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Monday, August 02, 2010

Grails Exception Handling with HTTP Status Code, URLMapping, and Email

The post describes how to:

1. Configure the UrlMapping.groovy to allow custom action on the specific http status code.
2. Display a customised "https status code handling page" to the user.
3. Send customised "https status code handling page" as an email to the admin staff if the admin email is configured in the Config.groovy file.

1. Configure the UrlMapping.groovy

class UrlMappings {
  static mappings {
    "403" (controller: "error", action: "forbidden")
    "404" (controller: "error", action: "notFound")
    "500" (controller: "error", action: "internalError")
  }
}


So any page status with 500 will be handled by the internalError action in the error controller.

Individual exceptions can be also configured in the response code to give more fine grained level control

"500" (controller: "error", action: "nullPointer", exception: NullPointerException)
  "500" (controller: "error", action: "illegalArgument", exception: IllegalArgumentException)

This allows any NullPointerException with 500 http status code to be handled by nullPointer action of error controller.


2. Display a customised "https status code handling page" to the user.

There are two properties available to the exception handling page. These properties are: exception and request. So you can copy the default error.gsp in the grails-app/view folder to a new file which is specified in the UrlMapping.groovy (i.e. error/internalError.gsp) and modified it to your needs.

...
Error ${request.'javax.servlet.error.status_code'}: ${request.'javax.servlet.error.message'.encodeAsHTML()}

Servlet: ${request.'javax.servlet.error.servlet_name'}

URI: ${request.'javax.servlet.error.request_uri'}

...

  

Stack Trace

${it.encodeAsHTML()}
...

The error page is as below:



3. Send customised "https status code handling page" as an email to the admin staff

The grails mail plugin is required to fulfil this requirement. Please refer to the Grail Mail plugin documentation

The following sending email code needs to be placed in the relevant action specified in the UrlMapping.groovy file.

import org.codehaus.groovy.grails.commons.ConfigurationHolder

class ErrorController {

  def mailService // mailService is provided by the grails mail plugin
 
  def index = { }
    
  def internalError = {
    // admin email is specified in the Config.groovy file
    // An email will be sent to the admin person whenever an internalError occurred. 
    def adminEmail = ConfigurationHolder.config.admin.email 
    try {
      mailService.sendMail {
 multipart true
 to adminEmail
 subject "500 Error"
 body (view: "/email/error")
      }
    }
    catch (Exception e) {
      log.info e
    }
  }
    
  def notFound = {}
}

The exception and request properties in the exception handling page are also available in the email template page. Thus the default error.gsp can be also copied to email template page (i.e. grails-app/email/error.gsp) and modified to your needs.

The error email is as below:

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