When an error happens in a web application a stack trace is shown to the user. How to avoid this and show a beautiful error page while logging internally the error that happened? Use the Struts exception handler.

Add the following code to your struts-config.xml. If you don’t want to show different error messages you only need that exception with type=”java.lang.Exception”. The other ones are to show different error messages using Spring exception hierarchy.

  <global-exceptions>
    <exception key="errors.optimistic.locking.failure" path=".error"
               type="org.springframework.dao.OptimisticLockingFailureException"/>
    <exception key="errors.data.access.resource.failure" path=".error"
               type="org.springframework.dao.DataAccessResourceFailureException"/>
    <exception key="errors.data.retrieval.failure" path=".error"
               type="org.springframework.dao.DataRetrievalFailureException"/>
    <exception key="errors.data.access" path=".error"
               type="org.springframework.dao.DataAccessException"/>
    <exception key="errors.transaction" path=".error"
               type="org.springframework.transaction.TransactionException"/>
    <exception key="errors.unknown" path=".error"
               type="java.lang.Exception"/>
  </global-exceptions>

• errors.optimistic.locking.failure=The object was already modified
• errors.data.access.resource.failure=Can’t connect to the database
• errors.data.retrieval.failure=The object you try to access doesn’t exist
• errors.data.access=Data access error
• errors.transaction=Transaction error
• errors.unknown=Unknown error

If you’re using log4j for logging add to your log4j.properties

log4j.rootLogger=ERROR, stdout
log4j.logger.org.apache.struts.action.ExceptionHandler=DEBUG, stdout

# Console output...
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] - %m%n

This way the stack traces are logged to standard output (in Tomcat this is logged to logs/stdout.txt)