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writingjavadocchecks.html
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writingjavadocchecks.html
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<!DOCTYPE html>
<!--
| Generated by Apache Maven Doxia Site Renderer 1.11.1 from src/xdocs/writingjavadocchecks.xml.vm at 2024-04-28
| Rendered using Apache Maven Default Skin
-->
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta charset="UTF-8" />
<meta name="viewport" content="width=device-width, initial-scale=1.0" />
<meta name="generator" content="Apache Maven Doxia Site Renderer 1.11.1" />
<title>checkstyle – Writing Javadoc Checks</title>
<link rel="stylesheet" href="./css/maven-base.css" />
<link rel="stylesheet" href="./css/maven-theme.css" />
<link rel="stylesheet" href="./css/site.css" />
<link rel="stylesheet" href="./css/print.css" media="print" />
<script type="text/javascript" src="./js/checkstyle.js"></script>
<script type="text/javascript"
src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.3/jquery.min.js"></script>
<script type="text/javascript" src="./js/anchors.js"></script>
<script type="text/javascript" src="./js/google-analytics.js"></script>
<link rel="icon" href="./images/favicon.png" type="image/x-icon" />
<link rel="shortcut icon" href="./images/favicon.ico" type="image/ico" />
</head>
<body class="composite">
<div id="banner">
<a href="./" id="bannerLeft" title="Checkstyle"><img src="images/header-checkstyle-logo.png" alt="Checkstyle"/></a><a href="./" id="bannerRight" title="Checkstyle"><img src="images/header-right-ruller.png" alt="Checkstyle"/></a> <div class="clear">
<hr/>
</div>
</div>
<div id="breadcrumbs">
<div class="xright"><a href="" title="toTop">toTop</a> | <span id="publishDate">Last Published: 2024-04-28</span>
| <span id="projectVersion">Version: 10.16.0</span>
</div>
<div class="clear">
<hr/>
</div>
</div>
<div id="leftColumn">
<div id="navcolumn">
<h5>About</h5>
<ul>
<li class="none"><a href="index.html" title="Checkstyle">Checkstyle</a></li>
<li class="none"><a href="releasenotes.html" title="Release Notes">Release Notes</a></li>
<li class="none"><a href="consulting.html" title="Consulting">Consulting</a></li>
<li class="none"><a href="sponsoring.html" title="Sponsoring">Sponsoring</a></li>
</ul>
<h5>Documentation</h5>
<ul>
<li class="expanded"><a href="config.html" title="Configuration">Configuration</a>
<ul>
<li class="none"><a href="property_types.html" title="Property Types">Property Types</a></li>
<li class="none"><a href="config_system_properties.html" title="System Properties">System Properties</a></li>
</ul></li>
<li class="expanded"><a href="running.html" title="Running">Running</a>
<ul>
<li class="none"><a href="anttask.html" title="Ant Task">Ant Task</a></li>
<li class="none"><a href="cmdline.html" title="Command Line">Command Line</a></li>
</ul></li>
<li class="expanded"><a href="checks.html" title="Checks">Checks</a>
<ul>
<li class="collapsed"><a href="checks/annotation/index.html" title="Annotations">Annotations</a></li>
<li class="collapsed"><a href="checks/blocks/index.html" title="Block Checks">Block Checks</a></li>
<li class="collapsed"><a href="checks/design/index.html" title="Class Design">Class Design</a></li>
<li class="collapsed"><a href="checks/coding/index.html" title="Coding">Coding</a></li>
<li class="collapsed"><a href="checks/header/index.html" title="Headers">Headers</a></li>
<li class="collapsed"><a href="checks/imports/index.html" title="Imports">Imports</a></li>
<li class="collapsed"><a href="checks/javadoc/index.html" title="Javadoc Comments">Javadoc Comments</a></li>
<li class="collapsed"><a href="checks/metrics/index.html" title="Metrics">Metrics</a></li>
<li class="collapsed"><a href="checks/misc/index.html" title="Miscellaneous">Miscellaneous</a></li>
<li class="collapsed"><a href="checks/modifier/index.html" title="Modifiers">Modifiers</a></li>
<li class="collapsed"><a href="checks/naming/index.html" title="Naming Conventions">Naming Conventions</a></li>
<li class="collapsed"><a href="checks/regexp/index.html" title="Regexp">Regexp</a></li>
<li class="collapsed"><a href="checks/sizes/index.html" title="Size Violations">Size Violations</a></li>
<li class="collapsed"><a href="checks/whitespace/index.html" title="Whitespace">Whitespace</a></li>
</ul></li>
<li class="collapsed"><a href="filters/index.html" title="Filters">Filters</a></li>
