title: ZipFile.getEntry causing java aplication to hang
body: <p>I have this application that is hanging with no apparent reason. I performed a thread dump in order to check what is being done by the application while on that state and found out almost all my HTTP threads were stuck on <code>ZipFile.getEntry</code> as follows:</p>
  
  <pre><code>"http-bio-8010-exec-217" #1059431 daemon prio=5 os_prio=0 tid=0x00007f1b99933000 nid=0x12ac waiting for monitor entry [0x00007f1b01841000]
     java.lang.Thread.State: BLOCKED (on object monitor)
      at java.util.zip.ZipFile.getEntry(ZipFile.java:308)
      - waiting to lock &lt;0x00000007100a9dd8&gt; (a java.util.jar.JarFile)
      at java.util.jar.JarFile.getEntry(JarFile.java:240)
      at java.util.jar.JarFile.getJarEntry(JarFile.java:223)
      at sun.misc.URLClassPath$JarLoader.getResource(URLClassPath.java:1005)
      at sun.misc.URLClassPath.getResource(URLClassPath.java:212)
      at sun.misc.URLClassPath.getResource(URLClassPath.java:265)
      at java.lang.ClassLoader.getBootstrapResource(ClassLoader.java:1264)
      at java.lang.ClassLoader.getResource(ClassLoader.java:1093)
      at java.lang.ClassLoader.getResource(ClassLoader.java:1091)
      at java.lang.ClassLoader.getSystemResource(ClassLoader.java:1226)
      at java.lang.ClassLoader.getSystemResourceAsStream(ClassLoader.java:1329)
      at com.sun.xml.internal.bind.v2.runtime.reflect.opt.AccessorInjector.tailor(AccessorInjector.java:103)
      at com.sun.xml.internal.bind.v2.runtime.reflect.opt.AccessorInjector.prepare(AccessorInjector.java:68)
      at com.sun.xml.internal.bind.v2.runtime.reflect.opt.OptimizedAccessorFactory.get(OptimizedAccessorFactory.java:110)
      at com.sun.xml.internal.bind.v2.runtime.reflect.Accessor$GetterSetterReflection.optimize(Accessor.java:388)
      at com.sun.xml.internal.bind.v2.runtime.property.SingleElementLeafProperty.&lt;init&gt;(SingleElementLeafProperty.java:77)
      at sun.reflect.GeneratedConstructorAccessor53.newInstance(Unknown Source)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
      at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:166)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:153)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:153)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.&lt;init&gt;(JAXBContextImpl.java:305)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.&lt;init&gt;(JAXBContextImpl.java:124)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
      at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
      at sun.reflect.GeneratedMethodAccessor57.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
      at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
      at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
      at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
      at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
      at foo.bar.app.core.base.Response.format(ServiceResponse.java:121)
      at foo.bar.app.bind.response.Response.serialize(BaseQueryInfoResponse.java:156)
      at foo.bar.app.core.Unicity.update(Idempotency.java:377)
      at foo.bar.app.core.Unicity.process(Idempotency.java:274)
      at foo.bar.app.core.dispatcher.RequestDispatcher.dispatch(RequestDispatcher.java:138)
      at foo.bar.app.web.controller.MainController.dispatch(MainController.java:57)
      at sun.reflect.GeneratedMethodAccessor79.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
      at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
      at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
      at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967)
      at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
      at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
      at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1082)
      at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:623)
      at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
      - locked &lt;0x0000000756283100&gt; (a org.apache.tomcat.util.net.SocketWrapper)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
      at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
      at java.lang.Thread.run(Thread.java:745)
  
     Locked ownable synchronizers:
      - &lt;0x00000007562831d0&gt; (a java.util.concurrent.ThreadPoolExecutor$Worker)
  </code></pre>
  
