WAR (file format)

Last updated
Web ARchive
Filename extension
.war
Internet media type application/java-archive
Magic number PK\x03\x04 (standard ZIP file)
Developed by Sun Microsystems
Container for JSP, Java Servlet
Extended from JAR

In software engineering, a WAR file (Web Application Resource [1] or Web application ARchive [2] ) is a file used to distribute a collection of JAR-files, JavaServer Pages, Java Servlets, Java classes, XML files, tag libraries, static web pages (HTML and related files) and other resources that together constitute a web application.

Contents

Content and structure

A WAR file may be digitally signed in the same way as a JAR file in order to allow others to determine where the source code came from.

There are special files and directories within a WAR file:

Advantages of WAR files

Assuming production environments do not promote a fix without sufficient testing prior to deployment, a WAR file has a distinct advantage when properties files are used to identify environment specific variables. For example, an LDAP server in a testing environment may be something like ldaps://testauth.example.com:636. The LDAP server in a production environment is ldaps://auth.example.com:636. An external properties file would define the link with some thing like:

LINKED_PAGE=ldaps://testauth.example.com:636

The source code reads the property file to determine the target LDAP server. In this way, developers can be certain that the WAR file tested and verified is exactly the same as that which is being promoted to production.

Disadvantages of WAR files

Some consider web deployment using WAR files to be disadvantageous when minor changes to source code are required for dynamic environments. Each change to source code must be repackaged and deployed in development. [3] This does not require stopping the web server if configured for runtime deployment. [4]

Example

The following sample web.xml file demonstrates the declaration and association of a servlet:

<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE web-app    PUBLIC "-//Sun Microsystems, Inc.//DTD Web Application 2.2//EN"    "http://java.sun.com/j2ee/dtds/web-app_2_2.dtd"><web-app><servlet><servlet-name>HelloServlet</servlet-name><servlet-class>mypackage.HelloServlet</servlet-class></servlet><servlet-mapping><servlet-name>HelloServlet</servlet-name><url-pattern>/HelloServlet</url-pattern></servlet-mapping><resource-ref><description>Resourcereferencetoafactoryforjavax.mail.Session instancesthatmaybeusedforsendingelectronicmailmessages, preconfiguredtoconnecttotheappropriateSMTPserver. </description><res-ref-name>mail/Session</res-ref-name><res-type>javax.mail.Session</res-type><res-auth>Container</res-auth></resource-ref></web-app>

The /WEB-INF/classes directory is on the ClassLoader's classpath. (The classpath consists of a list of locations from which .class files can be loaded and executed by the JVM.) The /WEB-INF/classes directory contains the classes associated with the web application itself.

Any JAR files placed in the /WEB-INF/lib directory will also be placed on the ClassLoader's classpath.

See also

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References

  1. ↑ Crossley, Allistair. "Apache Tomcat 8 (8.0.44) - Tomcat Web Application Deployment". Apache Software Foundation . Retrieved 2017-06-27.
  2. ↑ Hunter, Jason (1999-10-15). "What's New in Java Servlet API 2.2?". JavaWorld . Retrieved 2020-11-08.
  3. ↑ "Web Application Lifecycle". The Java EE 6 Tutorial. Oracle.
  4. ↑ "Deploying on a running Tomcat server". Apache Software Foundation.
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