You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
arthas/en/advice-class.html

362 lines
14 KiB
HTML

This file contains ambiguous Unicode characters!

This file contains ambiguous Unicode characters that may be confused with others in your current locale. If your use case is intentional and legitimate, you can safely ignore this warning. Use the Escape button to highlight these characters.

<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="en" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="en" > <!--<![endif]-->
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>Fundamental Fields in Expressions &mdash; Arthas 3.0.5-SNAPSHOT documentation</title>
<link rel="shortcut icon" href="_static/favicon.ico"/>
<link rel="stylesheet" href="_static/css/theme.css" type="text/css" />
<link rel="stylesheet" href="_static/pygments.css" type="text/css" />
<link rel="stylesheet" href="_static/overrides.css" type="text/css" />
<link rel="index" title="Index" href="genindex.html" />
<link rel="search" title="Search" href="search.html" />
<link rel="next" title="trace" href="trace.html" />
<link rel="prev" title="watch" href="watch.html" />
<script src="_static/center_page.js"></script>
<script src="_static/js/modernizr.min.js"></script>
</head>
<body class="wy-body-for-nav">
<div class="wy-grid-for-nav">
<nav data-toggle="wy-nav-shift" class="wy-nav-side">
<div class="wy-side-scroll">
<div class="wy-side-nav-search">
<a href="index.html" class="icon icon-home"> Arthas
</a>
<div class="version">
3.0.5-SNAPSHOT
</div>
<div role="search">
<form id="rtd-search-form" class="wy-form" action="search.html" method="get">
<input type="text" name="q" placeholder="Search docs" />
<input type="hidden" name="check_keywords" value="yes" />
<input type="hidden" name="area" value="default" />
</form>
</div>
</div>
<div class="wy-menu wy-menu-vertical" data-spy="affix" role="navigation" aria-label="main navigation">
<ul class="current">
<li class="toctree-l1"><a class="reference internal" href="install-detail.html">Installation</a></li>
<li class="toctree-l1"><a class="reference internal" href="quick-start.html">Quick start</a></li>
<li class="toctree-l1"><a class="reference internal" href="advanced-use.html">Advanced usage</a></li>
<li class="toctree-l1 current"><a class="reference internal" href="commands.html">Commands</a><ul class="current">
<li class="toctree-l2"><a class="reference internal" href="dashboard.html">dashboard</a></li>
<li class="toctree-l2"><a class="reference internal" href="thread.html">thread</a></li>
<li class="toctree-l2"><a class="reference internal" href="jvm.html">jvm</a></li>
<li class="toctree-l2"><a class="reference internal" href="sysprop.html">sysprop</a></li>
<li class="toctree-l2"><a class="reference internal" href="getstatic.html">getstatic</a></li>
<li class="toctree-l2"><a class="reference internal" href="sc.html">sc</a></li>
<li class="toctree-l2"><a class="reference internal" href="sm.html">sm</a></li>
<li class="toctree-l2"><a class="reference internal" href="dump.html">dump</a></li>
<li class="toctree-l2"><a class="reference internal" href="jad.html">jad</a></li>
<li class="toctree-l2"><a class="reference internal" href="classloader.html">classloader</a></li>
<li class="toctree-l2"><a class="reference internal" href="redefine.html">redefine</a></li>
<li class="toctree-l2"><a class="reference internal" href="monitor.html">monitor</a></li>
<li class="toctree-l2 current"><a class="reference internal" href="watch.html">watch</a><ul class="current">
<li class="toctree-l3 current"><a class="reference internal" href="watch.html#parameters-options">Parameters &amp; Options</a><ul class="current">
<li class="toctree-l4 current"><a class="current reference internal" href="#">Critical fields in</a></li>
<li class="toctree-l4"><a class="reference external" href="https://github.com/alibaba/arthas/issues/71">Special usages</a></li>
<li class="toctree-l4"><a class="reference external" href="https://commons.apache.org/proper/commons-ognl/language-guide.html">OGNL official guide</a></li>
</ul>
</li>
<li class="toctree-l3"><a class="reference internal" href="watch.html#usage">Usage</a></li>
