版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/boonya/article/details/89335873
此问题在阿里编程规范中也有提及，为什么不建议foreach或者for里面执行add/remove原因是遍历的对象长度改变之后引起并发异常，轻则抛异常重则tomcat服务挂掉。这里以一个老项目中定期移除Token为例。
目录
Java并发remove代码
问题代码
/**
* 移除失效token
*/
@SuppressWarnings("unchecked")
public void removeInvalidToken(){
int i = 0;
Long invalidTime = new Date().getTime() - invalidatInterval;
HashMap<String, Token> tokenMap = (HashMap<String, Token>) XHTCacheManager.getModeByCache("moblieTokenList");
if(null != tokenMap){//tokenMap不为空
for (Entry<String, Token> entry : tokenMap.entrySet()) {
Token token = entry.getValue();
Long time = token.getCreateTime().getTime();
if(time < invalidTime){
String tokenUUID = entry.getKey();
tokenMap.remove(tokenUUID);
i ++;
}
}
}
System.out.println("removeInvalidToken = "+i);
}解决方法
使用Iterator遍历修改，这个操作跟长度无关了。
public static Object obj=new Object();
/**
* 移除失效token
*/
@SuppressWarnings("unchecked")
public void removeInvalidToken(){
int i = 0;
Long invalidTime = new Date().getTime() - invalidatInterval;
HashMap<String, Token> tokenMap = (HashMap<String, Token>) XHTCacheManager.getModeByCache("moblieTokenList");
if(null != tokenMap){//tokenMap不为空
/*for (Entry<String, Token> entry : tokenMap.entrySet()) {
Token token = entry.getValue();
Long time = token.getCreateTime().getTime();
if(time < invalidTime){
String tokenUUID = entry.getKey();
tokenMap.remove(tokenUUID);
i ++;
}
}*/
Iterator<Entry<String, Token>> iter=tokenMap.entrySet().iterator();
while (iter.hasNext()) {
Entry<String, Token> entry=iter.next();
Token token = entry.getValue();
Long time = token.getCreateTime().getTime();
if(time < invalidTime){
String tokenUUID = entry.getKey();
// 防止并发移除问题
synchronized (obj) {
tokenMap.remove(tokenUUID);
}
i ++;
}
}
}
System.out.println("removeInvalidToken = "+i);
}
public void createToken(Token token){
synchronized(obj){
tokenMap = (HashMap<String, Token>) XHTCacheManager.getModeByCache("moblieTokenList");
userMap = (HashMap<String, String>) XHTCacheManager.getModeByCache("moblieUserList");
if (null == tokenMap){
tokenMap = new HashMap<String, Token>();
XHTCacheManager.addMode("moblieTokenList", tokenMap);
}
if (null == userMap){
userMap = new HashMap<String, String>();
XHTCacheManager.addMode("moblieUserList", userMap);
}
}
.....
}注：并发场景下remove操作加锁，而不是Iterator加锁，这个是很多网文的谬误，HashMap是非线程安全的它的put和remove都应该加锁处理，可以使用HashTable建议使用ConcurrentHashMap。
Tomcat异常输出日志
Timer的调用
Timer整体来说没有Quartz好用，因为是很早的项目代码，最好改为springframework.scheduling.quartz的方式
Exception in thread "Timer-3" java.util.ConcurrentModificationException
at
java.util.HashMap$HashIterator.nextNode(HashMap.java:1442)
at java.util.HashMap
$EntryIterator.next(HashMap.java:1476)
at java.util.HashMap$EntryIterator.next
(HashMap.java:1474)
at
com.forestar.webservice.manager.MobileTokenManager.removeInvalidToken
(MobileTokenManager.java:61)
at
com.forestar.webservice.manager.MobileTokenTimerManager$1.run
(MobileTokenTimerManager.java:32)
at java.util.TimerThread.mainLoop(Timer.java:555)
at java.util.TimerThread.run(Timer.java:505)Tomcat服务重载问题
tomcat重载导致第三方库dll或者so二次加载失败
四月 16, 2019 11:47:29 上午 net.sf.ehcache.constructs.web.filter.Filter logThrowable
警告:
Throwable thrown during doFilter on request with URI: /webService/uploadAttach.do and
Query: token=4d5065ad-6667-4641-88c6-20eed14b4c1c&attachType=1&eventCode=6f95800d-7a2a-
41ad-a29a-bbb1d6fa003dHandler processing failed; nested exception is
java.lang.UnsatisfiedLinkError: Native Library /usr/lib64/libwebp-imageio.so already
loaded in another classloader
org.springframework.web.util.NestedServletException: Handler
processing failed; nested exception is java.lang.UnsatisfiedLinkError: Native Library
/usr/lib64/libwebp-imageio.so already loaded in another classloader
at
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:839)
at org.springframework.web.servlet.DispatcherServlet.doService
(DispatcherServlet.java:719)
at
org.springframework.web.servlet.FrameworkServlet.processRequest
(FrameworkServlet.java:644)
at
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
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 com.forestar.listener.UserFilter.doFilter(UserFilter.java:42)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter
(ApplicationFilterChain.java:241)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.forestar.core.session.RequestFilter.doFilter(RequestFilter.java:44)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter
(ApplicationFilterChain.java:241)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.forestar.core.filter.GZIPFilter.doFilter(GZIPFilter.java:22)
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:88)
at
org.springframework.web.filter.OncePerRequestFilter.doFilter
(OncePerRequestFilter.java:76)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter
(ApplicationFilterChain.java:241)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.forestar.core.cache.ehcache.PageCacheFilter.doFilter(PageCacheFilter.java:51)
at net.sf.ehcache.constructs.web.filter.Filter.doFilter(Filter.java:86)
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:505)