<li class="collapsed"><a href="filefilters/index.html" title="File Filters">File Filters</a></li>
<li class="expanded"><a href="style_configs.html" title="Style Configurations">Style Configurations</a>
<ul>
<li class="none"><a href="google_style.html" title="Google's Style">Google's Style</a></li>
<li class="none"><a href="sun_style.html" title="Sun's Style">Sun's Style</a></li>
</ul></li>
</ul>
<h5>Developers</h5>
<ul>
<li class="expanded"><a href="extending.html" title="Extending Checkstyle">Extending Checkstyle</a>
<ul>
<li class="none"><a href="writingchecks.html" title="Writing Checks">Writing Checks</a></li>
<li class="none"><strong>Writing Javadoc Checks</strong></li>
<li class="none"><a href="writingfilters.html" title="Writing Filters">Writing Filters</a></li>
<li class="none"><a href="writingfilefilters.html" title="Writing File Filters">Writing File Filters</a></li>
<li class="none"><a href="writinglisteners.html" title="Writing Listeners">Writing Listeners</a></li>
</ul></li>
<li class="none"><a href="contributing.html" title="Contributing">Contributing</a></li>
<li class="expanded"><a href="beginning_development.html" title="Beginning Development">Beginning Development</a>
<ul>
<li class="none"><a href="eclipse.html" title="Eclipse IDE">Eclipse IDE</a></li>
<li class="none"><a href="netbeans.html" title="NetBeans IDE">NetBeans IDE</a></li>
<li class="none"><a href="idea.html" title="IntelliJ IDE">IntelliJ IDE</a></li>
</ul></li>
<li class="none"><a href="apidocs/index.html" title="Javadoc">Javadoc</a></li>
</ul>
<h5>Project Documentation</h5>
<ul>
<li class="collapsed"><a href="project-info.html" title="Project Information">Project Information</a></li>
<li class="collapsed"><a href="project-reports.html" title="Project Reports">Project Reports</a></li>
</ul>
<a href="https://github.com/checkstyle/checkstyle" title="GitHub" class="poweredBy">
<img class="poweredBy" alt="GitHub" src="images/github_logo_social_coding_outlined.png" />
</a>
<a href="https://twitter.com/checkstyle_java/" title="Twitter" class="poweredBy">
<img class="poweredBy" alt="Twitter" src="images/twitter_button.png" />
</a>
<a href="https://stackoverflow.com/questions/tagged/checkstyle" title="Stackoverflow" class="poweredBy">
<img class="poweredBy" alt="Stackoverflow" src="images/stackoverflow.jpeg" />
</a>
<a href="https://groups.google.com/forum/#!forum/checkstyle" title="GoogleGroups" class="poweredBy">
<img class="poweredBy" alt="GoogleGroups" src="images/groups.png" />
</a>
<a href="https://www.ej-technologies.com/products/jprofiler/overview.html" title="JProfiler" class="poweredBy">
<img class="poweredBy" alt="JProfiler" src="https://www.ej-technologies.com/images/product_banners/jprofiler_medium.png" />
</a>
</div>
</div>
<div id="bodyColumn">
<div id="contentBox">
<section>
<h2><a name="Content"></a>Content</h2>
<ul>
<li><a href="#Content">Content</a></li>
<li><a href="#What_is_Javadoc_comment">What is Javadoc comment</a></li>
<li><a href="#Limitations">Limitations</a></li>
<li><a href="#Tight-HTML_rules">Tight-HTML rules</a></li>
<li><a href="#How_to_create_Javadoc_Check">How to create Javadoc Check</a></li>
<li><a href="#Difference_between_Java_Grammar_and_Javadoc_comments_Grammar">Difference between Java Grammar and Javadoc comments Grammar</a></li>
<li><a href="#Tool_to_print_Javadoc_tree_structure">Tool to print Javadoc tree structure</a></li>
<li><a href="#Access_Java_AST_from_Javadoc_Check">Access Java AST from Javadoc Check</a></li>
<li><a href="#HTML_Code_In_Javadoc_Comments">HTML Code In Javadoc Comments</a></li>
<li><a href="#Checkstyle_SDK_GUI">Checkstyle SDK GUI</a></li>
<li><a href="#Customize_token_types_in_Javadoc_Checks">Customize token types in Javadoc Checks</a></li>
<li><a href="#Integrating_new_Javadoc_Check">Integrating new Javadoc Check</a></li>
<li><a href="#Declare_check.27s_external_resource_locations">Declare check's external resource locations</a></li>
<li><a href="#Examples_of_Javadoc_Checks">Examples of Javadoc Checks</a></li>
<li><a href="#Javadoc_parser_behavior_for_current_HTML_version_and_new_HTML_version">Javadoc parser behavior for current HTML version and new HTML version</a></li></ul>
</section>
<section>
<h2><a name="What_is_Javadoc_comment"></a>What is Javadoc comment</h2>
<p>
Javadoc comment is a multiline comment <code>/* */</code> that starts with the <b>*</b>
character and placed above the class definition, interface definition, enum definition,
method definition or field definition.
