Singleton类中的邮件会话

Question

将邮件会话(javax.mail.Session)存储在单例中是一种很好的做法吗？我和我的团队决定在Singleton类中的一个静态变量中保留一个邮件会话.

所以,在私有构造函数中,我们这样做:

try {
        Properties props = new Properties();

        props.put("mail.transport.protocol", config.getMailTransportProtocol());
        props.put("mail.smtp.starttls.enable", config.getMailStarttlsEnable());
        props.put("mail.smtp.host", config.getMailHost());
        props.put("mail.smtp.auth", config.getMailAuth());
        props.put("mail.smtp.user", config.getMailFrom());
        props.put("mail.debug", config.getMailDebug());
        props.put("mail.smtp.port", config.getMailPort());
        props.put("mail.smtp.socketFactory.port", config.getMailPort());
        props.put("mail.smtp.socketFactory.class", config.getMailSocketFactoryClass());
        props.put("mail.smtp.socketFactory.fallback", config.getMailSocketFactoryFallback());

        props.put("mail.pop3.host", config.getMailPop3Host());
        props.put("mail.store.protocol", config.getMailStoreProtocol());

        SimpleAuth auth = new SimpleAuth(config.getMailUser(), config.getMailPass());

        MailSession.session = Session.getDefaultInstance(props, auth);
        session.setDebug(config.getMailDebug());
    } catch (Throwable ex) {
        System.err.println("Initial MailSession creation failed." + ex);
        throw new ExceptionInInitializerError(ex);
    }

但我担心最好是保持这样,还是为每封电子邮件打开和关闭一个会话.

Answer 1

首先,您需要阅读有关常见错误的 JavaMail FAQ条目.

如果您阅读了Session.getDefaultInstance方法的javadoc,您将看到JavaMail已经为您维护了一个单例会话.如果您从未更改会话的配置,这可能对您有用,尽管我通常建议不要这样做.