Class ExceptionMappingInterceptor

java.lang.Object
org.apache.struts2.interceptor.AbstractInterceptor
org.apache.struts2.interceptor.ExceptionMappingInterceptor
All Implemented Interfaces:
Serializable, ConditionalInterceptor, Interceptor

public class ExceptionMappingInterceptor extends AbstractInterceptor

This interceptor forms the core functionality of the exception handling feature. Exception handling allows you to map an exception to a result code, just as if the action returned a result code instead of throwing an unexpected exception. When an exception is encountered, it is wrapped with an ExceptionHolder and pushed on the stack, providing easy access to the exception from within your result.

Note: While you can configure exception mapping in your configuration file at any point, the configuration will not have any effect if this interceptor is not in the interceptor stack for your actions. It is recommended that you make this interceptor the first interceptor on the stack, ensuring that it has full access to catch any exception, even those caused by other interceptors.

Interceptor parameters:

  • logEnabled (optional) - Should exceptions also be logged? (boolean true|false)
  • logLevel (optional) - what log level should we use (trace, debug, info, warn, error, fatal)? - defaut is debug
  • logCategory (optional) - If provided we would use this category (eg. com.mycompany.app). Default is to use ExceptionMappingInterceptor.

The parameters above enables us to log all thrown exceptions with stacktace in our own logfile, and present a friendly webpage (with no stacktrace) to the end user.

Extending the interceptor:

If you want to add custom handling for publishing the Exception, you may override publishException(org.apache.struts2.ActionInvocation, ExceptionHolder). The default implementation pushes the given ExceptionHolder on value stack. A custom implementation could add additional logging etc.

Example code:

 
 <xwork>
     <package name="default" extends="xwork-default">
         <global-results>
             <result name="error" type="freemarker">error.ftl</result>
         </global-results>

         <global-exception-mappings>
             <exception-mapping exception="java.lang.Exception" result="error"/>
         </global-exception-mappings>

         <action name="test">
             <interceptor-ref name="exception"/>
             <interceptor-ref name="basicStack"/>
             <exception-mapping exception="com.acme.CustomException" result="custom_error"/>
             <result name="custom_error">custom_error.ftl</result>
             <result name="success" type="freemarker">test.ftl</result>
         </action>
     </package>
 </xwork>
 
 

This second example will also log the exceptions using our own category com.mycompany.app.unhandled at WARN level.

 
 <xwork>
   <package name="something" extends="xwork-default">
      <interceptors>
          <interceptor-stack name="exceptionmappingStack">
              <interceptor-ref name="exception">
                  <param name="logEnabled">true</param>
                  <param name="logCategory">com.mycompany.app.unhandled</param>
                  <param name="logLevel">WARN</param>
              </interceptor-ref>
              <interceptor-ref name="i18n"/>
              <interceptor-ref name="staticParams"/>
              <interceptor-ref name="params"/>
              <interceptor-ref name="validation">
                  <param name="excludeMethods">input,back,cancel,browse</param>
              </interceptor-ref>
          </interceptor-stack>
      </interceptors>

      <default-interceptor-ref name="exceptionmappingStack"/>

      <global-results>
           <result name="unhandledException">/unhandled-exception.jsp</result>
      </global-results>

      <global-exception-mappings>
           <exception-mapping exception="java.lang.Exception" result="unhandledException"/>
      </global-exception-mappings>

      <action name="exceptionDemo" class="org.apache.struts2.showcase.exceptionmapping.ExceptionMappingAction">
          <exception-mapping exception="org.apache.struts2.showcase.exceptionmapping.ExceptionMappingException"
                             result="damm"/>
          <result name="input">index.jsp</result>
          <result name="success">success.jsp</result>
          <result name="damm">damm.jsp</result>
      </action>

   </package>
 </xwork>
 
 
Author:
Matthew E. Porter (matthew dot porter at metissian dot com), Claus Ibsen
See Also:
  • Field Details

    • categoryLogger

      protected org.apache.logging.log4j.Logger categoryLogger
    • logEnabled

      protected boolean logEnabled
    • logCategory

      protected String logCategory
    • logLevel

      protected String logLevel
  • Constructor Details

    • ExceptionMappingInterceptor

      public ExceptionMappingInterceptor()
  • Method Details

    • isLogEnabled

      public boolean isLogEnabled()
    • setLogEnabled

      public void setLogEnabled(boolean logEnabled)
    • getLogCategory

      public String getLogCategory()
    • setLogCategory

      public void setLogCategory(String logCatgory)
    • getLogLevel

      public String getLogLevel()
    • setLogLevel

      public void setLogLevel(String logLevel)
    • intercept

      public String intercept(ActionInvocation invocation) throws Exception
      Description copied from class: AbstractInterceptor
      Override to handle interception
      Specified by:
      intercept in interface Interceptor
      Specified by:
      intercept in class AbstractInterceptor
      Parameters:
      invocation - the action invocation
      Returns:
      the return code, either returned from ActionInvocation.invoke(), or from the interceptor itself.
      Throws:
      Exception - any system-level error, as defined in Action.execute().
    • handleLogging

      protected void handleLogging(Exception e)
      Handles the logging of the exception.
      Parameters:
      e - the exception to log.
    • doLog

      protected void doLog(org.apache.logging.log4j.Logger logger, Exception e)
      Performs the actual logging.
      Parameters:
      logger - the provided logger to use.
      e - the exception to log.
    • findMappingFromExceptions

      protected ExceptionMappingConfig findMappingFromExceptions(List<ExceptionMappingConfig> exceptionMappings, Throwable t)
      Try to find appropriate ExceptionMappingConfig based on provided Throwable
      Parameters:
      exceptionMappings - list of defined exception mappings
      t - caught exception
      Returns:
      appropriate mapping or null
    • getDepth

      public int getDepth(String exceptionMapping, Throwable t)
      Return the depth to the superclass matching. 0 means ex matches exactly. Returns -1 if there's no match. Otherwise, returns depth. Lowest depth wins.
      Parameters:
      exceptionMapping - the mapping classname
      t - the cause
      Returns:
      the depth, if not found -1 is returned.
    • publishException

      protected void publishException(ActionInvocation invocation, ExceptionHolder exceptionHolder)
      Default implementation to handle ExceptionHolder publishing. Pushes given ExceptionHolder on the stack. Subclasses may override this to customize publishing.
      Parameters:
      invocation - The invocation to publish Exception for.
      exceptionHolder - The exceptionHolder wrapping the Exception to publish.