关于eclipse中出现Cannot create JDBC driver of class '' for connect URL 'null'

eclipse中出现这个问题

应该去新增的server下面的context.xml中配置
<WatchedResource>WEB-INF/web.xml</WatchedResource>

<Resource
name="jdbc/donghuaDB"
auth="Container"
type="javax.sql.DataSource"
maxActive="100"
maxIdle="30"
maxWait="10000"
username="guolv"
password="guolvpassword"
driverClassName="oracle.jdbc.OracleDriver"
url="jdbc:oracle:thin:@172.16.5.162:1521:phonedb"/>

注意观察下web.xml下面配置的连接

<resource-ref>
<res-ref-name>jdbc/donghuaDB</res-ref-name>
<res-type>javax.sql.DataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>