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<html><head><META http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><title>Catalina Functional Specifications - Invoker Servlet</title><meta content="Craig McClanahan" name="author"><style media="print" type="text/css"> .noPrint {display: none;} td#mainBody {width: 100%;} </style></head><body vlink="#525D76" alink="#525D76" link="#525D76" text="#000000" bgcolor="#ffffff"><table cellspacing="0" width="100%" border="0"><!--PAGE HEADER--><tr><td><!--PROJECT LOGO--><a href="http://tomcat.apache.org/"><img border="0" alt=" Catalina Functional Specifications " align="right" src="../images/tomcat.gif"></a></td><td><h1><font face="arial,helvetica,sanserif">Apache Tomcat 6.0</font></h1></td><td><!--APACHE LOGO--><a href="http://www.apache.org/"><img border="0" alt="Apache Logo" align="right" src="../images/asf-logo.gif"></a></td></tr></table><table cellspacing="4" width="100%" border="0"><!--HEADER SEPARATOR--><tr><td colspan="2"><hr size="1" noshade></td></tr><tr><!--LEFT SIDE NAVIGATION--><td class="noPrint" nowrap valign="top" width="20%"><p><strong>Links</strong></p><ul><li><a href="../index.html">Docs Home</a></li><li><a href="index.html">Functional Specs</a></li></ul><p><strong>Administrative Apps</strong></p><ul><li><a href="fs-admin-apps.html">Overall Requirements</a></li><li><a href="mbean-names.html">Tomcat MBean Names</a></li><li><a href="fs-admin-objects.html">Administered Objects</a></li><li><a href="fs-admin-opers.html">Supported Operations</a></li></ul><p><strong>Internal Servlets</strong></p><ul><li><a href="fs-default.html">Default Servlet</a></li><li><a href="fs-invoker.html">Invoker Servlet</a></li></ul><p><strong>Realm Implementations</strong></p><ul><li><a href="fs-jdbc-realm.html">JDBC Realm</a></li><li><a href="fs-jndi-realm.html">JNDI Realm</a></li><li><a href="fs-memory-realm.html">Memory Realm</a></li></ul></td><!--RIGHT SIDE MAIN BODY--><td id="mainBody" align="left" valign="top" width="80%"><h1>Catalina Functional Specifications</h1><h2>Invoker Servlet</h2><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Table of Contents"><strong>Table of Contents</strong></a></font></td></tr><tr><td><blockquote> <ul><li><a href="#Overview">Overview</a><ol><li><a href="#Introduction">Introduction</a></li><li><a href="#External Specifications">External Specifications</a></li><li><a href="#Implementation Requirements">Implementation Requirements</a></li></ol></li><li><a href="#Dependencies">Dependencies</a><ol><li><a href="#Environmental Dependencies">Environmental Dependencies</a></li><li><a href="#Container Dependencies">Container Dependencies</a></li></ol></li><li><a href="#Functionality">Functionality</a><ol><li><a href="#Initialization Functionality">Initialization Functionality</a></li><li><a href="#Per-Request Functionality">Per-Request Functionality</a></li><li><a href="#Finalization Functionality">Finalization Functionality</a></li></ol></li><li><a href="#Testable Assertions">Testable Assertions</a></li></ul> </blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Overview"><strong>Overview</strong></a></font></td></tr><tr><td><blockquote> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Introduction"><strong>Introduction</strong></a></font></td></tr><tr><td><blockquote> <p>The purpose of the <strong>Invoker Servlet</strong> is to allow a web application to dynamically register new <em>servlet definitions</em> that correspond with a <code><servlet></code> element in the <code>/WEB-INF/web.xml</code> deployment descriptor, and execute requests utilizing the new servlet definitions. From the perspective of the newly registered servlets, all servlet lifecycle requirements of the Servlet Specification (such as calling <code>init()</code> and <code>destroy()</code> at the correct times) will be respected.</p> </blockquote></td></tr></table> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="External Specifications"><strong>External Specifications</strong></a></font></td></tr><tr><td><blockquote> <p>I do not know of any formal specification of the behavior of an invoker servlet that is publicly available. Anyone know of one?</p> </blockquote></td></tr></table> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Implementation Requirements"><strong>Implementation Requirements</strong></a></font></td></tr><tr><td><blockquote> <p>The implementation of this functionality shall conform to the following requirements:</p> <ul> <li>Implemented as a servlet.</li> <li>Exist in the <code>org.apache.catalina.servlets</code> package so that it can be loaded by the Catalina class loader.