<liclass="toctree-l1"><aclass="reference external"href="https://github.com/alibaba/arthas/issues?q=label%3Aquestion-answered">Questions and answers</a></li>
<liclass="toctree-l1"><aclass="reference external"href="https://github.com/alibaba/arthas">Fork me at GitHub</a></li>
<p>Monitor methods in data aspect including <codeclass="docutils literal notranslate"><spanclass="pre">return</span><spanclass="pre">values</span></code>, <codeclass="docutils literal notranslate"><spanclass="pre">exceptions</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">parameters</span></code>.</p>
<p>With the help of <aclass="reference external"href="https://en.wikipedia.org/wiki/OGNL">OGNL</a>, you can easily check the details of variables when methods being invoked.</p>
<spanid="parameters-options"></span><h2>Parameters & Options<aclass="headerlink"href="#parameters-options"title="Permalink to this headline">¶</a></h2>
<p>There are four different scenarios for <codeclass="docutils literal notranslate"><spanclass="pre">watch</span></code> command, which makes it rather complicated.</p>
<tdalign="left">the depth to print the specified property with default value: 1</td>
</tr>
</tbody>
</table><p>F.Y.I</p>
<olclass="simple">
<li>any valid OGNL expression as <codeclass="docutils literal notranslate"><spanclass="pre">"{params,returnObj}"</span></code> supported</li>
<li>there are four <em>watching</em> points: <codeclass="docutils literal notranslate"><spanclass="pre">-b</span></code>, <codeclass="docutils literal notranslate"><spanclass="pre">-e</span></code>, <codeclass="docutils literal notranslate"><spanclass="pre">-s</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">-f</span></code> (the first three are off in default while <codeclass="docutils literal notranslate"><spanclass="pre">-f</span></code> on);</li>
<li>at the <em>watching</em> point, Arthas will use the <em>expression</em> to evaluate the variables and print them out;</li>
<li><codeclass="docutils literal notranslate"><spanclass="pre">in</span><spanclass="pre">parameters</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">out</span><spanclass="pre">parameters</span></code> are different since they can be modified within the invoked methods; <codeclass="docutils literal notranslate"><spanclass="pre">params</span></code> stands for <codeclass="docutils literal notranslate"><spanclass="pre">in</span><spanclass="pre">parameters</span></code> in <codeclass="docutils literal notranslate"><spanclass="pre">-b</span></code>while <codeclass="docutils literal notranslate"><spanclass="pre">out</span><spanclass="pre">parameters</span></code> in other <em>watching</em> points;</li>
<li>there are no <codeclass="docutils literal notranslate"><spanclass="pre">return</span><spanclass="pre">values</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">exceptions</span></code> when using <codeclass="docutils literal notranslate"><spanclass="pre">-b</span></code>.</li>
<liclass="toctree-l1"><aclass="reference external"href="https://commons.apache.org/proper/commons-ognl/language-guide.html">OGNL official guide</a></li>
</ul>
</div>
</div>
<divclass="section"id="usage">
<spanid="usage"></span><h2>Usage<aclass="headerlink"href="#usage"title="Permalink to this headline">¶</a></h2>
<spanid="check-the-out-parameters-and-return-value"></span><h3>Check the <codeclass="docutils literal notranslate"><spanclass="pre">out</span><spanclass="pre">parameters</span></code> and <codeclass="docutils literal notranslate"><spanclass="pre">return</span><spanclass="pre">value</span></code><aclass="headerlink"href="#check-the-out-parameters-and-return-value"title="Permalink to this headline">¶</a></h3>
<spanid="check-in-parameters"></span><h3>Check <codeclass="docutils literal notranslate"><spanclass="pre">in</span><spanclass="pre">parameters</span></code><aclass="headerlink"href="#check-in-parameters"title="Permalink to this headline">¶</a></h3>
<li>size of <codeclass="docutils literal notranslate"><spanclass="pre">params[0]</span></code> is <codeclass="docutils literal notranslate"><spanclass="pre">2</span></code> instead of <codeclass="docutils literal notranslate"><spanclass="pre">4</span></code>;</li>
<li><codeclass="docutils literal notranslate"><spanclass="pre">return</span><spanclass="pre">value</span></code> is <codeclass="docutils literal notranslate"><spanclass="pre">null</span></code> since it’s <codeclass="docutils literal notranslate"><spanclass="pre">-b</span></code>.</li>
