Logback is intended as a successor to the popular log4j project, and was designed by log4j's founder, Ceki Gulcu. The basic architecture is sufficiently generic so as to apply under different circumstances. It is divided into three modules. The Core module lays the groundwork for the other two modules, whereas the Classic module can be assimilated to an improved version of log4j. It natively implements the SLF4J API so that you can readily switch back and forth between logback and other logging systems, such as log4j or JDK14 Logging. The Access module integrates with Servlet containers to provide HTTP access log functionality. You can easily build your own modules on top of the Core module.
Restlet is a REST framework for Java. It supports all REST concepts (Resource, Representation, Connector, Component, etc.) and is suitable for both client and server Web applications. It supports major Web standards like HTTP, SMTP, XML, JSON, WADL, and Atom. Many extensions are also available to integrate with Servlet, Spring, Jetty, Grizzly, Simple, JAXB, JAX-RS, JiBX, Velocity, or FreeMarker. A GWT version is also available.