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<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Application Developer's Guide - Deployment</title><meta name="author" value="Craig R. McClanahan"><meta name="email" value="craigmcc@apache.org"></head><body bgcolor="#ffffff" text="#000000" link="#525D76" alink="#525D76" vlink="#525D76"><table border="0" width="100%" cellspacing="0"><!--PAGE HEADER--><tr><td><!--PROJECT LOGO--><a href="http://tomcat.apache.org/"><img src="../../images/tomcat.gif" align="right" alt="
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The Apache Tomcat Servlet/JSP Container
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" border="0"></a></td><td><font face="arial,helvetica,sanserif"><h1>Apache Tomcat 6.0</h1></font></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img src="../../images/asf-logo.gif" align="right" alt="Apache Logo" border="0"></a></td></tr></table><table border="0" width="100%" cellspacing="4"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr noshade="noshade" size="1"></td></tr><tr><!--RIGHT SIDE MAIN BODY--><td width="80%" valign="top" align="left"><table border="0" width="100%" cellspacing="4"><tr><td align="left" valign="top"><h1>Application Developer's Guide</h1><h2>Deployment</h2></td><td align="right" valign="top" nowrap="true"><img src="../../images/void.gif" width="1" height="1" vspace="0" hspace="0" border="0"></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Background"><strong>Background</strong></a></font></td></tr><tr><td><blockquote>
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<p>Before describing how to organize your source code directories,
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it is useful to examine the runtime organization of a web application.
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Prior to the Servlet API Specification, version 2.2, there was little
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consistency between server platforms. However, servers that conform
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to the 2.2 (or later) specification are required to accept a
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<em>Web Application Archive</em> in a standard format, which is discussed
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further below.</p>
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<p>A web application is defined as a hierarchy of directories and files
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in a standard layout. Such a hierarchy can be accessed in its "unpacked"
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form, where each directory and file exists in the filesystem separately,
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or in a "packed" form known as a Web ARchive, or WAR file. The former format
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is more useful during development, while the latter is used when you
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distribute your application to be installed.</p>
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<p>The top-level directory of your web application hierarchy is also the
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<em>document root</em> of your application. Here, you will place the HTML
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files and JSP pages that comprise your application's user interface. When the
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system administrator deploys your application into a particular server, he
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or she assigns a <em>context path</em> to your application (a later section
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of this manual describes deployment on Tomcat). Thus, if the
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system administrator assigns your application to the context path
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<code>/catalog</code>, then a request URI referring to
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<code>/catalog/index.html</code> will retrieve the <code>index.html</code>
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file from your document root.</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Standard Directory Layout"><strong>Standard Directory Layout</strong></a></font></td></tr><tr><td><blockquote>
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<p>To facilitate creation of a Web Application Archive file in the required
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format, it is convenient to arrange the "executable" files of your web
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application (that is, the files that Tomcat actually uses when executing
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your app) in the same organization as required by the WAR format itself.
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To do this, you will end up with the following contents in your
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application's "document root" directory:</p>
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<ul>
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<li><strong>*.html, *.jsp, etc.</strong> - The HTML and JSP pages, along
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with other files that must be visible to the client browser (such as
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JavaScript, stylesheet files, and images) for your application.
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In larger applications you may choose to divide these files into
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a subdirectory hierarchy, but for smaller apps, it is generally
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much simpler to maintain only a single directory for these files.
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<br><br></li>
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<li><strong>/WEB-INF/web.xml</strong> - The <em>Web Application Deployment
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Descriptor</em> for your application. This is an XML file describing
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the servlets and other components that make up your application,
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along with any initialization parameters and container-managed
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security constraints that you want the server to enforce for you.
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This file is discussed in more detail in the following subsection.
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<br><br></li>
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<li><strong>/WEB-INF/classes/</strong> - This directory contains any Java
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class files (and associated resources) required for your application,
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including both servlet and non-servlet classes, that are not combined
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into JAR files. If your classes are organized into Java packages,
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you must reflect this in the directory hierarchy under
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<code>/WEB-INF/classes/</code>. For example, a Java class named
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<code>com.mycompany.mypackage.MyServlet</code>
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would need to be stored in a file named
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<code>/WEB-INF/classes/com/mycompany/mypackage/MyServlet.class</code>.
