tomcat應用服務器啓動報錯如下：
org.apache.catalina.startup.Catalina start
嚴重: Catalina.start:
LifecycleException: No UserDatabase component found under key UserDatabase
at org.apache.catalina.realm.UserDatabaseRealm.start(UserDatabaseRealm.java:261)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1037)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443)
at org.apache.catalina.core.StandardService.start(StandardService.java:516)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:710)
at org.apache.catalina.startup.Catalina.start(Catalina.java:578)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.lang.reflect.Method.invoke(Unknown Source)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:288)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:413)
並且tomcat服務器也不能夠正常運行，究其原因，一般情況下是tomcat-users.xml有問題。我報錯是xml讀寫的問題，發現tomcat-users.xml直接是亂碼了。重新拷貝一個過來上訴問題得以解決。