phoedos/pmd
1
1
Fork 1
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
pmd/pmd_userdocs_extending_writing_rules_intro.html

2148 lines
54 KiB
HTML
Raw Permalink Blame History

This file contains ambiguous Unicode characters

This file contains Unicode characters that might be confused with other characters. If you think that this is intentional, you can safely ignore this warning. Use the Escape button to reveal them.

<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="description" content="Writing your own PMD rules">
<meta name="keywords" content="extendinguserdocsgetting_started, ">
<title>Introduction to writing PMD rules | PMD Source Code Analyzer</title>
<link rel="stylesheet" type="text/css" href="assets/fontawesome-free-5.15.4-web/css/all.min.css">
<link rel="stylesheet" type="text/css" href="assets/bootstrap-4.5.2-dist/css/bootstrap.min.css">
<link rel="stylesheet" type="text/css" href="css/syntax.css">
<link rel="stylesheet" type="text/css" href="css/modern-business.css">
<link rel="stylesheet" type="text/css" href="css/customstyles.css">
<link rel="stylesheet" type="text/css" href="css/theme-green.css">
<link rel="stylesheet" type="text/css" href="css/pmd-customstyles.css">
<link rel="shortcut icon" href="images/logo/favicon.ico" type="image/x-icon">
<link rel="icon" href="images/logo/favicon.ico" type="image/x-icon">
<link rel="alternate" type="application/rss+xml" title="" href="feed.xml">
</head>
<body>
<!-- Content is offset by the height of the topnav bar. -->
<!-- There's already a padding-top rule in modern-business.css, but it apparently doesn't work on Firefox 60 and Chrome 67 -->
<div id="topbar-content-offset">
<!-- Navigation -->
<nav class="navbar navbar-expand-lg fixed-top navbar-dark">
<div class="container topnavlinks">
<a class="navbar-brand fas fa-home fa-lg" href="index.html">&nbsp;<span class="projectTitle"> PMD Source Code Analyzer Project</span></a>
<button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarSupportedContent" aria-controls="navbarSupportedContent" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
</button>
<div class="collapse navbar-collapse" id="navbarSupportedContent">
<ul class="navbar-nav mr-auto mt-2 mt-lg-0"></ul>
<ul class="navbar-nav">
<!-- toggle sidebar button -->
<li class="nav-item"><a id="tg-sb-link" class="nav-link" href="#"><i id="tg-sb-icon" class="fas fa-toggle-on"></i> Nav</a></li>
<!-- entries without drop-downs appear here -->
<li class="nav-item"><a class="nav-link" href="https://github.com/pmd/pmd/releases/latest" target="_blank">Download</a></li>
<li class="nav-item"><a class="nav-link" href="https://github.com/pmd/pmd" target="_blank">Fork us on github</a></li>
<!-- entries with drop-downs appear here -->
<!-- conditional logic to control which topnav appears for the audience defined in the configuration file.-->
</ul>
<form class="form-inline my-2 my-lg-0">
<input class="form-control mr-sm-2" type="search" placeholder="search..." id="search-input">
<ul id="results-container"></ul>
</form>
</div>
</div>
</nav>
<!-- Page Content -->
<div class="container-toc-wrapper">
<div class="container">
<div class="col-lg-12">&nbsp;</div>
<!-- Content Row -->
<div class="row">
<!-- Sidebar Column -->
<div class="col-md-3" id="tg-sb-sidebar">
<ul id="mysidebar" class="nav">
<li class="sidebarTitle">PMD 7.8.0-SNAPSHOT</li>
<div class="sidebarTitleDate">Release date: 29-November-2024</div>
<li>
<a href="#">About</a>
<ul>
<li><a href="index.html">Home</a></li>
<li><a href="pmd_release_notes.html">Release notes</a></li>
<li><a href="pmd_release_notes_pmd7.html">Release notes (PMD 7)</a></li>
<li><a href="pmd_about_help.html">Getting help</a></li>
<li><a href="pmd_about_release_policies.html">Release policies</a></li>
