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< li > watch< / li >
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< a href = "https://github.com/alibaba/arthas/blob/master/site/src/site/sphinx/watch.md" class = "fa fa-github" > Edit on GitHub< / a >
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< h1 > watch< a class = "headerlink" href = "#watch" title = "永久链接至标题" > ¶< / a > < / h1 >
< blockquote >
< div > < p > 方法执行数据观测< / p >
< / div > < / blockquote >
< p > 让你能方便的观察到指定方法的调用情况。能观察到的范围为:< code class = "docutils literal notranslate" > < span class = "pre" > 返回值< / span > < / code > 、< code class = "docutils literal notranslate" > < span class = "pre" > 抛出异常< / span > < / code > 、< code class = "docutils literal notranslate" > < span class = "pre" > 入参< / span > < / code > ,通过编写 OGNL 表达式进行对应变量的查看。< / p >
< div class = "section" id = "id1" >
< h2 > 参数说明< a class = "headerlink" href = "#id1" title = "永久链接至标题" > ¶< / a > < / h2 >
< p > watch 的参数比较多,主要是因为它能在 4 个不同的场景观察对象< / p >
< table border = "1" class = "docutils" >
< thead >
< tr >
< th align = "right" > 参数名称< / th >
< th align = "left" > 参数说明< / th >
< / tr >
< / thead >
< tbody >
< tr >
< td align = "right" > < em > class-pattern< / em > < / td >
< td align = "left" > 类名表达式匹配< / td >
< / tr >
< tr >
< td align = "right" > < em > method-pattern< / em > < / td >
< td align = "left" > 方法名表达式匹配< / td >
< / tr >
< tr >
< td align = "right" > < em > express< / em > < / td >
< td align = "left" > 观察表达式< / td >
< / tr >
< tr >
< td align = "right" > < em > condition-express< / em > < / td >
< td align = "left" > 条件表达式< / td >
< / tr >
< tr >
< td align = "right" > [b]< / td >
< td align = "left" > 在< strong > 方法调用之前< / strong > 观察< / td >
< / tr >
< tr >
< td align = "right" > [e]< / td >
< td align = "left" > 在< strong > 方法异常之后< / strong > 观察< / td >
< / tr >
< tr >
< td align = "right" > [s]< / td >
< td align = "left" > 在< strong > 方法返回之后< / strong > 观察< / td >
< / tr >
< tr >
< td align = "right" > [f]< / td >
< td align = "left" > 在< strong > 方法结束之后< / strong > (正常返回和异常返回)观察< / td >
< / tr >
< tr >
< td align = "right" > [E]< / td >
< td align = "left" > 开启正则表达式匹配,默认为通配符匹配< / td >
< / tr >
< tr >
< td align = "right" > [x:]< / td >
< td align = "left" > 指定输出结果的属性遍历深度,默认为 1< / td >
< / tr >
< / tbody >
< / table > < p > 这里重点要说明的是观察表达式,观察表达式的构成主要由 ognl 表达式组成,所以你可以这样写< code class = "docutils literal notranslate" > < span class = "pre" > " {params,returnObj}" < / span > < / code > ,只要是一个合法的 ognl 表达式,都能被正常支持。< / p >
< p > 观察的维度也比较多,主要体现在参数 < code class = "docutils literal notranslate" > < span class = "pre" > advice< / span > < / code > 的数据结构上。< code class = "docutils literal notranslate" > < span class = "pre" > Advice< / span > < / code > 参数最主要是封装了通知节点的所有信息。请参考< a class = "reference internal" href = "advice-class.html" > < span class = "doc" > 表达式核心变量< / span > < / a > 中关于该节点的描述。< / p >
< ul class = "simple" >
< li > < p > 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 > < / p > < / li >
< li > < p > 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 > < / p > < / li >
< / ul >
< p > < strong > 特别说明< / strong > : < / p >
< ul class = "simple" >
< li > < p > watch 命令定义了4个观察事件点, 即 < code class = "docutils literal notranslate" > < span class = "pre" > -b< / span > < / code > 方法调用前,< code class = "docutils literal notranslate" > < span class = "pre" > -e< / span > < / code > 方法异常后,< code class = "docutils literal notranslate" > < span class = "pre" > -s< / span > < / code > 方法返回后,< code class = "docutils literal notranslate" > < span class = "pre" > -f< / span > < / code > 方法结束后< / p > < / li >
