独立的Java应用程序，在Spring Application Context中没有创建bean吗？ （IntelliJ，JavaConfig）

Question

I am new to Spring so I've no doubt I've probably overlooked something simple. I am making a standalone application using Spring to aid with dependency injection and AOP.

The problem is none of the beans are available in the spring application context when I run the application. The bean I want to inject is of type: WatchKey. The application seems to run fine but when an event occurs in the "watched" folder I'll get NullPointerException saying the WatchKey variable is null.

---

These are the beans I'm declaring in my config file

@Configuration
public class FileManagerConfig
{
    @Bean
    public Path FTPPath ()
    {
        Path FTPDir = null;
        try {
            FTPDir = FileSystems.getDefault().getPath("PATH_TO_FOLDER");
        } catch (Exception e) {
        e.printStackTrace();
        }
        return FTPDir;
    }

    @Bean
    public WatchService getWatcher ()
    {
        WatchService watcher = null;
        try {
            watcher = FileSystems.getDefault().newWatchService();
        } catch (IOException e) {
            System.out.println(e.getMessage());
        }
        return watcher;
    }

    @Bean
    public WatchKey getKey(Path path, WatchService FTPWatcher)
    {
        WatchKey key = null;
        try {
            key = path.register(FTPWatcher, ENTRY_CREATE);
            key = FTPWatcher.take();
        } catch (IOException | InterruptedException e) {
            System.out.println(e.getMessage());
        }
        return key;
    }
}

The last bean is the one I want to autowire in the main application. The other beans are injected into the last bean.

Please note I have told IntelliJ about this configuration file in Project Structure > Facets.

Please also note when getKey is run, the key is NOT null (I put an if statement in the try block to check).

---

The following is the class that requires the WatchKey dependency:

public class FTPWatchZip extends Observable
{
    private boolean run;

    @Autowired
    private WatchKey key;

    public FTPWatchZip()
    {
        run = true;
        watch(key);
    }

    @Autowired
    private void watch(WatchKey key)
    {
        try {
            while(run)
            {
                for (WatchEvent<?> event : key.pollEvents())
                {
                    if (event.kind() == ENTRY_CREATE) {
                        System.out.println("New file detected in FTP Folder\nDownloading...");
                        TimeUnit.SECONDS.sleep(30);
                        System.out.println("Notify subscribers\n");
                    }
                }
                key.reset();
            }
        } catch(InterruptedException e) {
            System.out.println(e.getMessage());
        }
    }
}

I have noticed IntelliJ tells me (when I hover over @Autowired):

Autowired members must be defined in valid Spring bean (@Component|@Servuce|...).

Which suggests to me the necessary beans are not being put into the Spring Application Context.

---

For completeness here is my main class, I have tried different versions of main in order to try and solve this issue but this is what it is at the moment:

public class DuckCreekMonitor
{
    public static void main(String[] args) {
        ApplicationContext context = new AnnotationConfigApplicationContext(FileManagerConfig.class);
        new FTPWatchZip();
    }
}

When I run the program the following is printed to the console:

Jun 07, 2017 5:01:25 PM org.springframework.context.annotation.AnnotationConfigApplicationContext prepareRefresh INFO: Refreshing org.springframework.context.annotation.AnnotationConfigApplicationContext@5ef04b5: startup date [Wed Jun 07 17:01:25 BST 2017]; root of context hierarchy

It then appears to "Watch" the folder for changes, anytime it detects a change in that directory I get a NullPointerException and a stacktrace.

Therefore I don't think the beans are being autowired into my function. Would anyone know anything I can try?

Answer 1

How would Spring be aware of your FTPWatchZip class? you should annotate it with @Component or @Service, and this is what IntelliJ is telling you. or Make it a bean as you did for the others:

    @Bean
    public FTPWatchZip getFTPWatch ()
    {

        return new FTPWatchZip();
    }