Graffito is a framework used to build content-based applications like CMSs, document management systems, forums, blogs, etc. It offers a complete platform for creating, managing, and publishing content in your portal or in any other kind of Java application. It integrates content repositories, workflow, collaboration, and personalization via existing open source projects and standards like WEBDAV.
jSieve is a Java implementation of the Sieve mail filtering language defined by RFC 3028. Sieve is an extensible mail filtering language. Its limited expressiveness (no loops or variables and no tests with side effects) allows user created scripts to be run safely on email servers. Sieve is targeted at the final delivery phase (where an incoming email is transferred to a user's mailbox). jSieve is implemented as a language processor that can be plugged into any Internet mail application to add Sieve support.
Apache Jackrabbit is a fully conforming implementation of the Content Repository for Java Technology API (JCR). A content repository is a hierarchical content store with support for structured and unstructured content, full text searching, versioning, transactions, observation, and more. Typical applications that use content repositories include content management, document management, and records management systems.
Jetspeed-2 is a full implementation of the Java Portlet API. It is fully compliant with the Portlet Specification 1.0 (JSR-168). It has passed the TCK (Test Compatibility Kit) suite and is fully CERTIFIED to the Java Portlet Standard. Notable features include security components backed by LDAP and database implementations, and some robust administration interfaces. Custom portals can be built and deployed using the Jetspeed plugin for Maven. Developers can use the Jetspeed PSML language to assemble portlets, and the Apache Portals Bridges project to 'bridge' portals with existing technologies including Struts, JSF, PHP, and Perl. For GUI designers, Jetspeed comes with several built-in templates used to decorate portals and portlets.
With MetaModel, you use a type-safe SQL-like API for querying any datastore. It is a data access framework providing a common interface for exploration and querying of different types of datastores. It isn't a data mapping framework. Instead, it emphasizes abstraction of metadata and the ability to add data sources at runtime, making MetaModel great for generic data processing applications, but less so for applications modeled around a particular domain.