JMeter HTTP脚本录制启动失败：DNSName组件需以字母开头错误

这个问题已经有明确的解决方案啦

看你描述的情况，之前用JMeter都好好的，今天启动HTTP脚本录制器突然报错，这个问题我碰到过，咱们来拆解一下：

报错原因 #

先看你贴的错误日志，核心问题是这句：keytool error: java.lang.RuntimeException: java.io.IOException: DNSName components must begin with a letter。
这是因为JMeter老版本（你用的是4.0）在生成代理证书时，把目标IP地址（104.211.242.218）当作DNS名称来处理了，但X.509证书的DNS名称要求必须以字母开头，纯IP地址不符合这个规范，所以keytool直接报错了。

快速解决办法 #

• 最省心的方案：升级JMeter版本
  JMeter 5.0及以上的版本已经修复了这个bug，新版本会自动识别IP地址，在生成证书时会把IP地址用ip:前缀添加到SAN扩展里，而不是错误地当作DNS名称，升级后直接就能正常录制了。
• 临时应急方案（不升级的情况）
  如果暂时没法升级，你可以手动修改JMeter的代理配置：
  1. 找到JMeter安装目录下的bin文件夹，删除里面的proxyserver.jks文件（这是临时代理证书）；
  2. 启动录制器前，把目标IP映射到本地hosts文件里的一个以字母开头的域名（比如test.example.com），这样JMeter生成证书时就会用符合规范的域名，不会再触发这个错误。

附上你提供的完整报错日志，方便对照：

java.io.IOException: >> keytool error: java.lang.RuntimeException: java.io.IOException: DNSName components must begin with a letter << Command failed, code: 1 'keytool -genkeypair -alias 104.211.242.218 -dname "cn=104.211.242.218, o=JMeter Proxy (TEMPORARY TRUST ONLY)" -keyalg RSA -keystore proxyserver.jks -storepass {redacted} -keypass {redacted} -validity 7 -ext san=dns:104.211.242.218' at org.apache.jorphan.exec.KeyToolUtils.genkeypair(KeyToolUtils.java:171) ~[jorphan.jar:4.0 r1823414] at org.apache.jorphan.exec.KeyToolUtils.generateSignedCert(KeyToolUtils.java:285) ~[jorphan.jar:4.0 r1823414] at org.apache.jorphan.exec.KeyToolUtils.generateHostCert(KeyToolUtils.java:276) ~[jorphan.jar:4.0 r1823414] at org.apache.jmeter.protocol.http.proxy.ProxyControl.initDynamicKeyStore(ProxyControl.java:1540) ~[ApacheJMeter_http.jar:4.0 r1823414] at org.apache.jmeter.protocol.http.proxy.ProxyControl.initKeyStore(ProxyControl.java:1447) ~[ApacheJMeter_http.jar:4.0 r1823414] at org.apache.jmeter.protocol.http.proxy.ProxyControl.startProxy(ProxyControl.java:530) [ApacheJMeter_http.jar:4.0 r1823414] at org.apache.jmeter.protocol.http.proxy.gui.ProxyControlGui.startProxy(ProxyControlGui.java:569) [ApacheJMeter_http.jar:4.0 r1823414] at org.apache.jmeter.protocol.http.proxy.gui.ProxyControlGui.actionPerformed(ProxyControlGui.java:424) [ApacheJMeter_http.jar:4.0 r1823414] at javax.swing.AbstractButton.fireActionPerformed(Unknown Source) [?:1.8.0_131] at javax.swing.AbstractButton$Handler.actionPerformed(Unknown Source) [?:1.8.0_131] at javax.swing.DefaultButtonModel.fireActionPerformed(Unknown Source) [?:1.8.0_131] at javax.swing.DefaultButtonModel.setPressed(Unknown Source) [?:1.8.0_131] at javax.swing.plaf.basic.BasicButtonListener.mouseReleased(Unknown Source) [?:1.8.0_131] at java.awt.Component.processMouseEvent(Unknown Source) [?:1.8.0_131] at javax.swing.JComponent.processMouseEvent(Unknown Source) [?:1.8.0_131] at java.awt.Component.processEvent(Unknown Source) [?:1.8.0_131] at java.awt.Container.processEvent(Unknown Source) [?:1.8.0_131] at java.awt.Component.dispatchEventImpl(Unknown Source) [?:1.8.0_131] at java.awt.Container.dispatchEventImpl(Unknown Source) [?:1.8.0_131] at java.awt.Component.dispatchEvent(Unknown Source) [?:1.8.0_131] at java.awt.LightweightDispatcher.retargetMouseEvent(Unknown Source) [?:1.8.0_131] at java.awt.LightweightDispatcher.processMouseEvent(Unknown Source) [?:1.8.0_131] at java.awt.LightweightDispatcher.dispatchEvent(Unknown Source) [?:1.8.0_131] at java.awt.Container.dispatchEventImpl(Unknown Source) [?:1.8.0_131] at java.awt.Window.dispatchEventImpl(Unknown Source) [?:1.8.0_131] at java.awt.Component.dispatchEvent(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue.dispatchEventImpl(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue.access$500(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue$3.run(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue$3.run(Unknown Source) [?:1.8.0_131] at java.security.AccessController.doPrivileged(Native Method) [?:1.8.0_131] at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) [?:1.8.0_131] at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue$4.run(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue$4.run(Unknown Source) [?:1.8.0_131] at java.security.AccessController.doPrivileged(Native Method) [?:1.8.0_131] at java.security.ProtectionDomain$JavaSecurityAccessImpl.doIntersectionPrivilege(Unknown Source) [?:1.8.0_131] at java.awt.EventQueue.dispatchEvent(Unknown Source) [?:1.8.0_131] at java.awt.EventDispatchThread.pumpOneEventForFilters(Unknown Source) [?:1.8.0_131] at java.awt.EventDispatchThread.pumpEventsForFilter(Unknown Source) [?:1.8.0_131] at java.awt.EventDispatchThread.pumpEventsForHierarchy(Unknown Source) [?:1.8.0_131] at java.awt.EventDispatchThread.pumpEvents(Unknown Source) [?:1.8.0_131] at java.awt.EventDispatchThread.pumpEvents(Unknown Source) [?:1.8.0_131] at java.awt.EventDispatchThread.run(Unknown Source) [?:1.8.0_131]

内容的提问来源于stack exchange，提问作者Sunil Sunny