subclasses of abstract class object is null when using autowired

Question

I have these classes. when I debug I see that the spring creates the service object in constructor and called the constructors in both classes but when I want to use the fields, they are null. What's the problem?! (type1Processor, type2Processor and type3Processor are null)

import com.vali.ReactiveSocketServer.service.ReceivedDataService;
import org.springframework.stereotype.Component;

public abstract class Processor {

public ReceivedDataService receivedDataService;

public Processor(ReceivedDataService receivedDataService) {
    this.receivedDataService = receivedDataService;
}

public abstract void readStream(String stream);
}

and this is its subclass

import com.vali.ReactiveSocketServer.model.ReceivedData;
import com.vali.ReactiveSocketServer.service.ReceivedDataService;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Component;

@Component
public class Type1Processor extends Processor {


@Autowired
public Type1Processor(ReceivedDataService receivedDataService) {
    super(receivedDataService);
}

@Override
public void readStream(String stream) {
    System.out.println("readStream "+ getClass().getSimpleName() + "-" + stream);
    receivedDataService.add(new ReceivedData(stream.getBytes()));
}
}

and this is its usage:

import com.vali.ReactiveSocketServer.processor.Processor;
import com.vali.ReactiveSocketServer.processor.Type1Processor;
import com.vali.ReactiveSocketServer.processor.Type2Processor;
import com.vali.ReactiveSocketServer.processor.Type3Processor;
import com.vali.ReactiveSocketServer.receivers.AppServer;
import com.vali.ReactiveSocketServer.socket.ClientHandler;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import java.util.HashMap;
import java.util.Map;

@SpringBootApplication
public class ReactiveSocketServerApplication {

private AppServer appServer;

@Autowired
Type1Processor type1Processor;

@Autowired
Type2Processor type2Processor;

@Autowired
Type3Processor type3Processor;

public static void main(String[] args) {
    SpringApplication.run(ReactiveSocketServerApplication.class, args);

    ReactiveSocketServerApplication reactiveSocketServerApplication = new ReactiveSocketServerApplication();
    reactiveSocketServerApplication.Start();
}


public void Start(){

    appServer = AppServer.getInstance();

    Map<Integer, Processor> processorMap = new HashMap<>();

    processorMap.put(7001, type1Processor);
    processorMap.put(7002, type2Processor);
    processorMap.put(7003, type3Processor);

    appServer.initialize(processorMap);

    new ClientHandler(7001, 1000);
    new ClientHandler(7002, 5000);
}
}

when I want to put them in Map they are null, in this line `processorMap.put(7001, type1Processor);` — masoud vali, Apr 29 '19 at 10:29
Look there, similar question: https://stackoverflow.com/questions/31399924/spring-boot-autowired-in-main-class-is-getting-null — mario45211, Apr 29 '19 at 10:33
@mario45211 thank you. I just add `@PostConstruct` to my start method and it's working. Thanks. — masoud vali, Apr 29 '19 at 10:40

score 3 · Accepted Answer · answered Apr 29 '19 at 10:40

You are instantiating ReactiveSocketServerApplication yourself.

So spring can't inject the @Autowired annotated beans, because the instance was created outside of it's life cycle.

Remove this completly:

ReactiveSocketServerApplication reactiveSocketServerApplication = new ReactiveSocketServerApplication();
reactiveSocketServerApplication.Start();

And annotate your Start() with @PostConstruct:

@PostConstruct
public void Start() { ... }

score -1 · Answer 2 · answered Apr 29 '19 at 10:31

-1

You are missing @Component in the abstract class ReceivedDataService.

This mean when you create the subclases using :

@Autowired
public Type1Processor(ReceivedDataService receivedDataService) {
   super(receivedDataService);
}

Can't inject ReceivedDataService and get the default value(null)

answered Apr 29 '19 at 10:31

Bastida

105
1
9

I tried that (with or without @Component) but it's not working – masoud vali Apr 29 '19 at 10:32
Did you try debugg at constructor of any child class? – Bastida Apr 29 '19 at 10:35
yes. I found it with help of mario. I should use `@PostConstruct` for my start method – masoud vali Apr 29 '19 at 10:41
Abstract classes don't need to be annotated as a `Component` as Spring can't instantiate them – Lino Apr 29 '19 at 10:43

subclasses of abstract class object is null when using autowired

2 Answers2