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:957)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.ha.session.JvmRouteBinderValve.invoke
(JvmRouteBinderValve.java:218)
at org.apache.catalina.ha.tcp.ReplicationValve.invoke
(ReplicationValve.java:333)
at org.apache.catalina.connector.CoyoteAdapter.service
(CoyoteAdapter.java:423)
at
org.apache.coyote.http11.AbstractHttp11Processor.process
(AbstractHttp11Processor.java:1079)
at org.apache.coyote.AbstractProtocol
$AbstractConnectionHandler.process(AbstractProtocol.java:620)
at
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.UnsatisfiedLinkError: Native
Library /usr/lib64/libwebp-imageio.so already loaded in another classloader
at
java.lang.ClassLoader.loadLibrary0(ClassLoader.java:1907)
at
java.lang.ClassLoader.loadLibrary(ClassLoader.java:1857)
at
java.lang.Runtime.loadLibrary0(Runtime.java:870)
at java.lang.System.loadLibrary
(System.java:1122)
at com.luciad.imageio.webp.WebP.loadNativeLibrary(WebP.java:29)
at com.luciad.imageio.webp.WebP.<clinit>(WebP.java:34)
at
com.luciad.imageio.webp.WebPReadParam.<clinit>(WebPReadParam.java:22)
at
com.forestar.webservice.MobileController.uploadAttach(MobileController.java:1106)
at sun.reflect.GeneratedMethodAccessor84.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at
org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod
(HandlerMethodInvoker.java:176)
at
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandl
erMethod(AnnotationMethodHandlerAdapter.java:426)
at
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle
(AnnotationMethodHandlerAdapter.java:414)
at
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
... 44 more
四月 16, 2019 11:47:29 上午 net.sf.ehcache.constructs.web.filter.Filter logThrowable
警告:
Throwable thrown during doFilter on request with URI: /webService/uploadAttach.do and
Query: token=4d5065ad-6667-4641-88c6-20eed14b4c1c&attachType=1&eventCode=6f95800d-7a2a-
41ad-a29a-bbb1d6fa003dHandler processing failed; nested exception is
java.lang.NoClassDefFoundError: Could not initialize class
com.luciad.imageio.webp.WebPReadParam
org.springframework.web.util.NestedServletException:
Handler processing failed; nested exception is java.lang.NoClassDefFoundError: Could not
initialize class com.luciad.imageio.webp.WebPReadParam
at
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:839)
at org.springframework.web.servlet.DispatcherServlet.doService
(DispatcherServlet.java:719)
at
org.springframework.web.servlet.FrameworkServlet.processRequest
(FrameworkServlet.java:644)
at
org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:560)
at javax.servlet.http.HttpServlet.service(HttpServlet.java:650)
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 com.forestar.listener.UserFilter.doFilter(UserFilter.java:42)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter
(ApplicationFilterChain.java:241)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.forestar.core.session.RequestFilter.doFilter(RequestFilter.java:44)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter
(ApplicationFilterChain.java:241)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.forestar.core.filter.GZIPFilter.doFilter(GZIPFilter.java:22)
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:88)
at
org.springframework.web.filter.OncePerRequestFilter.doFilter
(OncePerRequestFilter.java:76)
at
org.apache.catalina.core.ApplicationFilterChain.internalDoFilter
(ApplicationFilterChain.java:241)
at
org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
at com.forestar.core.cache.ehcache.PageCacheFilter.doFilter(PageCacheFilter.java:51)
at net.sf.ehcache.constructs.web.filter.Filter.doFilter(Filter.java:86)
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:505)
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:957)
at
org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
at org.apache.catalina.ha.session.JvmRouteBinderValve.invoke
(JvmRouteBinderValve.java:218)
at org.apache.catalina.ha.tcp.ReplicationValve.invoke
(ReplicationValve.java:333)
at org.apache.catalina.connector.CoyoteAdapter.service
(CoyoteAdapter.java:423)
at
org.apache.coyote.http11.AbstractHttp11Processor.process
(AbstractHttp11Processor.java:1079)
at org.apache.coyote.AbstractProtocol
$AbstractConnectionHandler.process(AbstractProtocol.java:620)
at
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
at java.lang.Thread.run(Thread.java:748)
Caused by: java.lang.NoClassDefFoundError: Could
not initialize class com.luciad.imageio.webp.WebPReadParam
at
com.forestar.webservice.MobileController.uploadAttach(MobileController.java:1106)
at sun.reflect.GeneratedMethodAccessor84.invoke(Unknown Source)
at
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at
org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod
(HandlerMethodInvoker.java:176)
at
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.invokeHandl
erMethod(AnnotationMethodHandlerAdapter.java:426)
at
org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter.handle
(AnnotationMethodHandlerAdapter.java:414)
at
org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:790)
... 44 more