<li><a href="pmd_about_support_lifecycle.html">Support lifecycle</a></li>
</ul>
</li>
<li>
<a href="#">User Documentation</a>
<ul>
<li><a href="pmd_userdocs_migrating_to_pmd7.html">Migration Guide for PMD 7</a></li>
<li><a href="pmd_userdocs_installation.html">Installation and basic CLI usage</a></li>
<li><a href="pmd_userdocs_making_rulesets.html">Making rulesets</a></li>
<li><a href="pmd_userdocs_configuring_rules.html">Configuring rules</a></li>
<li><a href="pmd_userdocs_best_practices.html">Best practices</a></li>
<li><a href="pmd_userdocs_suppressing_warnings.html">Suppressing warnings</a></li>
<li><a href="pmd_userdocs_incremental_analysis.html">Incremental analysis</a></li>
<li><a href="pmd_userdocs_cli_reference.html">PMD CLI reference</a></li>
<li><a href="pmd_userdocs_report_formats.html">PMD Report formats</a></li>
<li><a href="pmd_userdocs_3rdpartyrulesets.html">3rd party rulesets</a></li>
<li class="subfolders">
<a href="#">CPD reference</a>
<ul>
<li><a href="pmd_userdocs_cpd.html">Copy-paste detection</a></li>
<li><a href="pmd_userdocs_cpd_report_formats.html">CPD Report formats</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Extending PMD</a>
<ul>
<li class="active"><a href="pmd_userdocs_extending_writing_rules_intro.html">Introduction to writing rules</a></li>
<li><a href="pmd_userdocs_extending_your_first_rule.html">Your first rule</a></li>
<li><a href="pmd_userdocs_extending_writing_xpath_rules.html">XPath rules</a></li>
<li><a href="pmd_userdocs_extending_writing_java_rules.html">Java rules</a></li>
<li><a href="pmd_userdocs_extending_designer_reference.html">Rule designer reference</a></li>
<li><a href="pmd_userdocs_extending_defining_properties.html">Defining rule properties</a></li>
<li><a href="pmd_userdocs_extending_rule_guidelines.html">Rule guidelines</a></li>
<li><a href="pmd_userdocs_extending_testing.html">Testing your rules</a></li>
<li><a href="pmd_userdocs_extending_ast_dump.html">Creating (XML) dump of the AST</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Tools / Integrations</a>
<ul>
<li><a href="pmd_userdocs_tools_maven.html">Maven PMD Plugin</a></li>
<li><a href="pmd_userdocs_tools_gradle.html">Gradle</a></li>
<li><a href="pmd_userdocs_tools_ant.html">Ant</a></li>
<li><a href="pmd_userdocs_tools_java_api.html">PMD Java API</a></li>
<li><a href="pmd_userdocs_tools_bld.html">bld PMD Extension</a></li>
<li><a href="pmd_userdocs_tools_ci.html">CI integrations</a></li>
<li><a href="pmd_userdocs_tools.html">Other Tools / Integrations</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#">Rule Reference</a>
<ul>
<li class="subfolders">
<a href="#">Apex Rules</a>
<ul>
<li><a href="pmd_rules_apex.html">Index</a></li>
<li><a href="pmd_rules_apex_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_apex_codestyle.html">Code Style</a></li>
<li><a href="pmd_rules_apex_design.html">Design</a></li>
<li><a href="pmd_rules_apex_documentation.html">Documentation</a></li>
<li><a href="pmd_rules_apex_errorprone.html">Error Prone</a></li>
<li><a href="pmd_rules_apex_performance.html">Performance</a></li>
<li><a href="pmd_rules_apex_security.html">Security</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">HTML Rules</a>
<ul>
<li><a href="pmd_rules_html.html">Index</a></li>
<li><a href="pmd_rules_html_bestpractices.html">Best Practices</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Java Rules</a>
<ul>
<li><a href="pmd_rules_java.html">Index</a></li>
<li><a href="pmd_rules_java_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_java_codestyle.html">Code Style</a></li>
<li><a href="pmd_rules_java_design.html">Design</a></li>
<li><a href="pmd_rules_java_documentation.html">Documentation</a></li>
<li><a href="pmd_rules_java_errorprone.html">Error Prone</a></li>
