jMock is a library for testing Java code using mock objects. Mock objects help you design and test the interactions between the objects in your programs. jMock makes it quick and easy to define mock objects, so you don't break the rhythm of programming. jMock lets you define flexible constraints over object interactions, reducing the brittleness of your tests. jMock is easy to extend.
MockDoclet is a tool for generating mock objects for Java classes and interfaces to aid in unit testing classes that are tightly coupled to other components. It is an active code generation tool that scans interfaces for JavaDoc style @mock tags at build time to generate the appropriate mock objects. It is built on top of XDoclet and the MockObjects framework, and is designed to be used with JUnit and Ant.
SiteMesh was built upon the Java Servlet 2.3 API. It is a web-page layout system and web-application integration system to aid in creating large sites consisting of many pages for which a consistent look/feel, navigation, and layout scheme is required. It 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. It is ideally suited for Java based sites (particularly JSP) but can be dropped into any existing site that uses a Servlet engine including static, CGI, PHP, and ColdFusion generated pages.
PicoContainer is a tiny embeddable container for Constructor Dependency Injection (CDI) Inversion of Control (IoC) Java components. There are implementations for Java, .NET, Ruby, and PHP. Simple components for PicoContainer do not have to extend, implement, or throw anything. They also do not ship with XML declarations.