今天在线上环境发现cpu利用率100%问题，top出来确实有个进程一直占着100%cpu,记下这个pid然后Shift+H查看线程占用资源情况，记下pid,这时pid其实是线程ID，到java堆栈去找要转为十六进制；
jstack [pid] |grep -n 'nid=0x249c' 这一行就是占用资源的线程
"New I/O server worker #1-11" prio=10 tid=0x000000005d8e8000 nid=0x249c runnable [0x0000000042216000] java.lang.Thread.State: RUNNABLE at java.util.regex.Pattern$CharProperty$1.isSatisfiedBy(Pattern.java:3337) at java.util.regex.Pattern$CharProperty.match(Pattern.java:3345) at java.util.regex.Pattern$Curly.match0(Pattern.java:3770) at java.util.regex.Pattern$Curly.match(Pattern.java:3744) at java.util.regex.Pattern$BmpCharProperty.match(Pattern.java:3366) at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168) at java.util.regex.Pattern$Loop.match(Pattern.java:4295) at java.util.regex.Pattern$GroupTail.match(Pattern.java:4227) at java.util.regex.Pattern$Curly.match0(Pattern.java:3782) at java.util.regex.Pattern$Curly.match(Pattern.java:3744) at java.util.regex.Pattern$BmpCharProperty.match(Pattern.java:3366) at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168) at java.util.regex.Pattern$Loop.match(Pattern.java:4295) at java.util.regex.Pattern$GroupTail.match(Pattern.java:4227) at java.util.regex.Pattern$Curly.match0(Pattern.java:3782) at java.util.regex.Pattern$Curly.match(Pattern.java:3744) at java.util.regex.Pattern$BmpCharProperty.match(Pattern.java:3366) at java.util.regex.Pattern$GroupHead.match(Pattern.java:4168) at java.util.regex.Pattern$Loop.match(Pattern.java:4295) .........
通过上下文可以看到是在用户登录时，调用了一个正则运算，通过日志查看到这一行不正常信息
request.body:{"login_name":"..\\/...\\/..\\/.\\/..\\/...\\/..\\/.\\/..\\/...\\/..\\/.\\/..\\/...\\/..\\/.\\/..\\/...\\/..\\/.\\/..\\/...\\/..\\/.\\/etc\\/passwd","password":"***"}
在本地试了下，果然重现了！
后来把正则表达式换成“^[\\w-]+(\\.[\\w-]+)*@[\\w-]+(\\.[\\w-]+)+$”就正常了...