<li><a href="pmd_rules_java_multithreading.html">Multithreading</a></li>
<li><a href="pmd_rules_java_performance.html">Performance</a></li>
<li><a href="pmd_rules_java_security.html">Security</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Java Server Pages Rules</a>
<ul>
<li><a href="pmd_rules_jsp.html">Index</a></li>
<li><a href="pmd_rules_jsp_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_jsp_codestyle.html">Code Style</a></li>
<li><a href="pmd_rules_jsp_design.html">Design</a></li>
<li><a href="pmd_rules_jsp_errorprone.html">Error Prone</a></li>
<li><a href="pmd_rules_jsp_security.html">Security</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">JavaScript Rules</a>
<ul>
<li><a href="pmd_rules_ecmascript.html">Index</a></li>
<li><a href="pmd_rules_ecmascript_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_ecmascript_codestyle.html">Code Style</a></li>
<li><a href="pmd_rules_ecmascript_errorprone.html">Error Prone</a></li>
<li><a href="pmd_rules_ecmascript_performance.html">Performance</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Kotlin Rules</a>
<ul>
<li><a href="pmd_rules_kotlin.html">Index</a></li>
<li><a href="pmd_rules_kotlin_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_kotlin_errorprone.html">Error Prone</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Maven POM Rules</a>
<ul>
<li><a href="pmd_rules_pom.html">Index</a></li>
<li><a href="pmd_rules_pom_errorprone.html">Error Prone</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Modelica Rules</a>
<ul>
<li><a href="pmd_rules_modelica.html">Index</a></li>
<li><a href="pmd_rules_modelica_bestpractices.html">Best Practices</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">PLSQL Rules</a>
<ul>
<li><a href="pmd_rules_plsql.html">Index</a></li>
<li><a href="pmd_rules_plsql_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_plsql_codestyle.html">Code Style</a></li>
<li><a href="pmd_rules_plsql_design.html">Design</a></li>
<li><a href="pmd_rules_plsql_errorprone.html">Error Prone</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Salesforce Visualforce Rules</a>
<ul>
<li><a href="pmd_rules_visualforce.html">Index</a></li>
<li><a href="pmd_rules_visualforce_security.html">Security</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Scala Rules</a>
<ul>
<li><a href="pmd_rules_scala.html">Index</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Swift Rules</a>
<ul>
<li><a href="pmd_rules_swift.html">Index</a></li>
<li><a href="pmd_rules_swift_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_swift_errorprone.html">Error Prone</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Velocity Template Language (VTL) Rules</a>
<ul>
<li><a href="pmd_rules_velocity.html">Index</a></li>
<li><a href="pmd_rules_velocity_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_velocity_design.html">Design</a></li>
<li><a href="pmd_rules_velocity_errorprone.html">Error Prone</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">WSDL Rules</a>
<ul>
<li><a href="pmd_rules_wsdl.html">Index</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">XML Rules</a>
<ul>
<li><a href="pmd_rules_xml.html">Index</a></li>
<li><a href="pmd_rules_xml_bestpractices.html">Best Practices</a></li>
<li><a href="pmd_rules_xml_errorprone.html">Error Prone</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">XSL Rules</a>
<ul>
<li><a href="pmd_rules_xsl.html">Index</a></li>
<li><a href="pmd_rules_xsl_codestyle.html">Code Style</a></li>
<li><a href="pmd_rules_xsl_performance.html">Performance</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#">Language-Specific Documentation</a>
<ul>
<li><a href="pmd_languages_index.html">Overview</a></li>
<li><a href="pmd_languages_configuration.html">Language configuration</a></li>
<li><a href="pmd_languages_apex.html">Apex</a></li>