If an annotation precedes any of the definitions listed above, then the javadoc comment
should be placed before the annotation.
If several multiline comments with javadoc identifiers are placed sequentially, only
the one closest to the definition, right above it, with the javadoc identifier will be used.
</p>
<p>
Javadoc comments should contain: a short summary (the first sentence), an optional
documentation section, an optional tag section. The first sentence has a special meaning
and should be clear, punchy, short, and is ended by a period symbol.
Immediately after the first sentence, the main description could begin,
which may be followed by the tag section. The tag section starts with the first block tag,
which is defined by the first <code>@</code> character that begins a line
(ignoring leading asterisks, white space, and leading separator <code>/**</code>).
</p>
<p>For example, here is java file:</p>
<div class="source">
<pre>
/**
* My <b>class</b>.
*
* @see Annotation
*/
public class MyClass {
/** Not a javadoc (ignored). */
/**
* Doubles the value.
* The long and detailed explanation what the method does.
*
* @param value for doubling.
* @return double value.
*/
/*
Multiline comment (ignored).
*/
@Annotation
/** Extra javadoc (ignored). */
// Single line comment (ignored).
public int method(int value) {
/** Inner javadoc (ignored). */
return value * 2;
}
}
</pre></div>
<p>Javadoc content for the MyClass will be:</p>
<div class="source">
<pre>
My <b>class</b>.
@see Annotation
</pre></div>
<p>Javadoc content for the MyClass.method will be:</p>
<div class="source">
<pre>
Doubles the value.
The long and detailed explanation what the method does.
@param value for doubling.
@return double value.
</pre></div>
<p>
Attention that java comment starts with <code>/*</code>, following with Identifier of
comment type. Javadoc Identifier is <code>*</code>. All symbols after Javadoc
Identifier till <code>*/</code> are part of javadoc comment.
</p>
<p>Please note that javadoc-like (multiline comment with javadoc identifier) comment inside
a method is not a javadoc comment and skipped by Sun/Oracle javadoc tool and by our javadoc
comment matcher, but such comment will be in AST.
</p>
<p>
You can find different types of documentation generation tools similar to javadoc on the
Internet. Such tools rely on specific Identifier: "!", "#", "$".
Comments look like <code>"/*! some comment */"</code> , <code>"/*# some comment */"</code> ,
<code>"/*$ some comment */"</code>. Such multiline comments are not a javadoc.
</p>
</section>
<section>
<h2><a name="Limitations"></a>Limitations</h2>
<p>
Javadoc by specification could contain any HTML tags that let user generate content he needs.
All tags are copied as is to result javadoc html pages by Sun/Oracle javadoc tool.
All bad formatting is responsibility of user and web-browser. To validate Checkstyle to parse
input to predictable structure - Abstract Syntax Tree(AST). It is very difficult to parse
free style format, so input text need to follow some format, so limitation appears.
</p>
<p>
The comment should be written in <a href="#Tight-HTML_rules">Tight-HTML</a>
to build nested AST Tree that most Checks expect.
</p>
<p>
For more details about parsing of HTML into AST read
<a href="#HTML_Code_In_Javadoc_Comments">HTML Code In Javadoc Comments</a>
and <a href="#Javadoc_parser_behavior_for_current_HTML_version_and_new_HTML_version">
Javadoc parser behavior
</a> section.
</p>
</section>
<section>
<h2><a name="Tight-HTML_rules"></a>Tight-HTML rules</h2>
<p>
Every HTML tag should have matching end HTML tag or it is a
<a class="externalLink" href="https://www.w3.org/TR/html/syntax.html#void-elements">void element</a>.
</p>
<p>
The only exceptions are HTML 4 tags whose end tag is optional (omittable) by
HTML specification (example is
<a class="externalLink" href="https://www.w3.org/TR/html5/tabular-data.html#the-tr-element">TR</a>), so,
Checkstyle won't show error about missing end tag, however,
it leads to broken Tight-HTML structure and as a result
leads to not-nested content of the HTML tags in Abstract Syntax Tree of the Javadoc comment.
<br />
In other words, if HTML tags are not closed Javadoc grammar cannot determine content
of these tags, so structure of the parse tree will not be nested like it is while using
<a href="#Tight-HTML_rules">Tight-HTML</a> code. It is done just to not fail on every
Javadoc comment, because there are tons of using unclosed tags, etc.
