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<!DOCTYPE document [
<!ENTITY project SYSTEM "project.xml">
]>
<document url="context.html">
&project;
<properties>
<author email="craigmcc@apache.org">Craig R. McClanahan</author>
<title>The Context Container</title>
</properties>
<body>
<section name="Table of Contents">
<toc/>
</section>
<section name="Introduction">
<p><em>
The description below uses the variable name $CATALINA_BASE to refer the
base directory against which most relative paths are resolved. If you have
not configured Tomcat for multiple instances by setting a CATALINA_BASE
directory, then $CATALINA_BASE will be set to the value of $CATALINA_HOME,
the directory into which you have installed Tomcat.
</em></p>
<p>The <strong>Context</strong> element represents a <em>web
application</em>, which is run within a particular virtual host.
Each web application is based on a <em>Web Application Archive</em>
(WAR) file, or a corresponding directory containing the corresponding
unpacked contents, as described in the Servlet Specification (version
2.2 or later). For more information about web application archives,
you can download the
<a href="http://wiki.apache.org/tomcat/Specifications">Servlet
Specification</a>, and review the Tomcat
<a href="../appdev/index.html">Application Developer's Guide</a>.</p>
<p>The web application used to process each HTTP request is selected
by Catalina based on matching the longest possible prefix of the
Request URI against the <em>context path</em> of each defined Context.
Once selected, that Context will select an appropriate servlet to
process the incoming request, according to the servlet mappings defined
by the web application deployment.</p>
<p>You may define as many <strong>Context</strong> elements as you
wish. Each such Context MUST have a unique context name within a virtual
host. The context path does not need to be unique (see <em>parallel
deployment</em> below). In addition, a Context must be present with a
context path equal to
a zero-length string. This Context becomes the <em>default</em>
web application for this virtual host, and is used to process all
requests that do not match any other Context's context path.</p>
<subsection name="Parallel deployment">
<p><b>You may deploy multiple versions of a web application with the same
context path at the same time.</b> The rules used to match requests to a
context version are as follows:
</p>
<ul>
<li>If no session information is present in the request, use the latest
version.</li>
<li>If session information is present in the request, check the session
manager of each version for a matching session and if one is found, use that
version.</li>
<li>If session information is present in the request but no matching session
can be found, use the latest version.</li>
</ul>
<p>The <a href="host.html">Host</a> may be configured (via the
<code>undeployOldVersions</code>) to remove old versions deployed in this way
once they are no longer in use.</p>
</subsection>
<subsection name="Naming">
<p>When <code>autoDeploy</code> or <code>deployOnStartup</code> operations
are performed by a Host, the name and context path of the web application are
derived from the name(s) of the file(s) that define(s) the web application.
Consequently, the context path <strong>may not</strong> be defined in a
<code>META-INF/context.xml</code> embedded in the application and there is a
close relationship between the <em>context name</em>, <em>context path</em>,
<em>context version</em> and the <em>base file name</em> (the name minus any
<code>.war</code> or <code>.xml</code> extension) of the file.</p>
<p>If no version is specified then the <em>context name</em> is always the
same as the <em>context path</em>. If the <em>context path</em> is the empty
string them the <em>base name</em> will be ROOT (always in upper case)
otherwise the <em>base name</em> will be the <em>context path</em> with the
leading '/' removed and any remaining '/' characters replaced with '#'.</p>
<p>If a version is specified then the <em>context path</em> remains unchanged
and both the <em>context name</em> and the <em>base name</em> have the string
'##' appended to them followed by the version identifier.</p>
<p>Some examples of these naming conventions are given below.</p>
<table class="detail-table">
<tr>
<th>Context Path</th>
<th>Context Version</th>
<th>Context Name</th>
<th>Base File Name</th>
<th>Example File Names (.xml, .war &amp; directory)</th>
</tr>
<tr>
<td>/foo</td>
<td><i>None</i></td>
<td>/foo</td>
<td>foo</td>
<td>foo.xml, foo.war, foo</td>
</tr>
<tr>
<td>/foo/bar</td>
<td><i>None</i></td>
<td>/foo/bar</td>
<td>foo#bar</td>
<td>foo#bar.xml, foo#bar.war, foo#bar</td>
</tr>
<tr>
<td><i>Empty String</i></td>
<td><i>None</i></td>
<td><i>Empty String</i></td>
<td>ROOT</td>
<td>ROOT.xml, ROOT.war, ROOT</td>
</tr>
<tr>
<td>/foo</td>
<td>42</td>
<td>/foo##42</td>
<td>foo##42</td>
<td>foo##42.xml, foo##42.war, foo##42</td>
</tr>
<tr>
<td>/foo/bar</td>
<td>42</td>
<td>/foo/bar##42</td>
<td>foo#bar##42</td>
<td>foo#bar##42.xml, foo#bar##42.war, foo#bar##42</td>
</tr>
<tr>
<td><i>Empty String</i></td>
<td>42</td>
<td>##42</td>
<td>ROOT##42</td>
<td>ROOT##42.xml, ROOT##42.war, ROOT##42</td>
</tr>
</table>
<p>The version component is treated as a <code>String</code> both for
performance reasons and to allow flexibility in versioning schemes. String
comparisons are used to determine version order. If version is not specified,
it is treated as the empty string.
Therefore,
<code>foo.war</code> will be treated as an earlier version than
<code>foo##11.war</code> and
<code>foo##11.war</code> will be treated as an earlier version than
<code>foo##2.war</code>. If using a purely numerical versioning scheme it is
recommended that zero padding is used so that <code>foo##002.war</code> is
treated as an earlier version than <code>foo##011.war</code>.