< li > < p > 4个观察事件点 < code class = "docutils literal notranslate" > < span class = "pre" > -b< / span > < / code > 、< code class = "docutils literal notranslate" > < span class = "pre" > -e< / span > < / code > 、< code class = "docutils literal notranslate" > < span class = "pre" > -s< / span > < / code > 默认关闭,< code class = "docutils literal notranslate" > < span class = "pre" > -f< / span > < / code > 默认打开,当指定观察点被打开后,在相应事件点会对观察表达式进行求值并输出< / p > < / li >
< li > < p > 这里要注意< code class = "docutils literal notranslate" > < span class = "pre" > 方法入参< / span > < / code > 和< code class = "docutils literal notranslate" > < span class = "pre" > 方法出参< / span > < / code > 的区别,有可能在中间被修改导致前后不一致,除了 < code class = "docutils literal notranslate" > < span class = "pre" > -b< / span > < / code > 事件点 < code class = "docutils literal notranslate" > < span class = "pre" > params< / span > < / code > 代表方法入参外,其余事件都代表方法出参< / p > < / li >
< li > < p > 当使用 < code class = "docutils literal notranslate" > < span class = "pre" > -b< / span > < / code > 时,由于观察事件点是在方法调用前,此时返回值或异常均不存在< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "id2" >
< h2 > 使用参考< a class = "headerlink" href = "#id2" title = "永久链接至标题" > ¶< / a > < / h2 >
< div class = "section" id = "demo" >
< h3 > 启动 Demo< a class = "headerlink" href = "#demo" title = "永久链接至标题" > ¶< / a > < / h3 >
< p > 启动< a class = "reference internal" href = "quick-start.html" > < span class = "doc" > 快速入门< / span > < / a > 里的< code class = "docutils literal notranslate" > < span class = "pre" > arthas-demo< / span > < / code > 。< / p >
< / div >
< div class = "section" id = "id3" >
< h3 > 观察方法出参和返回值< a class = "headerlink" href = "#id3" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors " {params,returnObj}" -x 2
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 44 ms.
ts=2018-12-03 19:16:51; [cost=1.280502ms] result=@ArrayList[
@Object[][
@Integer[535629513],
],
@ArrayList[
@Integer[3],
@Integer[19],
@Integer[191],
@Integer[49199],
],
]< / pre > < / div >
< / div >
< / div >
< div class = "section" id = "id4" >
< h3 > 观察方法入参< a class = "headerlink" href = "#id4" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors " {params,returnObj}" -x 2 -b
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 50 ms.
ts=2018-12-03 19:23:23; [cost=0.0353ms] result=@ArrayList[
@Object[][
@Integer[-1077465243],
],
null,
]< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > 对比前一个例子,返回值为空(事件点为方法执行前,因此获取不到返回值)< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "id5" >
< h3 > 同时观察方法调用前和方法返回后< a class = "headerlink" href = "#id5" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors " {params,target,returnObj}" -x 2 -b -s -n 2
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 46 ms.
ts=2018-12-03 19:29:54; [cost=0.01696ms] result=@ArrayList[
@Object[][
@Integer[1544665400],
],
@MathGame[
random=@Random[java.util.Random@522b408a],
illegalArgumentCount=@Integer[13038],
],
null,
]
ts=2018-12-03 19:29:54; [cost=4.277392ms] result=@ArrayList[
@Object[][
@Integer[1544665400],
],
@MathGame[
random=@Random[java.util.Random@522b408a],
illegalArgumentCount=@Integer[13038],
],
@ArrayList[
@Integer[2],
@Integer[2],
@Integer[2],
@Integer[5],
@Integer[5],
@Integer[73],
@Integer[241],
@Integer[439],
],
]< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > 参数里< code class = "docutils literal notranslate" > < span class = "pre" > -n< / span > < span class = "pre" > 2< / span > < / code > ,表示只执行两次< / p > < / li >
< li > < p > 这里输出结果中,第一次输出的是方法调用前的观察表达式的结果,第二次输出的是方法返回后的表达式的结果< / p > < / li >
< li > < p > 结果的输出顺序和事件发生的先后顺序一致,和命令中 < code class = "docutils literal notranslate" > < span class = "pre" > -s< / span > < span class = "pre" > -b< / span > < / code > 的顺序无关< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "x" >
< h3 > 调整< code class = "docutils literal notranslate" > < span class = "pre" > -x< / span > < / code > 的值,观察具体的方法参数值< a class = "headerlink" href = "#x" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors " {params,target}" -x 3
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 58 ms.
