tomcat7 - Tomcat permGen space out of memory exception. Tomcat hangs and stops responding -

i using spring, struts, , tomcat 7. after every few days wake find out server has chocked checked hibernate sessions , made sure closed

to keep question short, tomcat hangs:

java.lang.nullpointerexception     @ com.x.x.a.pageactions.getuserpage(unknown source)     @ com.x.x.a.pageactions$$fastclassbycglib$$ac0e4af0.invoke(<generated>)     @ org.springframework.cglib.proxy.methodproxy.invoke(methodproxy.java:204)     @ org.springframework.aop.framework.cglibaopproxy$cglibmethodinvocation.invokejoinpoint(cglibaopproxy.java:698)     @ org.springframework.aop.framework.reflectivemethodinvocation.proceed(reflectivemethodinvocation.java:150)     @ org.springframework.transaction.interceptor.transactioninterceptor.invoke(transactioninterceptor.java:110)     @ org.springframework.aop.framework.reflectivemethodinvocation.proceed(reflectivemethodinvocation.java:172)     @ org.springframework.aop.interceptor.exposeinvocationinterceptor.invoke(exposeinvocationinterceptor.java:91)     @ org.springframework.aop.framework.reflectivemethodinvocation.proceed(reflectivemethodinvocation.java:172)     @ org.springframework.aop.framework.cglibaopproxy$dynamicadvisedinterceptor.intercept(cglibaopproxy.java:631)     @ com.x.x.a.pageactions$$enhancerbycglib$$e7f27547.getuserpage(<generated>)     @ com.x.x.c.page.h.usepageservlet.service(unknown source)     @ javax.servlet.http.httpservlet.service(httpservlet.java:728)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:305)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210)     @ com.x.x.frontpagefilter.dofilter(unknown source)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:243)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210)     @ com.x.x.redirect301filter.dofilter(unknown source)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:243)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210)     @ com.x.x.securefilter.dofilter(unknown source)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:243)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210)     @ com.x.x.loginfilter.dofilter(unknown source)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:243)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210)     @ com.x.x.stripjsessionfilter.dofilter(unknown source)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:243)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210)     @ org.apache.catalina.core.standardwrappervalve.invoke(standardwrappervalve.java:222)     @ org.apache.catalina.core.standardcontextvalve.invoke(standardcontextvalve.java:123)     @ org.apache.catalina.authenticator.authenticatorbase.invoke(authenticatorbase.java:472)     @ org.apache.catalina.core.standardhostvalve.invoke(standardhostvalve.java:171)     @ org.apache.catalina.valves.errorreportvalve.invoke(errorreportvalve.java:99)     @ org.apache.catalina.valves.accesslogvalve.invoke(accesslogvalve.java:947)     @ org.apache.catalina.core.standardenginevalve.invoke(standardenginevalve.java:118)     @ org.apache.catalina.connector.coyoteadapter.service(coyoteadapter.java:408)     @ org.apache.coyote.http11.abstracthttp11processor.process(abstracthttp11processor.java:1009)     @ org.apache.coyote.abstractprotocol$abstractconnectionhandler.process(abstractprotocol.java:589)     @ org.apache.tomcat.util.net.jioendpoint$socketprocessor.run(jioendpoint.java:310)     @ java.util.concurrent.threadpoolexecutor.runworker(unknown source)     @ java.util.concurrent.threadpoolexecutor$worker.run(unknown source)     @ java.lang.thread.run(unknown source) exception in thread "http-bio-80-exec-259" java.lang.outofmemoryerror: permgen space     @ sun.misc.unsafe.defineclass(native method)     @ sun.reflect.classdefiner.defineclass(unknown source)     @ sun.reflect.methodaccessorgenerator$1.run(unknown source)     @ sun.reflect.methodaccessorgenerator$1.run(unknown source)     @ java.security.accesscontroller.doprivileged(native method)     @ sun.reflect.methodaccessorgenerator.generate(unknown source)     @ sun.reflect.methodaccessorgenerator.generateconstructor(unknown