</p>
<p>If you want to deploy a WAR file or a directory using a context path that
is not related to the base file name then one of the following options must
be used to prevent double-deployment:
</p>
<ul>
<li>Disable autoDeploy and deployOnStartup and define all
<strong>Context</strong>s in server.xml</li>
<li>Locate the WAR and/or directory outside of the Host&apos;s appBase and use
a context.xml file with a docBase attribute to define it.</li>
</ul>
</subsection>
<subsection name="Defining a context">
<p><b>It is NOT recommended to place &lt;Context&gt; elements directly in the
server.xml file.</b> This is because it makes modifying the
<strong>Context</strong> configuration more invasive since the main
<code>conf/server.xml</code> file cannot be reloaded without restarting
Tomcat.</p>
<p>Individual <strong>Context</strong> elements may be explicitly defined:
</p>
<ul>
<li>In an individual file at <code>/META-INF/context.xml</code> inside the
application files. Optionally (based on the Host&apos;s copyXML attribute)
this may be copied to
<code>$CATALINA_BASE/conf/[enginename]/[hostname]/</code> and renamed to
application&apos;s base file name plus a ".xml" extension.</li>
<li>In individual files (with a ".xml" extension) in the
<code>$CATALINA_BASE/conf/[enginename]/[hostname]/</code> directory.
The context path and version will be derived from the base name of the file
(the file name less the .xml extension). This file will always take precedence
over any context.xml file packaged in the web application&apos;s META-INF
directory.</li>
<li>Inside a <a href="host.html">Host</a> element in the main
<code>conf/server.xml</code>.</li>
</ul>
<p>Default <strong>Context</strong> elements may be defined that apply to
multiple web applications. Configuration for an individual web application
will override anything configured in one of these defaults. Any nested
elements, e.g. &lt;Resource&gt; elements, that are defined in a default
<strong>Context</strong> will be created once for each
<strong>Context</strong> to which the default applies. They will <b>not</b> be
shared between <strong>Context</strong> elements.
</p>
<ul>
<li>In the <code>$CATALINA_BASE/conf/context.xml</code> file:
the Context element information will be loaded by all web applications.</li>
<li>In the
<code>$CATALINA_BASE/conf/[enginename]/[hostname]/context.xml.default</code>
file: the Context element information will be loaded by all web applications
of that host.</li>
</ul>
<p>With the exception of server.xml, files that define <strong>Context
</strong> elements may only define a single <strong>Context</strong> element.
</p>
<p>In addition to explicitly specified Context elements, there are
several techniques by which Context elements can be created automatically
for you. See <a href="host.html#Automatic_Application_Deployment">
Automatic Application Deployment</a> and
<a href="host.html#User_Web_Applications">User Web Applications</a>
for more information.</p>
<p>To define multiple contexts that use a single WAR file or directory,
use one of the options described in the <a href="#Naming">Naming</a>
section above for creating a <strong>Context</strong> that has a path
that is not related to the base file name.</p>
</subsection>
</section>
<section name="Attributes">
<subsection name="Common Attributes">
<p>All implementations of <strong>Context</strong>
support the following attributes:</p>
<attributes>
<attribute name="allowCasualMultipartParsing" required="false">
<p>Set to true if Tomcat should automatically parse
multipart/form-data request bodies when HttpServletRequest.getPart*
or HttpServletRequest.getParameter* is called, even when the
target servlet isn't marked with the @MultipartConfig annotation
(See Servlet Specification 3.0, Section 3.2 for details).
Note that any setting other than <code>false</code> causes Tomcat
to behave in a way that is not technically spec-compliant.
The default is <code>false</code></p>
</attribute>
<attribute name="backgroundProcessorDelay" required="false">
<p>This value represents the delay in seconds between the
invocation of the backgroundProcess method on this context and
its child containers, including all wrappers.
Child containers will not be invoked if their delay value is not
negative (which would mean they are using their own processing
thread). Setting this to a positive value will cause
a thread to be spawn. After waiting the specified amount of time,
the thread will invoke the backgroundProcess method on this host
and all its child containers. A context will use background
processing to perform session expiration and class monitoring for
reloading. If not specified, the default value for this attribute is
-1, which means the context will rely on the background processing
thread of its parent host.</p>
</attribute>
<attribute name="className" required="false">
<p>Java class name of the implementation to use. This class must
implement the <code>org.apache.catalina.Context</code> interface.
If not specified, the standard value (defined below) will be used.</p>
</attribute>
<attribute name="containerSciFilter" required="false">
<p>The regular expression that specifies which container provided SCIs
should be filtered out and not used for this context. Matching uses
<code>java.util.regex.Matcher.find()</code> so the regular expression
only has to match a sub-string of the fully qualified class name of the
container provided SCI for it to be filtered out. If not specified,
no filtering will be applied.</p>
</attribute>
<attribute name="cookies" required="false">
<p>Set to <code>true</code> if you want cookies to be used for
session identifier communication if supported by the client (this
is the default). Set to <code>false</code> if you want to disable
the use of cookies for session identifier communication, and rely
only on URL rewriting by the application.</p>
</attribute>
<attribute name="crossContext" required="false">
<p>Set to <code>true</code> if you want calls within this application
to <code>ServletContext.getContext()</code> to successfully return a
request dispatcher for other web applications running on this virtual
host. Set to <code>false</code> (the default) in security
conscious environments, to make <code>getContext()</code> always
return <code>null</code>.</p>
</attribute>
<attribute name="docBase" required="true">
<p>The <em>Document Base</em> (also known as the <em>Context
Root</em>) directory for this web application, or the pathname
to the web application archive file (if this web application is
being executed directly from the WAR file). You may specify
an absolute pathname for this directory or WAR file, or a pathname
that is relative to the <code>appBase</code> directory of the
owning <a href="host.html">Host</a>.</p>
<p>The value of this field must not be set unless the Context element is
defined in server.xml or the <code>docBase</code> is not located under
the <a href="host.html">Host</a>&apos;s <code>appBase</code>.</p>
<p>If a symbolic link is used for docBase then changes to the
symbolic link will only be effective after a Tomcat restart or
