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<!DOCTYPE document [
<!ENTITY project SYSTEM "project.xml">
]>
<document url="http.html">
&project;
<properties>
<author email="craigmcc@apache.org">Craig R. McClanahan</author>
<author email="yoavs@apache.org">Yoav Shapira</author>
<title>The HTTP Connector</title>
</properties>
<body>
<section name="Table of Contents">
<toc/>
</section>
<section name="Introduction">
<p>The <strong>HTTP Connector</strong> element represents a
<strong>Connector</strong> component that supports the HTTP/1.1 protocol.
It enables Catalina to function as a stand-alone web server, in addition
to its ability to execute servlets and JSP pages. A particular instance
of this component listens for connections on a specific TCP port number
on the server. One or more such <strong>Connectors</strong> can be
configured as part of a single <a href="service.html">Service</a>, each
forwarding to the associated <a href="engine.html">Engine</a> to perform
request processing and create the response.</p>
<p>If you wish to configure the <strong>Connector</strong> that is used
for connections to web servers using the AJP protocol (such as the
<code>mod_jk 1.2.x</code> connector for Apache 1.3), see
<a href="ajp.html">here</a> instead.</p>
<p>At server startup time, this <strong>Connector</strong> will create a
number of request processing threads (based on the value configured for
the <code>minSpareThreads</code> attribute). Each incoming request requires
a thread for the duration of that request. If more simultaneous requests
are received than can be handled by the currently available request
processing threads, additional threads will be created up to the
configured maximum (the value of the <code>maxThreads</code> attribute).
If still more simultaneous requests are received, they are stacked up
inside the server socket created by the <strong>Connector</strong>, up to
the configured maximum (the value of the <code>acceptCount</code>
attribute). Any further simultaneous requests will receive "connection
refused" errors, until resources are available to process them.</p>
</section>
<section name="Attributes">
<subsection name="Common Attributes">
<p>All implementations of <strong>Connector</strong>
support the following attributes:</p>
<attributes>
<attribute name="allowTrace" required="false">
<p>A boolean value which can be used to enable or disable the TRACE
HTTP method. If not specified, this attribute is set to false.</p>
</attribute>
<attribute name="emptySessionPath" required="false">
<p>If set to <code>true</code>, all paths for session cookies will be set
to <code>/</code>. This can be useful for portlet specification implementations,
but will greatly affect performance if many applications are accessed on a given
server by the client.
If not specified, this attribute is set to <code>false</code>.</p>
</attribute>
<attribute name="enableLookups" required="false">
<p>Set to <code>true</code> if you want calls to
<code>request.getRemoteHost()</code> to perform DNS lookups in
order to return the actual host name of the remote client. Set
to <code>false</code> to skip the DNS lookup and return the IP
address in String form instead (thereby improving performance).
By default, DNS lookups are enabled.</p>
</attribute>
<attribute name="maxParameterCount" required="false">
<p>The maximum number of parameters (GET plus POST) which will be
automatically parsed by the container. A value of less than 0 means no
limit. If not specified, a default of 10000 is used. Note that
<code>FailedRequestFilter</code> <a href="filter.html">filter</a> can be
used to reject requests that hit the limit.</p>
</attribute>
<attribute name="maxPostSize" required="false">
<p>The maximum size in bytes of the POST which will be handled by
the container FORM URL parameter parsing. The limit can be disabled by
setting this attribute to a value less than or equal to 0.
If not specified, this attribute is set to 2097152 (2 megabytes).</p>
</attribute>
<attribute name="maxSavePostSize" required="false">
<p>The maximum size in bytes of the POST which will be saved/buffered by
the container during FORM or CLIENT-CERT authentication. For both types
of authentication, the POST will be saved/buffered before the user is
authenticated. For CLIENT-CERT authentication, the POST is buffered for
the duration of
the SSL handshake and the buffer emptied when the request
is processed. For FORM authentication the POST is
saved whilst the user
is re-directed to the login form and is retained until the user
successfully authenticates or the session associated with the
authentication request expires. The limit can be disabled by setting this
attribute to -1. Setting the attribute to
zero will disable the saving of
POST data during authentication
. If not
specified, this attribute is set
to
4096 (4 kilobytes).</p>
</attribute>
<attribute name="protocol" required="false">
<p>This attribute value must be <code>HTTP/1.1</code> to use the HTTP
handler, which is the default.</p>
</attribute>
<attribute name="proxyName" required="false">
<p>If this <strong>Connector</strong> is being used in a proxy
configuration, configure this attribute to specify the server name
to be returned for calls to <code>request.getServerName()</code>.
See <a href="#Proxy Support">Proxy Support</a> for more
information.</p>
</attribute>
<attribute name="proxyPort" required="false">
<p>If this <strong>Connector</strong> is being used in a proxy
configuration, configure this attribute to specify the server port
to be returned for calls to <code>request.getServerPort()</code>.
