Arthas在线教程体验 - 案例: 排查函数调用异常现象 - 《JAVA虚拟机-JVM》

查看UserController的参数/异常
返回值表达式
条件表达式
当异常时捕获
按照耗时进行过滤

目前，访问 http://localhost:8089/user/0 ，会返回500异常：
curl http://localhost:8089/user/0

{"timestamp":1576811497687,"status":500,"error":"Internal Server Error","exception":"java.lang.IllegalArgumentException","message":"id < 1","path":"/user/0"}

但请求的具体参数，异常栈是什么呢？我们单从上面的信息获取不到

查看UserController的参数/异常

在Arthas里执行：
watch com.example.demo.arthas.user.UserController * ‘{params, throwExp}’

第一个参数是类名
第二个参数是函数名，支持通配

执行：curl http://localhost:8089/user/0，watch命令会打印调用的参数和异常

watch com.example.demo.arthas.user.UserController findUserById '{params, throwExp}'
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 34 ms.
ts=2019-12-20 04:10:55; [cost=0.9ms] result=@ArrayList[
    @Object[][isEmpty=false;size=1],
    @IllegalArgumentException[java.lang.IllegalArgumentException: id < 1],
]

如果想把获取到的结果展开，可以用-x参数：
watch com.example.demo.arthas.user.UserController * ‘{params, throwExp}’ -x 2

 [arthas@3205]$ watch com.example.demo.arthas.user.UserController findUserById '{params, throwExp}' -x 2
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:1) cost in 33 ms.
ts=2019-12-20 04:18:26; [cost=0.805ms] result=@ArrayList[
    @Object[][
        @Integer[0],
    ],
    java.lang.IllegalArgumentException: id < 1
        at com.example.demo.arthas.user.UserController.findUserById(UserController.java:19)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:498)
        at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:205)
        at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
        at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:97)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandlerMethod(RequestMappingHandlerAdapter.java:827)
        at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:738)
        at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
        at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
        at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
        at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
        at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:861)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:635)
        at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
        at javax.servlet.http.HttpServlet.service(HttpServlet.java:742)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.RequestContextFilter.doFilterInternal(RequestContextFilter.java:99)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HttpPutFormContentFilter.doFilterInternal(HttpPutFormContentFilter.java:109)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:81)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:197)
        at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
        at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
        at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
        at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
        at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
        at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:496)
        at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
        at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:81)
        at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
        at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342)
        at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:803)
        at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
        at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:790)
        at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1468)
        at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
        at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
        at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
        at java.lang.Thread.run(Thread.java:748)
,
]

返回值表达式

在上面的例子里，第三个参数是返回值表达式，它实际上是一个ognl表达式，它支持一些内置对象
这里列一个表格来说明不同变量的含义

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 `isReturn==true` 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 `void`，则值为 null
throwExp	本次调用抛出的异常。当且仅当 `isThrow==true` 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 `isBefore==true` 成立，同时 `isThrow==false` 和 `isReturn==false`，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。

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。
例如：

[arthas@16]$ watch com.example.demo.arthas.user.UserController * '{params[0], target, method}'
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:2) cost in 30 ms.
ts=2019-12-20 07:53:18; [cost=0.75ms] result=@ArrayList[
    @Integer[0],
    @UserController[com.example.demo.arthas.user.UserController@5c08f482],
    @ArthasMethod[public com.example.demo.arthas.user.User com.example.demo.arthas.user.UserController.findUserById(java.lang.Integer)],
]



[arthas@16]$ watch com.example.demo.arthas.user.UserController * '{params[0], target, method,loader}'
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:2) cost in 25 ms.
ts=2019-12-20 08:06:08; [cost=0.808ms] result=@ArrayList[
    @Integer[0],
    @UserController[com.example.demo.arthas.user.UserController@5c08f482],
    @ArthasMethod[public com.example.demo.arthas.user.User com.example.demo.arthas.user.UserController.findUserById(java.lang.Integer)],
    @LaunchedURLClassLoader[org.springframework.boot.loader.LaunchedURLClassLoader@5674cd4d],
]

条件表达式

watch命令支持在第4个参数里写条件表达式，比如
watch com.example.demo.arthas.user.UserController * returnObj ‘params[0] > 100’
当执行curl http://localhost:8089/user/0`watch`命令没有输出。
当执行curl http://localhost:8089/user/101命令时输出：

[arthas@16]$ watch com.example.demo.arthas.user.UserController * returnObj 'params[0] > 100'
Press Q or Ctrl+C to abort.
Affect(class-cnt:1 , method-cnt:2) cost in 26 ms.
ts=2019-12-20 08:15:18; [cost=0.849ms] result=@User[
    id=@Integer[101],
    name=@String[name101],
]

当异常时捕获

watch命令支持-e选项，表示只捕获抛出异常时的请求：
watch com.example.demo.arthas.user.UserController * “{params[0],throwExp}” -e

按照耗时进行过滤

watch命令支持按请求耗时进行过滤，比如：
watch com.example.demo.arthas.user.UserController * ‘{params, returnObj}’ ‘#cost>200’<br />

案例: 排查函数调用异常 现象

查看UserController的 参数/异常

返回值表达式

条件表达式

当异常时捕获

按照耗时进行过滤

案例: 排查函数调用异常现象

查看UserController的参数/异常