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<br><br></li>
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<li><strong>/WEB-INF/lib/</strong> - This directory contains JAR files that
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contain Java class files (and associated resources) required for your
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application, such as third party class libraries or JDBC drivers.</li>
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</ul>
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<p>When you install an application into Tomcat (or any other
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2.2/2.3-compatible server), the classes in the <code>WEB-INF/classes/</code>
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directory, as well as all classes in JAR files found in the
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<code>WEB-INF/lib/</code> directory, are made visible to other classes
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within your particular web application. Thus, if
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you include all of the required library classes in one of these places (be
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sure to check licenses for redistribution rights for any third party libraries
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you utilize), you will simplify the installation of your web application --
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no adjustment to the system class path (or installation of global library
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files in your server) will be necessary.</p>
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<p>Much of this information was extracted from Chapter 9 of the Servlet
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API Specification, version 2.3, which you should consult for more details.</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Shared Library Files"><strong>Shared Library Files</strong></a></font></td></tr><tr><td><blockquote>
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<p>Like most servlet containers, Tomcat 5 also supports mechanisms to install
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library JAR files (or unpacked classes) once, and make them visible to all
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installed web applications (without having to be included inside the web
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application itself. The details of how Tomcat locates and shares such
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classes are described in the
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<a href="../../class-loader-howto.html">Class Loader HOW-TO</a> documentation.
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For the purposes of our discussion, there are two locations that are commonly
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used within a Tomcat 5 installation for shared code:</p>
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<ul>
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<li><strong>$CATALINA_HOME/common/lib</strong> - JAR files placed here are
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visible both to web applications and internal Tomcat code. This is a
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good place to put JDBC drivers that are required for both your application
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and internal Tomcat use (such as for a JDBCRealm).
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<br><br></li>
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<li><strong>$CATALINA_BASE/shared/lib</strong> - JAR files placed here are
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visible to all web applications, but not to internal Tomcat code. This
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is the right place for shared libraries that are specific to your
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application.<br><br></li>
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</ul>
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<p>Out of the box, a standard Tomcat 5 installation includes a variety
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of pre-installed shared library files, including:</p>
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<ul>
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<li>The <em>Servlet 2.4</em> and <em>JSP 2.0</em> APIs that are fundamental
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to writing servlets and JavaServer Pages.<br><br></li>
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<li>An <em>XML Parser</em> compliant with the JAXP (version 1.2) APIs, so
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your application can perform DOM-based or SAX-based processing of
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XML documents.<br><br></li>
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</ul>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Web Application Deployment Descriptor"><strong>Web Application Deployment Descriptor</strong></a></font></td></tr><tr><td><blockquote>
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<blockquote><em>
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<p>The description below uses the variable name $CATALINA_HOME
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to refer to the directory into which you have installed Tomcat 5,
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and is the base directory against which most relative paths are
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resolved. However, if you have configured Tomcat 5 for multiple
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instances by setting a CATALINA_BASE directory, you should use
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$CATALINA_BASE instead of $CATALINA_HOME for each of these
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references.</p>
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</em></blockquote>
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<p>As mentioned above, the <code>/WEB-INF/web.xml</code> file contains the
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Web Application Deployment Descriptor for your application. As the filename
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extension implies, this file is an XML document, and defines everything about
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your application that a server needs to know (except the <em>context path</em>,
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which is assigned by the system administrator when the application is
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deployed).</p>
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<p>The complete syntax and semantics for the deployment descriptor is defined
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in Chapter 13 of the Servlet API Specification, version 2.3. Over time, it
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is expected that development tools will be provided that create and edit the
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deployment descriptor for you. In the meantime, to provide a starting point,
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a <a href="web.xml.txt">basic web.xml file</a>
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is provided. This file includes comments that describe the purpose of each
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included element.</p>
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<p><strong>NOTE</strong> - The Servlet Specification includes a Document
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Type Descriptor (DTD) for the web application deployment descriptor, and
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Tomcat 5 enforces the rules defined here when processing your application's
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<code>/WEB-INF/web.xml</code> file. In particular, you <strong>must</strong>
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enter your descriptor elements (such as <code><filter></code>,
