.