在我東，下下來一個項目總會出現啟動不了的問題，這些問題往往在編譯的時候發現不了，當你的服務器啟動的時候，就是一片片的報錯，有些問題可以通過異常的提示信息，判斷出來哪里配置錯了，但是也有些情況下，從異常的提示信息中壓根看不出來具體哪個地方出現問題了，比如下面的這段異常信息，我就不能一下子定位到哪里錯了。
八月 05, 2017 11:09:53 上午 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc
嚴重: The web application [] registered the JDBC 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.
八月 05, 2017 11:09:53 上午 org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
嚴重: The web application [] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@45c7519]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@520bbe8b]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
八月 05, 2017 11:09:53 上午 org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
嚴重: The web application [] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@45c7519]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@10ac1c2]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
八月 05, 2017 11:09:53 上午 org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
嚴重: The web application [] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@45c7519]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@5ec4258c]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
八月 05, 2017 11:09:53 上午 org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
嚴重: The web application [] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@45c7519]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@1f7d3aef]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
八月 05, 2017 11:09:53 上午 org.apache.catalina.loader.WebappClassLoader checkThreadLocalMapForLeaks
嚴重: The web application [] created a ThreadLocal with key of type [java.lang.ThreadLocal] (value [java.lang.ThreadLocal@45c7519]) and a value of type [io.netty.util.internal.InternalThreadLocalMap] (value [io.netty.util.internal.InternalThreadLocalMap@56a8310f]) but failed to remove it when the web application was stopped. Threads are going to be renewed over time to try and avoid a probable memory leak.
八月 05, 2017 11:09:54 上午 org.apache.catalina.loader.WebappClassLoader loadClass
信息: Illegal access: this web application instance has been stopped already. Could not load org.apache.jute.BinaryInputArchive$BinaryIndex. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
java.lang.IllegalStateException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1612)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at org.apache.jute.BinaryInputArchive.startVector(BinaryInputArchive.java:120)
at org.apache.zookeeper.proto.GetChildrenResponse.deserialize(GetChildrenResponse.java:54)
at org.apache.zookeeper.ClientCnxn$SendThread.readResponse(ClientCnxn.java:808)
at org.apache.zookeeper.ClientCnxnSocketNIO.doIO(ClientCnxnSocketNIO.java:89)
at org.apache.zookeeper.ClientCnxnSocketNIO.doTransport(ClientCnxnSocketNIO.java:291)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1041)
八月 05, 2017 11:09:54 上午 org.apache.catalina.loader.WebappClassLoader loadClass
信息: Illegal access: this web application instance has been stopped already. Could not load org.apache.logging.log4j.core.impl.ThrowableProxy. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
java.lang.IllegalStateException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1612)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at org.apache.logging.log4j.core.impl.Log4jLogEvent.getThrownProxy(Log4jLogEvent.java:530)
at org.apache.logging.log4j.core.pattern.ExtendedThrowablePatternConverter.format(ExtendedThrowablePatternConverter.java:61)
at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:38)
at org.apache.logging.log4j.core.layout.PatternLayout$PatternSerializer.toSerializable(PatternLayout.java:288)
at org.apache.logging.log4j.core.layout.PatternLayout.toText(PatternLayout.java:194)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:180)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:57)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:120)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:113)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:104)
at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:155)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:128)
at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:119)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:390)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:375)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:359)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:349)
at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)
at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)
at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2002)
at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1974)
at org.apache.logging.slf4j.Log4jLogger.warn(Log4jLogger.java:259)
at org.apache.zookeeper.ClientCnxn$SendThread.run(ClientCnxn.java:1063)
八月 05, 2017 11:09:54 上午 org.apache.catalina.loader.WebappClassLoader loadClass
信息: Illegal access: this web application instance has been stopped already. Could not load org.apache.logging.log4j.core.impl.ThrowableProxy. The eventual following stack trace is caused by an error thrown for debugging purposes as well as to attempt to terminate the thread which caused the illegal access, and has no functional impact.
