Apache Tomcat

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Apache Tomcat
Apache Tomcat Logo
Developer(s) Apache Software Foundation
Stable release 7.0.54 (May 22, 2014; 2 months ago (2014-05-22) [1]) [±]
Preview release 8.0.9 (beta) (June 25, 2014; 28 days ago (2014-06-25)) [±]
Development status Active
Written in Java
Operating system Cross-platform
Type Servlet container
HTTP web server
License Apache License 2.0
Website tomcat.apache.org

Apache Tomcat (or simply Tomcat, formerly also Jakarta Tomcat) is an open source web server and servlet container developed by the Apache Software Foundation (ASF). Tomcat implements the Java Servlet and the JavaServer Pages (JSP) specifications from Sun Microsystems, and provides a "pure Java" HTTP web server environment for Java code to run in. In the simplest config Tomcat runs in a single operating system process. The process runs a Java virtual machine (JVM). Every single HTTP request from a browser to Tomcat is processed in the Tomcat process in a separate thread.

Apache Tomcat includes tools for configuration and management, but can also be configured by editing XML configuration files.

Components[edit]

Tomcat 4.x was released with Catalina (a servlet container), Coyote (an HTTP connector) and Jasper (a JSP engine).

Catalina[edit]

Catalina is Tomcat's servlet container. Catalina implements Sun Microsystems' specifications for servlet and JavaServer Pages (JSP). In Tomcat, a Realm element represents a "database" of usernames, passwords, and roles (similar to Unix groups) assigned to those users. Different implementations of Realm allow Catalina to be integrated into environments where such authentication information is already being created and maintained, and then use that information to implement Container Managed Security as described in the Servlet Specification.[2]

Coyote[edit]

Coyote is Tomcat's HTTP Connector component that supports the HTTP 1.1 protocol for the web server or application container. Coyote listens for incoming connections on a specific TCP port on the server and forwards the request to the Tomcat Engine to process the request and send back a response to the requesting client. It can execute JSP's and Servlets.

Jasper[edit]

Jasper is Tomcat's JSP Engine. Jasper parses JSP files to compile them into Java code as servlets (that can be handled by Catalina). At runtime, Jasper detects changes to JSP files and recompiles them.

As of version 5, Tomcat uses Jasper 2, which is an implementation of the Sun Microsystems's JSP 2.0 specification. From Jasper to Jasper 2, important features were added:

  • JSP Tag library pooling - Each tag markup in JSP file is handled by a tag handler class. Tag handler class objects can be pooled and reused in the whole JSP servlet.
  • Background JSP compilation - While recompiling modified JSP Java code, the older version is still available for server requests. The older JSP servlet is deleted once the new JSP servlet has finished being recompiled.
  • Recompile JSP when included page changes - Pages can be inserted and included into a JSP at runtime. The JSP will not only be recompiled with JSP file changes but also with included page changes.
  • JDT Java compiler - Jasper 2 can use the Eclipse JDT (Java Development Tools) Java compiler instead of Ant and javac.

Three new components were added with the release of Tomcat 7:

Cluster[edit]

This component has been added to manage large applications. It is used for load balancing that can be achieved through many techniques. Clustering support currently requires the JDK version 1.5 or later.

High availability[edit]

A high-availability feature has been added to facilitate the scheduling of system upgrades (e.g. new releases, change requests) without affecting the live environment. This is done by dispatching live traffic requests to a temporary server on a different port while the main server is upgraded on the main port. It is very useful in handling user requests on high-traffic web applications.[3]

Web Application[edit]

It has also added user as well as system based web applications enhancement to add support for deployment across the variety of environments. It also tries to manage session as well as applications across the network.

Tomcat is building additional components. A number of additional components may be used with Apache Tomcat. These components may be built by users should they need them or they can be downloaded from one of the mirrors.[4]

Features[edit]

Tomcat 7.x implements the Servlet 3.0 and JSP 2.2 specifications.[5] It requires Java version 1.6, although previous versions have run on Java 1.1 through 1.5. Versions 5 through 6 saw improvements in garbage collection, JSP parsing, performance and scalability. Native wrappers, known as "Tomcat Native", are available for Microsoft Windows and Unix for platform integration.

History[edit]

Tomcat started off as a servlet reference implementation by James Duncan Davidson, a software architect at Sun Microsystems. He later helped make the project open source and played a key role in its donation by Sun Microsystems to the Apache Software Foundation. The Apache Ant software build automation tool was developed as a side-effect of the creation of Tomcat as an open source project.

Davidson had initially hoped that the project would become open sourced and, since many open source projects had O'Reilly books associated with them featuring an animal on the cover, he wanted to name the project after an animal. He came up with Tomcat since he reasoned the animal represented something that could fend for itself. Although the tomcat was already in use for another O'Reilly title,[6] his wish to see an animal cover eventually came true when O'Reilly published their Tomcat book with a snow leopard on the cover in 2003.[7]

Releases[edit]

Apache Tomcat versions
Version Release Date Description
3.0.x. (initial release) 1999 Merger of donated Sun Java Web Server code and ASF and Implements Servlet 2.2 and JSP 1.1 specifications.
3.3.2 2004-03-09 Latest 3.x release.
4.1.31 2004-10-11
4.1.40 2009-06-25 Latest 4.x release.
5.0.0 2002-10-09
5.0.30 2004-08-30 Latest 5.0.x release
5.5.0 2004-08-31
5.5.36 2012-10-10 Latest 5.5.x release,[8]
6.0.0 2006-12-01
6.0.41 2014-05-23 Latest 6.x release.
7.0.0 beta 2010-06-29 First Apache Tomcat release to support the Servlet 3.0, JSP 2.2, and EL 2.2 specifications.
7.0.54 2014-05-22 Current stable version.
8.0. 2013-08-18 dev version.
8.0.9 2014-06-25 Current stable version.

Communities[edit]

Apache software is built as part of a community process that involves both user and developer mailing lists. The developer list is where discussion on building and testing the next release takes place, while the user list is where users can discuss their problems with the developers and other users.

Some of the free Apache Tomcat resources and communities include Tomcatexpert.com (a SpringSource sponsored community for developers and operators who are running Apache Tomcat in large-scale production environments) and MuleSoft's Apache Tomcat Resource Center (which has instructional guides on installing, updating, configuring, monitoring, troubleshooting and securing various versions of Tomcat).

Apache TomEE[edit]

Apache TomEE (pronounced "Tommy") is the Java Enterprise Edition of Apache Tomcat (Tomcat + Java EE = TomEE) that combines several Java enterprise projects including Apache OpenEJB, Apache OpenWebBeans, Apache OpenJPA, Apache MyFaces and others.[9] In October 2011, the project obtained certification by Oracle Corporation as a compatible implementation of the Java EE 6 Web Profile.[10][11]

See also[edit]

References[edit]

Bibliography[edit]

External links[edit]