source)     @ sun.reflect.nativeconstructoraccessorimpl.newinstance(unknown source)     @ sun.reflect.delegatingconstructoraccessorimpl.newinstance(unknown source)     @ java.lang.reflect.constructor.newinstance(unknown source)     @ java.lang.class.newinstance0(unknown source)     @ java.lang.class.newinstance(unknown source)     @ java.util.resourcebundle$control.newbundle(unknown source)     @ java.util.resourcebundle.loadbundle(unknown source)     @ java.util.resourcebundle.findbundle(unknown source)     @ java.util.resourcebundle.getbundleimpl(unknown source)     @ java.util.resourcebundle.getbundle(unknown source)     @ sun.util.resources.localedata$1.run(unknown source)     @ sun.util.resources.localedata$1.run(unknown source)     @ java.security.accesscontroller.doprivileged(native method)     @ sun.util.resources.localedata.getbundle(unknown source)     @ sun.util.resources.localedata.gettimezonenames(unknown source)     @ sun.util.timezonenameutility.getbundle(unknown source)     @ sun.util.timezonenameutility.retrievedisplaynames(unknown source)     @ java.util.timezone.getdisplaynames(unknown source)     @ java.util.timezone.getdisplayname(unknown source)     @ java.text.simpledateformat.subformat(unknown source)     @ java.text.simpledateformat.format(unknown source)     @ java.text.simpledateformat.format(unknown source)     @ java.text.dateformat.format(unknown source)     @ org.apache.tomcat.util.http.fasthttpdateformat.getcurrentdate(fasthttpdateformat.java:114)     @ org.apache.coyote.http11.abstracthttp11processor.prepareresponse(abstracthttp11processor.java:1438) exception in thread "http-bio-80-exec-270" java.lang.outofmemoryerror: permgen space     @ sun.misc.unsafe.defineclass(native method)     @ sun.reflect.classdefiner.defineclass(unknown source)     @ sun.reflect.methodaccessorgenerator$1.run(unknown source)     @ sun.reflect.methodaccessorgenerator$1.run(unknown source)     @ java.security.accesscontroller.doprivileged(native method)     @ sun.reflect.methodaccessorgenerator.generate(unknown source)     @ sun.reflect.methodaccessorgenerator.generateconstructor(unknown source)     @ sun.reflect.nativeconstructoraccessorimpl.newinstance(unknown source)     @ sun.reflect.delegatingconstructoraccessorimpl.newinstance(unknown source)     @ java.lang.reflect.constructor.newinstance(unknown source)     @ java.lang.class.newinstance0(unknown source)     @ java.lang.class.newinstance(unknown source)     @ java.util.resourcebundle$control.newbundle(unknown source)     @ java.util.resourcebundle.loadbundle(unknown source)     @ java.util.resourcebundle.findbundle(unknown source)     @ java.util.resourcebundle.findbundle(unknown source)     @ java.util.resourcebundle.getbundleimpl(unknown source)     @ java.util.resourcebundle.getbundle(unknown source)     @ sun.util.resources.localedata$1.run(unknown source)     @ sun.util.resources.localedata$1.run(unknown source)     @ java.security.accesscontroller.doprivileged(native method)     @ sun.util.resources.localedata.getbundle(unknown source)     @ sun.util.resources.localedata.getlocalenames(unknown source)     @ java.util.locale.getdisplaystring(unknown source)     @ java.util.locale.getdisplaycountry(unknown source)     @ java.util.locale.getdisplaycountry(unknown source)     @ com.x.x.web.mainbasecontroller.createuseranonymoussession(unknown source)     @ com.x.x.c.web.mainbasecontroller.checkcookies(unknown source)     @ com.x.x.web.maincontroller.service(unknown source)     @ javax.servlet.http.httpservlet.service(httpservlet.java:728)     @ org.apache.catalina.core.applicationfilterchain.internaldofilter(applicationfilterchain.java:305)     @ org.apache.catalina.core.applicationfilterchain.dofilter(applicationfilterchain.java:210) exception in thread "http-bio-80-exec-272" java.lang.outofmemoryerror: permgen space exception in thread "http-bio-80-exec-274" java.lang.outofmemoryerror: permgen space exception in thread "http-bio-80-exec-273" java.lang.outofmemoryerror: permgen space ... repeated lot ... exception in thread "http-bio-80-exec-372" java.lang.outofmemoryerror: permgen space java.lang.outofmemoryerror: permgen space