<li><a href="pmd_languages_cpp.html">C/C++</a></li>
<li><a href="pmd_languages_cs.html">C#</a></li>
<li><a href="pmd_languages_coco.html">Coco</a></li>
<li><a href="pmd_languages_dart.html">Dart</a></li>
<li><a href="pmd_languages_fortran.html">Fortran</a></li>
<li><a href="pmd_languages_gherkin.html">Gherkin</a></li>
<li><a href="pmd_languages_go.html">Go</a></li>
<li><a href="pmd_languages_html.html">HTML</a></li>
<li><a href="pmd_languages_java.html">Java</a></li>
<li><a href="pmd_languages_js_ts.html">JavaScript / TypeScript</a></li>
<li><a href="pmd_languages_jsp.html">JSP</a></li>
<li><a href="pmd_languages_julia.html">Julia</a></li>
<li><a href="pmd_languages_kotlin.html">Kotlin</a></li>
<li><a href="pmd_languages_lua.html">Lua</a></li>
<li><a href="pmd_languages_matlab.html">Matlab</a></li>
<li><a href="pmd_languages_modelica.html">Modelica</a></li>
<li><a href="pmd_languages_objectivec.html">Objective-C</a></li>
<li><a href="pmd_languages_perl.html">Perl</a></li>
<li><a href="pmd_languages_php.html">PHP</a></li>
<li><a href="pmd_languages_plsql.html">PLSQL</a></li>
<li><a href="pmd_languages_python.html">Python</a></li>
<li><a href="pmd_languages_ruby.html">Ruby</a></li>
<li><a href="pmd_languages_scala.html">Scala</a></li>
<li><a href="pmd_languages_swift.html">Swift</a></li>
<li><a href="pmd_languages_tsql.html">T-SQL</a></li>
<li><a href="pmd_languages_visualforce.html">Visualforce</a></li>
<li><a href="pmd_languages_velocity.html">Velocity Template Language (VTL)</a></li>
<li><a href="pmd_languages_xml.html">XML and XML dialects</a></li>
</ul>
</li>
<li>
<a href="#">Developer Documentation</a>
<ul>
<li><a href="pmd_devdocs_development.html">Developer resources</a></li>
<li><a href="pmd_devdocs_building.html">Building PMD from source</a></li>
<li><a href="https://github.com/pmd/pmd/blob/main/CONTRIBUTING.md" target="_blank">Contributing</a></li>
<li><a href="pmd_devdocs_writing_documentation.html">Writing documentation</a></li>
<li><a href="pmd_devdocs_roadmap.html">Roadmap</a></li>
<li><a href="pmd_devdocs_how_pmd_works.html">How PMD works</a></li>
<li><a href="pmd_devdocs_pmdtester.html">Pmdtester</a></li>
<li><a href="pmd_devdocs_rule_deprecation_policy.html">Rule Deprecation Policy</a></li>
<li class="subfolders">
<a href="#">Major contributions</a>
<ul>
<li><a href="pmd_devdocs_major_rule_guidelines.html">Rule Guidelines</a></li>
<li><a href="pmd_devdocs_major_adding_new_language_javacc.html">Adding a new language (JavaCC)</a></li>
<li><a href="pmd_devdocs_major_adding_new_language_antlr.html">Adding a new language (ANTLR)</a></li>
<li><a href="pmd_devdocs_major_adding_new_cpd_language.html">Adding a new CPD language</a></li>
</ul>
</li>
<li class="subfolders">
<a href="#">Experimental features</a>
<ul>
<li><a href="tag_experimental.html">List of experimental Features</a></li>
</ul>
</li>
</ul>
</li>
<li>
<a href="#">Project documentation</a>
<ul>
<li class="subfolders">
<a href="#">Trivia about PMD</a>
<ul>
<li><a href="pmd_projectdocs_trivia_news.html">PMD in the press</a></li>
<li><a href="pmd_projectdocs_trivia_products.html">Products & books related to PMD</a></li>
<li><a href="pmd_projectdocs_trivia_similarprojects.html">Similar projects</a></li>
<li><a href="pmd_projectdocs_trivia_meaning.html">What does 'PMD' mean?</a></li>
</ul>
</li>
<li><a href="pmd_projectdocs_logo.html">Logo</a></li>
<li><a href="pmd_projectdocs_faq.html">FAQ</a></li>
<li><a href="license.html">License</a></li>
<li><a href="pmd_projectdocs_credits.html">Credits</a></li>
<li><a href="pmd_release_notes_old.html">Old release notes</a></li>
<li><a href="pmd_projectdocs_decisions.html">Decisions</a></li>
<li class="subfolders">
<a href="#">Project management</a>
<ul>