</li> <li>Implement the <code>org.apache.catalina.ContainerServlet</code> interface, so that it gains knowledge of the <code>Wrapper</code> that is responsible for itself and, therefore, access to other internal Catalina components.</li> <li>Support a configurable debugging detail level.</li> <li>Log debugging and operational messages (suitably internationalized) via the <code>getServletContext().log()</code> method.</li> </ul> </blockquote></td></tr></table> </blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Dependencies"><strong>Dependencies</strong></a></font></td></tr><tr><td><blockquote> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Environmental Dependencies"><strong>Environmental Dependencies</strong></a></font></td></tr><tr><td><blockquote> <p>The following environmental dependencies must be met in order for the Invoker servlet to operate correctly:</p> <ul> <li>The invoker servlet must be registered in the application deployment descriptor (or the default deployment descriptor in file <code>$CATALINA_BASE/conf/web.xml</code>) using a "path mapped" servlet mapping. The historical default mapping is to URL pattern "<code>/servlet/</code>", although the invoker servlet must operate correctly with an arbitrary mapping.</li> </ul> </blockquote></td></tr></table> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Container Dependencies"><strong>Container Dependencies</strong></a></font></td></tr><tr><td><blockquote> <p>Correct operation of the invoker servlet depends on the following specific features of the surrounding container:</p> <ul> <li>Correct support for the <code>ContainerServlet</code> interface, including calling <code>setWrapper()</code> <strong>before</strong> the <code>init()</code> method of the invoker servlet is called.</li> <li>The web application class loader must be stored as the context class loader of the request processing thread.</li> </ul> </blockquote></td></tr></table> </blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Functionality"><strong>Functionality</strong></a></font></td></tr><tr><td><blockquote> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Initialization Functionality"><strong>Initialization Functionality</strong></a></font></td></tr><tr><td><blockquote> <p>The following processing must be performed when the <code>init()</code> method of the invoker servlet is called:</p> <ul> <li>Ensure that the container has called <code>setWrapper()</code>. If not, throw a permanent <code>UnavailableException</code>.</li> <li>Look up and cache the <code>Context</code> that corresponds to our <code>Wrapper</code>. This is the component with which new servlet definitions and mappings will be registered.</li> </ul> </blockquote></td></tr></table> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Per-Request Functionality"><strong>Per-Request Functionality</strong></a></font></td></tr><tr><td><blockquote> <p>On each request, the following processing shall be performed:</p> <ol> <li>Calculate the <code>{ServletPath}</code> for this request, either from request attribute <code>javax.servlet.include.servlet_path</code> or by calling <code>request.getServletPath()</code>.</li> <li>Calculate the <code>{PathInfo}</code> for this request, either from request attribute <code>javax.servlet.include.path_info</code> or by calling <code>request.getPathInfo()</code>. If the calculated <code>{PathInfo}</code> is null, return HTTP status 400 (bad request).</li> <li>Parse the calculated <code>{PathInfo}</code> value as follows: <ol> <li>Ignore the leading slash character.</li> <li>Accumulate characters up to the next '/' (if any) as the <code>{ServletSelector}</code>.</li> <li>If a '/' was encountered, accumulate all characters from that slash (inclusive) to the end of the string as <code>{PathRemainder}</code>. If no slash was encountered, set <code>{PathRemainder}</code> to a zero-length string.</li> </ol></li> <li>Determine whether <code>{ServletSelector}</code> is the name of an existing servlet definition, and process it as follows: <ol> <li>Ask our associated <code>Context</code> to find and return a child <code>Wrapper</code> named <code>{ServletSelector}</code>. </li> <li>If there is no such child, skip to the next major step.</li> <li>Register a new servlet mapping for this <code>Wrapper</code>, using a URL pattern calculated as follows: <code>{ServletPath}</code> + "/" + <code>{ServletSelector}</code> + "/"</li> <li>Create a request dispatcher using a path calculated as follows: <code>{ServletPath}</code> + "/" + <code>{ServletSelector}</code> + <code>{PathRemainder}</code></li> <li>Forward this request to the created request dispatcher, and exit from this request.