src/site/xdoc/bestpractices.xml - platform/external/apache-commons-io - Git at Google

 <?xml version="1.0"?>
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      http://www.apache.org/licenses/LICENSE-2.0

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 <document>
  <properties>
   <title>Best practices</title>
   <author email="[email protected]">Commons Documentation Team</author>
  </properties>
   <body>

     <section name="Best practices">
         <p>
             This document presents a number of 'best practices' in the IO area.
         </p>
     </section>

     <section name="java.io.File">

         <p>
             Often, you have to deal with files and filenames. There are many
             things that can go wrong:
         </p>
         <ul>
             <li>A class works in Unix but doesn't on Windows (or vice versa)</li>
             <li>Invalid filenames due to double or missing path separators</li>
             <li>UNC filenames (on Windows) don't work with my home-grown filename utility function</li>
             <li>etc. etc.</li>
         </ul>
         <p>
             These are good reasons not to work with filenames as Strings.
             Using java.io.File instead handles many of the above cases nicely.
             Thus, our best practice recommendation is to use java.io.File
             instead of String for filenames to avoid platform dependencies.
         </p>
         <p>
             <i>
             Version 1.1 of commons-io now includes a dedicated filename
             handling class - <a href="apidocs/index.html?org/apache/commons/io/FilenameUtils.html">FilenameUtils</a>.
             This does handle many of these filename issues, however we still
             recommend, wherever possible, that you use java.io.File objects.
             </i>
         </p>
         <p>
             Let's look at an example.
         </p>
         <source>
  public static String getExtension(String filename) {
    int index = filename.lastIndexOf('.');
    if (index == -1) {
      return "";
    } else {
      return filename.substring(index + 1);
    }
  }</source>
         <p>
             Easy enough? Right, but what happens if someone passes in a full path
             instead of only a filename? Consider the following, perfectly legal path:
             "C:\Temp\documentation.new\README".
             The method as defined above would return "new\README" - definitely
             not what you wanted.
         </p>
         <p>
             Please use java.io.File for filenames instead of Strings.
             The functionality that the class provides is well tested.
             In FileUtils you will find other useful utility functions
             around java.io.File.
         </p>
         <p>
             Instead of:
         </p>
         <source>
  String tmpdir = "/var/tmp";
  String tmpfile = tmpdir + System.getProperty("file.separator") + "test.tmp";
  InputStream in = new java.io.FileInputStream(tmpfile);</source>
         <p>
             ...write:
         </p>
         <source>
  File tmpdir = new File("/var/tmp");
  File tmpfile = new File(tmpdir, "test.tmp");
  InputStream in = new java.io.FileInputStream(tmpfile);</source>

     </section>

     <section name="Buffering streams">
         <p>
             IO performance depends a lot on the buffering strategy. Usually, it's
             quite fast to read packets with the size of 512 or 1024 bytes because
             these sizes match well with the packet sizes used on hard disks in
             file systems or file system caches. But as soon as you have to read only
             a few bytes and that many times performance drops significantly.
         </p>
         <p>
             Make sure you're properly buffering streams when reading or writing
             streams, especially when working with files. Just decorate your
             FileInputStream with a BufferedInputStream:
         </p>
         <source>
  InputStream in = new java.io.FileInputStream(myfile);
  try {
    in = new java.io.BufferedInputStream(in);

    in.read(.....
  } finally {
    IOUtils.closeQuietly(in);
  }</source>
         <p>
             Pay attention that you're not buffering an already buffered stream. Some
             components like XML parsers may do their own buffering so decorating
             the InputStream you pass to the XML parser does nothing but slowing down
             your code. If you use our CopyUtils or IOUtils you don't need to
             additionally buffer the streams you use as the code in there already
             buffers the copy process. Always check the Javadocs for information.
             Another case where buffering is unnecessary is when you write to a
             ByteArrayOutputStream since you're writing to memory only.
         </p>
     </section>