<spanid="check-before-and-after-at-the-same-time"></span><h3>Check <em>before</em> and <em>after</em> at the same time<aclass="headerlink"href="#check-before-and-after-at-the-same-time"title="Permalink to this headline">¶</a></h3>
<li>the first block of output is the <em>before watching</em> point;</li>
<li>the order of the output determined by the <em>watching</em> order itself (nothing to do with the order of the options <codeclass="docutils literal notranslate"><spanclass="pre">-b</span><spanclass="pre">-s</span></code>).</li>
<spanid="use-x-to-check-more-details"></span><h3>Use <codeclass="docutils literal notranslate"><spanclass="pre">-x</span></code> to check more details<aclass="headerlink"href="#use-x-to-check-more-details"title="Permalink to this headline">¶</a></h3>
<spanid="use-condition-expressions-to-locate-specific-call"></span><h3>Use condition expressions to locate specific call<aclass="headerlink"href="#use-condition-expressions-to-locate-specific-call"title="Permalink to this headline">¶</a></h3>
<spanid="check-exceptions"></span><h3>Check <codeclass="docutils literal notranslate"><spanclass="pre">exceptions</span></code><aclass="headerlink"href="#check-exceptions"title="Permalink to this headline">¶</a></h3>
at com.alibaba.sample.petstore.biz.impl.UserManagerImpl.testAdd<spanclass="o">(</span>UserManagerImpl.java:75<spanclass="o">)</span>
at com.alibaba.sample.petstore.biz.impl.UserManagerImpl.register<spanclass="o">(</span>UserManagerImpl.java:60<spanclass="o">)</span>
at com.alibaba.sample.petstore.web.user.module.action.RegisterAction.doRegister<spanclass="o">(</span>RegisterAction.java:45<spanclass="o">)</span>
at com.alibaba.sample.petstore.web.user.module.action.RegisterAction<spanclass="nv">$$</span>FastClassByCGLIB<spanclass="nv">$$</span>ad5428f1.invoke<spanclass="o">(</span><generated><spanclass="o">)</span>
at net.sf.cglib.reflect.FastMethod.invoke<spanclass="o">(</span>FastMethod.java:53<spanclass="o">)</span>
at com.alibaba.citrus.service.moduleloader.impl.adapter.MethodInvoker.invoke<spanclass="o">(</span>MethodInvoker.java:70<spanclass="o">)</span>
at com.alibaba.citrus.service.moduleloader.impl.adapter.AbstractModuleEventAdapter.executeAndReturn<spanclass="o">(</span>AbstractModuleEventAdapter.java:100<spanclass="o">)</span>
at com.alibaba.citrus.service.moduleloader.impl.adapter.AbstractModuleEventAdapter.execute<spanclass="o">(</span>AbstractModuleEventAdapter.java:58<spanclass="o">)</span>
at com.alibaba.citrus.turbine.pipeline.valve.PerformActionValve.invoke<spanclass="o">(</span>PerformActionValve.java:63<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invoke<spanclass="o">(</span>PipelineImpl.java:210<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.valve.ChooseValve.invoke<spanclass="o">(</span>ChooseValve.java:98<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invoke<spanclass="o">(</span>PipelineImpl.java:210<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.valve.LoopValve.invokeBody<spanclass="o">(</span>LoopValve.java:105<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.valve.LoopValve.invoke<spanclass="o">(</span>LoopValve.java:83<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.turbine.pipeline.valve.PageAuthorizationValve.invoke<spanclass="o">(</span>PageAuthorizationValve.java:105<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.turbine.pipeline.valve.CheckCsrfTokenValve.invoke<spanclass="o">(</span>CheckCsrfTokenValve.java:123<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.turbine.pipeline.valve.AnalyzeURLValve.invoke<spanclass="o">(</span>AnalyzeURLValve.java:126<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.turbine.pipeline.valve.SetLoggingContextValve.invoke<spanclass="o">(</span>SetLoggingContextValve.java:66<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.turbine.pipeline.valve.PrepareForTurbineValve.invoke<spanclass="o">(</span>PrepareForTurbineValve.java:52<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invokeNext<spanclass="o">(</span>PipelineImpl.java:157<spanclass="o">)</span>
at com.alibaba.citrus.service.pipeline.impl.PipelineImpl<spanclass="nv">$PipelineContextImpl</span>.invoke<spanclass="o">(</span>PipelineImpl.java:210<spanclass="o">)</span>