  <p>The thread blocking all others on ZipFile.getEntry was:</p>
  
  <pre><code>"http-bio-8010-exec-40" #932346 daemon prio=5 os_prio=0 tid=0x00007f1b2c0cf000 nid=0x1ae0 runnable [0x00007f1b0d94f000]
     java.lang.Thread.State: RUNNABLE
      at java.util.zip.ZipFile.freeEntry(Native Method)
      at java.util.zip.ZipFile.getEntry(ZipFile.java:313)
      - locked &lt;0x00000007100a9dd8&gt; (a java.util.jar.JarFile)
      at java.util.jar.JarFile.getEntry(JarFile.java:240)
      at java.util.jar.JarFile.getJarEntry(JarFile.java:223)
      at sun.misc.URLClassPath$JarLoader.getResource(URLClassPath.java:1005)
      at sun.misc.URLClassPath.getResource(URLClassPath.java:212)
      at sun.misc.URLClassPath.getResource(URLClassPath.java:265)
      at java.lang.ClassLoader.getBootstrapResource(ClassLoader.java:1264)
      at java.lang.ClassLoader.getResource(ClassLoader.java:1093)
      at java.lang.ClassLoader.getResource(ClassLoader.java:1091)
      at java.lang.ClassLoader.getSystemResource(ClassLoader.java:1226)
      at java.lang.ClassLoader.getSystemResourceAsStream(ClassLoader.java:1329)
      at com.sun.xml.internal.bind.v2.runtime.reflect.opt.AccessorInjector.tailor(AccessorInjector.java:103)
      at com.sun.xml.internal.bind.v2.runtime.reflect.opt.AccessorInjector.prepare(AccessorInjector.java:68)
      at com.sun.xml.internal.bind.v2.runtime.reflect.opt.OptimizedAccessorFactory.get(OptimizedAccessorFactory.java:110)
      at com.sun.xml.internal.bind.v2.runtime.reflect.Accessor$GetterSetterReflection.optimize(Accessor.java:388)
      at com.sun.xml.internal.bind.v2.runtime.reflect.TransducedAccessor$CompositeTransducedAccessorImpl.&lt;init&gt;(TransducedAccessor.java:220)
      at com.sun.xml.internal.bind.v2.runtime.reflect.TransducedAccessor.get(TransducedAccessor.java:160)
      at com.sun.xml.internal.bind.v2.runtime.property.SingleElementLeafProperty.&lt;init&gt;(SingleElementLeafProperty.java:79)
      at sun.reflect.GeneratedConstructorAccessor53.newInstance(Unknown Source)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
      at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:166)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:507)
      at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementProperty.&lt;init&gt;(ArrayElementProperty.java:97)
      at com.sun.xml.internal.bind.v2.runtime.property.ArrayElementNodeProperty.&lt;init&gt;(ArrayElementNodeProperty.java:47)
      at sun.reflect.GeneratedConstructorAccessor150.newInstance(Unknown Source)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
      at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:166)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:507)
      at com.sun.xml.internal.bind.v2.runtime.property.SingleElementNodeProperty.&lt;init&gt;(SingleElementNodeProperty.java:90)
      at sun.reflect.GeneratedConstructorAccessor59.newInstance(Unknown Source)
      at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
      at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
      at com.sun.xml.internal.bind.v2.runtime.property.PropertyFactory.create(PropertyFactory.java:113)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:166)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.ClassBeanInfoImpl.&lt;init&gt;(ClassBeanInfoImpl.java:153)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.getOrCreate(JAXBContextImpl.java:488)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.&lt;init&gt;(JAXBContextImpl.java:305)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl.&lt;init&gt;(JAXBContextImpl.java:124)
      at com.sun.xml.internal.bind.v2.runtime.JAXBContextImpl$JAXBContextBuilder.build(JAXBContextImpl.java:1123)
      at com.sun.xml.internal.bind.v2.ContextFactory.createContext(ContextFactory.java:147)
      at sun.reflect.GeneratedMethodAccessor57.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:247)
      at javax.xml.bind.ContextFinder.newInstance(ContextFinder.java:234)
      at javax.xml.bind.ContextFinder.find(ContextFinder.java:462)
      at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:641)
      at javax.xml.bind.JAXBContext.newInstance(JAXBContext.java:584)
      at foo.bar.app.core.base.Response.format(ServiceResponse.java:121)
      at foo.bar.app.bind.response.Response.serialize(BaseQueryInfoResponse.java:156)
      at foo.bar.app.core.Unicity.update(Idempotency.java:377)
      at foo.bar.app.core.Unicity.process(Idempotency.java:274)
      at foo.bar.app.core.dispatcher.RequestDispatcher.dispatch(RequestDispatcher.java:138)
      at foo.bar.app.web.controller.MainController.dispatch(MainController.java:57)
      at sun.reflect.GeneratedMethodAccessor79.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
      at java.lang.reflect.Method.invoke(Method.java:498)
      at org.springframework.web.method.support.InvocableHandlerMethod.doInvoke(InvocableHandlerMethod.java:221)
      at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:137)
      at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:110)
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:776)
      at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:705)
      at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:85)
      at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:959)
      at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:893)
      at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:967)
      at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:869)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
      at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:843)
      at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
      at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
      at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
      at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
      at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:218)
      at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
      at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
      at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:169)
      at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
      at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
      at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
      at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:442)
      at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1082)
      at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:623)
      at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:318)
      - locked &lt;0x0000000752b0b840&gt; (a org.apache.tomcat.util.net.SocketWrapper)
      at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
      at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
      at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
      at java.lang.Thread.run(Thread.java:745)
  
     Locked ownable synchronizers:
      - &lt;0x0000000749f0d580&gt; (a java.util.concurrent.ThreadPoolExecutor$Worker)
  </code></pre>
  
  <p>As it could be seen there is one thread blocking others, but what causes could lead to freeEntry stuck like that?</p>