See <a href="#Proxy Support">Proxy Support</a> for more
information.</p>
</attribute>
<attribute name="redirectPort" required="false">
<p>If this <strong>Connector</strong> is supporting non-SSL
requests, and a request is received for which a matching
<code>&lt;security-constraint&gt;</code> requires SSL transport,
Catalina will automatically redirect the request to the port
number specified here.</p>
</attribute>
<attribute name="scheme" required="false">
<p>Set this attribute to the name of the protocol you wish to have
returned by calls to <code>request.getScheme()</code>. For
example, you would set this attribute to "<code>https</code>"
for an SSL Connector. The default value is "<code>http</code>".
See <a href="#SSL Support">SSL Support</a> for more information.</p>
</attribute>
<attribute name="secure" required="false">
<p>Set this attribute to <code>true</code> if you wish to have
calls to <code>request.isSecure()</code> to return <code>true</code>
for requests received by this Connector (you would want this on an
SSL Connector). The default value is <code>false</code>.</p>
</attribute>
<attribute name="URIEncoding" required="false">
<p>This specifies the character encoding used to decode the URI bytes,
after %xx decoding the URL. If not specified, ISO-8859-1 will be used.
</p>
</attribute>
<attribute name="useBodyEncodingForURI" required="false">
<p>This specifies if the encoding specified in contentType should be used
for URI query parameters, instead of using the URIEncoding. This
setting is present for compatibility with Tomcat 4.1.x, where the
encoding specified in the contentType, or explicitly set using
Request.setCharacterEncoding method was also used for the parameters from
the URL. The default value is <code>false</code>.
</p>
</attribute>
<attribute name="useIPVHosts" required="false">
<p>Set this attribute to <code>true</code> to cause Tomcat to use
the IP address that the request was received on to determine the Host
to send the request to. The default value is <code>false</code>.</p>
</attribute>
<attribute name="xpoweredBy" required="false">
<p>Set this attribute to <code>true</code> to cause Tomcat to advertise
support for the Servlet specification using the header recommended in the
specification. The default value is <code>false</code>.</p>
</attribute>
</attributes>
</subsection>
<subsection name="Standard Implementation">
<p>
HTTP supports the following additional attributes (in addition to the
common attributes listed above):</p>
<attributes>
<attribute name="acceptCount" required="false">
<p>The maximum queue length for incoming connection requests when
all possible request processing threads are in use. Any requests
received when the queue is full will be refused. The default
value is 100.</p>
</attribute>
<attribute name="address" required="false">
<p>For servers with more than one IP address, this attribute
specifies which address will be used for listening on the specified
port. By default, this port will be used on all IP addresses
associated with the server.</p>
</attribute>
<attribute name="bufferSize" required="false">
<p>The size (in bytes) of the buffer to be provided for input
streams created by this connector. By default, buffers of
2048 bytes will be provided.</p>
</attribute>
<attribute name="compressableMimeType" required="false">
<p>The value is a comma separated list of MIME types for which HTTP
compression may be used.
The default value is <code>text/html,text/xml,text/plain</code>.</p>
</attribute>
<attribute name="compression" required="false">
<p>The <strong>Connector</strong> may use HTTP/1.1 GZIP compression in
an attempt to save server bandwidth. The acceptable values for the
parameter is "off" (disable compression), "on" (allow compression, which
causes text data to be compressed), "force" (forces compression in all
cases), or a numerical integer value (which is equivalent to "on", but
specifies the minimum amount of data before the output is compressed). If
the content-length is not known and compression is set to "on" or more
aggressive, the output will also be compressed. If not specified, this
attribute is set to "off".</p>
</attribute>
<attribute name="connectionLinger" required="false">
<p>The number of milliseconds during which the sockets used by this
<strong>Connector</strong> will linger when they are closed.
The default value is -1 (socket linger is disabled).</p>
</attribute>
<attribute name="connectionTimeout" required="false">
<p>The number of milliseconds this <strong>Connector</strong> will wait,
after accepting a connection, for the request URI line to be
presented. The default value is 60000 (i.e. 60 seconds).</p>
</attribute>
<attribute name="disableUploadTimeout" required="false">
<p>This flag allows the servlet container to use a different, longer
connection timeout while a servlet is being executed, which in the end
allows either the servlet a longer amount of time to complete its
execution, or a longer timeout during data upload. If not specified,
this attribute is set to "true".</p>
</attribute>
<attribute name="maxHeaderCount" required="false">
<p>The maximum number of headers in a request that are allowed by the
container. A request that contains more headers than the specified limit
will be rejected. A value of less than 0 means no limit.