   </body>

 </document>
	<?xml version="1.0"?>
	<!--
	Licensed to the Apache Software Foundation (ASF) under one or more
	contributor license agreements. See the NOTICE file distributed with
	this work for additional information regarding copyright ownership.
	The ASF licenses this file to You under the Apache License, Version 2.0
	(the "License"); you may not use this file except in compliance with
	the License. You may obtain a copy of the License at

	http://www.apache.org/licenses/LICENSE-2.0

	Unless required by applicable law or agreed to in writing, software
	distributed under the License is distributed on an "AS IS" BASIS,
	WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
	See the License for the specific language governing permissions and
	limitations under the License.
	-->
	<document>
	<properties>
	<title>Best practices</title>
	<author email="[email protected]">Commons Documentation Team</author>
	</properties>
	<body>

	<section name="Best practices">
	<p>
	This document presents a number of 'best practices' in the IO area.
	</p>
	</section>

	<section name="java.io.File">

	<p>
	Often, you have to deal with files and filenames. There are many
	things that can go wrong:
	</p>
	<ul>
	<li>A class works in Unix but doesn't on Windows (or vice versa)</li>
	<li>Invalid filenames due to double or missing path separators</li>
	<li>UNC filenames (on Windows) don't work with my home-grown filename utility function</li>
	<li>etc. etc.</li>
	</ul>
	<p>
	These are good reasons not to work with filenames as Strings.
	Using java.io.File instead handles many of the above cases nicely.
	Thus, our best practice recommendation is to use java.io.File
	instead of String for filenames to avoid platform dependencies.
	</p>
	<p>
	<i>
	Version 1.1 of commons-io now includes a dedicated filename
	handling class - <a href="apidocs/index.html?org/apache/commons/io/FilenameUtils.html">FilenameUtils</a>.
	This does handle many of these filename issues, however we still
	recommend, wherever possible, that you use java.io.File objects.
	</i>
	</p>
	<p>
	Let's look at an example.
	</p>
	<source>
	public static String getExtension(String filename) {
	int index = filename.lastIndexOf('.');
	if (index == -1) {
	return "";
	} else {
	return filename.substring(index + 1);
	}
	}</source>
	<p>
	Easy enough? Right, but what happens if someone passes in a full path
	instead of only a filename? Consider the following, perfectly legal path:
	"C:\Temp\documentation.new\README".
	The method as defined above would return "new\README" - definitely
	not what you wanted.
	</p>
	<p>
	Please use java.io.File for filenames instead of Strings.
	The functionality that the class provides is well tested.
	In FileUtils you will find other useful utility functions
	around java.io.File.
	</p>
	<p>
	Instead of:
	</p>
	<source>
	String tmpdir = "/var/tmp";
	String tmpfile = tmpdir + System.getProperty("file.separator") + "test.tmp";
	InputStream in = new java.io.FileInputStream(tmpfile);</source>
	<p>
	...write:
	</p>
	<source>
	File tmpdir = new File("/var/tmp");
	File tmpfile = new File(tmpdir, "test.tmp");
	InputStream in = new java.io.FileInputStream(tmpfile);</source>

	</section>

	<section name="Buffering streams">
	<p>
	IO performance depends a lot on the buffering strategy. Usually, it's
	quite fast to read packets with the size of 512 or 1024 bytes because
	these sizes match well with the packet sizes used on hard disks in
	file systems or file system caches. But as soon as you have to read only
	a few bytes and that many times performance drops significantly.
	</p>
	<p>
	Make sure you're properly buffering streams when reading or writing
	streams, especially when working with files. Just decorate your
	FileInputStream with a BufferedInputStream:
	</p>
	<source>
	InputStream in = new java.io.FileInputStream(myfile);
	try {
	in = new java.io.BufferedInputStream(in);

	in.read(.....
	} finally {
	IOUtils.closeQuietly(in);
	}</source>
	<p>
	Pay attention that you're not buffering an already buffered stream. Some
	components like XML parsers may do their own buffering so decorating
	the InputStream you pass to the XML parser does nothing but slowing down
	your code. If you use our CopyUtils or IOUtils you don't need to
	additionally buffer the streams you use as the code in there already
	buffers the copy process. Always check the Javadocs for information.
	Another case where buffering is unnecessary is when you write to a
	ByteArrayOutputStream since you're writing to memory only.
	</p>
	</section>

	</body>

	</document>