</p>
<p>
Other rules:
</p>
<ul>
<li>Document Structure elements (DOCTYPE, <html>, <body>, etc) are
not mandatory.</li>
<li>Elements must always be closed, except HTML4 elements whose end tag is optional
(omittable) and HTML4
<a class="externalLink" href="https://www.w3.org/TR/html/syntax.html#void-elements">void elements</a>.
See <a href="#HTML_Code_In_Javadoc_Comments">HTML Code In Javadoc Comments</a>
section
</li>
<li>HTML elements can be either in lowercase or in uppercase</li>
<li>Attribute names can be either in lowercase or in uppercase</li>
<li>Attribute values can be either quoted or not be quoted</li>
</ul>
</section>
<section>
<h2><a name="How_to_create_Javadoc_Check"></a>How to create Javadoc Check</h2>
<p>
Principle of writing Javadoc Checks is similar to writing regular Checks. You just extend
another abstract class and use another token types.
</p>
<p>
To start implementing new Check create a new class and extend <a href="apidocs/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheck.html">
AbstractJavadocCheck</a>.
It has two abstract methods you should implement:
</p>
<ul>
<li>
<a href="apidocs/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheck.html#getDefaultJavadocTokens--">
getDefaultJavadocTokens()</a> - return int array of
javadoc token types your Check is going to process.
The array should contain int constants from
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/JavadocTokenTypes.html">
JavadocTokenTypes</a> class. (There is also
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html">
TokenTypes</a> class in Checkstyle. Make sure you use
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/JavadocTokenTypes.html">
JavadocTokenTypes</a> class in your Check, because the
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/TokenTypes.html">
TokenTypes</a> is used to describe standard Java
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/DetailAST.html">
DetailAST</a> token type.)
</li>
<li>
<a href="apidocs/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheck.html#visitJavadocToken-com.puppycrawl.tools.checkstyle.api.DetailNode-">
visitJavadocToken(DetailNode)</a> - it's a place you should put tree nodes processing.
The argument is Javadoc tree node of type you described before in
<a href="apidocs/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheck.html#getDefaultJavadocTokens--">
getDefaultJavadocTokens()</a> method.
</li>
</ul>
</section>
<section>
<h2><a name="Difference_between_Java_Grammar_and_Javadoc_comments_Grammar"></a>Difference between Java Grammar and Javadoc comments Grammar</h2>
<p>
Java grammar parses java file base on Java language specifications. So, there are
singleline comments and multiline/block comments in it.
Java compiler doesn't know about Javadoc because it is just a multiline comment.
To parse multiline comment as a Javadoc comment, checkstyle has special Parser
that is based on ANTLR Javadoc grammar. So, it's supposed to process block comments
that start with Javadoc Identifier and parse them to Abstract Syntax Tree (AST).
</p>
<p>
The difference is that Java grammar uses ANTLR v2, while Javadoc grammar uses ANTLR v4.
Because of that, these two grammars and their trees are not compatible.
Java AST consists of
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/DetailAST.html">DetailAST</a>
objects, while Javadoc AST consists of
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/DetailNode.html">DetailNode</a>
objects.
</p>
<p>
Main Java grammar skips any whitespaces and newlines, so in Java Abstract Syntax Tree there
are no whitespace/newline nodes. In Javadoc comment every whitespace matters, and Javadoc
Checks need all those whitespaces and newline nodes to verify format and content of the
Javadoc comment. Because of that Javadoc grammar includes all whitespaces, newlines to
the parse tree
(<a href="apidocs/com/puppycrawl/tools/checkstyle/api/JavadocTokenTypes.html#WS">WS</a>,
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/JavadocTokenTypes.html#NEWLINE">
NEWLINE</a>).
</p>
</section>
<section>
<h2><a name="Tool_to_print_Javadoc_tree_structure"></a>Tool to print Javadoc tree structure</h2>
<p>
Checkstyle can print Abstract Syntax Tree for Java and Javadoc trees. You need to run
checkstyle jar file with <b>-J</b> argument, providing java file.
</p>
<p>For example, here is MyClass.java file:</p>
<div class="source">
<pre>
/**
* My <b>class</b>.