If not specified, a default of 100 is used.</p>
</attribute>
<attribute name="maxHttpHeaderSize" required="false">
<p>The maximum size of the request and response HTTP header, specified
in bytes.
If not specified, this attribute is set to 4096 (4 KB).</p>
</attribute>
<attribute name="maxKeepAliveRequests" required="false">
<p>The maximum number of HTTP requests which can be pipelined until
the connection is closed by the server. Setting this attribute to 1 will
disable HTTP/1.0 keep-alive, as well as HTTP/1.1 keep-alive and
pipelining. Setting this to -1 will allow an unlimited amount of
pipelined or keep-alive HTTP requests.
If not specified, this attribute is set to 100.</p>
</attribute>
<attribute name="maxSpareThreads" required="false">
<p>The maximum number of unused request processing threads that
will be allowed to exist until the thread pool starts stopping the
unnecessary threads. The default value is 50.</p>
</attribute>
<attribute name="maxThreads" required="false">
<p>The maximum number of request processing threads to be created
by this <strong>Connector</strong>, which therefore determines the
maximum number of simultaneous requests that can be handled. If
not specified, this attribute is set to 200.</p>
</attribute>
<attribute name="minSpareThreads" required="false">
<p>The number of request processing threads that will be created
when this <strong>Connector</strong> is first started. The connector
will also make sure it has the specified number of idle processing
threads available. This attribute should be set to a value smaller
than that set for <code>maxThreads</code>. The default value is 4.</p>
</attribute>
<attribute name="noCompressionUserAgents" required="false">
<p>The value is a comma separated list of regular expressions matching
user-agents of HTTP clients for which compression should not be used,
because these clients, although they do advertise support for the
feature, have a broken implementation.
The default value is an empty String (regexp matching disabled).</p>
</attribute>
<attribute name="port" required="true">
<p>The TCP port number on which this <strong>Connector</strong>
will create a server socket and await incoming connections. Your
operating system will allow only one server application to listen
to a particular port number on a particular IP address.</p>
</attribute>
<attribute name="restrictedUserAgents" required="false">
<p>The value is a comma separated list of regular expressions matching
user-agents of HTTP clients for which HTTP/1.1 or HTTP/1.0 keep alive
should not be used, even if the clients advertise support for these
features.
The default value is an empty String (regexp matching disabled).</p>
</attribute>
<attribute name="server" required="false">
<p>Overrides the Server header for the http response. If set, the value
for this attribute overrides the Tomcat default and any Server header set
by a web application. If not set, any value specified by the application
is used. If the application does not specify a value then
<code>Apache-Coyote/1.1</code> is used. Unless you are paranoid, you won't
need this feature.
</p>
</attribute>
<attribute name="socketBuffer" required="false">
<p>The size (in bytes) of the buffer to be provided for socket
output buffering. -1 can be specified to disable the use of a buffer.
By default, a buffers of 9000 bytes will be used.</p>
</attribute>
<attribute name="strategy" required="false">
<p>The thread pooling strategy which will be used. The default strategy does
not use a master thread, but a more conventional strategy using a
master listener thread can be used by setting "ms" as this attribute's value.
The master strategy will work significantly better using the threadPriority
attribute, which will apply only to the thread which listens on the server socket.
This is set to <code>lf</code> by default.
</p>
</attribute>
<attribute name="tcpNoDelay" required="false">
<p>If set to <code>true</code>, the TCP_NO_DELAY option will be
set on the server socket, which improves performance under most
circumstances. This is set to <code>true</code> by default.</p>
</attribute>
<attribute name="threadPriority" required="false">
<p>The priority of the request processing threads within the JVM.
The default value is <code>java.lang.Thread#NORM_PRIORITY</code>.
See the JavaDoc for the java.lang.Thread class for more details on
what this priority means.
</p>
</attribute>
</attributes>
</subsection>
</section>
<section name="Nested Components">
<p>None at this time.</p>
</section>
<section name="Special Features">
<subsection name="HTTP/1.1 and HTTP/1.0 Support">
<p>This <strong>Connector</strong> supports all of the required features
of the HTTP/1.1 protocol, as described in RFC 2616, including persistent
connections, pipelining, expectations and chunked encoding. If the client
(typically a browser) supports only HTTP/1.0, the
<strong>Connector</strong> will gracefully fall back to supporting this
protocol as well. No special configuration is required to enable this
support. The <strong>Connector</strong> also supports HTTP/1.0
keep-alive.</p>
<p>RFC 2616 requires that HTTP servers always begin their responses with
the highest HTTP version that they claim to support. Therefore, this
<strong>Connector</strong> will always return <code>HTTP/1.1</code> at
the beginning of its responses.</p>
</subsection>
<subsection name="Proxy Support">
<p>The <code>proxyName</code> and <code>proxyPort</code> attributes can
be used when Tomcat is run behind a proxy server. These attributes
modify the values returned to web applications that call the
<code>request.getServerName()</code> and <code>request.getServerPort()</code>
methods, which are often used to construct absolute URLs for redirects.