<li><a href="pmd_projectdocs_committers_infrastructure.html">Infrastructure</a></li>
<li><a href="pmd_projectdocs_committers_releasing.html">Release process</a></li>
<li><a href="pmd_projectdocs_committers_merging_pull_requests.html">Merging pull requests</a></li>
<li><a href="pmd_projectdocs_committers_main_landing_page.html">Main Landing page</a></li>
</ul>
</li>
</ul>
</li>
</ul>
</div>
<!-- Content Column -->
<div class="col-md-9" id="tg-sb-content">
<header>
<div class="row">
<div class="col-lg-12">
<a href="./" role="button"
><i class="fa fa-home fa-lg"></i
></a>
» Introduction to writing PMD rules
<a
target="_blank"
href="https://github.com/pmd/pmd/blob/main/docs/pages/pmd/userdocs/extending/writing_rules_intro.md"
class="float-right"
role="button"
><i class="fab fa-github fa-lg"></i> Edit on GitHub</a
>
</div>
</div>
<hr />
</header>
<div class="post-header">
<h1 class="post-title-main">Introduction to writing PMD rules</h1>
</div>
<div class="post-content" data-github-edit-url="https://github.com/pmd/pmd/blob/main/docs/pages/pmd/userdocs/extending/writing_rules_intro.md">
<div class="summary">Writing your own PMD rules</div>
<details id="inline-toc-details">
<summary>Table of Contents</summary>
<div id="inline-toc"><!-- empty, move TOC here when screen size too small --></div>
</details>
<p>PMD is a framework to perform code analysis. You can create your own rules to
check for patterns specific to your codebase, or the coding practices of your
team.</p>
<h2 id="how-rules-work-the-ast">How rules work: the AST</h2>
<p>Before running rules, PMD parses the source file into a data structure called an
<strong><a href="https://en.wikipedia.org/wiki/Abstract_syntax_tree">abstract syntax tree (AST)</a></strong>.
This tree represents the syntactic structure of the
code, and encodes syntactic relations between source code elements. For instance,
in Java, method declarations belong to a class: in the AST, the nodes representing
method declarations will be descendants of a node representing the declaration of
their enclosing class. This representation is thus much richer than the original
source code (which, for a program, is just a chain of characters), or the token
chain produced by a lexer. For example:</p>
<table>
<thead>
<tr class="header">
<th>Sample code (Java)</th>
<th>AST</th>
</tr>
</thead>
<tbody>
<tr>
<td>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">class</span> <span class="nc">Foo</span> <span class="kd">extends</span> <span class="nc">Object</span> <span class="o">{</span>
<span class="o">}</span>
</code></pre></div> </div>
</td>
<td>
<div class="language-java highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="err">└─</span> <span class="nc">CompilationUnit</span>
<span class="err">└─</span> <span class="nc">TypeDeclaration</span>
<span class="err">└─</span> <span class="nc">ClassDeclaration</span> <span class="s">"Foo"</span>
<span class="err">├─</span> <span class="nc">ModifierList</span>
<span class="err">├─</span> <span class="nc">ExtendsList</span>
<span class="err">│</span> <span class="err">└─</span> <span class="nc">ClassType</span> <span class="s">"Object"</span>
<span class="err">└─</span> <span class="nc">ClassBody</span>
</code></pre></div> </div>
</td>
</tr>
</tbody>
</table>
<p>Conceptually, PMD rules work by <strong>matching a “pattern” against the AST</strong> of a
file.
Rules explore the AST and find nodes that satisfy some conditions that are characteristic
of the specific thing the rule is trying to flag. Rules then report a violation on these nodes.</p>
<h3 id="discovering-the-ast">Discovering the AST</h3>
<p>ASTs are represented by Java classes deriving from <a href="https://docs.pmd-code.org/apidocs/pmd-core/7.8.0-SNAPSHOT/net/sourceforge/pmd/lang/ast/Node.html#"><code>Node</code></a>.
