Scheduler with name 'DefaultQuartzScheduler' already exists.

Question

[shiro.session.mgt.quartz.QuartzSessionValidationScheduler] - Error starting the Quartz session validation job.  Session validation may not occur.
org.quartz.SchedulerException: Scheduler with name 'DefaultQuartzScheduler' already exists.
    at org.quartz.impl.SchedulerRepository.bind(SchedulerRepository.java:83)
    at org.quartz.impl.StdSchedulerFactory.instantiate(StdSchedulerFactory.java:1237)
    at org.quartz.impl.StdSchedulerFactory.getScheduler(StdSchedulerFactory.java:1371)
    at org.quartz.impl.StdSchedulerFactory.getDefaultScheduler(StdSchedulerFactory.java:1387)
    at org.apache.shiro.session.mgt.quartz.QuartzSessionValidationScheduler.getScheduler(QuartzSessionValidationScheduler.java:110)
    at org.apache.shiro.session.mgt.quartz.QuartzSessionValidationScheduler.enableSessionValidation(QuartzSessionValidationScheduler.java:164)
    at org.apache.shiro.session.mgt.AbstractValidatingSessionManager.enableSessionValidation(AbstractValidatingSessionManager.java:232)
    at org.apache.shiro.session.mgt.AbstractValidatingSessionManager.enableSessionValidationIfNecessary(AbstractValidatingSessionManager.java:86)
    at org.apache.shiro.session.mgt.AbstractValidatingSessionManager.doGetSession(AbstractValidatingSessionManager.java:114)
    at org.apache.shiro.session.mgt.AbstractNativeSessionManager.lookupSession(AbstractNativeSessionManager.java:108)
    at org.apache.shiro.session.mgt.AbstractNativeSessionManager.getSession(AbstractNativeSessionManager.java:100)
    at org.apache.shiro.mgt.SessionsSecurityManager.getSession(SessionsSecurityManager.java:125)
    at org.apache.shiro.mgt.DefaultSecurityManager.resolveContextSession(DefaultSecurityManager.java:456)
    at org.apache.shiro.mgt.DefaultSecurityManager.resolveSession(DefaultSecurityManager.java:442)
    at org.apache.shiro.mgt.DefaultSecurityManager.createSubject(DefaultSecurityManager.java:338)
    at org.apache.shiro.subject.Subject$Builder.buildSubject(Subject.java:846)
    at org.apache.shiro.web.subject.WebSubject$Builder.buildWebSubject(WebSubject.java:148)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.createSubject(AbstractShiroFilter.java:292)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:359)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2462)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2451)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)
2016-07-01 12:02:38,518 ERROR [shiro.session.mgt.quartz.QuartzSessionValidationScheduler] - Error starting the Quartz session validation job.  Session validation may not occur.
org.quartz.SchedulerException: Scheduler with name 'DefaultQuartzScheduler' already exists.
    at org.quartz.impl.SchedulerRepository.bind(SchedulerRepository.java:83)
    at org.quartz.impl.StdSchedulerFactory.instantiate(StdSchedulerFactory.java:1237)
    at org.quartz.impl.StdSchedulerFactory.getScheduler(StdSchedulerFactory.java:1371)
    at org.quartz.impl.StdSchedulerFactory.getDefaultScheduler(StdSchedulerFactory.java:1387)
    at org.apache.shiro.session.mgt.quartz.QuartzSessionValidationScheduler.getScheduler(QuartzSessionValidationScheduler.java:110)
    at org.apache.shiro.session.mgt.quartz.QuartzSessionValidationScheduler.enableSessionValidation(QuartzSessionValidationScheduler.java:164)
    at org.apache.shiro.session.mgt.AbstractValidatingSessionManager.enableSessionValidation(AbstractValidatingSessionManager.java:232)
    at org.apache.shiro.session.mgt.AbstractValidatingSessionManager.enableSessionValidationIfNecessary(AbstractValidatingSessionManager.java:86)
    at org.apache.shiro.session.mgt.AbstractValidatingSessionManager.doGetSession(AbstractValidatingSessionManager.java:114)
    at org.apache.shiro.session.mgt.AbstractNativeSessionManager.lookupSession(AbstractNativeSessionManager.java:108)
    at org.apache.shiro.session.mgt.AbstractNativeSessionManager.getSession(AbstractNativeSessionManager.java:100)
    at org.apache.shiro.mgt.SessionsSecurityManager.getSession(SessionsSecurityManager.java:125)
    at org.apache.shiro.mgt.DefaultSecurityManager.resolveContextSession(DefaultSecurityManager.java:456)
    at org.apache.shiro.mgt.DefaultSecurityManager.resolveSession(DefaultSecurityManager.java:442)
    at org.apache.shiro.mgt.DefaultSecurityManager.createSubject(DefaultSecurityManager.java:338)
    at org.apache.shiro.subject.Subject$Builder.buildSubject(Subject.java:846)
    at org.apache.shiro.web.subject.WebSubject$Builder.buildWebSubject(WebSubject.java:148)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.createSubject(AbstractShiroFilter.java:292)
    at org.apache.shiro.web.servlet.AbstractShiroFilter.doFilterInternal(AbstractShiroFilter.java:359)
    at org.apache.shiro.web.servlet.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:125)
    at org.springframework.web.filter.DelegatingFilterProxy.invokeDelegate(DelegatingFilterProxy.java:344)
    at org.springframework.web.filter.DelegatingFilterProxy.doFilter(DelegatingFilterProxy.java:261)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.springframework.web.filter.CharacterEncodingFilter.doFilterInternal(CharacterEncodingFilter.java:85)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:107)
    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:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:421)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1070)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:611)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2462)
    at org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2451)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Thread.java:745)