by undeploying and redeploying the context. A context reload is not
sufficient.</p>
</attribute>
<attribute name="failCtxIfServletStartFails" required="false">
<p>Set to <code>true</code> to have the context fail its startup if any
servlet that has load-on-startup &gt;=0 fails its own startup.</p>
<p>If not specified, the attribute of the same name in the parent Host
configuration is used if specified. Otherwise the default value of
<code>false</code> is used.</p>
</attribute>
<attribute name="fireRequestListenersOnForwards" required="false">
<p>Set to <code>true</code> to fire any configured
ServletRequestListeners when Tomcat forwards a request. This is
primarily of use to users of CDI frameworks that use
ServletRequestListeners to configure the necessary environment for a
request. If not specified, the default value of <code>false</code> is
used.</p>
</attribute>
<attribute name="logEffectiveWebXml" required="false">
<p>Set to <code>true</code> if you want the effective web.xml used for a
web application to be logged (at INFO level) when the application
starts. The effective web.xml is the result of combining the
application's web.xml with any defaults configured by Tomcat and any
web-fragment.xml files and annotations discovered. If not specified, the
default value of <code>false</code> is used.</p>
</attribute>
<attribute name="mapperContextRootRedirectEnabled" required="false">
<p>If enabled, requests for a web application context root will be
redirected (adding a trailing slash) if necessary by the Mapper rather
than the default Servlet. This is more efficient but has the side effect
of confirming that the context path exists. If not specified, the
default value of <code>false</code> is used.</p>
</attribute>
<attribute name="mapperDirectoryRedirectEnabled" required="false">
<p>If enabled, requests for a web application directory will be
redirected (adding a trailing slash) if necessary by the Mapper rather
than the default Servlet. This is more efficient but has the side effect
of confirming that the directory is exists. If not specified, the
default value of <code>false</code> is used.</p>
</attribute>
<attribute name="override" required="false">
<p>Set to <code>true</code> to ignore any settings in both the global
or <a href="host.html">Host</a> default contexts. By default, settings
from a default context will be used but may be overridden by a setting
the same attribute explicitly for the Context.</p>
</attribute>
<attribute name="path" required="false">
<p>The <em>context path</em> of this web application, which is
matched against the beginning of each request URI to select the
appropriate web application for processing. All of the context paths
within a particular <a href="host.html">Host</a> must be unique.
If you specify a context path of an empty string (""), you are
defining the <em>default</em> web application for this Host, which
will process all requests not assigned to other Contexts.</p>
<p>This attribute must only be used when statically defining a Context
in server.xml. In all other circumstances, the path will be inferred
from the filenames used for either the .xml context file or the docBase.
</p>
<p>Even when statically defining a Context in server.xml, this attribute
must not be set unless either the docBase is not located under the
<a href="host.html">Host</a>&apos;s <code>appBase</code> or both
<code>deployOnStartup</code> and <code>autoDeploy</code> are false. If
this rule is not followed, double deployment is likely to result.</p>
</attribute>
<attribute name="preemptiveAuthentication" required="false">
<p>When set to <code>true</code> and the user presents credentials for a
resource that is not protected by a security constraint, if the
authenticator supports preemptive authentication (the standard
authenticators provided with Tomcat do) then the user&apos; credentials
will be processed. If not specified, the default of <code>false</code>is
used.
</p>
</attribute>
<attribute name="privileged" required="false">
<p>Set to <code>true</code> to allow this context to use container
servlets, like the manager servlet. Use of the <code>privileged</code>
attribute will change the context's parent class loader to be the
<em>Server</em> class loader rather than the <em>Shared</em> class
loader. Note that in a default installation, the <em>Common</em> class
loader is used for both the <em>Server</em> and the <em>Shared</em>
class loaders.</p>
</attribute>
<attribute name="reloadable" required="false">
<p>Set to <code>true</code> if you want Catalina to monitor classes in
<code>/WEB-INF/classes/</code> and <code>/WEB-INF/lib</code> for
changes, and automatically reload the web application if a change
is detected. This feature is very useful during application
development, but it requires significant runtime overhead and is
not recommended for use on deployed production applications. That's
why the default setting for this attribute is <i>false</i>. You
can use the <a href="../manager-howto.html">Manager</a> web
application, however, to trigger reloads of deployed applications
on demand.</p>
</attribute>
<attribute name="resourceOnlyServlets" required="false">
<p>Comma separated list of Servlet names (as used in
<code>/WEB-INF/web.xml</code>) that expect a resource to be present.
Ensures that welcome files associated with Servlets that expect a
resource to be present (such as the JSP Servlet) are not used when there
is no resource present. This prevents issues caused by the clarification
of welcome file mapping in section 10.10 of the Servlet 3.0
specification. If the
<code>org.apache.catalina.STRICT_SERVLET_COMPLIANCE</code>
<a href="systemprops.html">system property</a> is set to
<code>true</code>, the default value of this attribute will be the empty
string, else the default value will be <code>jsp</code>.</p>
</attribute>
<attribute name="sendRedirectBody" required="false">
<p>If <code>true</code>, redirect responses will include a short
response body that includes details of the redirect as recommended by
RFC 2616. This is disabled by default since including a response body
may cause problems for some application component such as compression
filters.</p>
</attribute>
<attribute name="sessionCookieDomain" required="false">
<p>The domain to be used for all session cookies created for this
context. If set, this overrides any domain set by the web application.
If not set, the value specified by the web application, if any, will be
used.</p>
</attribute>
<attribute name="sessionCookieName" required="false">
<p>The name to be used for all session cookies created for this
context. If set, this overrides any name set by the web application.
If not set, the value specified by the web application, if any, will be
used, or the name <code>JSESSIONID</code> if the web application does
not explicitly set one.</p>
</attribute>
<attribute name="sessionCookiePath" required="false">
<p>The path to be used for all session cookies created for this
context. If set, this overrides any path set by the web application.