Each PMD language has its own set of such classes, and its own rules about how
these classes relate to one another, based on the grammar of the language. For
example, all Java AST nodes extend <a href="https://docs.pmd-code.org/apidocs/pmd-java/7.8.0-SNAPSHOT/net/sourceforge/pmd/lang/java/ast/JavaNode.html#"><code>JavaNode</code></a>.</p>
<p>The structure of the AST can be discovered through</p>
<ul>
<li>the <a href="pmd_userdocs_extending_designer_reference.html#ast-inspection">Rule Designer</a></li>
<li>the <a href="pmd_userdocs_extending_ast_dump.html">AST dump feature</a></li>
</ul>
<h2 id="writing-new-rules">Writing new rules</h2>
<p>PMD supports two ways to define rules: using an <strong>XPath query</strong>, or using a
<strong>Java visitor</strong>. XPath rules are much easier to set up, since they’re defined
directly in your ruleset XML, and are expressive enough for nearly any task.</p>
<p>On the other hand, some parts of PMD’s API are only accessible from Java, e.g.
accessing the usages of a declaration. And Java rules allow you to do some
complicated processing, to which an XPath rule couldn’t scale.</p>
<p>In the end, choosing one strategy or the other depends on the difficulty of what
your rule does. I’d advise to keep to XPath unless you have no other choice.</p>
<p>Note: Despite that fact, the Java rules are written in Java, any language that PMD supports
can be analyzed. E.g. you can write a Java rule to analyze Apex source code.</p>
<h2 id="xml-rule-definition">XML rule definition</h2>
<p>New rules must be declared in a ruleset before they’re referenced. This is the
case for both XPath and Java rules. To do this, the <code class="language-plaintext highlighter-rouge">rule</code> element is used, but
instead of mentioning the <code class="language-plaintext highlighter-rouge">ref</code> attribute, it mentions the <code class="language-plaintext highlighter-rouge">class</code> attribute,
with the implementation class of your rule.</p>
<ul>
<li><strong>For Java rules:</strong> this is the concrete class extending AbstractRule (transitively)</li>
<li><strong>For XPath rules:</strong> this is <code class="language-plaintext highlighter-rouge">net.sourceforge.pmd.lang.rule.xpath.XPathRule</code>.</li>
<li><strong>For XPath rules analyzing XML-based languages:</strong> this is <code class="language-plaintext highlighter-rouge">net.sourceforge.pmd.lang.xml.rule.DomXPathRule</code>.
See <a href="pmd_languages_xml.html#xpath-rules-in-xml">XPath rules in XML</a> for more info.</li>
</ul>
<p>Example for Java rule:</p>
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt">&lt;rule</span> <span class="na">name=</span><span class="s">"MyJavaRule"</span>
<span class="na">language=</span><span class="s">"java"</span>
<span class="na">message=</span><span class="s">"Violation!"</span>
<span class="na">class=</span><span class="s">"com.me.MyJavaRule"</span><span class="nt">&gt;</span>
<span class="nt">&lt;description&gt;</span>
Description
<span class="nt">&lt;/description&gt;</span>
<span class="nt">&lt;priority&gt;</span>3<span class="nt">&lt;/priority&gt;</span>
<span class="nt">&lt;/rule&gt;</span>
</code></pre></div></div>
<p>Example for XPath rule:</p>
<div class="language-xml highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt">&lt;rule</span> <span class="na">name=</span><span class="s">"MyXPathRule"</span>
<span class="na">language=</span><span class="s">"java"</span>
<span class="na">message=</span><span class="s">"Violation!"</span>
<span class="na">class=</span><span class="s">"net.sourceforge.pmd.lang.rule.xpath.XPathRule"</span><span class="nt">&gt;</span>
<span class="nt">&lt;description&gt;</span>
Description
<span class="nt">&lt;/description&gt;</span>
<span class="nt">&lt;priority&gt;</span>3<span class="nt">&lt;/priority&gt;</span>
