Grails log4j SMTPAppender NoClassDefFoundError

Question

How do I configure SMTPAppender in a new Grails 2.4.5 project? I receive a NoClassDefFoundError when running in the development environment:

| Error log4j:ERROR Error initializing log4j: javax/mail/Message

| Error java.lang.NoClassDefFoundError: javax/mail/Message

Gist: Detailed stacktrace

I have configured a dependency for javax.mail and configured log4j as follows:

dependencies {
    provided 'javax.mail:mail:1.4.7'
}

log4j = {
    appenders {
        appender new org.apache.log4j.net.SMTPAppender(
            name: 'smtp',
            layout: pattern(conversionPattern: '%d{MM-dd-yyyy HH:mm:ss.SSS} [%t] %c %M %x%n%p: %m%n')
            to: '[email protected]',
            from: '[email protected]',
            subject: 'Grails Message',
            SMTPHost: '127.0.0.1')
        )
    }
}

GitHub: Example Project

Answer 1

I know this post is old, but I struggled with the same till I found a solution that is at least working for me (not with SMTPAppender but with Sentry - same purpose).

The explanation I found with the errors you where receiving

Error log4j:ERROR Error initializing log4j: javax/mail/Message

Error java.lang.NoClassDefFoundError: javax/mail/Message

Come from this piece of code:

dependencies {
    provided 'javax.mail:mail:1.4.7'
}

The thing is that when you compile things work, when you try to do grails run-app you receive this error.

The explanation I found is that the log4j initializes before the maven dependency is resolved.

I wrote a comment of how I've used Sentry as an appender. https://github.com/getsentry/raven-java/issues/184#issuecomment-259432057

Basically, instead of adding the maven dependency I've downloaded the java file, and added it to the grails project in src/java

So for Sentry por example I added the SentryAppender.java to my.package.sentry so then in log4j I added:

  appenders {
    environments {
        // This block is set up to use the stock raven SentryAppender in
        // production. Sentry Appender runs into all kinds of
        // class loading weirdness when used in a forked grails environment
        production {
            appender new my.package.sentry.SentryAppender(
                name: 'sentry',
                dsn: 'REDACTED',                
                threshold: org.apache.log4j.Level.WARN
            )
        }

        // Uncomment this block if you need to test sentry
        // in a dev environment
        development {
            appender new my.package.sentry.SentryAppender(
                name: 'sentry',
                dsn: 'REDACTED',                
                threshold: org.apache.log4j.Level.WARN
            )
        }
    }    

  }

  root {
    warn 'stdout', 'sentry'
    error 'stdout', 'sentry'
    additivity = false
  }

in that way, it does not depend on an external dependency.

I guess that you could do something similar to the mail dependency and add the java files to the src folder.

I hope it helps!