Apache Jakarta Regexp is a 100% pure Java regular expression package. Expression syntax supports all of Perl5 syntax, with the exception of back reference substitution markers (several people have mentioned this lack, so please feel free to contribute a solution). It also supports a very limited subset of POSIX features. Performance and features are somewhat inferior to ORO, and the new JDK 1.4 (java.util.regex) package, but the package is especially small and features the ability to precompile expressions (without using object serialization) into byte arrays, thus avoiding the need to load the expression compiler.
The Apache JMeter is a 100% pure Java desktop application designed for performance and load testing of servers. It was primarily designed for Web/HTTP testing but it has been expanded to include support for a variety of testing modules. It ships with modules for HTTP and SQL databases (using JDBC). It may be used to test server performance both on static and dynamic resources, to simulate a heavy load on a server or network to test its strength, or to analyse overall performance under different load types. It also provides pluggable interfaces for customizing data visualization, test synchronization, and the construction and execution of tests.
When building server side applications for the Web, independently of the language used (Java, PHP, Perl, etc), a lot of time is spent writing embedded HTML code and dealing with the fact that HTTP is a stateless protocol. SPFC allows you to write HTML forms like you write a Java GUI.
Avalon is Apache's Java Server Framework project. It is separated into six subprojects: Framework, Excalibur, LogKit, Cornerstone, Phoenix, and Apps. Its purpose is to simplify server side programming for Java-based projects. It formalizes several best practices and patterns for server side programming. Framework describes the interfaces and contracts for the component-based architecture. Excalibur provides a number of useful components and utilities. LogKit is a logging implementation. Cornerstone is a group of reusable server components and services. Phoenix is an enterprise container implementation that uses all of the other subprojects to automatically deploy and manage one or more componentized servers. Apps is a home for several Phoenix-compatible server applications and reusable components (like FtpServer).
Batik is a Java-based toolkit for applications that want to use images in the Scalable Vector Graphics (SVG) format for various purposes, such as viewing, generation, or manipulation. It gives developers a set of core modules (parsers, generators, DOM implementation) which can be used together or individually, and be highly extensible. It comes with a full-fledged SVG viewer.
Apache Cocoon is a Web development framework built around the concepts of separation of concerns and component-based Web development. Cocoon implements these concepts around the notion of "component pipelines", each component on the pipeline specializing on a particular operation. This makes it possible to use a Lego(tm)-like approach in building Web solutions, hooking together components into pipelines without any required programming.
DBPrism is an open source framework to generate dynamic XML from a database. It connects Oracle databases with Apache Cocoon, providing a high performance DBGenerator with functionality such as parallel content aggregation and ESI cache protocol. It also includes a powerlful database oriented CMS built on top of Apache Cocoon2 and DBPrism.