<span class="nt">&lt;properties&gt;</span>
<span class="nt">&lt;property</span> <span class="na">name=</span><span class="s">"xpath"</span><span class="nt">&gt;</span>
<span class="nt">&lt;value&gt;</span><span class="cp">&lt;![CDATA[
//ClassOrInterfaceDeclaration
]]&gt;</span><span class="nt">&lt;/value&gt;</span>
<span class="nt">&lt;/property&gt;</span>
<span class="nt">&lt;/properties&gt;</span>
<span class="nt">&lt;/rule&gt;</span>
</code></pre></div></div>
<div class="alert alert-info" role="alert"><i class="fas fa-info-circle"></i> <b>Note:</b> Since PMD 7, the <code class="language-plaintext highlighter-rouge">language</code> attribute is required on all <code class="language-plaintext highlighter-rouge">rule</code>
elements that declare a new rule. In PMD 6, this was optional, as the base rule classes sometimes set
the language implicitly in their constructor.</div>
<h2 id="resource-index">Resource index</h2>
<p>To learn how to write a rule:</p>
<ul>
<li><a href="pmd_userdocs_extending_your_first_rule.html">Your First Rule</a>
introduces the basic development process of a rule with a running example</li>
<li><a href="pmd_userdocs_extending_writing_xpath_rules.html">Writing XPath Rules</a>
explains a bit more about XPath rules and our XPath API</li>
<li><a href="pmd_userdocs_extending_writing_java_rules.html">Writing Java Rules</a>
describes how to write a rule in Java</li>
</ul>
<p>To go further:</p>
<ul>
<li><a href="pmd_userdocs_extending_defining_properties.html">Defining Properties</a>
describes how to make your rules more configurable with rule properties</li>
<li><a href="pmd_userdocs_extending_testing.html">Testing your Rules</a> introduces
our testing framework and how you can use it to safeguard the quality of
your rule</li>
</ul>
<div class="tags">
<b>Tags: </b>
<a href="tag_extending.html" class="btn btn-outline-secondary navbar-btn cursorNorm" role="button">extending</a>
<a href="tag_userdocs.html" class="btn btn-outline-secondary navbar-btn cursorNorm" role="button">userdocs</a>
<a href="tag_getting_started.html" class="btn btn-outline-secondary navbar-btn cursorNorm" role="button">getting_started</a>
</div>
</div>
<footer>
<hr />
<div>
This documentation is written in markdown. <br />
If there is something missing or can be improved, edit this page on
github and create a PR:
<a
target="_blank"
href="https://github.com/pmd/pmd/blob/main/docs/pages/pmd/userdocs/extending/writing_rules_intro.md"
role="button"
><i class="fab fa-github fa-lg"></i> Edit on GitHub</a
>
</div>
<hr />
<div class="row">
<div class="col-lg-12 footer">
&copy;2024 PMD Open Source Project. All rights
reserved. <br />
<span>Page last updated:</span>
December 2023 (7.0.0)<br /> Site last generated: Nov 21, 2024 <br />
<p>
<img src="images/logo/pmd-logo-70px.png" alt="PMD
logo"/>
</p>
</div>
</div>
</footer>
</div>
<!-- /.row -->
</div>
<!-- /.container -->
</div>
<!-- Sticky TOC column -->
<div class="toc-col">
<div id="toc"></div>
</div>
<!-- /.toc-container-wrapper -->
</div>
</div>
<script type="application/javascript" src="assets/jquery-3.5.1/jquery-3.5.1.min.js"></script>
<script type="application/javascript" src="assets/anchorjs-4.2.2/anchor.min.js"></script>
<script type="application/javascript" src="assets/navgoco-0.2.1/src/jquery.navgoco.min.js"></script>
<script type="application/javascript" src="assets/bootstrap-4.5.2-dist/js/bootstrap.bundle.min.js"></script>
<script type="application/javascript" src="assets/Simple-Jekyll-Search-1.0.8/dest/jekyll-search.js"></script>
<script type="application/javascript" src="assets/jekyll-table-of-contents/toc.js"></script>
<script type="application/javascript" src="js/tabstate.js"></script>
<script type="application/javascript" src="js/customscripts.js"></script>
</body>
</html>
Reference in New Issue View Git Blame Copy Permalink