</ul>
</li>
<li class="toctree-l2"><a class="reference internal" href="trace.html">trace</a></li>
<li class="toctree-l2"><a class="reference internal" href="stack.html">stack</a></li>
<li class="toctree-l2"><a class="reference internal" href="tt.html">tt</a></li>
<li class="toctree-l2"><a class="reference internal" href="options.html">options</a></li>
<li class="toctree-l2"><a class="reference internal" href="commands.html#basic-commands">Basic Commands</a></li>
</ul>
</li>
<li class="toctree-l1"><a class="reference external" href="https://github.com/alibaba/arthas/issues?q=label%3Auser-case">User cases</a></li>
<li class="toctree-l1"><a class="reference internal" href="release-notes.html">Release Notes</a></li>
<li class="toctree-l1"><a class="reference external" href="https://github.com/alibaba/arthas/issues?q=label%3Aquestion-answered">Questions and answers</a></li>
<li class="toctree-l1"><a class="reference external" href="https://github.com/alibaba/arthas">Fork me at GitHub</a></li>
<li class="toctree-l1"><a class="reference external" href="https://github.com/alibaba/arthas/blob/master/CONTRIBUTING.md">CONTRIBUTING</a></li>
</ul>
</div>
</div>
</nav>
<section data-toggle="wy-nav-shift" class="wy-nav-content-wrap">
<nav class="wy-nav-top" aria-label="top navigation">
<i data-toggle="wy-nav-top" class="fa fa-bars"></i>
<a href="index.html">Arthas</a>
</nav>
<div class="wy-nav-content">
<div class="rst-content">
<div role="navigation" aria-label="breadcrumbs navigation">
<ul class="wy-breadcrumbs">
<li><a href="index.html">Docs</a> &raquo;</li>
<li><a href="commands.html">All Commands</a> &raquo;</li>
<li><a href="watch.html">watch</a> &raquo;</li>
<li>Fundamental Fields in Expressions</li>
<li class="wy-breadcrumbs-aside">
<a href="https://github.com/alibaba/arthas/blob/master/site/src/site/sphinx/en/advice-class.md" class="fa fa-github"> Edit on GitHub</a>
</li>
</ul>
<hr/>
</div>
<div role="main" class="document" itemscope="itemscope" itemtype="http://schema.org/Article">
<div itemprop="articleBody">
<div class="section" id="fundamental-fields-in-expressions">
<span id="fundamental-fields-in-expressions"></span><h1>Fundamental Fields in Expressions<a class="headerlink" href="#fundamental-fields-in-expressions" title="Permalink to this headline"></a></h1>
<p>There is a very fundamental class <code class="docutils literal notranslate"><span class="pre">Advice</span></code> for the expressions used in filtering, tracing or monitoring and other aspects in commands.</p>
<div class="highlight-java notranslate"><div class="highlight"><pre><span></span><span class="kd">public</span> <span class="kd">class</span> <span class="nc">Advice</span> <span class="o">{</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">ClassLoader</span> <span class="n">loader</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">Class</span><span class="o">&lt;?&gt;</span> <span class="n">clazz</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">ArthasMethod</span> <span class="n">method</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">Object</span> <span class="n">target</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">Object</span><span class="o">[]</span> <span class="n">params</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">Object</span> <span class="n">returnObj</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="n">Throwable</span> <span class="n">throwExp</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="kt">boolean</span> <span class="n">isBefore</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="kt">boolean</span> <span class="n">isThrow</span><span class="o">;</span>
<span class="kd">private</span> <span class="kd">final</span> <span class="kt">boolean</span> <span class="n">isReturn</span><span class="o">;</span>
<span class="c1">// getter/setter </span>
<span class="o">}</span>
</pre></div>
</div>
<p>Description for the variables in the class <code class="docutils literal notranslate"><span class="pre">Advice</span></code>:</p>
<table border="1" class="docutils">
<thead>
<tr>
<th align="right">Name</th>
<th align="left">Specification</th>