If not set, the value specified by the web application will be used, or
the context path used if the web application does not explicitly set
one. To configure all web application to use an empty path (this can be
useful for portlet specification implementations) set this attribute to
<code>/</code> in the global <code>CATALINA_BASE/conf/context.xml</code>
file.</p>
<p>Note: Once one web application using
<code>sessionCookiePath=&quot;/&quot;</code> obtains a session, all
subsequent sessions for any other web application in the same host also
configured with <code>sessionCookiePath=&quot;/&quot;</code> will always
use the same session ID. This holds even if the session is invalidated
and a new one created. This makes session fixation protection more
difficult and requires custom, Tomcat specific code to change the
session ID shared by the multiple applications.</p>
</attribute>
<attribute name="sessionCookiePathUsesTrailingSlash" required="false">
<p>Some browsers, such as IE, will send a session cookie for a context
with a path of /foo with a request to /foobar. To prevent this, Tomcat
will add a trailing slash to the path associated with the session cookie
so, in the above example, the cookie path becomes /foo/. However, with a
cookie path of /foo/, IE will no longer send the cookie with a request
to /foo. This should not be a problem unless there is a servlet mapped
to /*. In this case this feature will need to be disabled. The default
value for this attribute is <code>true.</code> To disable this feature,
set the attribute to <code>false</code>.</p>
</attribute>
<attribute name="swallowAbortedUploads" required="false">
<p>Set to false if Tomcat should <b>not</b> read any additional request
body data for aborted uploads and instead abort the client connection.
This setting is used in the following situations:
</p>
<ul>
<li>the size of the request body is larger than the
<code>maxPostSize</code> configured in the connector</li>
<li>the size limit of a MultiPart upload is reached</li>
<li>the servlet sets the response status to 413 (Request Entity Too
Large) </li>
</ul>
<p>
Not reading the additional data will free the request processing thread
more quickly. Unfortunately most HTTP clients will not read the response
if they can not write the full request.</p>
<p>The default is <code>true</code>, so additional data will be
read.</p>
<p>Note if an error occurs during the request processing that triggers
a 5xx response, any unread request data will always be ignored and the
client connection will be closed once the error response has been
written.</p>
</attribute>
<attribute name="swallowOutput" required="false">
<p>If the value of this flag is <code>true</code>, the bytes output to
System.out and System.err by the web application will be redirected to
the web application logger. If not specified, the default value
of the flag is <code>false</code>.</p>
</attribute>
<attribute name="tldValidation" required="false">
<p>If the value of this flag is <code>true</code>, the TLD files
will be XML validated on context startup. If the
<code>org.apache.catalina.STRICT_SERVLET_COMPLIANCE</code>
<a href="systemprops.html">system property</a> is set to
<code>true</code>, the default value of this attribute will be
<code>true</code>, else the default value will be <code>false</code>.
Setting this attribute to <code>true</code> will incur a performance
penalty.</p>
</attribute>
<attribute name="useHttpOnly" required="false">
<p>Should the HttpOnly flag be set on session cookies to prevent client
side script from accessing the session ID? Defaults to
<code>true</code>.</p>
</attribute>
<attribute name="validateClientProvidedNewSessionId" required="false">
<p>When a client provides the ID for a new session, this attribute
controls whether that ID is validated. The only use case for using a
client provided session ID is to have a common session ID across
multiple web applications. Therefore, any client provided session ID
should already exist in another web application. If this check is
enabled, the client provided session ID will only be used if the session
ID exists in at least one other web application for the current host.
Note that the following additional tests are always applied,
irrespective of this setting:</p>
<ul>
<li>The session ID is provided by a cookie</li>
<li>The session cookie has a path of {@code /}</li>
</ul>
<p>If not specified, the default value of <code>true</code> will be
used.</p>
</attribute>
<attribute name="wrapperClass" required="false">
<p>Java class name of the <code>org.apache.catalina.Wrapper</code>
implementation class that will be used for servlets managed by this
Context. If not specified, a standard default value will be used.</p>
</attribute>
<attribute name="xmlBlockExternal" required="false">
<p>If the value of this flag is <code>true</code>, the parsing of
<code>web.xml</code>, <code>web-fragment.xml</code>, <code>*.tld</code>,
<code>*.jspx</code>, <code>*.tagx</code> and <code>tagPlugins.xml</code>
files for this web application will not permit external entities to be
loaded. If not specified, the default value of <code>true</code> will
be used.</p>
</attribute>
<attribute name="xmlNamespaceAware" required="false">
<p>If the value of this flag is <code>true</code>, the parsing of
<code>web.xml</code> and <code>web-fragment.xml</code> files for this
web application will be namespace-aware. Note that <code>*.tld</code>,
<code>*.jspx</code> and <code>*.tagx</code> files are always parsed
using a namespace-aware parser and that the <code>tagPlugins.xml</code>
file (if any) is never parsed using a namespace-aware parser. Note also
that if you turn this flag on, you should probably also turn
<code>xmlValidation</code> on. If the
<code>org.apache.catalina.STRICT_SERVLET_COMPLIANCE</code>
<a href="systemprops.html">system property</a> is set to
<code>true</code>, the default value of this attribute will be
<code>true</code>, else the default value will be <code>false</code>.
Setting this attribute to <code>true</code> will incur a performance
penalty.</p>
</attribute>
<attribute name="xmlValidation" required="false">
<p>If the value of this flag is <code>true</code>, the parsing of
<code>web.xml</code> and <code>web-fragment.xml</code> files for this
web application will use a validating parser. If the
<code>org.apache.catalina.STRICT_SERVLET_COMPLIANCE</code>
<a href="systemprops.html">system property</a> is set to
<code>true</code>, the default value of this attribute will be
<code>true</code>, else the default value will be <code>false</code>.
Setting this attribute to <code>true</code> will incur a performance
penalty.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Standard Implementation">
<p>The standard implementation of <strong>Context</strong> is
<strong>org.apache.catalina.core.StandardContext</strong>.