* @see AbstractClass
*/
public class MyClass {
}
</pre></div>
<p>Command:</p>
<div class="wrap-content">
<div class="source">
<pre>
java -jar checkstyle-X.XX-all.jar -J MyClass.java
</pre></div>
</div>
<p>Output:</p>
<div class="source">
<pre>
CLASS_DEF -> CLASS_DEF [5:0]
|--MODIFIERS -> MODIFIERS [5:0]
| |--BLOCK_COMMENT_BEGIN -> /* [1:0]
| | |--COMMENT_CONTENT -> *\n * My <b>class</b>.\n * @see AbstractClass\n [1:2]
| | | `--JAVADOC -> JAVADOC [1:3]
| | | |--NEWLINE -> \n [1:3]
| | | |--LEADING_ASTERISK -> * [2:0]
| | | |--TEXT -> My [2:2]
| | | |--HTML_ELEMENT -> HTML_ELEMENT [2:6]
| | | | `--HTML_TAG -> HTML_TAG [2:6]
| | | | |--HTML_ELEMENT_START -> HTML_ELEMENT_START [2:6]
| | | | | |--START -> < [2:6]
| | | | | |--HTML_TAG_NAME -> b [2:7]
| | | | | `--END -> > [2:8]
| | | | |--TEXT -> class [2:9]
| | | | `--HTML_ELEMENT_END -> HTML_ELEMENT_END [2:14]
| | | | |--START -> < [2:14]
| | | | |--SLASH -> / [2:15]
| | | | |--HTML_TAG_NAME -> b [2:16]
| | | | `--END -> > [2:17]
| | | |--TEXT -> . [2:18]
| | | |--NEWLINE -> \n [2:19]
| | | |--LEADING_ASTERISK -> * [3:0]
| | | |--WS -> [3:2]
| | | |--JAVADOC_TAG -> JAVADOC_TAG [3:3]
| | | | |--SEE_LITERAL -> @see [3:3]
| | | | |--WS -> [3:7]
| | | | |--REFERENCE -> REFERENCE [3:8]
| | | | | `--CLASS -> AbstractClass [3:8]
| | | | |--NEWLINE -> \n [3:21]
| | | | `--WS -> [4:0]
| | | `--EOF -> <EOF> [4:1]
| | `--BLOCK_COMMENT_END -> */ [4:1]
| `--LITERAL_PUBLIC -> public [5:0]
|--LITERAL_CLASS -> class [5:7]
|--IDENT -> MyClass [5:13]
`--OBJBLOCK -> OBJBLOCK [5:21]
|--LCURLY -> { [5:21]
`--RCURLY -> } [7:0]
</pre></div>
<p>
As you see very small java file transforms to a huge Abstract Syntax Tree, because that is
the most detailed tree including all components of the java file: classes, methods,
comments, etc.
</p>
<p>
In most cases while developing Javadoc Check, you need to only parse the tree of the exact
Javadoc comment. To do that just copy Javadoc comment to separate file and remove <b>/**</b>
at the beginning and <b>*/</b> at the end. After that, run checkstyle with <b>-j</b>
argument.
</p>
<p>MyJavadocComment.javadoc file:</p>
<div class="source">
<pre>
* My <b>class</b>.
* @see AbstractClass
</pre></div>
<p>Command:</p>
<div class="wrap-content">
<div class="source">
<pre>
java -jar checkstyle-X.XX-all.jar \
    -j MyJavadocComment.javadoc
</pre></div>
</div>
<p>Output:</p>
<div class="source">
<pre>
JAVADOC -> JAVADOC [0:0]
|--LEADING_ASTERISK -> * [0:0]
|--TEXT -> My [0:2]
|--HTML_ELEMENT -> HTML_ELEMENT [0:6]
| `--HTML_TAG -> HTML_TAG [0:6]
| |--HTML_ELEMENT_START -> HTML_ELEMENT_START [0:6]
| | |--START -> < [0:6]
| | |--HTML_TAG_NAME -> b [0:7]
| | `--END -> > [0:8]
| |--TEXT -> class [0:9]
| `--HTML_ELEMENT_END -> HTML_ELEMENT_END [0:14]
| |--START -> < [0:14]
| |--SLASH -> / [0:15]
| |--HTML_TAG_NAME -> b [0:16]
| `--END -> > [0:17]
|--TEXT -> . [0:18]
|--NEWLINE -> \n [0:19]
|--LEADING_ASTERISK -> * [1:0]
|--WS -> [1:2]
|--JAVADOC_TAG -> JAVADOC_TAG [1:3]
| |--SEE_LITERAL -> @see [1:3]
| |--WS -> [1:7]
| `--REFERENCE -> REFERENCE [1:8]
| `--CLASS -> AbstractClass [1:8]
`--EOF -> <EOF> [1:21]
</pre></div>
</section>
<section>
<h2><a name="Access_Java_AST_from_Javadoc_Check"></a>Access Java AST from Javadoc Check</h2>
<p>
As you already know Javadoc parse tree is a result of parsing block comment. There is a
method to get the original block comment from Javadoc Check.