ts=2018-12-03 19:34:19; [cost=0.587833ms] result=@ArrayList[
@Object[][
@Integer[47816758],
],
@MathGame[
random=@Random[
serialVersionUID=@Long[3905348978240129619],
seed=@AtomicLong[3133719055989],
multiplier=@Long[25214903917],
addend=@Long[11],
mask=@Long[281474976710655],
DOUBLE_UNIT=@Double[1.1102230246251565E-16],
BadBound=@String[bound must be positive],
BadRange=@String[bound must be greater than origin],
BadSize=@String[size must be non-negative],
seedUniquifier=@AtomicLong[-3282039941672302964],
nextNextGaussian=@Double[0.0],
haveNextNextGaussian=@Boolean[false],
serialPersistentFields=@ObjectStreamField[][isEmpty=false;size=3],
unsafe=@Unsafe[sun.misc.Unsafe@2eaa1027],
seedOffset=@Long[24],
],
illegalArgumentCount=@Integer[13159],
],
]< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > < code class = "docutils literal notranslate" > < span class = "pre" > -x< / span > < / code > 表示遍历深度, 可以调整来打印具体的参数和结果内容, 默认值是1。< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "id6" >
< h3 > 条件表达式的例子< a class = "headerlink" href = "#id6" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors " {params[0],target}" " params[0]< 0"
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 68 ms.
ts=2018-12-03 19:36:04; [cost=0.530255ms] result=@ArrayList[
@Integer[-18178089],
@MathGame[demo.MathGame@41cf53f9],
]< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > 只有满足条件的调用,才会有响应。< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "id7" >
< h3 > 观察异常信息的例子< a class = "headerlink" href = "#id7" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors " {params[0],throwExp}" -e -x 2
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 62 ms.
ts=2018-12-03 19:38:00; [cost=1.414993ms] result=@ArrayList[
@Integer[-1120397038],
java.lang.IllegalArgumentException: number is: -1120397038, need > = 2
at demo.MathGame.primeFactors(MathGame.java:46)
at demo.MathGame.run(MathGame.java:24)
at demo.MathGame.main(MathGame.java:16)
,
]< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > < code class = "docutils literal notranslate" > < span class = "pre" > -e< / span > < / code > 表示抛出异常时才触发< / p > < / li >
< li > < p > express中, 表示异常信息的变量是< code class = "docutils literal notranslate" > < span class = "pre" > throwExp< / span > < / code > < / p > < / li >
< / ul >
< / div >
< div class = "section" id = "id8" >
< h3 > 按照耗时进行过滤< a class = "headerlink" href = "#id8" title = "永久链接至标题" > ¶< / a > < / h3 >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors ' {params, returnObj}' ' #cost> 200' -x 2
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 66 ms.
ts=2018-12-03 19:40:28; [cost=2112.168897ms] result=@ArrayList[
@Object[][
@Integer[2141897465],
],
@ArrayList[
@Integer[5],
@Integer[428379493],
],
]< / pre > < / div >
< / div >
< ul class = "simple" >
< li > < p > < code class = "docutils literal notranslate" > < span class = "pre" > #cost> 200< / span > < / code > (单位是< code class = "docutils literal notranslate" > < span class = "pre" > ms< / span > < / code > )表示只有当耗时大于200ms时才会输出, 过滤掉执行时间小于200ms的调用< / p > < / li >
< / ul >
< / div >
< div class = "section" id = "id9" >
< h3 > 观察当前对象中的属性< a class = "headerlink" href = "#id9" title = "永久链接至标题" > ¶< / a > < / h3 >
< p > 如果想查看方法运行前后,当前对象中的属性,可以使用< code class = "docutils literal notranslate" > < span class = "pre" > target< / span > < / code > 关键字,代表当前对象< / p >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors ' target'
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 52 ms.
ts=2018-12-03 19:41:52; [cost=0.477882ms] result=@MathGame[
random=@Random[java.util.Random@522b408a],
illegalArgumentCount=@Integer[13355],
]< / pre > < / div >
< / div >
< p > 然后使用< code class = "docutils literal notranslate" > < span class = "pre" > target.field_name< / span > < / code > 访问当前对象的某个属性< / p >
< div class = "highlight-bash notranslate" > < div class = "highlight hljs" > < pre class = "bash" > $ watch demo.MathGame primeFactors ' target.illegalArgumentCount'
Press Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 67 ms.
ts=2018-12-03 20:04:34; [cost=131.303498ms] result=@Integer[8]
ts=2018-12-03 20:04:35; [cost=0.961441ms] result=@Integer[8]< / pre > < / div >
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