Using Mailgun with Groovy in Heroku

EmailService.groovy

import org.apache.http.*
import org.apache.http.entity.*
import org.apache.http.client.*
import org.apache.http.client.methods.*
import org.apache.http.impl.client.*
import org.apache.http.params.*
import org.codehaus.groovy.grails.plugins.codecs.URLCodec

/** Uses MailGun to send emails. */
class EmailService {

	static API_KEY = System.env.MAILGUN_API_KEY

    def sendEmail(to, subject, text) {
		final codec = URLCodec.newInstance()
		Object.metaClass."encodeAsURL" = { -> codec.encode(delegate) }
		Object.metaClass."decodeURL" = { -> codec.decode(delegate) }
		
		def url = 'https://api.mailgun.net/v2/your-app.mailgun.org/messages'
		def params = [from: "you@email.com", to: to, subject: subject, text: text]
		def httpclient = new DefaultHttpClient()
		def post = new HttpPost(url);
		def creds = new UsernamePasswordCredentials('api', API_KEY)
		post.addHeader(BasicScheme.authenticate(creds, "US-ASCII", false));
		post.addHeader("Content-Type", "application/x-www-form-urlencoded");
		def list = []
		params.each {k,v -> list << "${k}=${v.encodeAsURL()}" }
		post.entity = new StringEntity(list.join('&'))
		def response = httpclient.execute(post);
		response
    }
}

import org.apache.http.auth.UsernamePasswordCredentials
import org.apache.http.impl.auth.BasicScheme