You may need this block comment to check its position or something else in java
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/DetailAST.html">DetailAST</a> tree.
</p>
<p>
For example, to write a JavadocCheck that verifies @param tags in Javadoc comment of
a method definition, you also need all method's parameter names. To get method
definition AST you should access java
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/DetailAST.html">DetailAST</a> tree
from javadoc Check. For this purpose use
<a href="apidocs/com/puppycrawl/tools/checkstyle/checks/javadoc/AbstractJavadocCheck.html#getBlockCommentAst--">
getBlockCommentAst()</a>
method that returns
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/DetailAST.html">DetailAST</a> node.
</p>
<p>
Example:
</p>
<div class="source">
<pre>
class MyCheck extends AbstractJavadocCheck {
@Override
public int[] getDefaultJavadocTokens() {
return new int[]{JavadocTokenTypes.PARAMETER_NAME};
}
@Override
public void visitJavadocToken(DetailNode paramNameNode) {
String javadocParamName = paramNameNode.getText();
DetailAST blockCommentAst = getBlockCommentAst();
if (BlockCommentPosition.isOnMethod(blockCommentAst)) {
DetailAST methodDef = blockCommentAst.getParent();
DetailAST methodParam = findMethodParameter(methodDef);
String methodParamName = methodParam.getText();
if (!javadocParamName.equals(methodParamName)) {
log(methodParam, "params.dont.match");
}
}
}
}
</pre></div>
</section>
<section>
<h2><a name="HTML_Code_In_Javadoc_Comments"></a>HTML Code In Javadoc Comments</h2>
<p>
Checkstyle supports HTML4 tags in Javadoc comments:
<a class="externalLink" href="https://www.w3.org/TR/html4/index/elements.html">
all HTML4 elements
</a>.
</p>
<p>
HTML4 is picked just to have a list of elements whose end tag is optional(omittable) and a
list of <a class="externalLink" href="https://www.w3.org/TR/html/syntax.html#void-elements">void elements</a>
(also known as <a class="externalLink" href="https://www.w3schools.com/html/html_elements.asp">empty html
tags</a>, for example <a class="externalLink" href="https://www.w3.org/TR/html4/struct/text.html#edef-BR">BR
tag</a>).
</p>
<p>
HTML4 elements whose end tag is optional (omittable): <P>, <LI>, <TR>,
<TD>, <TH>, <BODY>, <COLGROUP>, <DD>, <DT>,
<HEAD>, <HTML>, <OPTION>, <TBODY>, <THEAD>, <TFOOT>.
</p>
<p>
Void HTML4 elements: <AREA>, <BASE>, <BASEFONT>, <BR>, <COL>,
<FRAME>, <HR>, <IMG>, <INPUT>, <ISINDEX>, <LINK>,
<META>, <PARAM>.
</p>
<p>
To make Checkstyle support HTML5 tags whose end tag is optional (omittable) and HTML5 void
elements we should update Javadoc Parser because each element that breaks
<a href="#Tight-HTML_rules">Tight-HTML rules</a> have to be defined in Javadoc grammar.
In the future, we should update Javadoc grammar if those tag lists extend (new tags,
new HTML standard, etc.).
(We already have an <a class="externalLink" href="https://github.com/checkstyle/checkstyle/issues/3332">issue
on updating Javadoc grammar to HTML5</a>)
</p>
<p>
If Checkstyle meets unknown tag (for example HTML5 tag)
it doesn't fail and parses this tag as
<a href="apidocs/com/puppycrawl/tools/checkstyle/api/JavadocTokenTypes.html#HTML_TAG">
HTML_TAG</a>
Javadoc token type.
Just follow <a href="#Tight-HTML_rules">Tight-HTML rules</a> to make
Checkstyle javadoc parser make nested AST, even though tags are unknown.