at com.alibaba.citrus.webx.impl.WebxControllerImpl.service<spanclass="o">(</span>WebxControllerImpl.java:43<spanclass="o">)</span>
at com.alibaba.citrus.webx.impl.WebxRootControllerImpl.handleRequest<spanclass="o">(</span>WebxRootControllerImpl.java:53<spanclass="o">)</span>
at com.alibaba.citrus.webx.support.AbstractWebxRootController.service<spanclass="o">(</span>AbstractWebxRootController.java:165<spanclass="o">)</span>
at com.alibaba.citrus.webx.servlet.WebxFrameworkFilter.doFilter<spanclass="o">(</span>WebxFrameworkFilter.java:152<spanclass="o">)</span>
at com.alibaba.citrus.webx.servlet.FilterBean.doFilter<spanclass="o">(</span>FilterBean.java:148<spanclass="o">)</span>
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter<spanclass="o">(</span>ApplicationFilterChain.java:241<spanclass="o">)</span>
at org.apache.catalina.core.ApplicationFilterChain.doFilter<spanclass="o">(</span>ApplicationFilterChain.java:208<spanclass="o">)</span>
at com.alibaba.citrus.webx.servlet.SetLoggingContextFilter.doFilter<spanclass="o">(</span>SetLoggingContextFilter.java:61<spanclass="o">)</span>
at com.alibaba.citrus.webx.servlet.FilterBean.doFilter<spanclass="o">(</span>FilterBean.java:148<spanclass="o">)</span>
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter<spanclass="o">(</span>ApplicationFilterChain.java:241<spanclass="o">)</span>
at org.apache.catalina.core.ApplicationFilterChain.doFilter<spanclass="o">(</span>ApplicationFilterChain.java:208<spanclass="o">)</span>
at org.apache.catalina.core.StandardWrapperValve.invoke<spanclass="o">(</span>StandardWrapperValve.java:220<spanclass="o">)</span>
at org.apache.catalina.core.StandardContextValve.invoke<spanclass="o">(</span>StandardContextValve.java:122<spanclass="o">)</span>
at com.taobao.tomcat.valves.ContextLoadFilterValve.invoke<spanclass="o">(</span>ContextLoadFilterValve.java:152<spanclass="o">)</span>
at org.apache.catalina.core.StandardHostValve.invoke<spanclass="o">(</span>StandardHostValve.java:170<spanclass="o">)</span>
at org.apache.catalina.valves.ErrorReportValve.invoke<spanclass="o">(</span>ErrorReportValve.java:103<spanclass="o">)</span>
at org.apache.catalina.core.StandardEngineValve.invoke<spanclass="o">(</span>StandardEngineValve.java:116<spanclass="o">)</span>
at org.apache.catalina.connector.CoyoteAdapter.service<spanclass="o">(</span>CoyoteAdapter.java:429<spanclass="o">)</span>
at org.apache.coyote.http11.AbstractHttp11Processor.process<spanclass="o">(</span>AbstractHttp11Processor.java:1085<spanclass="o">)</span>
at org.apache.coyote.AbstractProtocol<spanclass="nv">$AbstractConnectionHandler</span>.process<spanclass="o">(</span>AbstractProtocol.java:625<spanclass="o">)</span>
at org.apache.tomcat.util.net.NioEndpoint<spanclass="nv">$SocketProcessor</span>.doRun<spanclass="o">(</span>NioEndpoint.java:1760<spanclass="o">)</span>
at org.apache.tomcat.util.net.NioEndpoint<spanclass="nv">$SocketProcessor</span>.run<spanclass="o">(</span>NioEndpoint.java:1719<spanclass="o">)</span>
at java.util.concurrent.ThreadPoolExecutor.runWorker<spanclass="o">(</span>ThreadPoolExecutor.java:1142<spanclass="o">)</span>
at java.util.concurrent.ThreadPoolExecutor<spanclass="nv">$Worker</span>.run<spanclass="o">(</span>ThreadPoolExecutor.java:617<spanclass="o">)</span>
at org.apache.tomcat.util.threads.TaskThread<spanclass="nv">$WrappingRunnable</span>.run<spanclass="o">(</span>TaskThread.java:61<spanclass="o">)</span>
at java.lang.Thread.run<spanclass="o">(</span>Thread.java:745<spanclass="o">)</span>,
<spanid="filter-based-on-time-cost"></span><h3>Filter based on time cost<aclass="headerlink"href="#filter-based-on-time-cost"title="Permalink to this headline">¶</a></h3>
<codeclass="docutils literal notranslate"><spanclass="pre">#cost>200</span></code> (<codeclass="docutils literal notranslate"><spanclass="pre">ms</span></code>) filter out all invokings that take less than <codeclass="docutils literal notranslate"><spanclass="pre">200ms</span></code>.</p>
<spanid="check-the-global-properties-of-the-target-object"></span><h3>Check the global properties of the target object<aclass="headerlink"href="#check-the-global-properties-of-the-target-object"title="Permalink to this headline">¶</a></h3>
<p><codeclass="docutils literal notranslate"><spanclass="pre">target</span></code> stands for the current object.</p>
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