89 lines
3.2 KiB
XML
89 lines
3.2 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<!--
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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<!DOCTYPE document [
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<!ENTITY project SYSTEM "project.xml">
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]>
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<document url="aio.html">
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&project;
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<properties>
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<title>Advanced IO and Tomcat</title>
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<author>Remy Maucherat</author>
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</properties>
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<body>
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<section name="Table of Contents">
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<toc/>
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</section>
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<section name="Introduction">
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<p>
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<b>IMPORTANT NOTE: Usage of these features requires using the
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HTTP connectors. The AJP connectors do not support them.</b>
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</p>
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</section>
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<section name="Asynchronous writes">
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<p>
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When using HTTP connectors (based on APR or NIO/NIO2),
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Tomcat supports using sendfile to send large static files.
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These writes, as soon as the system load increases, will be performed
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asynchronously in the most efficient way. Instead of sending a large response using
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blocking writes, it is possible to write content to a static file, and write it
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using a sendfile code. A caching valve could take advantage of this to cache the
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response data in a file rather than store it in memory. Sendfile support is
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available if the request attribute <code>org.apache.tomcat.sendfile.support</code>
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is set to <code>Boolean.TRUE</code>.
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</p>
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<p>
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Any servlet can instruct Tomcat to perform a sendfile call by setting the appropriate
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request attributes. It is also necessary to correctly set the content length
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for the response. When using sendfile, it is best to ensure that neither the
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request or response have been wrapped, since as the response body will be sent later
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by the connector itself, it cannot be filtered. Other than setting the 3 needed
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request attributes, the servlet should not send any response data, but it may use
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any method which will result in modifying the response header (like setting cookies).
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</p>
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<ul>
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<li><code>org.apache.tomcat.sendfile.filename</code>: Canonical filename of the file which will be sent as
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a String</li>
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<li><code>org.apache.tomcat.sendfile.start</code>: Start offset as a Long</li>
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<li><code>org.apache.tomcat.sendfile.end</code>: End offset as a Long</li>
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</ul>
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<p>
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In addition to setting these parameters it is necessary to set the content-length header.
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Tomcat will not do that for you, since you may have already written data to the output stream.
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</p>
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<p>
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Note that the use of sendfile will disable any compression that Tomcat may
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otherwise have performed on the response.
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</p>
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</section>
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</body>
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</document>
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