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< 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 hljs" > < pre class = "java" > public class Advice {
private final ClassLoader loader;
private final Class< ?> clazz;
private final ArthasMethod method;
private final Object target;
private final Object[] params;
private final Object returnObj;
private final Throwable throwExp;
private final boolean isBefore;
private final boolean isThrow;
private final boolean isReturn;
// getter/setter
} < / 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 there’ < / p >
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< li > < p > < a class = "reference external" href = "https://commons.apache.org/proper/commons-ognl/language-guide.html" > OGNL language guide< / a > .< / p > < / li >
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