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<code><servlet></code>, and <code><servlet-mapping></code> in
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the order defined by the DTD (see Section 13.3).</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Tomcat Context Descriptor"><strong>Tomcat Context Descriptor</strong></a></font></td></tr><tr><td><blockquote>
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<blockquote><em>
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<p>The description below uses the variable name $CATALINA_HOME
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to refer to the directory into which you have installed Tomcat 5,
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and is the base directory against which most relative paths are
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resolved. However, if you have configured Tomcat 5 for multiple
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instances by setting a CATALINA_BASE directory, you should use
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$CATALINA_BASE instead of $CATALINA_HOME for each of these
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references.</p>
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</em></blockquote>
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<p>A /META-INF/context.xml file can be used to define Tomcat specific
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configuration options, such as loggers, data sources, session manager
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configuration and more. This XML file must contain one Context element, which
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will be considered as if it was the child of the Host element corresponding
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to the Host to which the The Tomcat configuration documentation contains
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information on the Context element.</p>
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</blockquote></td></tr></table><table border="0" cellspacing="0" cellpadding="2"><tr><td bgcolor="#525D76"><font color="#ffffff" face="arial,helvetica.sanserif"><a name="Deployment With Tomcat 5"><strong>Deployment With Tomcat 5</strong></a></font></td></tr><tr><td><blockquote>
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<p>In order to be executed, a web application must be deployed on
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a servlet container. This is true even during development.
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We will describe using Tomcat 5 to provide the execution environment.
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A web application can be deployed in Tomcat by one of the following
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approaches:</p>
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<ul>
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<li><em>Copy unpacked directory hierarchy into a subdirectory in directory
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<code>$CATALINA_HOME/webapps/</code></em>. Tomcat will assign a
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context path to your application based on the subdirectory name you
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choose. We will use this technique in the <code>build.xml</code>
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file that we construct, because it is the quickest and easiest approach
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during development. Be sure to restart Tomcat after installing or
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updating your application.
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<br><br></li>
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<li><em>Copy the web application archive file into directory
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<code>$CATALINA_HOME/webapps/</code></em>. When Tomcat is started, it will
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automatically expand the web application archive file into its unpacked
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form, and execute the application that way. This approach would typically
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be used to install an additional application, provided by a third party
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vendor or by your internal development staff, into an existing
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Tomcat installation. <strong>NOTE</strong> - If you use this approach,
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and wish to update your application later, you must both replace the
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web application archive file <strong>AND</strong> delete the expanded
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directory that Tomcat created, and then restart Tomcat, in order to reflect
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your changes.
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<br><br></li>
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<li><em>Use the Tomcat 5 "Manager" web application to deploy and undeploy
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web applications</em>. Tomcat 5 includes a web application, deployed
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by default on context path <code>/manager</code>, that allows you to
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deploy and undeploy applications on a running Tomcat server without
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restarting it. See the administrator documentation (TODO: hyperlink)
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for more information on using the Manager web application.<br><br></li>
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<li><em>Use "Manager" Ant Tasks In Your Build Script</em>. Tomcat 5
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includes a set of custom task definitions for the <code>Ant</code>
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build tool that allow you to automate the execution of commands to the
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"Manager" web application. These tasks are used in the Tomcat deployer.
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<br><br></li>
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<li><em>Use the Tomcat Deployer</em>. Tomcat 5 includes a packaged tool
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bundling the Ant tasks, and can be used to automatically precompile JSPs
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which are part of the web application before deployment to the server.
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<br><br></li>
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</ul>
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<p>Deploying your app on other servlet containers will be specific to each
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container, but all containers compatible with the Servlet API Specification
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(version 2.2 or later) are required to accept a web application archive file.
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Note that other containers are <strong>NOT</strong> required to accept an
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unpacked directory structure (as Tomcat does), or to provide mechanisms for
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shared library files, but these features are commonly available.</p>
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</blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr noshade="noshade" size="1"></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font color="#525D76" size="-1"><em>
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Copyright © 1999-2006, Apache Software Foundation
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</em></font></div></td></tr></table></body></html>
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