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<?xml version="1.0" encoding="UTF-8"?>
<document xmlns="http://maven.apache.org/XDOC/2.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/XDOC/2.0 http://maven.apache.org/xsd/xdoc-2.0.xsd">
<head>
<title>Writing Before Execution Filters</title>
<script type="text/javascript" src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"/>
<script type="text/javascript" src="js/anchors.js"/>
<script type="text/javascript" src="js/google-analytics.js"/>
<link rel="icon" href="images/favicon.png" type="image/x-icon" />
<link rel="shortcut icon" href="images/favicon.ico" type="image/ico" />
</head>
<body>
<section name="Content">
<macro name="toc">
<param name="fromDepth" value="1"/>
<param name="toDepth" value="1"/>
</macro>
</section>
<section name="Overview">
<p>
A <code>Checker</code> has a set of <code>BeforeExecutionFileFilter</code>s that decide which files the <code>Checker</code> processes. Interface
<code>BeforeExecutionFileFilter</code> and class <code>BeforeExecutionFileFilterSet</code> are intended to support general file uri filtering using a set of <code>BeforeExecutionFileFilter</code>s.
</p>
<p>
A <code>BeforeExecutionFileFilter</code> has <code>boolean</code> method <code>accept(String uri)</code> that returns <code>true</code> if the <code>BeforeExecutionFileFilter</code>
accepts the <code>file uri</code> parameter and returns
<code>false</code> if the <code>file uri</code> rejects it.
</p>
<p>
A <code>BeforeExecutionFileFilterSet</code> is a particular <code>BeforeExecutionFileFilter</code> that contains a set of <code>BeforeExecutionFileFilter</code>s. A <code>BeforeExecutionFileFilterSet</code>
accepts an <code>file uri</code> if and only if all
<code>BeforeExecutionFileFilter</code>s in the set accept the <code>file uri</code>.
</p>
</section>
<section name="Writing Before Execution File Filters">
<p>
The <code>BeforeExecutionFileFilter</code> that we demonstrate here rejects
file uris whose name matches a <a
href="property_types.html#regexp">regular expression</a>. In order to
enable the specification of the file name pattern as a property in a
configuration file, the <code>BeforeExecutionFileFilter</code> is an <a
href="apidocs/com/puppycrawl/tools/checkstyle/api/AutomaticBean.html">AutomaticBean</a>
with mutator method <code>setFiles(String)</code> that
receives the file name pattern. An <code>AutomaticBean</code> uses JavaBean introspection to set
JavaBean properties such as <code>files</code>.
</p>
<source>
package com.mycompany.filefilters;
import java.util.regex.Matcher;
import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;
import com.puppycrawl.tools.checkstyle.api.AutomaticBean;
import com.puppycrawl.tools.checkstyle.api.BeforeExecutionFileFilter;
import com.puppycrawl.tools.checkstyle.api.Utils;
public class FilesBeforeExecutionFileFilter
extends AutomaticBean
implements BeforeExecutionFileFilter
{
private Pattern mFileRegexp;
public FilesBeforeExecutionFileFilter()
throws PatternSyntaxException
{
setFiles("^$");
}
public boolean accept(String uri)
{
return ((uri == null) || !mFileRegexp.matcher(uri).find());
}
public void setFiles(String aFilesPattern)
throws PatternSyntaxException
{
mFileRegexp = Utils.getPattern(aFilesPattern);
}
}
</source>
</section>
<section name="Using Before Execution File Filters">
<p>
To incorporate a <code>BeforeExecutionFileFilter</code> in the before execution file filter set
for a <code>Checker</code>, include a module element for
the <code>BeforeExecutionFileFilter</code> in the <a
href="config.html#Before Execution File Filters">configuration file</a>. For example, to
configure a <code>Checker</code> so that it uses custom
filter <code>FilesBeforeExecutionFileFilter</code> to prevent processing
files whose name contains "Generated",
include the following module in the configuration file:
</p>
<source>
<module name="com.mycompany.filters.FilesBeforeExecutionFileFilter">
<property name="files" value="Generated"/>
</module>
</source>
</section>
<section name="Huh? I can't figure it out!">
<p>
That's probably our fault, and it means that we have to provide
better documentation. Please do not hesitate to ask questions on the
user mailing list, this will help us to improve this document. Please
ask your questions as precisely as possible. We will not be able to
answer questions like "I want to write a filter but I don't
know how, can you help me?". Tell us what you are trying to do
(the purpose of the filter), what you have understood so far, and what
exactly you are getting stuck on.
</p>
</section>
<section name="Contributing">
<p>
We need <em>your</em> help to keep improving Checkstyle. Whenever you
write a before execution file filter that you think is generally useful,
please consider <a href="contributing.html">contributing</a> it to the Checkstyle
community and submit it for inclusion in the next release of
Checkstyle.
</p>
</section>
</body>
</document>
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