<!DOCTYPE html>
<!--[if IE 8]><html class="no-js lt-ie9" lang="zh-CN" > <![endif]-->
<!--[if gt IE 8]><!--> <html class="no-js" lang="zh-CN" > <!--<![endif]-->
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>表达式核心变量 — Arthas 3.0.1-RC-SNAPSHOT 文档</title>
<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="索引" href="genindex.html" />
<link rel="search" title="搜索" href="search.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">
3.0.1-RC-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>
<li class="toctree-l1"><a class="reference internal" href="install-detail.html">安装</a></li>
<li class="toctree-l1"><a class="reference internal" href="quick-start.html">快速入门</a></li>
<li class="toctree-l1"><a class="reference internal" href="advanced-use.html">进阶使用</a></li>
<li class="toctree-l1"><a class="reference internal" href="commands.html">命令列表</a></li>
<li class="toctree-l1"><a class="reference external" href="https://github.com/alibaba/arthas/labels/user-case">用户案例</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/labels/question-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/CONTRIBUTING.md">参与贡献</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> »</li>
<li>表达式核心变量</li>
<li class="wy-breadcrumbs-aside">
<a href="https://github.com/alibaba/arthas/blob/master/site/src/site/sphinx/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="">
<span id="id1"></span><h1>表达式核心变量<a class="headerlink" href="#" title="永久链接至标题">¶</a></h1>
<p>无论是匹配表达式也好、观察表达式也罢，他们核心判断变量都是围绕着一个 Arthas 中的通用通知对象 <code class="docutils literal notranslate"><span class="pre">Advice</span></code> 进行。</p>
<p>它的简略代码结构如下</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"><?></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>这里列一个表格来说明不同变量的含义</p>
<p>|变量名|变量解释|
|—|—|
|loader|本次调用类所在的 ClassLoader|
|clazz|本次调用类的 Class 引用|
|method|本次调用方法反射引用|
|target|本次调用类的实例|
|params|本次调用参数列表，这是一个数组，如果方法是无参方法则为空数组|
|returnObj|本次调用返回的对象。当且仅当 <code class="docutils literal notranslate"><span class="pre">isReturn==true</span></code> 成立时候有效，表明方法调用是以正常返回的方式结束。如果当前方法无返回值 <code class="docutils literal notranslate"><span class="pre">void</span></code>，则值为 null|
|throwExp|本次调用抛出的异常。当且仅当 <code class="docutils literal notranslate"><span class="pre">isThrow==true</span></code> 成立时有效，表明方法调用是以抛出异常的方式结束。|
|isBefore|辅助判断标记，当前的通知节点有可能是在方法一开始就通知，此时 <code class="docutils literal notranslate"><span class="pre">isBefore==true</span></code> 成立，同时 <code class="docutils literal notranslate"><span class="pre">isThrow==false</span></code> 和 <code class="docutils literal notranslate"><span class="pre">isReturn==false</span></code>，因为在方法刚开始时，还无法确定方法调用将会如何结束。|
|isThrow|辅助判断标记，当前的方法调用以抛异常的形式结束。|
|isReturn|辅助判断标记，当前的方法调用以正常返回的形式结束。|</p>
<p>所有变量都可以在表达式中直接使用，如果在表达式中编写了不符合 OGNL 脚本语法或者引入了不在表格中的变量，则退出命令的执行；用户可以根据当前的异常信息修正<code class="docutils literal notranslate"><span class="pre">条件表达式</span></code>或<code class="docutils literal notranslate"><span class="pre">观察表达式</span></code></p>
<blockquote>
<div>OGNL表达式官网：https://commons.apache.org/proper/commons-ognl/language-guide.html</div></blockquote>
<blockquote>
<div>一些特殊的用法：</div></blockquote>
<p>TODO</p>
<p>middleware-container/arthas/issues/263</p>
</div>
</div>
</div>
<footer>
<hr/>
<div role="contentinfo">
<p>
© 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:'3.0.1-RC-SNAPSHOT',
LANGUAGE:'zh_CN',
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="_static/translations.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>