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289 lines
8.8 KiB
Markdown
289 lines
8.8 KiB
Markdown
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Monitor methods in data aspect including `return values`, `exceptions` and `parameters`.
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With the help of [OGNL](https://commons.apache.org/proper/commons-ognl/index.html), you can easily check the details of variables when methods being invoked.
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### Parameters & Options
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There are four different scenarios for `watch` command, which makes it rather complicated.
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|Name|Specification|
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|---:|:---|
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|*class-pattern*|pattern for the class name|
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|*method-pattern*|pattern for the method name|
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|*expression*|expression to monitor|
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|*condition-expression*|condition expression to filter|
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|[b]|before method being invoked|
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|[e]|when method encountering exceptions|
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|[s]|when method exits normally|
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|[f]|when method exits (either succeed or fail with exceptions)|
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|[E]|turn on regex matching while the default is wildcard matching|
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|[x:]|the depth to print the specified property with default value: 1|
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F.Y.I
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1. any valid OGNL expression as `"{params,returnObj}"` supported
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2. there are four *watching* points: `-b`, `-e`, `-s` and `-f` (the first three are off in default while `-f` on);
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3. at the *watching* point, Arthas will use the *expression* to evaluate the variables and print them out;
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4. `in parameters` and `out parameters` are different since they can be modified within the invoked methods; `params` stands for `in parameters` in `-b`while `out parameters` in other *watching* points;
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5. there are no `return values` and `exceptions` when using `-b`.
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Advanced:
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* [Special usages](https://github.com/alibaba/arthas/issues/71)
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* [OGNL official guide](https://commons.apache.org/proper/commons-ognl/language-guide.html)
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### Usage
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#### Check the `out parameters` and `return value`
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`watch demo.MathGame primeFactors "{params,returnObj}" -x 2`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors "{params,returnObj}" -x 2
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 44 ms.
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ts=2018-12-03 19:16:51; [cost=1.280502ms] result=@ArrayList[
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@Object[][
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@Integer[535629513],
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],
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@ArrayList[
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@Integer[3],
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@Integer[19],
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@Integer[191],
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@Integer[49199],
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],
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]
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```
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#### Check `in parameters`
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`watch demo.MathGame primeFactors "{params,returnObj}" -x 2 -b`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors "{params,returnObj}" -x 2 -b
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 50 ms.
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ts=2018-12-03 19:23:23; [cost=0.0353ms] result=@ArrayList[
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@Object[][
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@Integer[-1077465243],
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],
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null,
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]
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```
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Compared to the previous *check*:
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* `return value` is `null` since it's `-b`.
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#### Check *before* and *after* at the same time
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`watch demo.MathGame primeFactors "{params,target,returnObj}" -x 2 -b -s -n 2`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors "{params,target,returnObj}" -x 2 -b -s -n 2
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 46 ms.
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ts=2018-12-03 19:29:54; [cost=0.01696ms] result=@ArrayList[
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@Object[][
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@Integer[1544665400],
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],
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@MathGame[
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random=@Random[java.util.Random@522b408a],
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illegalArgumentCount=@Integer[13038],
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],
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null,
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]
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ts=2018-12-03 19:29:54; [cost=4.277392ms] result=@ArrayList[
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@Object[][
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@Integer[1544665400],
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],
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@MathGame[
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random=@Random[java.util.Random@522b408a],
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illegalArgumentCount=@Integer[13038],
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],
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@ArrayList[
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@Integer[2],
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@Integer[2],
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@Integer[2],
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@Integer[5],
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@Integer[5],
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@Integer[73],
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@Integer[241],
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@Integer[439],
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],
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]
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```
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F.Y.I
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* `-n 2`: threshold of execution times is 2.
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* the first block of output is the *before watching* point;
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* *the order of the output determined by the *watching* order itself (nothing to do with the order of the options `-b -s`).
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#### Use `-x` to check more details
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`watch demo.MathGame primeFactors "{params,target}" -x 3`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors "{params,target}" -x 3
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 58 ms.
