Jakarta Slide is a content management system composed of multiple modules tied together using the WebDAV protocol. It includes a content management system with a Java API, a servlet implementing the WebDAV protocol on top of the content management system, a Java WebDAV and HTTP client library, and a WebDAV command line client.
OpenIM is a Java implementation of a Jabber server. It is a complete rewrite of the Jaba Server project, and it supports the Jabber server to server communication protocol. It also supports Presence, Message, and Roster. Persistent storage is done in an XML file using XStream lib. It has been tested successfully with many clients such as Exodus, Rhymbox, GAIM, Psi, Greenthumb, and the Kopete.
mod_log_sql (formerly known as mod_log_mysql) is an Apache module that enables access logging to an SQL database. This capability can replace or coexist with Apache's regular text-file logging mechanisms. The currently supported database backend is MySQL, with PostgreSQL and others in development.
DataBind is a library to simplify the persistance of Java objects to a datastore. A data store may be a relational database, XML files, or any other type of datastore. Java objects which are persisted do not need to be modified in any way. The only requirement for persisted objects is that they have read and write methods for each field that you would like to persist and an empty constructor. The read and write methods are specified at deployment time in an XML file and thus can be any method (in other words they do not have to be getter and setter methods, although this is the preferred method signature.) DataBind also supports loading and storing collections of objects. Objects can be retrieved from the database using search elements to select a subset of the available objects.
Apache Byte Code Engineering Library (formerly known as JavaClass) is intended to give users a convenient utility to analyze, create, and manipulate (binary) Java class. Classes are represented by objects which contain all the symbolic information of the given class, in particular the methods, fields and byte code instructions. Such objects can be read from an existing file, be transformed by a program (e.g. a class loader at run-time), and can be dumped to a file. One interesting application is the creation of classes from scratch at run-time. Apache Byte Code Engineering Library (BCEL) may be also useful if you want to learn about the Java Virtual Machine (JVM) and the format of Java .class files.