Though it started out as a pure information resource, freely accessible to people all over the globe, the world wide web has evolved to offer much more today. As opposed to the passive information repository it was before, now Internet offers many services ranging from online banking, social networking, email, e-shopping, video sharing, online auctions to multiplayer gaming and much more, which are all made possible due to the advances in web technologies.
All these services are enabled by web servers, which host the pages and handle all the client queries. Associated technologies like web containers are used to extend server functionality and provide additional services through usage of Java servlets. In this Buzzle article, I present a web container vs web server comparison which clarifies the differences between these two commonly used web technologies.
What is a Web Server?
The whole TCP/IP (Transmission Control Protocol / Internet Protocol) based Internet architecture is based on a 'Client-Server' model. Every time you type in a web site address in your browser, a query is sent to the web server, hosting the pages. All the web site resources (pages, images) and services are hosted on it, which are then served to the client web browsers, according to request. Through HTTP (Hypertext Transfer Protocol), a server communicates with client computers to facilitate the sharing of data and resources.
Of the different types of computer servers, these types have the most complicated software architecture and are usually run on high-end machines with great processing power, with 24x7 battery backup. Ergo, when one refers to a web server, it refers to the server software, as well as computer hardware. Microsoft's Internet Information Services (IIS), Apache HTTP Server and nginx are some of the most commonly used web servers on the Internet.
What is a Web Container?
A web container (more commonly known as a servlet container) is an application implemented on web servers to makes the implementation of 'Java Servlets' and 'Java Server Pages' possible. A container creates a completely independent environment for running servlets and Java server pages for the purpose of offering dynamic content to website visitors. It is primarily designed to run Java coding on a web server. All web containers are JEE (Java Platform Enterprise Edition) compliant. The servlets are executed in the run time environment provided by the container through the use of JSP engine and servlet engines. One of the most popular web containers is Apache Tomcat. It is an open source software program developed by the Apache Software Foundation.
Difference Between Web Container and Web Server
A web container is purely devoted to running of servlets while a web server is involved in delivering web page data and resources, according to client requests. A web server runs several applications including a web container software. Therefore a web server is a super set, of which a web container is only a part. However, some modern web containers can function without the support of a web server and act as standalone servers, for providing dynamic content. With the help of web containers, a web server can offer applications running on the Java platform. The fact that modern web containers can be implemented independently, may have led to the confusion between the two technologies.
To conclude, a web container is an application run by a web server to provide added site functionality for a hosted website and is primarily an environment in which servlets are implemented. On the other hand, a web server is the 'mother-ship' of all technologies deployed by a web site which directly handles all the client requests for data and resources hosted by it. For more information on servlets and web containers, it's suggested that you refer to Sun's tutorial on the same topic.