</p>
<div class="source">
<pre>
<audio><source src="horse.ogg" type="audio/ogg"/></audio>
</pre></div>
<div class="source">
<pre>
JAVADOC -> JAVADOC [0:0]
|--HTML_ELEMENT -> HTML_ELEMENT [0:0]
| `--HTML_TAG -> HTML_TAG [0:0]
| |--HTML_ELEMENT_START -> HTML_ELEMENT_START [0:0]
| | |--START -> < [0:0]
| | |--HTML_TAG_NAME -> audio [0:1]
| | `--END -> > [0:6]
| |--HTML_ELEMENT -> HTML_ELEMENT [0:7]
| | `--SINGLETON_ELEMENT -> SINGLETON_ELEMENT [0:7]
| | `--EMPTY_TAG -> EMPTY_TAG [0:7]
| | |--START -> < [0:7]
| | |--HTML_TAG_NAME -> source [0:8]
| | |--WS -> [0:14]
| | |--ATTRIBUTE -> ATTRIBUTE [0:15]
| | | |--HTML_TAG_NAME -> src [0:15]
| | | |--EQUALS -> = [0:18]
| | | `--ATTR_VALUE -> "horse.ogg" [0:19]
| | |--WS -> [0:31]
| | |--ATTRIBUTE -> ATTRIBUTE [0:32]
| | | |--HTML_TAG_NAME -> type [0:32]
| | | |--EQUALS -> = [0:36]
| | | `--ATTR_VALUE -> "audio/ogg" [0:37]
| | `--SLASH_END -> /> [0:49]
| `--HTML_ELEMENT_END -> HTML_ELEMENT_END [0:51]
| |--START -> < [0:51]
| |--SLASH -> / [0:52]
| |--HTML_TAG_NAME -> audio [0:53]
| `--END -> > [0:58]
`--EOF -> <EOF> [0:59]
</pre></div>
<p>
Here is what you get if unknown tag doesn't have matching end tag (for example, HTML5 tag
<audio>): <br />
Input:
</p>
<div class="source">
<pre><audio>test</pre></div>
Output:
<div class="wrap-content">
<div class="source">
<pre>
[ERROR:0] Javadoc comment at column 1 has parse error. Missed HTML close tag 'audio'.
Sometimes it means that close tag missed for one of previous tags.
</pre></div>
</div>
<p>
As you see Javadoc parser prints error and doesn't build AST if unknown HTML tag doesn't
have matching end tag. If that a case please create an issue against Checkstyle to
upgrade parser.
</p>
<p>
There are also HTML tags that are marked as "Not supported in HTML5"
(<a class="externalLink" href="https://www.w3schools.com/tags/default.asp">HTML Element Reference</a>).
Checkstyle Javadoc parser can parse those tags too if they are written in
<a href="#Tight-HTML_rules">Tight-HTML</a>.
<br />
Example.
<br />
Input:
</p>
<div class="source">
<pre>
<acronym title="as soon as possible">ASAP</acronym>
</pre></div>
<br />
Output:
<div class="source">
<pre>
JAVADOC -> JAVADOC [0:0]
|--HTML_ELEMENT -> HTML_ELEMENT [0:0]
| `--HTML_TAG -> HTML_TAG [0:0]
| |--HTML_ELEMENT_START -> HTML_ELEMENT_START [0:0]
| | |--START -> < [0:0]
| | |--HTML_TAG_NAME -> acronym [0:1]
| | |--WS -> [0:8]
| | |--ATTRIBUTE -> ATTRIBUTE [0:9]
| | | |--HTML_TAG_NAME -> title [0:9]
| | | |--EQUALS -> = [0:14]
| | | `--ATTR_VALUE -> "as soon as possible" [0:15]
| | `--END -> > [0:37]
| |--TEXT -> ASAP [0:38]
| `--HTML_ELEMENT_END -> HTML_ELEMENT_END [0:42]
| |--START -> < [0:42]
| |--SLASH -> / [0:43]
| |--HTML_TAG_NAME -> acronym [0:44]
| `--END -> > [0:51]
`--EOF -> <EOF> [0:52]
</pre></div>
<p>More examples:</p>
<div class="wrapper">
<table border="0" class="bodyTable" style="table-layout: fixed;">
<tr class="a">
<td align="left">
1) Unclosed paragraph HTML tag. As you see in the tree, content of the paragraph tag
is not nested to this tag.
That is because HTML tags are not closed by pair tag </p>, and Checkstyle
requires <a href="#Tight-HTML_rules">Tight-HTML</a> code to predictably parse
Javadoc comments.
</td>
<td>
2) Here is correct version with open and closed HTML tags.
