Cayenne

Cayenne is a powerful, full-featured Java Object Relational Mapping framework. It is open source and completely free. One of the main Cayenne distinctions is that it comes with cross-platform modeling GUI tools. This places Cayenne in the league of its own, making it a very attractive choice over both closed source commerical products and traditional ""edit your own XML"" open source solutions.

Platform: Linux, Mac OS, Windows;License: Apache

Castor

Castor is an open source data binding framework for Javatm. It's basically the shortest path between Java objects, XML documents and SQL tables. Castor provides Java to XML binding, Java to SQL persistence, and then some more.

Platform: Linux;License: Apache

Apache Cocoon Project

Apache Cocoon  is a major rewrite of Cocoon 2.2. Like Cocoon 2 it is based around the concept of pipelines and sitemaps and it is very similar to Cocoon 2.2 in many respects but is slimmed down and designed to be easily used with Java code (= no frameworks required!). On top of this, Cocoon 3 has the goal of becoming the best available platform for RESTful webservices and web applications.

Platform: Linux;License: Apache

Reference: https://cocoon.apache.org/3.0/

ZK

ZK is the most proven Ajax + Mobile framework designed to maximize enterprise operation efficiency and minimize the development cost by its groundbreaking Direct RIA architecture.

Platform: Linux;License: GPL

Zope

Zope is an open source web application server primarily written in the Python programming language. It features a transactional object database which can store not only content and custom data, but also dynamic HTML templates, scripts, a search engine, and relational database (RDBMS) connections and code. It features a strong through-the-web development model, allowing you to update your web site from anywhere in the world.

Platform: Linux;License: Zope Public License

XWork

XWork is an command-pattern framework that is used to power Struts 2 as well as other applications. XWork provides an Inversion of Control container, a powerful expression language, data type conversion, validation, and pluggable configuration.

Platform: Linux, Windows, Mac OS;License: OpenSymphony Software License

WebWork

WebWork is a Java web-application development framework. It is built specifically with developer productivity and code simplicity in mind, providing robust support for building reusable UI templates, such as form controls, UI themes, internationalization, dynamic form parameter mapping to JavaBeans, robust client and server side validation, and much more.

Platform: Linux, Windows, Mac OS;License: OpenSymphony Software License

PropertySet

PropertySet is a persistence-agnostic module that can be used to fulfill storage requirements in applications that can change constantly. An example of this might be a "User Preferences" storage device. It may be impossible to know what the user can store at any given time in your application's life cycle, so employing a PropertySet can help. Backed by XML, EJB, Ofbiz, JDBC, Castor JDO, or any other persistence mechanism, you can provide a complete typed key-value pair implementation.

Platform: Linux, Windows, Mac OS;License: OpenSymphony Software License

SiteMesh

SiteMesh is a web-page layout and decoration framework and web-application integration framework to aid in creating large sites consisting of many pages for which a consistent look/feel, navigation and layout scheme is required. SiteMesh intercepts requests to any static or dynamically generated HTML page requested through the web-server, parses the page, obtains properties and data from the content and generates an appropriate final page with modifications to the original.

Platform: Linux, Windows, Mac OS;License: OpenSymphony Software License

Orbeon Forms

Orbeon Forms is an open source forms solution designed to handle complex forms typical of the enterprise or government. It includes: a forms platform based on our solid W3C XForms implementation, form Builder, the web-based visual form designer, and Form Runner, the run time environment which delivers forms to your users.

Platform: Linux, Windows, Mac OS;License: OpenSymphony Software License

Apache Struts

Apache Struts is a free open-source framework for creating Java web applications. The Struts framework is designed to help developers create web applications that utilize a MVC architecture. The framework provides three key components: a "request" handler provided by the application developer that is mapped to a standard URI, a "response" handler that transfers control to another resource which completes the response, a tag library that helps developers create interactive form-based applications with server pages. The framework's architecture and tags are buzzword compliant. Struts works well with conventional REST applications and with nouveau technologies like SOAP and AJAX.

Platform: Linux;License: Apache