java.lang.IllegalStateException
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1612)
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
at org.apache.logging.log4j.core.impl.Log4jLogEvent.getThrownProxy(Log4jLogEvent.java:530)
at org.apache.logging.log4j.core.pattern.ExtendedThrowablePatternConverter.format(ExtendedThrowablePatternConverter.java:61)
at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:38)
at org.apache.logging.log4j.core.layout.PatternLayout$PatternSerializer.toSerializable(PatternLayout.java:288)
at org.apache.logging.log4j.core.layout.PatternLayout.toText(PatternLayout.java:194)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:180)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:57)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:120)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:113)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:104)
at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:155)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:128)
at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:119)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:390)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:375)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:359)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:349)
at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)
at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)
at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2002)
at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1974)
at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:199)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
Exception in thread "pool-3-thread-1" java.lang.NoClassDefFoundError: org/apache/logging/log4j/core/impl/ThrowableProxy
at org.apache.logging.log4j.core.impl.Log4jLogEvent.getThrownProxy(Log4jLogEvent.java:530)
at org.apache.logging.log4j.core.pattern.ExtendedThrowablePatternConverter.format(ExtendedThrowablePatternConverter.java:61)
at org.apache.logging.log4j.core.pattern.PatternFormatter.format(PatternFormatter.java:38)
at org.apache.logging.log4j.core.layout.PatternLayout$PatternSerializer.toSerializable(PatternLayout.java:288)
at org.apache.logging.log4j.core.layout.PatternLayout.toText(PatternLayout.java:194)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:180)
at org.apache.logging.log4j.core.layout.PatternLayout.encode(PatternLayout.java:57)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.directEncodeEvent(AbstractOutputStreamAppender.java:120)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.tryAppend(AbstractOutputStreamAppender.java:113)
at org.apache.logging.log4j.core.appender.AbstractOutputStreamAppender.append(AbstractOutputStreamAppender.java:104)
at org.apache.logging.log4j.core.config.AppenderControl.tryCallAppender(AppenderControl.java:155)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender0(AppenderControl.java:128)
at org.apache.logging.log4j.core.config.AppenderControl.callAppenderPreventRecursion(AppenderControl.java:119)
at org.apache.logging.log4j.core.config.AppenderControl.callAppender(AppenderControl.java:84)
at org.apache.logging.log4j.core.config.LoggerConfig.callAppenders(LoggerConfig.java:390)
at org.apache.logging.log4j.core.config.LoggerConfig.processLogEvent(LoggerConfig.java:375)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:359)
at org.apache.logging.log4j.core.config.LoggerConfig.log(LoggerConfig.java:349)
at org.apache.logging.log4j.core.config.AwaitCompletionReliabilityStrategy.log(AwaitCompletionReliabilityStrategy.java:63)
at org.apache.logging.log4j.core.Logger.logMessage(Logger.java:146)
at org.apache.logging.log4j.spi.AbstractLogger.logMessage(AbstractLogger.java:2002)
at org.apache.logging.log4j.spi.AbstractLogger.logIfEnabled(AbstractLogger.java:1974)
at org.apache.logging.slf4j.Log4jLogger.info(Log4jLogger.java:199)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:745)
我以前分析過一些異常問題，不過現在的情況是，以前的那些方法貌似都不太靈驗了，因為，異常信息中沒有什么和我們直接編寫的代碼相關的東西，這個咋弄？我看到有類沒找到的問題，於是我就搜一下，如下圖所示：
有啊！奇怪了，是maven依賴沖突了嗎？我再搜一下看看
沒有依賴沖突呀！我去，這咋弄？
編譯沒問題，啟動tomcat服務器愣是啟動不起來，那說明代碼本身沒問題，應該是配置的問題，但是到底哪里配置錯了哪？沒法子我只能重頭到尾的再次檢查一下各個配置文件的配置，數據庫、緩存、遠程接口調用、異步消息的發送、分布式配置管理等等，都查看了一遍還是沒有發現問題。百度吧！從網上找了找，還是沒有什么思路，后來就詢問了同事M看看他遇到過類似的問題沒有，不得不服，我花費了小半天沒解決的問題，他一會就找到了原因。（這可能是當局者迷，旁觀者清的一種情形）
我的web.xml文件中配置的日志文件是這樣的，如下圖所示：
但是實際上我們的項目現在使用的是log4j2，將對應的配置修改成這樣就行了
最終定位到問題了——是配置文件的問題，然后我又回憶了一下為什么會出現這樣的情況那？我怎么配置錯了哪？配置錯了我怎么一點印象都沒有哪？
現在我們的環境有好多種，如下所示：
1：生產環境
2：預發布環境
3：測試環境
4：開發環境
每套環境，都有好多的配置，比如：數據庫、緩存、遠程接口調用、異步消息發送、分布式配置管理等等。弄錯了任何一套都不好玩，常常分析問題的時候也是一件比較麻煩的事情，如果環境不同，看似相同的操作或則入參，可能會產生完全不一樣的結果。
現在我是開發好了兩個遠程調用的接口，但是上游的測試環境不可用，只能使用預發布環境的機器聯調，我們的緩存刷新的應用和接口所在的應用是不同的，所以，需要將對應的應用配置上預發布環境配置，在配置的過程中我需要比對一下原來預發布環境和本地環境有什么區別（除了一些環境配置還要別的配置文件是抽出來的），並且需要明白當初為什么這樣配置，中間涉及好幾個應用的配置多個配置文件的修改，在這個時間段中我不小心將配置文件的配置在比較的過程中給弄亂了。
上面這一段描述，可能僅對我自己有作用吧！
簡單點講就是，我將配置文件配置錯了，所以，tomcat啟動不了啦！
由於自己的不小心，犯下了這種錯誤，恰巧我的記憶力不好，忘記了，異常信息也提示的不明顯，所以自己花了不少時間來排查！
好記性不如爛筆頭，何況是爛記性哪！我想下一次，我一定能更快的定位和解決類似的問題吧！