intertwingly

On Friday, I said Next task is to repackage the htmlparser as a library, and to reimplement the HTML2XML tool itself in C++.  This is now done.  In the process, I also converted a SystemErrErrorHandler class into C++ so that I could be sure that I was able to do both Java=>C++ and C++=>Java calls.

A few things learned along the way:

• Installing libjaxp1.3-java-gcj doesn’t give you headers, but you can generate these yourself using gcjh.
• At least on Ubuntu, there is a bug that prevents gcjh from working.  The workaround is to add /usr/share/java/libgcj.jar to the classpath.
• In gcj, everything inherits directly from java.lang.Object.  This means that you can’t even pass an instance to a subclass to a method that is expecting an instance of a superclass without an explicit cast.
• If you wish to implement a class in C++ that can be used from Java, there is a lot of work to be done.  Much of this can be avoided if you define the class in Java, marking the methods you wish to implement in C++ as native, compiling the Java, and generating a header.
• Constructors can’t be native methods.  The workaround is to have the constructor call a private method.
• If you with to try the executable, remember to set LD_LIBRARY_PATH.