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< li > 表达式核心变量< / li >
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< 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 >
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< p > 这里列一个表格来说明不同变量的含义< / p >
< table border = "1" class = "docutils" >
< thead >
< tr >
< th align = "right" > 变量名< / th >
< th align = "left" > 变量解释< / th >
< / tr >
< / thead >
< tbody >
< tr >
< td align = "right" > loader< / td >
< td align = "left" > 本次调用类所在的 ClassLoader< / td >
< / tr >
< tr >
< td align = "right" > clazz< / td >
< td align = "left" > 本次调用类的 Class 引用< / td >
< / tr >
< tr >
< td align = "right" > method< / td >
< td align = "left" > 本次调用方法反射引用< / td >
< / tr >
< tr >
< td align = "right" > target< / td >
< td align = "left" > 本次调用类的实例< / td >
< / tr >
< tr >
< td align = "right" > params< / td >
< td align = "left" > 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< / td >
< / tr >
< tr >
< td align = "right" > returnObj< / td >
< td align = "left" > 本次调用返回的对象。当且仅当 < code > isReturn==true< / 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 > void< / code > ，则值为 null< / td >
< / tr >
< tr >
< td align = "right" > throwExp< / td >
< td align = "left" > 本次调用抛出的异常。当且仅当 < code > isThrow==true< / code > 成立时有效，表明方法调用是以抛出异常的方式结束。< / td >
< / tr >
< tr >
< td align = "right" > isBefore< / td >
< td align = "left" > 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 > isBefore==true< / code > 成立，同时 < code > isThrow==false< / code > 和 < code > isReturn==false< / 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。< / td >
< / tr >
< tr >
< td align = "right" > isThrow< / td >
< td align = "left" > 辅助判断标记，当前的方法调用以抛异常的形式结束。< / td >
< / tr >
< tr >
< td align = "right" > isReturn< / td >
< td align = "left" > 辅助判断标记，当前的方法调用以正常返回的形式结束。< / td >
< / tr >
< / tbody >
< / table > < 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 >
< ul class = "simple" >
< li > 特殊用法请参考：< a class = "reference external" href = "https://github.com/alibaba/arthas/issues/71" > https://github.com/alibaba/arthas/issues/71< / a > < / li >
< li > OGNL表达式官网： < a class = "reference external" href = "https://commons.apache.org/proper/commons-ognl/language-guide.html" > https://commons.apache.org/proper/commons-ognl/language-guide.html< / a > < / li >
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