The web app occasionally get hang for about 30 seconds when user request a web page, the server's CPU and memory usage are ok, and the jstack shows:

"http-9999-3" daemon prio=6 tid=0x552f3400 nid=0xf40 runnable [0x578fc000]
   java.lang.Thread.State: RUNNABLE
    at org.eclipse.jdt.internal.compiler.parser.Parser.getTypeReference(Parser.java:8354)
    at org.eclipse.jdt.internal.compiler.parser.Parser.consumeClassHeaderExtends(Parser.java:2125)
    at org.eclipse.jdt.internal.compiler.parser.Parser.consumeRule(Parser.java:5107)
    at org.eclipse.jdt.internal.compiler.parser.Parser.parse(Parser.java:9020)
    at org.eclipse.jdt.internal.compiler.parser.Parser.parse(Parser.java:9251)
    at org.eclipse.jdt.internal.compiler.parser.Parser.parse(Parser.java:9208)
    at org.eclipse.jdt.internal.compiler.parser.Parser.dietParse(Parser.java:7864)
    at org.eclipse.jdt.internal.compiler.Compiler.internalBeginToCompile(Compiler.java:587)
    at org.eclipse.jdt.internal.compiler.Compiler.beginToCompile(Compiler.java:357)
    at org.eclipse.jdt.internal.compiler.Compiler.compile(Compiler.java:371)
    at org.apache.jasper.compiler.JDTCompiler.generateClass(JDTCompiler.java:413)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:317)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:295)
    at org.apache.jasper.compiler.Compiler.compile(Compiler.java:282)
    at org.apache.jasper.JspCompilationContext.compile(JspCompilationContext.java:586)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:317)
    - locked <0x10a75fc0> (a org.apache.jasper.servlet.JspServletWrapper)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:342)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:267)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:717)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:290)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206)
    at org.apache.catalina.core.ApplicationDispatcher.invoke(ApplicationDispatcher.java:630)
    at org.apache.catalina.core.ApplicationDispatcher.doInclude(ApplicationDispatcher.java:535)
    at org.apache.catalina.core.ApplicationDispatcher.include(ApplicationDispatcher.java:472)
    ......

seems it's related with some jsp files, how to find the root cause? thanks.