Question

我创建了一个用于管理发送电子邮件的类，我想通过属性文件注入smtp配置。但是我的字段属性保持为null。这是我的代码：

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";
}

我用简单的Main测试了代码，但它不起作用。我用tomcat测试了它，并且仍然在Properties对象上获得了NPE。我错过了什么？请帮助：）

Answer 1

请考虑使用此Java EE方式：

如果使用Tomcat，请确保使用How to install and use CDI on Tomcat?或Application servers and environments supported by Weld中所述的CDI实施进行设置。
将JavaMail实现jar从您的应用程序的WEB-INF/lib移动到Tomcat lib目录。

通过在Tomcat的config/Context.xml文件中添加以下内容，在Tomcat中配置您的电子邮件会话：

<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>

还有其他地方可以使用此配置，但这是最简单的解释。有关详细信息，请参阅Tomcat JNDI documentation。

简化您的代码：

    @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);
        }
    }

您的服务器（本例中为Tomcat）负责为您配置邮件会话和身份验证。

类似的机制适用于设置JDBC DataSource对象FWIW。

Answer 2

使用PropertyReader和@Named为您的@ApplicationScoped课程添加注释，以使其知道CDI容器，以便对其进行管理。在课程路径中留空beans.xml。

@Inject属性在Tomcat上返回null

2 个答案: