我将tomcat配置为使用不同的外部开源。
然而，在tomcat运行几分钟后，我得到：
严重：Web应用程序[/ MyProject]创建了一个ThreadLocal 类型为[java.lang.ThreadLocal]的键（值 [java.lang.ThreadLocal@1b3f02f]）和类型的值 [org.apache.axis.MessageContext]（值 [org.apache.axis.MessageContext@5dbd4e]）但无法删除它 Web应用程序已停止。这很有可能创造一个 记忆泄漏。
可能导致什么原因？
我在哪里看？它可能是Tomcat上的数据池吗？
Tomcat中的Threads是什么意思？
EDITED
这是我的完整痕迹。该应用程序似乎在它仍在运行时重新加载其上下文 - 我不知道为什么！
Mar 13, 2011 10:56:12 PM org.apache.catalina.core.StandardContext reload
INFO: Reloading this Context has started
Mar 13, 2011 10:56:12 PM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 1 instance(s) to be deallocated
Mar 13, 2011 10:56:13 PM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 1 instance(s) to be deallocated
Mar 13, 2011 10:56:14 PM org.apache.catalina.core.StandardWrapper unload
INFO: Waiting for 1 instance(s) to be deallocated
Mar 13, 2011 10:56:14 PM org.apache.catalina.core.ApplicationContext log
INFO: Closing Spring root WebApplicationContext
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
SEVERE: The web application [/MyProject] registered the JBDC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
SEVERE: The web application [/MyProject] registered the JBDC driver [oracle.jdbc.driver.OracleDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [NioSocketAcceptor-1] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [NioProcessor-1] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [NioProcessor-4] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [bitronix-disk-force-batcher] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [bitronix-scheduler] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] is still processing a request that has yet to finish. This is very likely to create a memory leak. You can control the time allowed for requests to finish by using the unloadDelay attribute of the standard Context implementation.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [NioProcessor-7] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/MyProject] appears to have started a thread named [NioProcessor-2] but has failed to stop it. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@1b5a8e1]) and a value of type [org.mvel2.debug.DebuggerContext] (value [org.mvel2.debug.DebuggerContext@16259fd]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [org.apache.axis.utils.XMLUtils.ThreadLocalDocumentBuilder] (value [org.apache.axis.utils.XMLUtils$ThreadLocalDocumentBuilder@84b0b4]) and a value of type [com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl] (value [com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl@16d2cfa]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [null] (value [com.sun.faces.util.Util$1@16bbac9]) and a value of type [java.util.HashMap] (value [{com.sun.faces.patternCache={ = }}]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@1b3f02f]) and a value of type [org.apache.axis.MessageContext] (value [org.apache.axis.MessageContext@5dbd4e]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [org.apache.axis.utils.XMLUtils.ThreadLocalDocumentBuilder] (value [org.apache.axis.utils.XMLUtils$ThreadLocalDocumentBuilder@84b0b4]) and a value of type [com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl] (value [com.sun.org.apache.xerces.internal.jaxp.DocumentBuilderImpl@378584]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [org.springframework.core.NamedThreadLocal] (value [Transactional resources]) and a value of type [java.util.HashMap] (value [{org.hibernate.impl.SessionFactoryImpl@ccc27b=org.springframework.orm.hibernate3.SessionHolder@4f6ada}]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
Mar 13, 2011 10:56:15 PM org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap
SEVERE: The web application [/MyProject] created a ThreadLocal with key of type [null] (value [com.sun.faces.application.ApplicationAssociate$1@1f01fcf]) and a value of type [com.sun.faces.application.ApplicationAssociate] (value [com.sun.faces.application.ApplicationAssociate@1b85528]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.
2011-03-13 22:57:27,734 ERROR ( ContextLoader.java:220) - Context initialization failed
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'transactionManager' defined in class path resource [applicationContext-hibernate.xml]: Cannot resolve reference to bean 'sessionFactory' while setting bean property 'sessionFactory'; nested exception is org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'sessionFactory' defined in class path resource [applicationContext-hibernate.xml]: Invocation of init method failed; nested exception is java.lang.OutOfMemoryError: Java heap space
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveReference(BeanDefinitionValueResolver.java:328)
at org.springframework.beans.factory.support.BeanDefinitionValueResolver.resolveValueIfNecessary(BeanDefinitionValueResolver.java:106)
at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.applyPropertyValues(AbstractAutowireCapableBeanFactory.java:1325)
答案 0 :(得分：23)
消息实际上非常清楚：有些东西会创建ThreadLocal，其值为org.apache.axis.MessageContext - 这是一个很好的提示。这很可能意味着Apache Axis框架在自身之后忘记/无法清理。例如，在Logback中发生了相同的problem。你不应该费心，但向Axis团队报告错误可能是个好主意。
Tomcat报告此错误，因为每个HTTP工作线程都会创建ThreadLocal。您的应用程序已取消部署，但HTTP线程仍然存在 - 以及这些ThreadLocal。这可能会导致内存泄漏（org.apache.axis.MessageContext无法卸载）以及将来重用这些线程时的一些问题。
有关详细信息，请参阅：http://wiki.apache.org/tomcat/MemoryLeakProtection
答案 1 :(得分：6)
我在CDI @ApplicationScoped bean的@PreDestroy方法中添加了以下内容，当我关闭TomEE 1.6.0（tomcat7.0.39，截至今天）时，它会清除线程本地。
/*
* To change this template, choose Tools | Templates
* and open the template in the editor.
