运行Jmeter脚本时获取Transformer异常

Question

在运行带有3个线程的JMeter脚本时，加速5秒我得到转换器异常。实际上在我的场景中我想随机点击页面的多个链接，所以我在JMeter中使用了随机变量但是在运行之后，我得到了以下错误，但是，XPath提取器中的XPath表达式看起来很好。

2016/09/23 23:44:03 INFO  - jmeter.engine.StandardJMeterEngine: Running the test! 
2016/09/23 23:44:03 INFO  - jmeter.samplers.SampleEvent: List of sample_variables: [] 
2016/09/23 23:44:03 INFO  - jmeter.gui.util.JMeterMenuBar: setRunning(true,*local*) 
2016/09/23 23:44:03 INFO  - jmeter.engine.StandardJMeterEngine: Starting ThreadGroup: 1 : Thread Group 
2016/09/23 23:44:03 INFO  - jmeter.engine.StandardJMeterEngine: Starting 3 threads for group Thread Group. 
2016/09/23 23:44:03 INFO  - jmeter.engine.StandardJMeterEngine: Thread will continue on error 
2016/09/23 23:44:03 INFO  - jmeter.threads.ThreadGroup: Starting thread group number 1 threads 3 ramp-up 5 perThread 1666.6666 delayedStart=false 
2016/09/23 23:44:03 INFO  - jmeter.threads.JMeterThread: Thread started: Thread Group 1-1 
2016/09/23 23:44:03 INFO  - jmeter.threads.ThreadGroup: Started thread group number 1 
2016/09/23 23:44:03 INFO  - jmeter.engine.StandardJMeterEngine: All thread groups have been started 
2016/09/23 23:44:05 INFO  - jmeter.threads.JMeterThread: Thread started: Thread Group 1-2 
2016/09/23 23:44:07 INFO  - jmeter.threads.JMeterThread: Thread started: Thread Group 1-3 
2016/09/23 23:44:09 WARN  - jmeter.extractor.XPathExtractor: TransformerException while processing ((//span[@class="title"]/a/@href)[$(RandomNumber)]) Expected ], but found: RandomNumber 
2016/09/23 23:44:10 INFO  - jmeter.threads.JMeterThread: Thread is done: Thread Group 1-1 
2016/09/23 23:44:10 INFO  - jmeter.threads.JMeterThread: Thread finished: Thread Group 1-1 
2016/09/23 23:44:10 WARN  - jmeter.extractor.XPathExtractor: TransformerException while processing ((//span[@class="title"]/a/@href)[$(RandomNumber)]) Expected ], but found: RandomNumber 
2016/09/23 23:44:11 INFO  - jmeter.threads.JMeterThread: Thread is done: Thread Group 1-3 
2016/09/23 23:44:11 INFO  - jmeter.threads.JMeterThread: Thread finished: Thread Group 1-3 
2016/09/23 23:44:11 WARN  - jmeter.extractor.XPathExtractor: TransformerException while processing ((//span[@class="title"]/a/@href)[$(RandomNumber)]) Expected ], but found: RandomNumber 
2016/09/23 23:44:12 INFO  - jmeter.threads.JMeterThread: Thread is done: Thread Group 1-2 
2016/09/23 23:44:12 INFO  - jmeter.threads.JMeterThread: Thread finished: Thread Group 1-2 
2016/09/23 23:44:12 INFO  - jmeter.engine.StandardJMeterEngine: Notifying test listeners of end of test 
2016/09/23 23:44:12 INFO  - jmeter.gui.util.JMeterMenuBar: setRunning(false,*local*)  

Answer 1

1. JMeter Variables被引用为${RandomNumber} - 您需要使用大括号而不是括号。或者，您可以使用__V()功能，如

   ${__V(RandomNumber)}
   

   因此，您需要将XPath查询更改为以下之一：

   • （//跨度[@类= “标题”] /一个/ @ HREF）[$ {RandomNumber}]
   • （// span [@ class =“title”] / a / @ href）[$ {__ V（RandomNumber）}]

2. 你的方法似乎很脆弱。我不知道页面上有多少链接以及如何生成${RandomNumber}变量，但我宁愿采用以下方式：

   • 将页面上的所有链接存储到JMeter变量中，例如：

     link_1=http://example.com
     link_2=http://jmeter.apache.org
     ...
     link_matchNr=50
     

   • 通过前面提到的__V()和__Random()函数组合，使用之前提取的随机JMeter变量，如：

     ${__V(link_${__Random(1,${link_matchNr},)})}
     

   演示：

   

   有关如何将不同的JMeter函数和变量组合到单个表达式中的更多信息，请参阅Here’s What to Do to Combine Multiple JMeter Variables文章。