Wednesday, December 30, 2009

Returning Java Exception Objects with Open BlueDragon

I'm working on a project that uses a pre-existing Java library to handle payment processing. This is great because it's a heck of a lot of stuff I don't have to write myself, but when payments fail I need to get a code that's contained in an exception object that's thrown in the Java code. This is a problem since given the way the Java code is written, the normal message and detail keys of the CFCATCH struct don't contain the code I need. To get the code I need to call a getCode() method on the Java exception object itself.

Open BlueDragon doesn't implement GetException() yet, which in theory lets you get the actual exception object thrown by Java (provided you specify the specific Java object type being thrown), but I figured since the Java class name is contained in the JAVAEXCEPTION key of the CFCATCH struct, it wouldn't be too hard to tell Open BlueDragon to put the actual Java object in that key instead of the class name.

It took a bit of hunting but it was extremely easy once I found the right spot. The CFCATCH struct is an instance of com.naryx.engine.cfCatchData (which extends cfStructData), and if a Java exception is thrown, the setJavaException() method in cfCatchData is called. This puts a new key called JAVAEXCEPTION in the CFCATCH struct and this key contains the name of the exception class thrown by Java.

Since I wanted to keep that key intact for the sake of compatibility, I decided to add another key called JAVAEXCEPTIONOBJECT to the CFCATCH struct, and this key contains the actual Java exception object. It was as simple as adding one line to the setJavaException() method. The original was this:

public void setJavaException(Throwable _value) {
    setData("javaexception", new cfStringData(_value.getClass().getName()));
}

So I changed it to this:

public void setJavaException(Throwable _value) {
    setData("javaexception", new cfStringData(_value.getClass().getName()));
    setData("javaexceptionobject", new cfJavaObjectData(_value));
}

Now any Java errors that are caught by CFCATCH will contain the Java exception class, which lets me get at everything I need. This turned out to be a much more useful solution than going down the path of writing a Java class to wrap everything just so I could return what I needed from the Java exception object to OpenBD.

Yet another small example of the power of open source. If you want something to work differently, get in there and make it happen!

3 comments:

arwilliamson said...

I love it Matt. I will implement the GetException() for OpenBD using your addition as the basis

Matthew Woodward said...

Excellent Alan--one of those things people probably don't need a lot, but in this case it's rather essential so GetException() will come in handy.

Matthew Woodward said...

Thought I'd follow up on this post and let people know this is now in the nightly builds of OpenBD, as is the GetException() function. Gotta love open source.