java - 除了 main() 之外， Autowiring 的存储库在任何地方都是 null

Question

我可以从 main() 内部获取存储库功能，但不能在其他地方使用。

从我读到的所有内容来看，这似乎与我试图使用在 Spring 的“上下文”或“容器”之外创建的 @Autowired 成员有关。

其他人似乎想出的典型罪魁祸首与使用“new”创建一个最终超出 Spring 范围的对象有关，但我已尽我所能来确保所有依赖于@的东西Autowired 是 Spring 自己创建的。

我的 main() 方法中有以下简单的 oneOff() 方法，用于打印前 10 个名称，该方法在运行时按预期工作:

@SpringBootApplication
public class Application extends SpringBootServletInitializer {

    @Autowired
    private AppointmentServlet appointmentServlet;

    @Autowired
    private IAppointmentRepository appointmentRepository;

    @Autowired
    private IStaffMemberRepository staffMemberRepository;

    @Autowired
    private IStaffMemberRepository clientRepository;

    public static void main(String[] args) {
        ConfigurableApplicationContext context = SpringApplication.run(Application.class, args);
        Application app = context.getBean(Application.class);
        app.oneOff();
    }

    @Bean
    public ServletRegistrationBean servletRegistrationBean() {
        return new ServletRegistrationBean(appointmentServlet,     "/AppointmentManager/NextAppointment");
    }

    private void oneOff() {
        System.out.println("\n=================== Starting lookup ===================");
        try {

        int limit = 10;
        for (int i = 0; i < limit; i++) {
            StaffMember member = staffMemberRepository.findAll().get(i);
            String firstName = member.getFirstName();
            String lastName = member.getLastName();
            if (firstName == null || firstName.equals("UNKNOWN") || firstName.isEmpty()) {
                limit++;
                continue;
            }
            System.out.println("Staff member: " + firstName + " " + lastName);
        }
    } catch (NullPointerException ex) {
        System.out.println("NPE: Lookup failed");
    } System.out.println("==================== Ending lookup ===================");
}

}

产生:

=================== Starting lookup ===================
Staff member: JOSE  BEJARANO
Staff member: KARIMAH ABDUL-AZIZ
Staff member: CONNIE ABED
Staff member: WALID ABI-SAAB
Staff member: BARRY ABRAHAM
Staff member: JENNA ACEYCEK
Staff member: DANIEL ADAMCZ YK
Staff member: TYMOTEUSZ ADAMCZYK
Staff member: ELIZABETH ADAMS
Staff member: ERIN ADAMS
==================== Ending lookup ===================

但是，当我调用刚刚粘贴到我的 servlet 类中的重复方法时，存储库永远不会被实例化，并且我会得到 NullPointerExceptions。

Servlet 类:

@Component
public class AppointmentServlet extends SpeechletServlet {

    @Autowired
    private AppointmentSpeechlet appointmentSpeechlet;

    public AppointmentServlet() {
        this.setSpeechlet(appointmentSpeechlet);
    }

}

实际使用存储库的 Speechlet 类:

@Component
public class AppointmentSpeechlet implements Speechlet {

    @Autowired
    private IAppointmentRepository appointmentRepository;

    @Autowired
    private IStaffMemberRepository staffMemberRepository;

    @Autowired
    private IClientRepository clientRepository;

    @Override
    public SpeechletResponse onIntent(final IntentRequest request, final Session session) throws SpeechletException {
        oneOff();
    }
}

再次使用oneOff()方法:

private void oneOff() {
    System.out.println("\n=================== Starting lookup ===================");
    try {

    int limit = 10;
    for (int i = 0; i < limit; i++) {
        StaffMember member = staffMemberRepository.findAll().get(i);
        String firstName = member.getFirstName();
        String lastName = member.getLastName();
        if (firstName == null || firstName.equals("UNKNOWN") || firstName.isEmpty()) {
            limit++;
            continue;
        }
        System.out.println("Staff member: " + firstName + " " + lastName);
    }
    } catch (NullPointerException ex) {
        System.out.println("NPE: Lookup failed");
    } System.out.println("==================== Ending lookup ===================");
}

Answer 1

您已将 @Component 添加到您的 servlet 类中，但这并不使其成为 Spring 管理的 bean。事实上，servlet 容器(例如 Tomcat)实例化并管理 servlet 类的实例，并且它对 Spring 一无所知 - 因此您的 servlet 不是作为 Spring bean 创建的，因此 Autowiring 不起作用。

最好的解决方案是使用 Spring Web MVC并编写一个 @Controller 类，而不是编写您自己的 servlet。如果您不能这样做，您可以使用 WebApplicationContextUtils从 servlet 中查找 Spring 应用程序上下文，您可以在其中查找 Spring bean(而不是在 servlet 中 Autowiring 它们)。