The bundle class loader consists of a server and a client.
The server accepts requests for files from the client. For each request, it sends the bundle containing the requested file. Because the bundles are pre-compressed, the server does not perform any compression at runtime. As a result, the server has little CPU overhead.
The client consists of an implementation of java.lang.ClassLoader. When a call to loadClass() or loadResource() is made to the class loader, it first checks to see if the data for the requested class or resource has already been received. If so, it handles the request using the data already received. Otherwise, it sends a request for the needed file to the server. In return, it receives a bundle from the server containing the requested file. Because the bundle generally contains files not explicitly requested by the client, the client caches the data for all files received in memory. Once the data for a class or resource has been used by the client, its cache entry is deleted, so that the memory can be reclaimed by the garbage collector.
The implementation of the client and server are written in Java, consisting of 733 lines of source overall. The total size of the client class files is approximately 20 KB. Both client and server use only the standard Java runtime classes in their implementation, and will work with any JVM compatible with Sun's JDK 1.2.
Our implementation currently supports only bundles compressed with zlib. Future work will add support for bundles in Pack format.