Without configuring these attributes, the values returned would reflect
the server name and port on which the connection from the proxy server
was received, rather than the server name and port to whom the client
directed the original request.</p>
<p>For more information, see the
<a href="../proxy-howto.html">Proxy Support HOW-TO</a>.</p>
</subsection>
<subsection name="SSL Support">
<p>You can enable SSL support for a particular instance of this
<strong>Connector</strong> by setting the <code>secure</code> attribute to
<code>true</code>. In addition, you may need to configure the following
attributes:</p>
<attributes>
<attribute name="algorithm" required="false">
<p>The certificate encoding algorithm to be used. This defaults to the Sun
implementation (<code>SunX509</code>). For IBM JVMs you should use the
value <code>IbmX509</code>. For other vendors, consult the JVM
documentation for the correct value.</p>
</attribute>
<attribute name="clientAuth" required="false">
<p>Set to <code>true</code> if you want the SSL stack to require a
valid certificate chain from the client before accepting a connection.
Set to <code>want</code> if you want the SSL stack to request a client
Certificate, but not fail if one isn't presented. A <code>false</code>
value (which is the default) will not require a certificate chain
unless the client requests a resource protected by a security
constraint that uses <code>CLIENT-CERT</code> authentication. See the
<a href="../ssl-howto.html">SSL HowTo</a> for an example. That SSL HowTo
also contains tips on using per-user or per-session certificate-based clientAuth.</p>
</attribute>
<attribute name="keystoreFile" required="false">
<p>The pathname of the keystore file where you have stored the
server certificate to be loaded. By default, the pathname is
the file "<code>.keystore</code>" in the operating system home
directory of the user that is running Tomcat.</p>
</attribute>
<attribute name="keystorePass" required="false">
<p>The password used to access the server certificate from the
specified keystore file. The default value is "<code>changeit</code>".
</p>
</attribute>
<attribute name="keystoreType" required="false">
<p>The type of keystore file to be used for the server certificate.
If not specified, the default value is "<code>JKS</code>".</p>
</attribute>
<attribute name="sslProtocol" required="false">
<p>The version of the SSL protocol to use. If not specified,
the default is "<code>TLS</code>".</p>
</attribute>
<attribute name="ciphers" required="false">
<p>The comma separated list of encryption ciphers that this socket is
allowed to use. By default, the default ciphers for the JVM will be used.
Note that this usually means that the weak export grade ciphers will be
included in the list of available ciphers. The ciphers are specified using
the JSSE cipher naming convention.</p>
</attribute>
<attribute name="keyAlias" required="false">
<p>The alias used to for the server certificate in the keystore. If not
specified the first key read in the keystore will be used.</p>
</attribute>
<attribute name="truststoreFile" required="false">
<p>The trust store file to use to validate client certificates. The
default is the value of the <code>javax.net.ssl.trustStore</code> system
property. If neither this attribute nor the default system property is
set, no trust store will be configured.</p>
</attribute>
<attribute name="truststorePass" required="false">
<p>The password to access the trust store. The default is the value of the
<code>javax.net.ssl.trustStorePassword</code> system property. If that
property is null, the value of <code>keystorePass</code> is used as the
default. If neither this attribute, the default system property nor
<code>keystorePass</code>is set, no trust store will be configured.</p>
</attribute>
<attribute name="truststoreType" required="false">
<p>The type of key store used for the trust store. The default is the
value of the <code>javax.net.ssl.trustStoreType</code> system property. If
that property is null, the value of <code>keystoreType</code> is used as
the default.</p>
</attribute>
<attribute name="allowUnsafeLegacyRenegotiation" required="false">
<p>Is unsafe legacy TLS renegotiation allowed which is likely to expose
users to CVE-2009-3555, a man-in-the-middle vulnerability in the TLS
protocol that allows an attacker to inject arbitrary data into the user's
request. If not specified, a default of <code>false</code> is used. This
attribute only has an effect if the JVM does not support RFC 5746 as
indicated by the presence of the pseudo-ciphersuite
TLS_EMPTY_RENEGOTIATION_INFO_SCSV. This is available JRE/JDK 6 update 22
onwards. Where RFC 5746 is supported the renegotiation - including support
for unsafe legacy renegotiation - is controlled by the JVM configuration.
</p>
</attribute>
</attributes>
<p>For more information, see the
<a href="../ssl-howto.html">SSL Configuration HOW-TO</a>.</p>
</subsection>
</section>
</body>
</document>