Using log4j to send email reports via the SMTPAppender

Question

I\'m trying to use log4j to send emailable reports that contain the logging statements from a background process. I want one email sent for each process run, not one email

Answer 1

Log4j 2.x onwards, the following configuration for log4j.xml can be used. It's pretty straightforward and can be used to send emails.

You need to edit it and enter your smtp host, username, password, port and subject.

<?xml version="1.0" encoding="UTF-8"?>
<Configuration status="WARN">
    <Appenders>

        <SMTP>
            <name>Mail1</name>
            <subject>SUBJECT</subject>
            <to>TO_EMAIL</to>
            <from>FROM_EMAIL</from>
            <smtpHost>smtp.gmail.com</smtpHost>
            <smtpPort>487</smtpPort>
            <ignoreExceptions>false</ignoreExceptions>
            <smtpUsername>username</smtpUsername>
            <smtpPassword>password</smtpPassword>
            <smtpProtocol>smtps</smtpProtocol>
            <HtmlLayout charset="UTF-8" locationInfo="true" />
            <ThresholdFilter level="ERROR"/>
        </SMTP>
    </Appenders>
    <Loggers>
        <Root level="INFO">
            <AppenderRef ref="Mail1"/>
        </Root>
    </Loggers>
</Configuration>

Reference: Log4j SMTP Appender

Answer 2

You shouldn't use any of log4j's methods, you should configure it properly instead.

First of all, define in your log4j.properties file your appender properly:

#CONFIGURE SMTP
log4j.appender.email=org.apache.log4j.net.SMTPAppender
log4j.appender.email.SMTPHost=mail.mydomain.com
log4j.appender.email.SMTPUsername=myuser@mydomain.com
log4j.appender.email.SMTPPassword=mypw
log4j.appender.email.From=myuser@mydomain.com
log4j.appender.email.To=myuser@mydomain.com
log4j.appender.email.Subject=Log of messages
log4j.appender.email.BufferSize=1
log4j.appender.email.EvaluatorClass=TriggerLogEvent
log4j.appender.email.layout=org.apache.log4j.PatternLayout
log4j.appender.email.layout.ConversionPattern=%m

Note: code taken from this post. More information can be obtained in SMTPAppender API.

Next, make a special class that will be used just for sending email. Example:

package com.foo.mailer;
import org.apache.log4j.Logger;

public class Mailer {
   private static final Logger logger = Logger.getLogger(Mailer.class);

   public void logMail(String mailString) {
      logger.info(mailString);
   }
}

Next, put in log4j.properties configuration for this class:

# INFO level will be logged
log4j.logger.com.foo.mailer = INFO, email
# turn off additivity
log4j.additivity.com.foo.mailer = false

Now, whenever you want to send an email using log4j, put this in your code:

new Mailer().logMail("This mail should be sent");

Disclaimer: I haven't tested any of this code.

Answer 3

If you are using an XML configuration file, the following should be helpful.

<appender name="ErrorEmailAppender" class="org.apache.log4j.net.SMTPAppender">
    <param name="SMTPHost" value="mail.mydomain.com" />
    <param name="SMTPUsername" value="myuser@mydomain.com" />
    <param name="SMTPPassword" value="password" />
    <param name="From" value="myuser@mydomain.com" />
    <param name="To" value="myuser@mydomain.com" />
    <param name="Subject" value="Log of messages" />
    <param name="BufferSize" value="1" />
    <param name="EvaluatorClass" value="TriggerLogEvent" />
    <layout class="org.apache.log4j.PatternLayout">
        <param name="ConversionPattern" value="%t %m%n"/>
    </layout>
</appender>

<logger name="com.foo.mailer">
    <level value="INFO" />
    <appender-ref ref="ErrorEmailAppender"/>
</logger>