*/
package pf;
import java.lang.ref.WeakReference;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
*
* @author Administrator
*
* google-gson issue # 402: Memory Leak in web application; comment # 25
* https://code.google.com/p/google-gson/issues/detail?id=402
*/
public class ThreadLocalImmolater {
final Logger logger = LoggerFactory.getLogger(ThreadLocalImmolater.class);
Boolean debug;
public ThreadLocalImmolater() {
debug = true;
}
public Integer immolate() {
int count = 0;
try {
final Field threadLocalsField = Thread.class.getDeclaredField("threadLocals");
threadLocalsField.setAccessible(true);
final Field inheritableThreadLocalsField = Thread.class.getDeclaredField("inheritableThreadLocals");
inheritableThreadLocalsField.setAccessible(true);
for (final Thread thread : Thread.getAllStackTraces().keySet()) {
count += clear(threadLocalsField.get(thread));
count += clear(inheritableThreadLocalsField.get(thread));
}
logger.info("immolated " + count + " values in ThreadLocals");
} catch (Exception e) {
throw new Error("ThreadLocalImmolater.immolate()", e);
}
return count;
}
private int clear(final Object threadLocalMap) throws Exception {
if (threadLocalMap == null)
return 0;
int count = 0;
final Field tableField = threadLocalMap.getClass().getDeclaredField("table");
tableField.setAccessible(true);
final Object table = tableField.get(threadLocalMap);
for (int i = 0, length = Array.getLength(table); i < length; ++i) {
final Object entry = Array.get(table, i);
if (entry != null) {
final Object threadLocal = ((WeakReference)entry).get();
if (threadLocal != null) {
log(i, threadLocal);
Array.set(table, i, null);
++count;
}
}
}
return count;
}
private void log(int i, final Object threadLocal) {
if (!debug) {
return;
}
if (threadLocal.getClass() != null &&
threadLocal.getClass().getEnclosingClass() != null &&
threadLocal.getClass().getEnclosingClass().getName() != null) {
logger.info("threadLocalMap(" + i + "): " +
threadLocal.getClass().getEnclosingClass().getName());
}
else if (threadLocal.getClass() != null &&
threadLocal.getClass().getName() != null) {
logger.info("threadLocalMap(" + i + "): " + threadLocal.getClass().getName());
}
else {
logger.info("threadLocalMap(" + i + "): cannot identify threadlocal class name");
}
}
}
答案 2 :(得分：2)
关键的“事务性资源”看起来就像是在没有正确的事务的情况下与数据库进行通信。确保正确配置事务管理，并且不存在不在@Transactional注释下运行的DAO调用路径。当您在Controller级别配置事务管理但是在计时器中调用DAO或正在使用@PostConstruct注释时，这很容易发生。我在这里写了http://georgovassilis.blogspot.nl/2014/01/tomcat-spring-and-memory-leaks-when.html
编辑：看起来这也是（也是？）spring-data-jpa的一个bug，它已经用v1.4.3修复了。我在LockModeRepositoryPostProcessor的spring-data-jpa源代码中查找了它，它设置了“Transactional Resources”键。在1.4.3中，它也会再次清除密钥。
答案 3 :(得分：1)
有时这与配置更改有关。当我们从Tomncat 6.0.14升级到6.0.26时，我们看到了类似的东西。这是解决方案 http://www.skill-guru.com/blog/2010/08/22/tomcat-6-0-26-shutdown-reports-a-web-application-created-a-threadlocal-threadlocal-has-been-forcibly-removed/
答案 4 :(得分：0)
当我们使用任何第三方解决方案而不使用处理程序进行清理活动时，会出现此问题。 对我而言，EhCache正在发生这种情况。我们在项目中使用EhCache进行缓存。 通常我们常常在日志中看到以下错误
SEVERE: The web application [/products] appears to have started a thread named [products_default_cache_configuration] but has failed to stop it. This is very likely to create a memory leak.
Aug 07, 2017 11:08:36 AM org.apache.catalina.loader.WebappClassLoader clearReferencesThreads
SEVERE: The web application [/products] appears to have started a thread named [Statistics Thread-products_default_cache_configuration-1] but has failed to stop it. This is very likely to create a memory leak.
我们经常注意到tomcat在开发过程中出现OutOfMemory错误，我们曾经做过后端更改并多次部署应用程序以反映我们的更改。
这是我们做的修复
<listener>
<listener-class>
net.sf.ehcache.constructs.web.ShutdownListener
</listener-class>
</listener>
我想说的是检查您正在使用的第三方库的文档。他们应该提供一些机制来在关机期间清理线程。您需要在应用程序中使用哪个。 除非它们没有提供，否则无需重新发明轮子。最糟糕的情况是提供您自己的实现。
EHCache Shutdown参考 http://www.ehcache.org/documentation/2.8/operations/shutdown.html