</td>
</tr>
<tr class="b">
<td align="left">
<div class="source">
<pre>
<p> First
<p> Second
</pre></div>
</td>
<td>
<div class="source">
<pre>
<p> First </p>
<p> Second </p>
</pre></div>
</td>
</tr>
<tr class="a">
<td align="left">
<div class="source">
<pre>
JAVADOC -> JAVADOC [0:0]
|--HTML_ELEMENT -> HTML_ELEMENT [0:0]
| `--P_TAG_START -> P_TAG_START [0:0]
| |--START -> < [0:0]
| |--P_HTML_TAG_NAME -> p [0:1]
| `--END -> > [0:2]
|--TEXT -> First [0:3]
|--NEWLINE -> \n [0:9]
|--HTML_ELEMENT -> HTML_ELEMENT [1:0]
| `--P_TAG_START -> P_TAG_START [1:0]
| |--START -> < [1:0]
| |--P_HTML_TAG_NAME -> p [1:1]
| `--END -> > [1:2]
|--TEXT -> Second [1:3]
`--EOF -> <EOF> [1:10]
</pre></div>
</td>
<td>
<div class="source">
<pre>
JAVADOC -> JAVADOC [0:0]
|--HTML_ELEMENT -> HTML_ELEMENT [0:0]
| `--PARAGRAPH -> PARAGRAPH [0:0]
| |--P_TAG_START -> P_TAG_START [0:0]
| | |--START -> < [0:0]
| | |--P_HTML_TAG_NAME -> p [0:1]
| | `--END -> > [0:2]
| |--TEXT -> First [0:3]
| `--P_TAG_END -> P_TAG_END [0:10]
| |--START -> < [0:10]
| |--SLASH -> / [0:11]
| |--P_HTML_TAG_NAME -> p [0:12]
| `--END -> > [0:13]
|--NEWLINE -> \n [0:14]
|--HTML_ELEMENT -> HTML_ELEMENT [1:0]
| `--PARAGRAPH -> PARAGRAPH [1:0]
| |--P_TAG_START -> P_TAG_START [1:0]
| | |--START -> < [1:0]
| | |--P_HTML_TAG_NAME -> p [1:1]
| | `--END -> > [1:2]
| |--TEXT -> Second [1:3]
| `--P_TAG_END -> P_TAG_END [1:11]
| |--START -> < [1:11]
| |--SLASH -> / [1:12]
| |--P_HTML_TAG_NAME -> p [1:13]
| `--END -> > [1:14]
`--EOF -> <EOF> [1:15]
</pre></div>
</td>
</tr>
</table>
</div>
<p>
Checks can also be configured to log violation on encountering non-tight HTML tags.
<code>violateExecutionOnNonTightHtml</code> property can be used for this purpose in the checks
that support it. A custom check needs to extend <code>AbstractJavadocCheck</code> for having
this functionality readily available. Do note that a check which has this property set to
true will log violation only for the first not-tight HTML tag found. To allow a check to
skip processing of javadocs with non-tight HTML, method
<code>acceptJavadocWithNonTightHtml</code> in class <code>AbstractJavadocCheck</code> can be
overridden in the check. The following example illustrates how to use this property.
</p>
<p>
Input:
</p>
<div class="source">
<pre>
/**
* <body>
* <p> This class is only meant for testing. </p>
* <p> This p tag is not closed. It is non-tight. Will lead to violations if
* <tt>violateExecutionOnNonTightHtml</tt> is set to true for the check.
* <li>tight li tag <p>non-tight p tag, but only the 1st non-tight tag is logged in violation</li>
* </body>
*/
public class Test {
/**
<p><p>
paraception. Will result in a violation from the <tt>JavadocParagraph</tt> check due to
redundant tags.
</p></p>
*/
private int field1;
/**<tr> Zero </p> nesting despite `tr` is closed </tr>*/
private int field2;
/**
* <p> this paragraph is closed and would be nested in javadoc tree </p>
* <li> this list has an <p> unclosed para, but still the list would get nested </li>
*/
private int field3;
/**
* <li> Complete <p> nesting </p> </li>
*/
private int field4;
}
</pre></div>
<p>
Output with <code>violateExecutionOnNonTightHtml</code> set to false:
</p>
<div class="wrapper">
<table border="0" class="bodyTable">
<tr class="a">
<td align="left">
<div class="source">
<pre>
<!DOCTYPE module PUBLIC
"-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
"https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
<module name="TreeWalker">
<module name="JavadocParagraph">
<property name="violateExecutionOnNonTightHtml" value="false"/>
</module>
</module>
</module>
</pre></div>
</td>
<td>
<div class="source">
<pre>
Starting audit...
[ERROR] Test.java:11: Redundant <p> tag. [JavadocParagraph]
Audit done.
Checkstyle ends with 1 errors.
</pre></div>
</td>
</tr>
</table>
</div>
<p>
Output with <code>violateExecutionOnNonTightHtml</code> set to true:
</p>
<div class="wrapper">
<table border="0" class="bodyTable">
<tr class="a">
<td align="left">
<div class="source">
<pre>
<!DOCTYPE module PUBLIC
"-//Checkstyle//DTD Checkstyle Configuration 1.3//EN"
"https://checkstyle.org/dtds/configuration_1_3.dtd">
<module name="Checker">
<module name="TreeWalker">
<module name="JavadocParagraph">
<property name="violateExecutionOnNonTightHtml" value="true"/>
</module>
</module>
</module>
</pre></div>
</td>
<td>
<div class="source">
<pre>
Starting audit...