@Inject properties returns null on Tomcat

Question

I create a class to manage sending emails and i want to inject smtp config via properties file. But i keep got null on my field properties. This is my code:

public class EmailUtils { 
    @Inject
    @PropertiesFromFile("smtp.properties")
    Properties properties;

    public void sendEmail(String destinator, String subject, String body) {
        final String username = properties.getProperty("smtp.email");
        final String password = properties.getProperty("smtp.password");

        Session session = Session.getInstance(properties,
          new javax.mail.Authenticator() {
            protected PasswordAuthentication getPasswordAuthentication() {
                return new PasswordAuthentication(username, password);
            }
          });

        try {

            Message message = new MimeMessage(session);
            message.setFrom(new InternetAddress(properties.getProperty("smtp.from")));
            message.setRecipients(Message.RecipientType.TO,
                InternetAddress.parse(destinator));
            message.setSubject(subject);
            message.setText(body);

            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
   }
}

public class PropertyReader {

    @Produces
    @PropertiesFromFile
    public Properties provideServerProperties(InjectionPoint ip) {
    //get filename from annotation
    String filename = ip.getAnnotated().getAnnotation(PropertiesFromFile.class).value();
    return readProperties(filename);
}

    private Properties readProperties(String fileInClasspath) {
        InputStream is = this.getClass().getClassLoader().getResourceAsStream(fileInClasspath);

        try {
            Properties properties = new Properties();
            properties.load(is);
            return properties;
       } catch (IOException e) {
           System.err.println("Could not read properties from file " + fileInClasspath + " in classpath. " + e);
       } catch (Exception e) {
           System.err.println("Exception catched:"+ e.getMessage());
       } 

       return null;
   }
}

@Qualifier
@Target({METHOD, FIELD})
@Retention(RUNTIME)
public @interface PropertiesFromFile {
    @Nonbinding
    String value() default "application.properties";
}

I tested the code with a simple Main, but it doesn't work. I tested it with tomcat and still got NPE on Properties object. I missed something ? Please help :)

Are both of your classes are managed beans ? Injection and producers only work in managed contexts. — Dimpre Jean-Sébastien, Sep 09 '17 at 06:06
hi Dimpre, should i annotated them ? there were no annotations on the tutorials that i read. — Khairy, Sep 09 '17 at 06:25
Tomcat has official distribution with EE technologies, TomEE, few version exists. Very good, and compatible with 'classic' Tomcat — Jacek Cz, Sep 09 '17 at 09:39

Steve C · Accepted Answer · 2017-09-11T08:26:05.087

Please consider doing this Java EE way:

If using Tomcat then ensure that you have set it up with a CDI implementation as described in How to install and use CDI on Tomcat? or Application servers and environments supported by Weld.
Move the JavaMail implementation jars from your application's WEB-INF/lib to the Tomcat lib directory.

Configure your email session in Tomcat by adding the following to it's config/Context.xml file:

<Context>
    ...
    <Resource name="mail/Session" auth="Container"
      type="javax.mail.Session"
      mail.smtp.host="your mail host here"
      mail.smtp.user="your user name here"
      password="your password"
      mail.from="noreply@yourdomain.com" />
    ...
</Context>

There are other places to put this configuration but this is the simplest to explain here. Refer to the Tomcat JNDI documentation for more information.

Simplify your code:

    @Resource(name="mail/Session")
    private Session session;

    public void sendEmail(String destinator, String subject, String body) {
        try {

            Message message = new MimeMessage(session);
            message.setRecipients(Message.RecipientType.TO,
                    InternetAddress.parse(destinator));
            message.setSubject(subject);
            message.setText(body);

            Transport.send(message);

            System.out.println("Done");

        } catch (MessagingException e) {
            throw new RuntimeException(e);
        }
    }

Your server (Tomcat in this case) looks after configuring the mail session and authentication for you.

A similar mechanism applies to setting up JDBC DataSource objects FWIW.

Thank you Steve,I use maven3 to manage dependencies, is there another way to solve the issues ? — Khairy, Sep 10 '17 at 10:38
At the very least you need to get CDI working in Tomcat. Step 1 gives you pointers for that. Life would be easier for you if you used Tomee, WildFly or Payara servers though.Then you could ignore step 1. — Steve C, Sep 10 '17 at 13:36

score 2 · Answer 2 · answered Sep 19 '17 at 21:14

2

Annotate your PropertyReader class with @Named and @ApplicationScoped to make it known to the CDI Container so it can be managed. Have a blank beans.xml in your class path.

answered Sep 19 '17 at 21:14

Ndumiso

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@Inject properties returns null on Tomcat

2 Answers2