</li> </ol></li> <li>Assume that <code>{ServletSelector}</code> is the fully qualified name of a Java class that implements <code>javax.servlet.Servlet</code> and process it as follows: <ol> <li>Synthesize a new <code>{ServletName}</code> for the servlet definition that will be created.</li> <li>If there is already a child <code>Wrapper</code> associated with this name, return HTTP status 500 (internal server error), because a mapping should have already been created for this servlet.</li> <li>Attempt to load a class named <code>{ServletSelector}</code> from the web application class loader (i.e. the context class loader for our current thread). If this fails, return HTTP status 404 (not found).</li> <li>Instantiate an instance of this class. If an error occurs, return HTTP status 404 (not found).</li> <li>If this class does not implement the <code>javax.servlet.Servlet</code> interface, return HTTP status 404 (not found).</li> <li>Create and register a new <code>Wrapper</code> child with our <code>Context</code>, under name <code>{ServletName}</code>.</li> <li>Register a new servlet mapping for this <code>Wrapper</code>, using a URL pattern calculated as follows: <code>{ServletPath}</code> + "/" + <code>{ServletSelector}</code> + "/*"</li> <li>Create a request dispatcher using a path calculated as follows: <code>{ServletPath}</code> + "/" + <code>{ServletSelector}</code> + <code>{PathRemainder}</code></li> <li>Forward this request to the created request dispatcher, and exit from this request.</li> </ol></li> </ol> </blockquote></td></tr></table> <table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#828DA6"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Finalization Functionality"><strong>Finalization Functionality</strong></a></font></td></tr><tr><td><blockquote> <p>No specific processing is required when the <code>destroy()</code> method is called:</p> </blockquote></td></tr></table> </blockquote></td></tr></table><table cellpadding="2" cellspacing="0" border="0"><tr><td bgcolor="#525D76"><font face="arial,helvetica.sanserif" color="#ffffff"><a name="Testable Assertions"><strong>Testable Assertions</strong></a></font></td></tr><tr><td><blockquote> <p>In addition the the assertions implied by the functionality requirements listed above, the following additional assertions shall be tested to validate the behavior of the invoker servlet:</p> <ul> <li>It is possible to access an existing servlet definition by name through the invoker. The existing servlet definition can include either a <code><servlet-class></code> or <code><jsp-file></code> subelement.</li> <li>When an existing servlet definition is accessed by name, the request will be ultimately processed by the same servlet instance that would have processed it had a mapping to that servlet definition been used on the request directly.</li> <li>It is possible to access an anonymous servlet by class name through the invoker.</li> <li>When an anonymous servlet is accessed, the servlet instance is processed according to the lifecycle requirements of the Servlet Specification. </li> <li>When an anonymous servlet is accessed, the servlet instance receives a <code>ServletConfig</code> instance with no servlet initialization parameters.</li> <li>It is possible to utilize the invoker servlet via a direct request.</li> <li>It is possible to utilize the invoker servlet via a call to <code>RequestDispatcher.forward()</code>, or the corresponding <code><jsp:forward></code> tag in a JSP page.</li> <li>It is possible to utilize the invoker servlet via a call to <code>RequestDispatcher.include()</code>, or the corresponding <code><jsp:include></code> tag in a JSP page.</li> <li>It is possible to use any HTTP method (including GET and POST) that is supported by the Servlet class that is ultimately executed.</li> <li>The invoker servlet should never be asked to process a second or subsequent request for the same <code>{ServletSelector}</code> (because it will have registered an appropriate servlet mapping.</li> </ul> </blockquote></td></tr></table></td></tr><!--FOOTER SEPARATOR--><tr><td colspan="2"><hr size="1" noshade></td></tr><!--PAGE FOOTER--><tr><td colspan="2"><div align="center"><font size="-1" color="#525D76"><em> Copyright © 1999-2010, Apache Software Foundation </em></font></div></td></tr></table></body></html>

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