Error trapping for a missing data source in a Spring MVC / Spring JDBC web app [migrated]
- by Geeb
I have written a web app that uses Spring MVC libraries and Spring JDBC to connect to an Oracle DB. (I don't use any ORM type libraries as I create stored procedures on Oracle that do my stuff and I'm quite happy with that.)
I use a connection pool to Oracle managed by the Tomcat container
The app generally works absolutely fine by the way!
BUT...
I noticed the other day when I tried to set up the app on another Tomcat instance that I had forgotten to configure the connection pool and obviously the app could not get hold of an org.apache.commons.dbcp.BasicDataSource object, so it crashed.
I define the pool params in the tomcat "context.conf"
In my "web.xml" I have:
<servlet>
<servlet-name>appServlet</servlet-name>
<servlet-class>org.springframework.web.servlet.DispatcherServlet</servlet-class>
<init-param>
<param-name>contextConfigLocation</param-name>
<param-value>/WEB-INF/Spring/appServlet/servlet-context.xml</param-value>
</init-param>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>appServlet</servlet-name>
<!-- Map *everything* to appServlet -->
<url-pattern>/</url-pattern>
</servlet-mapping>
<resource-ref>
<description>Oracle Datasource example</description>
<res-ref-name>jdbc/ora1</res-ref-name>
<res-type>org.apache.commons.dbcp.BasicDataSource</res-type>
<res-auth>Container</res-auth>
</resource-ref>
And I have a Spring "servlet-context.xml" where JNDI is used to map the data source object provided by the connection pool to a Spring bean with the ID of "dataSource":
<jee:jndi-lookup id="dataSource" jndi-name="java:comp/env/jdbc/ora1"
resource-ref="true" />
Here's the question: Where do I trap the case where the database cannot be accessed for whatever reason?
I don't want the user to see a yard-and-a-half of Java stack trace in their browser, rather a nicer message that tells them there is a database problem etc.
It seems that my app tries to configure the "dataSource" bean (in "servlet-context.xml") before any code has tested it can actually provide a dataSource object from the pool?!
Maybe I'm not fully understanding exactly what is going on in these stages of the app firing up ...
Thanks for any advice!