It supports the following additional attributes (in addition to the
common attributes listed above):</p>
<attributes>
<attribute name="addWebinfClassesResources" required="false">
<p>This attribute controls if, in addition to static resources being
served from <code>META-INF/resources</code> inside web application JAR
files, static resources are also served from
<code>WEB-INF/classes/META-INF/resources</code>. This only applies to
web applications with a major version of 3 or higher. Since this is a
proprietary extension to the Servlet 3 specification, it is disabled by
default. To enable this feature, set the attribute to <code>true</code>.
</p>
</attribute>
<attribute name="antiResourceLocking" required="false">
<p>If true, Tomcat will prevent any file locking.
This will significantly impact startup time of applications,
but allows full webapp hot deploy and undeploy on platforms
or configurations where file locking can occur.
If not specified, the default value is <code>false</code>.</p>
<p>Please note that setting this to <code>true</code> has some side
effects, including the disabling of JSP reloading in a running server:
see <a href="http://bz.apache.org/bugzilla/show_bug.cgi?id=37668">
Bugzilla 37668</a>.</p>
<p>Please note that setting this flag to true in applications that are
outside the appBase for the Host (the <code>webapps</code> directory
by default) will cause the application to be <strong>deleted</strong> on
Tomcat shutdown. You probably don't want to do this, so think twice
before setting antiResourceLocking=true on a webapp that's outside the
appBase for its Host.</p>
</attribute>
<attribute name="clearReferencesHttpClientKeepAliveThread" required = "false">
<p>If <code>true</code> and an <code>sun.net.www.http.HttpClient</code>
keep-alive timer thread has been started by this web application and is
still running, Tomcat will change the context class loader for that
thread from the web application class loader to the parent of the web
application class loader to prevent a memory leak. Note that the
keep-alive timer thread will stop on its own once the keep-alives all
expire however, on a busy system that might not happen for some time. If
not specified, the default value of <code>true</code> will be used.</p>
</attribute>
<attribute name="clearReferencesStatic" required = "false">
<p>If <code>true</code>, Tomcat attempts to null out any static or final
fields from loaded classes when a web application is stopped as a work
around for apparent garbage collection bugs and application coding
errors. There have been some issues reported with log4j when this
is <code>true</code>. Applications without memory leaks using recent
JVMs should operate correctly with this attribute set to
<code>false</code>. If not specified, the default value of
<code>false</code> will be used.</p>
</attribute>
<attribute name="clearReferencesStopThreads" required = "false">
<p>If <code>true</code>, Tomcat attempts to terminate threads that have
been started by the web application. Stopping threads is performed via
the deprecated (for good reason) <code>Thread.stop()</code> method and
is likely to result in instability. As such, enabling this should be
viewed as an option of last resort in a development environment and is
not recommended in a production environment. If not specified, the
default value of <code>false</code> will be used. If this feature is
enabled, web applications may take up to two seconds longer to stop as
executor threads are given up to two seconds to stop gracefully before
<code>Thread.stop()</code> is called on any remaining threads.</p>
</attribute>
<attribute name="clearReferencesStopTimerThreads" required = "false">
<p>If <code>true</code>, Tomcat attempts to terminate
<code>java.util.Timer</code> threads that have been started by the web
application. Unlike standard threads, timer threads can be stopped
safely although there may still be side-effects for the application. If
not specified, the default value of <code>false</code> will be used.</p>
</attribute>
<attribute name="copyXML" required="false">
<p>Set to <code>true</code> if you want a context XML descriptor
embedded inside the application (located at
<code>/META-INF/context.xml</code>) to be copied to the owning
<a href="host.html">Host</a>'s <code>xmlBase</code> when the application
is deployed. On subsequent starts, the copied context XML descriptor
will be used in preference to any context XML descriptor embedded inside
the application even if the descriptor embedded inside the application
is more recent. The flag's value defaults to <code>false</code>. Note if
the <strong>deployXML</strong> attribute of the owning
<a href="host.html">Host</a> is <code>false</code> or if the
<strong>copyXML</strong> attribute of the owning
<a href="host.html">Host</a> is <code>true</code>, this attribute will
have no effect.</p>
</attribute>
<attribute name="jndiExceptionOnFailedWrite" required="false">
<p>If <code>true</code>, any attempt by an application to modify the
provided JNDI context with a call to bind(), unbind(),
createSubContext(), destroySubContext() or close() will trigger a
<code>javax.naming.OperationNotSupportedException</code> as required by
section EE.5.3.4 of the Java EE specification. This exception can be
disabled by setting this attribute to true in which case any calls to
modify the JNDI context will return <b>without</b> making any changes
and methods that return values will return <code>null</code>. If not
specified, the specification compliant default of <code>true</code> will
be used.</p>
</attribute>
<attribute name="renewThreadsWhenStoppingContext" required="false">
<p>If <code>true</code>, when this context is stopped, Tomcat renews all
the threads from the thread pool that was used to serve this context.
This also requires that the
<code>ThreadLocalLeakPreventionListener</code> be configured in
<code>server.xml</code> and that the <code>threadRenewalDelay</code>
property of the <code>Executor</code> be &gt;=0. If not specified, the
default value of <code>true</code> will be used.</p>
</attribute>
<attribute name="unloadDelay" required="false">
<p>Number of ms that the container will wait for servlets to unload.
