How to send an email from jsp/servlet?

The mailer logic should go in its own standalone class which you can reuse everywhere. The JSP file should contain presentation logic and markup only. The Servlet class should just process the request the appropriate way and call the mailer class. Here are the steps which you need to take:

1. First decide which SMTP server you’d like to use so that you would be able to send emails. The one of your ISP? The one of Gmail? Yahoo? Website hosting provider? A self-maintained one? Regardless, figure the hostname, port, username and password of this SMTP server. You’re going to need this information.

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2. Create a plain vanilla Java class which uses JavaMail API to send a mail message. The JavaMail API comes with an excellent tutorial and FAQ. Name the class Mailer and give it a send() method (or whatever you want). Test it using some tester class with a main() method like this:

   public class TestMail {
       public static void main(String... args) throws Exception {
           // Create mailer.
           String hostname = "smtp.example.com";
           int port = 2525;
           String username = "nobody";
           String password = "idonttellyou";
           Mailer mailer = new Mailer(hostname, port, username, password);
   
           // Send mail.
           String from = "[email protected]";
           String to = "[email protected]";
           String subject = "Interesting news";
           String message = "I've got JavaMail to work!";
           mailer.send(from, to, subject, message);
       }
   }
   

   You can make it as simple or advanced as you want. It doesn’t matter, as long as you have a class with which you can send a mail like that.

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3. Now the JSP part, it’s not entirely clear why you mentioned JSP, but since a JSP is supposed to represent only HTML, I bet that you’d like to have something like a contact form in a JSP. Here’s a kickoff example:

   <form action="contact" method="post">
       <p>Your email address: <input name="email"></p>
       <p>Mail subject: <input name="subject"></p>
       <p>Mail message: <textarea name="message"></textarea></p>
       <p><input type="submit"><span class="message">${message}</span></p>
   </form>
   

   Yes, plain simple, just markup/style it whatever way you want.

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4. Now, create a Servlet class which listens on an url-pattern of /contact (the same as the form is submitting to) and implement the doPost() method (the same method as the form is using) as follows:

   public class ContactServlet extends HttpServlet {
       private Mailer mailer;
       private String to;
   
       public void init() {
           // Create mailer. You could eventually obtain the settings as
           // web.xml init parameters or from some properties file.
           String hostname = "smtp.example.com";
           int port = 2525;
           String username = "nobody";
           String password = "forgetit";
           this.mailer = new Mailer(hostname, port, username, password);
           this.to = "[email protected]";
       }
   
       protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
           String email = request.getParameter("email");
           String subject = request.getParameter("subject");
           String message = request.getParameter("message");
           // Do some validations and then send mail:
   
           try {
               mailer.send(email, to, subject, message);
               request.setAttribute("message", "Mail succesfully sent!");
               request.getRequestDispatcher("/WEB-INF/contact.jsp").forward(request, response);
           } catch (MailException e) {
               throw new ServletException("Mailer failed", e);
           }
       }
   }
   

   That’s it. Keep it simple and clean. Each thing has its own clear responsibilities.