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ts=2018-12-03 19:34:19; [cost=0.587833ms] result=@ArrayList[
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@Object[][
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@Integer[47816758],
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],
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@MathGame[
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random=@Random[
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serialVersionUID=@Long[3905348978240129619],
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seed=@AtomicLong[3133719055989],
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multiplier=@Long[25214903917],
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addend=@Long[11],
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mask=@Long[281474976710655],
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DOUBLE_UNIT=@Double[1.1102230246251565E-16],
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BadBound=@String[bound must be positive],
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BadRange=@String[bound must be greater than origin],
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BadSize=@String[size must be non-negative],
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seedUniquifier=@AtomicLong[-3282039941672302964],
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nextNextGaussian=@Double[0.0],
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haveNextNextGaussian=@Boolean[false],
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serialPersistentFields=@ObjectStreamField[][isEmpty=false;size=3],
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unsafe=@Unsafe[sun.misc.Unsafe@2eaa1027],
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seedOffset=@Long[24],
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],
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illegalArgumentCount=@Integer[13159],
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],
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]
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```
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* `-x`: Expand level of object (1 by default)
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#### Use condition expressions to locate specific call
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`watch demo.MathGame primeFactors "{params[0],target}" "params[0]<0"`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors "{params[0],target}" "params[0]<0"
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 68 ms.
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ts=2018-12-03 19:36:04; [cost=0.530255ms] result=@ArrayList[
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@Integer[-18178089],
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@MathGame[demo.MathGame@41cf53f9],
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]
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```
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* Only calls that meet the conditions will respond.
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* `Watch Express` single value can not be added '{}', and multiple values need to be added '{a, B, C}'.
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* `condition Express` cannot add '{}', you can use commas to separate subexpressions and take the last value of the expression to judge.
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If there are other overloaded methods with the same name in the watch method, you can filter them by the following methods:
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* Filter according to parameter type
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`watch demo.MathGame primeFactors '{params, params[0].class.name}' 'params[0].class.name == "java.lang.Integer"'`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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* Filter according to the number of parameters
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`watch demo.MathGame primeFactors '{params, params.length}' 'params.length==1'`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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#### Check `exceptions`
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`watch demo.MathGame primeFactors "{params[0],throwExp}" -e -x 2`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors "{params[0],throwExp}" -e -x 2
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 62 ms.
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ts=2018-12-03 19:38:00; [cost=1.414993ms] result=@ArrayList[
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@Integer[-1120397038],
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java.lang.IllegalArgumentException: number is: -1120397038, need >= 2
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at demo.MathGame.primeFactors(MathGame.java:46)
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at demo.MathGame.run(MathGame.java:24)
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at demo.MathGame.main(MathGame.java:16)
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,
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]
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```
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* `-e`: Trigger when an exception is thrown
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* `throwExp`: the exception object
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Filter according to exception type or message:
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`watch demo.MathGame primeFactors '{params, throwExp}' '#msg=throwExp.toString(), #msg.contains("IllegalArgumentException")' -e -x 2`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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#### Filter by time cost
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`watch demo.MathGame primeFactors '{params, returnObj}' '#cost>200' -x 2`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors '{params, returnObj}' '#cost>200' -x 2
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 66 ms.
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ts=2018-12-03 19:40:28; [cost=2112.168897ms] result=@ArrayList[
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@Object[][
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@Integer[2141897465],
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],
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@ArrayList[
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@Integer[5],
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@Integer[428379493],
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],
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]
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```
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* `#cost>200` (`ms`) filter out all invokings that take less than `200ms`.
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#### Check the field of the target object
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* `target` is the `this` object in java.
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`watch demo.MathGame primeFactors 'target'`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors 'target'
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 52 ms.
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ts=2018-12-03 19:41:52; [cost=0.477882ms] result=@MathGame[
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random=@Random[java.util.Random@522b408a],
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illegalArgumentCount=@Integer[13355],
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]
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```
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* `target.field_name`: the field of the current object.
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`watch demo.MathGame primeFactors 'target.illegalArgumentCount'`{{execute T2}}
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Press `Q`{{execute T2}} or `Ctrl+C` to abort
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```bash
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$ watch demo.MathGame primeFactors 'target.illegalArgumentCount'
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Press Ctrl+C to abort.
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Affect(class-cnt:1 , method-cnt:1) cost in 67 ms.
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ts=2018-12-03 20:04:34; [cost=131.303498ms] result=@Integer[8]
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ts=2018-12-03 20:04:35; [cost=0.961441ms] result=@Integer[8]
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```
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