</tr>
</thead>
<tbody>
<tr>
<td align="right">loader</td>
<td align="left">the class loader for the current called class</td>
</tr>
<tr>
<td align="right">clazz</td>
<td align="left">the reference to the current called class</td>
</tr>
<tr>
<td align="right">method</td>
<td align="left">the reference to the current called method</td>
</tr>
<tr>
<td align="right">target</td>
<td align="left">the instance of the current called class</td>
</tr>
<tr>
<td align="right">params</td>
<td align="left">the parameters for the current call, which is an array (when there's no parameter, it will be an empty array)</td>
</tr>
<tr>
<td align="right">returnObj</td>
<td align="left">the return value from the current call - only available when the method call returns normally (<code>isReturn==true</code>), and <code>null</code> is for <code>void</code> return value</td>
</tr>
<tr>
<td align="right">throwExp</td>
<td align="left">the exceptions thrown from the current call - only available when the method call throws exception (<code>isThrow==true</code>)</td>
</tr>
<tr>
<td align="right">isBefore</td>
<td align="left">flag to indicate the method is about to execute. <code>isBefore==true</code> but <code>isThrow==false</code> and <code>isReturn==false</code> since it's no way to know how the method call will end</td>
</tr>
<tr>
<td align="right">isThrow</td>
<td align="left">flag to indicate the method call ends with exception thrown</td>
</tr>
<tr>
<td align="right">isReturn</td>
<td align="left">flag to indicate the method call ends normally without exception thrown</td>
</tr>
</tbody>
</table><p>All variables listed above can be used directly in the <a class="reference external" href="https://commons.apache.org/proper/commons-ognl/language-guide.html">OGNL expression</a>. The command will not execute and exit if theres illegal OGNL grammar or unexpected variable in the expression.</p>
<ul class="simple">
<li><a class="reference external" href="https://github.com/alibaba/arthas/issues/71">typical use cases</a>;</li>
<li><a class="reference external" href="https://commons.apache.org/proper/commons-ognl/language-guide.html">OGNL language guide</a>.</li>
</ul>
</div>
</div>
</div>
<footer>
<div class="rst-footer-buttons" role="navigation" aria-label="footer navigation">
<a href="trace.html" class="btn btn-neutral float-right" title="trace" accesskey="n" rel="next">Next <span class="fa fa-arrow-circle-right"></span></a>
<a href="watch.html" class="btn btn-neutral" title="watch" accesskey="p" rel="prev"><span class="fa fa-arrow-circle-left"></span> Previous</a>
</div>
<hr/>
<div role="contentinfo">
<p>
&copy; Copyright 2018, Alibaba Middleware Group, and contributors.
</p>
</div>
Built with <a href="http://sphinx-doc.org/">Sphinx</a> using a <a href="https://github.com/rtfd/sphinx_rtd_theme">theme</a> provided by <a href="https://readthedocs.org">Read the Docs</a>.
</footer>
</div>
</div>
</section>
</div>
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT:'./',
VERSION:'3.0.5-SNAPSHOT',
LANGUAGE:'en',
COLLAPSE_INDEX:false,
FILE_SUFFIX:'.html',
HAS_SOURCE: true,
SOURCELINK_SUFFIX: '.txt'
};
</script>
<script type="text/javascript" src="_static/jquery.js"></script>
<script type="text/javascript" src="_static/underscore.js"></script>
<script type="text/javascript" src="_static/doctools.js"></script>
<script type="text/javascript" src="https://cdnjs.cloudflare.com/ajax/libs/mathjax/2.7.1/MathJax.js?config=TeX-AMS-MML_HTMLorMML"></script>
<script type="text/javascript" src="_static/js/theme.js"></script>
<script type="text/javascript">
jQuery(function () {
SphinxRtdTheme.Navigation.enable(true);
});
</script>
<div class="github-fork-ribbon-wrapper right">
<div class="github-fork-ribbon">
<a href="https://github.com/alibaba/arthas">Fork me at GitHub</a>
</div>
</div>
<script type="text/javascript" src="_static/add_badges.js"></script>
<script>
var _hmt = _hmt || [];
(function() {
var hm = document.createElement("script");
hm.src = "https://hm.baidu.com/hm.js?d5c5e25b100f0eb51a4c35c8a86ea9b4";
var s = document.getElementsByTagName("script")[0];
s.parentNode.insertBefore(hm, s);
})();
</script>
</body>
</html>