If not specified, the default value is <code>2000</code> ms.</p>
</attribute>
<attribute name="unpackWAR" required="false">
<p>If <code>false</code>, the <strong>unpackWARs</strong> attribute of
the owning <a href="host.html">Host</a> will be overridden and the WAR
file will not be unpacked. If <code>true</code>, the value of the owning
<a href="host.html">Host</a>&apos;s <strong>unpackWARs</strong>
attribute will determine if the WAR is unpacked. If not specified, the
default value is <code>true</code>.</p>
</attribute>
<attribute name="useNaming" required="false">
<p>Set to <code>true</code> (the default) to have Catalina enable a
JNDI <code>InitialContext</code> for this web application that is
compatible with Java2 Enterprise Edition (J2EE) platform
conventions.</p>
</attribute>
<attribute name="workDir" required="false">
<p>Pathname to a scratch directory to be provided by this Context
for temporary read-write use by servlets within the associated web
application. This directory will be made visible to servlets in the
web application by a servlet context attribute (of type
<code>java.io.File</code>) named
<code>javax.servlet.context.tempdir</code> as described in the
Servlet Specification. If not specified, a suitable directory
underneath <code>$CATALINA_BASE/work</code> will be provided.</p>
</attribute>
</attributes>
</subsection>
</section>
<section name="Nested Components">
<p>You can nest at most one instance of the following utility components
by nesting a corresponding element inside your <strong>Context</strong>
element:</p>
<ul>
<li><a href="cookie-processor.html"><strong>Cookie Processor</strong></a> -
Configure parsing and generation of HTTP cookie headers.</li>
<li><a href="loader.html"><strong>Loader</strong></a> -
Configure the web application class loader that will be used to load
servlet and bean classes for this web application. Normally, the
default configuration of the class loader will be sufficient.</li>
<li><a href="manager.html"><strong>Manager</strong></a> -
Configure the session manager that will be used to create, destroy,
and persist HTTP sessions for this web application. Normally, the
default configuration of the session manager will be sufficient.</li>
<li><a href="realm.html"><strong>Realm</strong></a> -
Configure a realm that will allow its
database of users, and their associated roles, to be utilized solely
for this particular web application. If not specified, this web
application will utilize the Realm associated with the owning
<a href="host.html">Host</a> or <a href="engine.html">Engine</a>.</li>
<li><a href="resources.html"><strong>Resources</strong></a> -
Configure the resource manager that will be used to access the static
resources associated with this web application. Normally, the
default configuration of the resource manager will be sufficient.</li>
<li><strong>WatchedResource</strong> - The auto deployer will monitor the
specified static resource of the web application for updates, and will
reload the web application if it is updated. The content of this element
must be a string.</li>
<li><a href="jar-scanner.html"><strong>JarScanner</strong></a> -
Configure the Jar Scanner that will be used to scan the web application
for JAR files and directories of class files. It is typically used during
web application start to identify configuration files such as TLDs o
web-fragment.xml files that must be processed as part of the web
application initialisation.. Normally, the default Jar Scanner
configuration will be sufficient.</li>
</ul>
</section>
<section name="Special Features">
<subsection name="Logging">
<p>A context is associated with the
<code>org.apache.catalina.core.ContainerBase.[enginename].[hostname].[path]</code>
log category. Note that the brackets are actually part of the name, don't omit them.</p>
</subsection>
<subsection name="Access Logs">
<p>When you run a web server, one of the output files normally generated
is an <em>access log</em>, which generates one line of information for
each request processed by the server, in a standard format. Catalina
includes an optional <a href="valve.html">Valve</a> implementation that
can create access logs in the same standard format created by web servers,
or in any number of custom formats.</p>
<p>You can ask Catalina to create an access log for all requests
processed by an <a href="engine.html">Engine</a>,
<a href="host.html">Host</a>, or <a href="context.html">Context</a>
by nesting a <a href="valve.html">Valve</a> element like this:</p>
<source><![CDATA[<Context>
...
<Valve className="org.apache.catalina.valves.AccessLogValve"
prefix="localhost_access_log." suffix=".txt"
pattern="common"/>
...
</Context>]]></source>
<p>See <a href="valve.html#Access_Logging">Access Logging Valves</a>
for more information on the configuration attributes that are
supported.</p>
</subsection>
<subsection name="Automatic Context Configuration">
<p>If you use the standard <strong>Context</strong> implementation,
the following configuration steps occur automatically when Catalina
is started, or whenever this web application is reloaded. No special
configuration is required to enable this feature.</p>
<ul>
<li>If you have not declared your own <a href="loader.html">Loader</a>
element, a standard web application class loader will be configured.
</li>
<li>If you have not declared your own <a href="manager.html">Manager</a>
element, a standard session manager will be configured.</li>
<li>If you have not declared your own <a href="resources.html">Resources</a>
element, a standard resources manager will be configured.</li>
<li>The web application properties listed in <code>conf/web.xml</code>
will be processed as defaults for this web application. This is used
to establish default mappings (such as mapping the <code>*.jsp</code>
extension to the corresponding JSP servlet), and other standard
features that apply to all web applications.</li>
<li>The web application properties listed in the
<code>/WEB-INF/web.xml</code> resource for this web application
will be processed (if this resource exists).</li>
<li>If your web application has specified security constraints that might
require user authentication, an appropriate Authenticator that
implements the login method you have selected will be configured.</li>
</ul>
</subsection>
<subsection name="Context Parameters">
<p>You can configure named values that will be made visible to the
web application as servlet context initialization parameters by nesting
<code>&lt;Parameter&gt;</code> elements inside this element. For
example, you can create an initialization parameter like this:</p>
<source><![CDATA[<Context>
...
<Parameter name="companyName" value="My Company, Incorporated"
override="false"/>
...
</Context>]]></source>
<p>This is equivalent to the inclusion of the following element in the
web application deployment descriptor (<code>/WEB-INF/web.xml</code>):
</p>
<source><![CDATA[<context-param>
<param-name>companyName</param-name>
<param-value>My Company, Incorporated</param-value>
</context-param>]]></source>
<p>but does <em>not</em> require modification of the deployment descriptor
to customize this value.</p>
<p>The valid attributes for a <code>&lt;Parameter&gt;</code> element
are as follows:</p>
<attributes>
<attribute name="description" required="false">
<p>Optional, human-readable description of this context
initialization parameter.</p>
</attribute>
<attribute name="name" required="true">
<p>The name of the context initialization parameter to be created.</p>
</attribute>
<attribute name="override" required="false">
<p>Set this to <code>false</code> if you do <strong>not</strong> want
a <code>&lt;context-param&gt;</code> for the same parameter name,
found in the web application deployment descriptor, to override the
value specified here. By default, overrides are allowed.</p>
</attribute>
<attribute name="value" required="true">
<p>The parameter value that will be presented to the application
when requested by calling
<code>ServletContext.getInitParameter()</code>.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Environment Entries">
<p>You can configure named values that will be made visible to the
web application as environment entry resources, by nesting
<code>&lt;Environment&gt;</code> entries inside this element. For
example, you can create an environment entry like this:</p>
<source><![CDATA[<Context>
...
