Alternative 2: Configuring JavaMail with JNDI

Server JNDI configuration (using Tomcat 6 as an example)

First you will need to expose a JavaMail session factory through JNDI in your server environment. This is environment-dependent, but let's look at an example.

Say you're using Tomcat 6. There are a couple things you must do. First, move mail.jar and activation.jar to your tomcat/lib directory. I say "move" rather than "copy" because you will get an odd error if you leave the two JARs in your application classpath. The error is

java.lang.IllegalArgumentException: 
    Cannot convert value of type [javax.mail.Session] to required type
    [javax.mail.Session] for property 'session': no matching editors
    or conversion strategy found

Second, define your Tomcat JNDI configuration, which might look like this (e.g. in your context.xml file):

<?xml version="1.0" encoding="UTF-8"?>

<Context path="/myapp" docBase="myapp" debug="5" crossContext="false">

    <!-- JavaMail session factory -->
    <Resource name="mail/Session"
              auth="Container"
              type="javax.mail.Session"
              username="yourusername"
              password="yourpassword"
              mail.debug="true"
              mail.user="yourusername"
              mail.password="yourpassword"
              mail.transport.protocol="smtp"
              mail.smtp.host="your.smtphost.com"
              mail.smtp.auth="true"
              mail.smtp.port="25"
              mail.smtp.starttls.enable="true"/>
</Context>

As with the non-JNDI example, I'm configuring for SMTP-AUTH and TLS. If you are using SMTP-AUTH (authenticated SMTP sessions, which you activate using mail.smtp.auth="true"), then you will need to specify the username and password twice, as shown above. Also, if your SMTP server supports it, you can tell JavaMail to encrypt sessions using TLS by setting mail.smtp.starttls.enable=true.

The above discussion applies only to Tomcat 6 (see Apache Tomcat 6.0 JNDI Resources HOWTO for detailed instructions); you'll need to consult your server docs to expose a JavaMail session factory through JNDI in your environment.

Spring configuration

We still need to create a mail sender, but the configuration is simpler since we did all the heavy lifting in context.xml (or whatever, depending on your server environment). So for the Spring application context, all we need is:

<bean id="mailSender" class="org.springframework.mail.javamail.JavaMailSenderImpl">
    <property name="session" ref="mailSession"/>
</bean>

IMPORTANT: As before, you will need to inject mailSender into your mail-sending service bean.

So that takes care of configuring the mail sender, and also the JavaMail session factory if you are using JNDI. Let's visit one more topic before we dive into the code itself.