TOMCAT报错,求救!!!!

SEVERE: Exception looking up UserDatabase under key UserDatabase
javax.naming.NameNotFoundException: Name [UserDatabase] is not bound in this Context. Unable to find [UserDatabase].
at org.apache.naming.NamingContext.lookup(NamingContext.java:820)
at org.apache.naming.NamingContext.lookup(NamingContext.java:168)
at org.apache.catalina.realm.UserDatabaseRealm.startInternal(UserDatabaseRealm.java:255)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.realm.CombinedRealm.startInternal(CombinedRealm.java:201)
at org.apache.catalina.realm.LockOutRealm.startInternal(LockOutRealm.java:120)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1109)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.startup.Catalina.start(Catalina.java:684)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:456)
Aug 6, 2013 5:50:42 PM org.apache.catalina.realm.CombinedRealm startInternal
SEVERE: Failed to start "org.apache.catalina.realm.UserDatabaseRealm/1.0" realm
org.apache.catalina.LifecycleException: Failed to start component [Realm[UserDatabaseRealm]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.realm.CombinedRealm.startInternal(CombinedRealm.java:201)
at org.apache.catalina.realm.LockOutRealm.startInternal(LockOutRealm.java:120)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1109)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:302)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:732)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.startup.Catalina.start(Catalina.java:684)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:322)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:456)
Caused by: org.apache.catalina.LifecycleException: No UserDatabase component found under key UserDatabase
at org.apache.catalina.realm.UserDatabaseRealm.startInternal(UserDatabaseRealm.java:264)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 17 more
--------------------编程问答-------------------- 在Web项目中的META-INF目录下新建一个文件context.xml,

<?xml version='1.0' encoding='utf-8'?>
<Context path="/musicStore">

    <Resource
        name="jdbc/music"
        auth="Container"
        maxActive="100" maxIdle="30" maxWait="10000"
        username="root" password="root"
        driverClassName="com.mysql.jdbc.Driver"
        url="jdbc:mysql://localhost:3306/music?autoReconnect=true"
        logAbandoned="true"
        removeAbandoned="true"
        removeAbandonedTimeout="60"
        type="javax.sql.DataSource" />

    <Realm className="org.apache.catalina.realm.DataSourceRealm" debug="99"
        dataSourceName="jdbc/music" localDataSource="true"
        userTable="UserPass" userNameCol="Username" userCredCol="Password"
        userRoleTable="UserRole" roleNameCol="Rolename" />

</Context>

不知道 <Realm 这部分是干啥用的 --------------------编程问答-------------------- tomcat/conf 下的:

context.xml:

<Context>

<WatchedResource>WEB-INF/web.xml</WatchedResource>

<ResourceLink type="javax.sql.DataSource" name="jdbc/music" global="jdbc/music"/></Context>

server.xml:

<GlobalNamingResources>

<Resource validationQuery="SELECT 1" validationInterval="30000" username="root" url="jdbc:mysql://localhost:3306/music" type="javax.sql.DataSource" timeBetweenEvictionRunsMillis="30000" testWhileIdle="true" testOnReturn="false" testOnBorrow="true" removeAbandonedTimeout="60" removeAbandoned="true" password="poiu0000" name="jdbc/music" minIdle="10" minEvictableIdleTimeMillis="30000" maxWait="10000" maxActive="100" logAbandoned="true" jmxEnabled="true" jdbcInterceptors="org.apache.tomcat.jdbc.pool.interceptor.ConnectionState; org.apache.tomcat.jdbc.pool.interceptor.StatementFinalizer" initialSize="10" factory="org.apache.tomcat.jdbc.pool.DataSourceFactory" driverClassName="com.mysql.jdbc.Driver" auth="Container"/></GlobalNamingResources>
<Realm className="org.apache.catalina.realm.LockOutRealm">

<Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/></Realm> --------------------编程问答-------------------- 几个关于context.xml, server.xml, web.xml的问题：

１.文件太乱，用什么编辑比较好读？

２.tomcat/conf和自己PROJECT下都有，运行时都被调用吗？

３.好象运行时系统会去修改这些文件？

另外，如上错误不影响程序（包括数据库）运行，但WebServices好象走不下去

补充：Java ,  Java EE