<Environment name="maxExemptions" value="10"
type="java.lang.Integer" override="false"/>
...
</Context>]]></source>
<p>This is equivalent to the inclusion of the following element in the
web application deployment descriptor (<code>/WEB-INF/web.xml</code>):
</p>
<source><![CDATA[<env-entry>
<env-entry-name>maxExemptions</env-entry-name>
<env-entry-value>10</env-entry-value>
<env-entry-type>java.lang.Integer</env-entry-type>
</env-entry>]]></source>
<p>but does <em>not</em> require modification of the deployment descriptor
to customize this value.</p>
<p>The valid attributes for an <code>&lt;Environment&gt;</code> element
are as follows:</p>
<attributes>
<attribute name="description" required="false">
<p>Optional, human-readable description of this environment entry.</p>
</attribute>
<attribute name="name" required="true">
<p>The name of the environment entry to be created, relative to the
<code>java:comp/env</code> context.</p>
</attribute>
<attribute name="override" required="false">
<p>Set this to <code>false</code> if you do <strong>not</strong> want
an <code>&lt;env-entry&gt;</code> for the same environment entry name,
found in the web application deployment descriptor, to override the
value specified here. By default, overrides are allowed.</p>
</attribute>
<attribute name="type" required="true">
<p>The fully qualified Java class name expected by the web application
for this environment entry. Must be a legal value for
<code>&lt;env-entry-type&gt;</code> in the web application deployment
descriptor.</p>
</attribute>
<attribute name="value" required="true">
<p>The parameter value that will be presented to the application
when requested from the JNDI context. This value must be convertable
to the Java type defined by the <code>type</code> attribute.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Lifecycle Listeners">
<p>If you have implemented a Java object that needs to know when this
<strong>Context</strong> is started or stopped, you can declare it by
nesting a <strong>Listener</strong> element inside this element. The
class name you specify must implement the
<code>org.apache.catalina.LifecycleListener</code> interface, and
the class must be packaged in a jar and placed in the
<code>$CATALINA_HOME/lib</code> directory.
It will be notified about the occurrence of the corresponding
lifecycle events. Configuration of such a listener looks like this:</p>
<source><![CDATA[<Context>
...
<Listener className="com.mycompany.mypackage.MyListener" ... >
...
</Context>]]></source>
<p>Note that a Listener can have any number of additional properties
that may be configured from this element. Attribute names are matched
to corresponding JavaBean property names using the standard property
method naming patterns.</p>
</subsection>
<subsection name="Request Filters">
<p>You can ask Catalina to check the IP address, or host name, on every
incoming request directed to the surrounding
<a href="engine.html">Engine</a>, <a href="host.html">Host</a>, or
<a href="context.html">Context</a> element. The remote address or name
will be checked against configured "accept" and/or "deny"
filters, which are defined using <code>java.util.regex</code> Regular
Expression syntax. Requests that come from locations that are
not accepted will be rejected with an HTTP "Forbidden" error.
Example filter declarations:</p>
<source><![CDATA[<Context>
...
<Valve className="org.apache.catalina.valves.RemoteHostValve"
allow=".*\.mycompany\.com|www\.yourcompany\.com"/>
<Valve className="org.apache.catalina.valves.RemoteAddrValve"
deny="192\.168\.1\.\d+"/>
...
</Context>]]></source>
<p>See <a href="valve.html#Remote_Address_Filter">Remote Address Filter</a>
and <a href="valve.html#Remote_Host_Filter">Remote Host Filter</a> for
more information about the configuration options that are supported.</p>
</subsection>
<subsection name="Resource Definitions">
<p>You can declare the characteristics of the resource
to be returned for JNDI lookups of <code>&lt;resource-ref&gt;</code> and
<code>&lt;resource-env-ref&gt;</code> elements in the web application
deployment descriptor. You <strong>MUST</strong> also define
the needed resource parameters as attributes of the <code>Resource</code>
element, to configure the object factory to be used (if not known to Tomcat
already), and the properties used to configure that object factory.</p>
<p>For example, you can create a resource definition like this:</p>
<source><![CDATA[<Context>
...
<Resource name="jdbc/EmployeeDB" auth="Container"
type="javax.sql.DataSource"
description="Employees Database for HR Applications"/>
...
</Context>]]></source>
<p>This is equivalent to the inclusion of the following element in the
web application deployment descriptor (<code>/WEB-INF/web.xml</code>):</p>
<source><![CDATA[<resource-ref>
<description>Employees Database for HR Applications</description>
<res-ref-name>jdbc/EmployeeDB</res-ref-name>
<res-ref-type>javax.sql.DataSource</res-ref-type>
<res-auth>Container</res-auth>
</resource-ref>]]></source>
<p>but does <em>not</em> require modification of the deployment
descriptor to customize this value.</p>
<p>The valid attributes for a <code>&lt;Resource&gt;</code> element
are as follows:</p>
<attributes>
<attribute name="auth" required="false">
<p>Specify whether the web Application code signs on to the
corresponding resource manager programatically, or whether the
Container will sign on to the resource manager on behalf of the
application. The value of this attribute must be
<code>Application</code> or <code>Container</code>. This
attribute is <strong>required</strong> if the web application
will use a <code>&lt;resource-ref&gt;</code> element in the web
application deployment descriptor, but is optional if the
application uses a <code>&lt;resource-env-ref&gt;</code> instead.</p>
</attribute>
<attribute name="closeMethod" required="false">
<p>Name of the zero-argument method to call on a singleton resource when
it is no longer required. This is intended to speed up clean-up of
resources that would otherwise happen as part of garbage collection.
