配置了derby数据库后启动tomcat 服务报错
在本应用中由于是以derby数据库作为数据存储，采用网络连接方式连接derby，在启动tomcat 服务是进行一些数据库的初始化工作，比如创建表之类的。
所以就特地创建了一个servlet 去做这些初始化工作。
在web.xml中配置如下：
<web-app>
...
<servlet>
<servlet-name>derbynet</servlet-name>
<servlet-class>org.apache.derby.drda.NetServlet</servlet-class>
<init-param>
<param-name>startNetworkServerOnInit</param-name>
<param-value>true</param-value>
<description>Starts the Network Server at servlet
initialization if 'true'. </description>
</init-param>
<init-param>
<param-name>portNumber</param-name>
<param-value>1527</param-value>
<description>Port number to use. The default is 1527.</description>
</init-param>
<init-param>
<param-name>host</param-name>
<param-value>localhost</param-value>
<description> Host Name to use. The default is "localhost". Please secure any server which listens on a public address. </description>
</init-param>
<init-param>
<param-name>tracingDirectory</param-name>
<param-value />
<description>Directory where trace files should be placed. </description>
</init-param>
<load-on-startup>true</load-on-startup>
</servlet>
<servlet>
<servlet-name>InitializeDatabase</servlet-name>
<servlet-class>com.sap.pf.prp.servlet.InitializeDatabase</servlet-class>
<load-on-startup>0</load-on-startup>
</servlet>
...
</web-app>
一切妥当之后，在eclipse下启动tomcat 服务，一切正常。
但是当我启动tomcat目录下的startup.bat时，就报错了，信息如下：
java.sql.SQLNonTransientConnectionException: java.net.ConnectException : Error c
onnecting to server localhost on port 1527 with message Connection refused: conn
ect.
at org.apache.derby.client.am.SQLExceptionFactory40.getSQLException(Unkn
own Source)
at org.apache.derby.client.am.SqlException.getSQLException(Unknown Sourc
e)
at org.apache.derby.jdbc.ClientDriver.connect(Unknown Source)
at java.sql.DriverManager.getConnection(DriverManager.java:582)
at java.sql.DriverManager.getConnection(DriverManager.java:185)
at com.sap.pf.prp.db.DBManager.getConnection(DBManager.java:56)
at com.sap.pf.prp.db.DBManager.initDB(DBManager.java:27)
at com.sap.pf.prp.servlet.InitializeDatabase.init(InitializeDatabase.jav
a:13)
at javax.servlet.GenericServlet.init(GenericServlet.java:212)
at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.
java:1139)
at org.apache.catalina.core.StandardWrapper.load(StandardWrapper.java:96
6)
at org.apache.catalina.core.StandardContext.loadOnStartup(StandardContex
t.java:3956)
at org.apache.catalina.core.StandardContext.start(StandardContext.java:4
230)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014)
at org.apache.catalina.core.StandardHost.start(StandardHost.java:736)
at org.apache.catalina.core.ContainerBase.start(ContainerBase.java:1014)
at org.apache.catalina.core.StandardEngine.start(StandardEngine.java:443
)
at org.apache.catalina.core.StandardService.start(StandardService.java:4
48)
at org.apache.catalina.core.StandardServer.start(StandardServer.java:700
)
at org.apache.catalina.startup.Catalina.start(Catalina.java:552)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.
java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAcces
sorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:295)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:433)
Caused by: org.apache.derby.client.am.DisconnectException: java.net.ConnectExcep
tion : Error connecting to server localhost on port 1527 with message Connection
refused: connect.
at org.apache.derby.client.net.NetAgent.<init>(Unknown Source)
at org.apache.derby.client.net.NetConnection.newAgent_(Unknown Source)
at org.apache.derby.client.am.Connection.<init>(Unknown Source)
at org.apache.derby.client.net.NetConnection.<init>(Unknown Source)
at org.apache.derby.client.net.NetConnection40.<init>(Unknown Source)
at org.apache.derby.client.net.ClientJDBCObjectFactoryImpl40.newNetConne
ction(Unknown Source)
... 24 more
Caused by: java.net.ConnectException: Connection refused: connect
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
at java.net.Socket.connect(Socket.java:529)
at java.net.Socket.connect(Socket.java:478)
at java.net.Socket.<init>(Socket.java:375)
at java.net.Socket.<init>(Socket.java:189)
at javax.net.DefaultSocketFactory.createSocket(SocketFactory.java:206)
at org.apache.derby.client.net.OpenSocketAction.run(Unknown Source)
at java.security.AccessController.doPrivileged(Native Method)
... 30 more
Feb 11, 2015 1:34:10 PM org.apache.coyote.http11.Http11BaseProtocol start
INFO: Starting Coyote HTTP/1.1 on http-80
在网上搜了好一阵子，都没有找到真正的解决办法。
https://db.apache.org/derby/docs/10.4/adminguide/tadmincbdjhhfd.html
http://db.apache.org/derby/papers/DerbyTut/ns_intro.html
http://stackoverflow.com/questions/10420902/data-sources-derby-connection-refused
最后经过仔细的排查，发现其实是我自己的web.xml配置中【servlet启动优先级设置】的问题。
只需要将derbynet中：
<load-on-startup>true</load-on-startup> =====> <load-on-startup>0</load-on-startup>
再将初始化数据库的那个servlet的load-on-startup 改为1 即：
<load-on-startup>0</load-on-startup> ====> <load-on-startup>1</load-on-startup>
改完了之后重新发布启动tomcat，一切正常。