WAR (Sun file format)

Infobox file format
name = Web ARchive
extension = .war
mime =
owner = Sun Microsystems
creatorcode =
genre =
containerfor = JSP, Java Servlet
containedby =
extendedfrom =
extendedto = In computing, a WAR file (which stands for "web application archive" [http://java.sun.com/developer/technicalArticles/Servlets/servletapi/] ) is a JAR file used to distribute a collection of JavaServer Pages, servlets, Java classes, XML files, tag libraries and static Web pages (HTML and related files) that together constitute a Web application.

Content and structure

A WAR file may be digitally signed in the same way as a JAR file in order to assert that the code is trusted.

There are special files and directories within a WAR file.

The /WEB-INF directory in the WAR file contains a file named web.xml which defines the structure of the web application. If the web application is only serving JSP files, the web.xml file is not strictly necessary. If the web application uses servlets, then the servlet container uses web.xml to ascertain to which servlet a URL request is to be routed. web.xml is also used to define context variables which can be referenced within the servlets and it is used to define environmental dependencies which the deployer is expected to set up. An example of this is a dependency on a mail session used to send email. The servlet container is responsible for providing this service.

One disadvantage of web deployment using WAR files in very dynamic environments is that minor changes cannot be made during runtime. Any change whatsoever requires regenerating and redeploying the entire WAR file. Most JEE web containers allow web applications to be deployed as a directory instead of a single file. This is known as an exploded archive. An exploded archive may be used during development to quickly test changes to a web application.

The following sample "web.xml" file demonstrates how a servlet is declared and associated. HelloServlet mypackage.HelloServlet HelloServlet /HelloServlet Resource reference to a factory for javax.mail.Session instances that may be used for sending electronic mail messages, preconfigured to connect to the appropriate SMTP server. mail/Session javax.mail.Session Container The /WEB-INF/classes directory is on the ClassLoader's classpath. This is where .class files are loaded from when the web application is executing.Any JAR files placed in the /WEB-INF/lib directory will also be placed on the ClassLoader's classpath.

See also

Related file formats:
* EAR (file format)
* JAR (file format)

External links

* [http://www.jsptube.com Servlet tutorial]
* [http://java.sun.com/j2ee/tutorial/1_3-fcs/doc/WCC3.html SDN J2EE 1.3 Tutorial: Web Application Archives]
* [http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd Sun Microsystems: XML Schema for the Servlet 2.5 Web ARchive (WAR) File]
* [http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd Sun Microsystems: XML Schema for the Servlet 2.4 Web ARchive (WAR) File]