This attribute is ignored if the <code>singleton</code> attribute is
false. If not specificed, no default is defined and no close method will
be called.</p>
<p>For Apache Commons DBCP and Apache Tomcat JDBC connection pools
you can use <code>closeMethod="close"</code>.</p>
</attribute>
<attribute name="description" required="false">
<p>Optional, human-readable description of this resource.</p>
</attribute>
<attribute name="name" required="true">
<p>The name of the resource to be created, relative to the
<code>java:comp/env</code> context.</p>
</attribute>
<attribute name="scope" required="false">
<p>Specify whether connections obtained through this resource
manager can be shared. The value of this attribute must be
<code>Shareable</code> or <code>Unshareable</code>. By default,
connections are assumed to be shareable.</p>
</attribute>
<attribute name="singleton" required="false">
<p>Specify whether this resource definition is for a singleton resource,
i.e. one where there is only a single instance of the resource. If this
attribute is <code>true</code>, multiple JNDI lookups for this resource
will return the same object. If this attribute is <code>false</code>,
multiple JNDI lookups for this resource will return different objects.
This attribute must be <code>true</code> for
<code>javax.sql.DataSource</code> resources to enable JMX registration
of the DataSource. The value of this attribute must be <code>true</code>
or <code>false</code>. By default, this attribute is <code>true</code>.
</p>
</attribute>
<attribute name="type" required="true">
<p>The fully qualified Java class name expected by the web
application when it performs a lookup for this resource.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Resource Links">
<p>This element is used to create a link to a global JNDI resource. Doing
a JNDI lookup on the link name will then return the linked global
resource.</p>
<p>For example, you can create a resource link like this:</p>
<source><![CDATA[<Context>
...
<ResourceLink name="linkToGlobalResource"
global="simpleValue"
type="java.lang.Integer"
...
</Context>]]></source>
<p>The valid attributes for a <code>&lt;ResourceLink&gt;</code> element
are as follows:</p>
<attributes>
<attribute name="global" required="true">
<p>The name of the linked global resource in the
global JNDI context.</p>
</attribute>
<attribute name="name" required="true">
<p>The name of the resource link to be created, relative to the
<code>java:comp/env</code> context.</p>
</attribute>
<attribute name="type" required="true">
<p>The fully qualified Java class name expected by the web
application when it performs a lookup for this resource link.</p>
</attribute>
<attribute name="factory" required="false">
<p>The fully qualified Java class name for the class creating these objects.
This class should implement the <code>javax.naming.spi.ObjectFactory</code> interface.</p>
</attribute>
</attributes>
<p>When the attribute <code>factory=&quot;org.apache.naming.factory.DataSourceLinkFactory&quot;</code> the resource link can be used with
two additional attributes to allow a shared data source to be used with different credentials.
When these two additional attributes are used in combination with the <code>javax.sql.DataSource</code>
type, different contexts can share a global data source with different credentials.
Under the hood, what happens is that a call to <a href="http://docs.oracle.com/javase/7/docs/api/javax/sql/DataSource.html#getConnection()"><code>getConnection()</code></a>
is simply translated to a call <a href="http://docs.oracle.com/javase/7/docs/api/javax/sql/DataSource.html#getConnection(java.lang.String,%20java.lang.String)">
<code>getConnection(username, password)</code></a> on the global data source. This is an easy way to get code to be transparent to what schemas are being used,
yet be able to control connections (or pools) in the global configuration.
</p>
<attributes>
<attribute name="username" required="false">
<p><code>username</code> value for the <code>getConnection(username, password)</code>
call on the linked global DataSource.
</p>
</attribute>
<attribute name="password" required="false">
<p><code>password</code> value for the <code>getConnection(username, password)</code>
call on the linked global DataSource.
</p>
</attribute>
</attributes>
<p>Shared Data Source Example:</p>
<p><strong>Warning:</strong> This feature works only if the global DataSource
supports <code>getConnection(username, password)</code> method.
<a href="http://commons.apache.org/dbcp/">Apache Commons DBCP</a> pool that
Tomcat uses by default does not support it. See its Javadoc for
<code>BasicDataSource</code> class.
<a href="../jdbc-pool.html">Apache Tomcat JDBC pool</a> does support it,
but by default this support is disabled and can be enabled by
<code>alternateUsernameAllowed</code> attribute. See its documentation
for details.</p>
<source><![CDATA[<GlobalNamingResources>
...
<Resource name="sharedDataSource"
global="sharedDataSource"
type="javax.sql.DataSource"
factory="org.apache.tomcat.jdbc.pool.DataSourceFactory"
alternateUsernameAllowed="true"
username="bar"
password="barpass"
...
...
</GlobalNamingResources>
<Context path="/foo"...>
...
<ResourceLink
name="appDataSource"
global="sharedDataSource"
type="javax.sql.DataSource"
factory="org.apache.naming.factory.DataSourceLinkFactory"
username="foo"
password="foopass"
...
</Context>
<Context path="/bar"...>
...
<ResourceLink
name="appDataSource"
global="sharedDataSource"
type="javax.sql.DataSource"
...
</Context>]]></source>
<p>When a request for <code>getConnection()</code> is made in the
<code>/foo</code> context, the request is translated into
<code>getConnection(&quot;foo&quot;,&quot;foopass&quot;)</code>,
while a request in the <code>/bar</code> gets passed straight through.</p>
</subsection>
<subsection name="Transaction">
<p>You can declare the characteristics of the UserTransaction
to be returned for JNDI lookup for <code>java:comp/UserTransaction</code>.
You <strong>MUST</strong> define an object factory class to instantiate
this object as well as the needed resource parameters as attributes of the
<code>Transaction</code>
element, and the properties used to configure that object factory.</p>
<p>The valid attributes for the <code>&lt;Transaction&gt;</code> element
are as follows:</p>
<attributes>
<attribute name="factory" required="true">
<p>The class name for the JNDI object factory.</p>
</attribute>
</attributes>
</subsection>
</section>
</body>
</document>