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Apache Tomcat Default Page
|Developer(s)||Apache Software Foundation|
|Stable release||8.5.20 (August 8, 2017)|
|Preview release||9.0.0.M26 (alpha) (August 8, 2017)|
HTTP web server
|License||Apache License 2.0|
Apache Tomcat, often referred to as Tomcat Server, is an open-source Java Servlet Container developed by the Apache Software Foundation (ASF). Tomcat implements several Java EE specifications including Java Servlet, JavaServer Pages (JSP), Java EL, and WebSocket, and provides a "pure Java" HTTP web server environment in which Java code can run.
Tomcat 4.x was released with Catalina (a servlet container), Coyote (an HTTP connector) and Jasper (a JSP engine).
Catalina is Tomcat's servlet container. Catalina implements Sun Microsystems's 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.
Coyote is a Connector component for Tomcat that supports the HTTP 1.1 protocol as a web server. This allows Catalina, nominally a Java Servlet or JSP container, to also act as a plain web server that serves local files as HTTP documents.
Coyote listens for incoming connections to the server on a specific TCP port and forwards the request to the Tomcat Engine to process the request and send back a response to the requesting client. Another Coyote Connector, Coyote JK, listens similarly but instead forwards its requests to another web server, such as Apache, using the JK protocol. This usually offers better performance.
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.
Three new components were added with the release of Tomcat 7:
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 higher.
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.
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 sessions 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.
Tomcat 7.x implements the Servlet 3.0 and JSP 2.2 specifications. 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.
Tomcat 8.x implements the Servlet 3.1 and JSP 2.4 Specifications. Apache Tomcat 8.5.x is intended to replace 8.0.x and includes new features pulled forward from Tomcat 9.0.x. The minimum Java version and implemented specification versions remain unchanged.
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, 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.
|Series||Declared stable||Description||Latest release||Latest release date|
|2.0||Tomcat started off in November 1998 as a servlet reference implementation by James Duncan Davidson, a software architect at Sun Microsystems.|
|Old version, no longer supported: 3.0||1999||Initial release. 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|
|Old version, no longer supported: 4.1||2002-09-06||First Apache Tomcat release to support the Servlet 2.3 and JSP 1.2 specifications.||4.1.40||2009-06-25|
|Old version, no longer supported: 5.0||2003-12-03||First Apache Tomcat release to support the Servlet 2.4, JSP 2.0, and EL 1.1 specifications.||5.0.30||2004-08-30|
|Old version, no longer supported: 5.5||2004-11-10||Designed for J2SE 5.0. Inclusion of Eclipse JDT allows Tomcat to run without a full Java Development Kit being installed.||5.5.36||2012-10-10|
|Old version, no longer supported: 6.0||2007-02-28||First Apache Tomcat release to support the Servlet 2.5, JSP 2.1, and EL 2.1 specifications.||6.0.53||2017-04-07|
|Older version, yet still supported: 7.0||2011-01-14||First Apache Tomcat release to support the Servlet 3.0, JSP 2.2, and EL 2.2 specifications.||7.0.81||2017-08-16|
|Older version, yet still supported: 8.0||2014-06-25||First Apache Tomcat release to support the Servlet 3.1, JSP 2.3, EL 3.0, and WebSocket specifications.||8.0.45||2017-07-01|
|Current stable version: 8.5||2016-06-13||Adds support for HTTP/2, OpenSSL for JSSE, TLS virtual hosting and JASPIC 1.1. Created from Tomcat 9, following delays to Java EE 8.||8.5.20||2017-08-08|
|Latest preview version of a future release: 9.0||alpha||First Apache Tomcat release to support the Servlet 4.0, JSP 2.4 (TBD), EL 3.1 (TBD), specifications.||9.0.0.M26 (alpha)||2017-08-08|
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 (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. In October 2011, the project obtained certification by Oracle Corporation as a compatible implementation of the Java EE 6 Web Profile.
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