For historical reasons, Java projects can be found both under the java.apache.org and jakarta.apache.org umbrellas. The final goal is that over time all Java projects will move under the Jakarta umbrella.
The goal of the Jakarta Project is to provide commercial-quality server solutions based on the Java Platform that are developed in an open and cooperative fashion.
The Java on Apache community is a very dynamic and active one, as shows the quantity and quality of its subprojects, which are described now.
You can think of Ant as the Java equivalent of make. It is a big success with Java related projects. Developers can write Java instead of shell commands. This means increased portability and extensibility. Instead of Makefiles Ant has XML files. You can learn more about ANT here.
ORO is a complete package that provides regular experession support for Java. It includes Perl5 regular expression support, glob expressions, etc. All under the Apache license. You can learn more about ORO here. You can find another lightweight regular expression package, Regexp.
Slide is a high-level content management framework. Conceptually, it provides a hierarchical organization of binary content which can be stored into arbitrary, heterogenous, distributed data stores. In addition, Slide integrates security, locking and versioning services.
If you are familiar with WedDAV, Slide uses it extensively. In simple words, what Slides provides is an unified, simple way to access resources and information. These resources can be stored in a database, the filesystem, etc. and accessed either thru a WebDAV interface or Slide own API.
You can learn more at the Slide home page.
Struts is an Apache project that tries to bring the Model-View-Controller (MVC) design paradigm to web development. It builds on Servlet and JavaServer Pages technologies. The model part are the Java server objects, which represent the internal estate of the application. Enterprise Java Beans are commonly used here. The view part is constructed via JavaServer Pages (JSP) which are a combination of static HTML/XML and Java. JSPs also allow the developer to define its own tags. The controller part are servlets, which take requests (GET/POST) from the client, perform actions on the model and update the view by providing the appropriate JSP. You can learn more at the Struts project pages.
The JavaServer pages technology allows developers to provide functionality by adding custom tags. The Taglibs project intends to be a common repository for these extensions. It includes tags for common utilities (for, date), SQL database access, etc.
You can learn about TagLibs here. More documentation is included in the package.
Tomcat is the flagship product of the Jakarta project. It is the official reference implementation for the Java Servlet 2.2 and JavaServer Pages 1.1 technologies.
You can learn more in the Tomcat homepage. The Tomcat project was started with a code donation from Sun Microsystems.
Velocity is a Java based template engine. It can be used as a stand-alone utility for generating source code, HTML, reports, or it can be combined with other systems to provide template services. Velocity has a Model View Controller paradigm that enforces separation of Java code and the HTML template.
You can learn more about Velocity here. Velocity is part of other projects like Turbine
The Watchdog project provides the validation tests for the Servlet and JavaServer Pages specifications. You can find more information here
Apache JServ is a 100% pure Java servlet engine fully compliant with the JavaSoft java Servlet APIs 2,0 specification.(...)The result is a pure servlet engine that works on any "version 1.1" Java Virtual Machine.
JServ is one of the original Java Apache projects. Tomcat will be the successor of JServ once it is finished. You can learn more at the JServ home page.
JSSI is an implementation of server side included in the Java language. Server side includes are tags includes in files that get processed before the page is served to the client (for example to include the current date) You can find more information here.
The Apache JMeter is a 100% pure Java desktop application designed to load test functional behavior and measure performance. It was originally designed for testing Web Applications but has since expanded to other test functions.
It can be used to test static and dynamic resources and get inmediate visual feedback.
You can see some screenshots and learn more here.
Is a set of libraries to help solve common problems in server side application development. They focus on two of them:
Element Construction Set (ECS) is a JAVA API or generating elements for various markup languages it directly supports HTML 4.0 and XML, but can easily be extended to create tags for any markup language.
It allows the generation of mark up tags using Java function calls, leading to a much cleaner solution that mixing HTML and Java code. You can learn more at the ECS project page.
If you are familiar with Perl or BSD systems, Avalon is roughly the equivalent of CPAN or the Ports collection for Java Apache technologies. It does not only provide guidelines for a common repository of code, it goes one step further: is an effort to create, design, develop and maintain a common framework for server applications written using the Java language. It provides the means so server side Java projects can be easily integrated and build on each other.
Complementary to the other Apache server side technologies, JAMES provides a 100% pure Java server designed to be a complete and portable enterprise mail engine solution based on currently available open protocols (SMTP, POP3, IMAP, HTTP)
More information can be found here.
A lightweight HTTP/1.0 server in pure Java. The project seems to be stalled and no code is available. The website can be found here.
Jetspeed is a web based portal written in Java. It has a modular API that allows aggregation of different data sources (XML, SMTP, iCalendar)
Turbine is a servlet based framework that allows experienced Java developers to quickly build secure web applications. Turbine brings together a platform for running Java code and reusable components, everything under the Apache license. Some of it features
The Jyve project is built on top of the Turbine framework. It is an application that provides a web based FAQ system
Alexandria is an integrated documentation management system. It brings together technologies common to many open source projects like CVS and JavaDoc. The goal is to integrate source code and documentation to encourage code documentation and sharing. More information here
This package provides a logging framework that Java applications can use. It can be enabled at runtime without modifying the binary and has been designed with performance in mind. It can be found here