Spring not injecting a bean into thread

Question

1.How to inject a spring bean into thread

2.How to start a thread inside spring bean.

here is my code.

MyThread.java

@Component
public class MyThread implements Runnable {

    @Autowired
    ApplicationContext applicationContext;

    @Autowired
    SessionFactory sessionFactory;

    public void run() {

        while (true) {
            System.out.println("Inside run()");
            try {
                System.out.println("SessionFactory : " + sessionFactory);
            } catch (Exception e) {
                e.printStackTrace();
            }

            try {
                Thread.sleep(10000);

                System.out.println(Arrays.asList(applicationContext.getBeanDefinitionNames()));

            } catch (Exception e) {
                e.printStackTrace();
            }
        }

    }

}

i am calling run method from below class like (Please suggest if i am following wrong appraoch for calling a thread inside spring bean )

@Component
public class MyServiceCreationListener implements ApplicationListener<ContextRefreshedEvent> {

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {

        if (event.getApplicationContext().getParent() == null) {
            System.out.println("\nThread Started");
            Thread t = new Thread(new MyThread());
            t.start();

        }
    }
}

spring is not performing dependency injection on MyThread class

Answer 1

There are a couple of things wrong with your setup.

1. You shouldn't be creating and managing threads yourself, Java has nice features for that use those.
2. You are creating new bean instances yourself and expect Spring to know about them and inject dependencies, that isn't going to work.

Spring provides an abstraction to execute tasks, the TaskExecutor. You should configure one and use that to execute your task not create a thread yourself.

Add this to your @Configuration class.

@Bean
public ThreadPoolTaskExecutor taskExecutor() {
    return new ThreadPoolTaskExecutor();
}

Your MyThread should be annotated with @Scope("prototype").

@Component
@Scope("prototype")
public class MyThread implements Runnable { ... }

Now you can inject these beans and an ApplicationContext into your MyServiceCreationListener

@Component
public class MyServiceCreationListener implements ApplicationListener<ContextRefreshedEvent> {

    @Autowired
    private ApplicationContext ctx;
    @Autowired
    private TaskExecutor taskExecutor;        

    @Override
    public void onApplicationEvent(ContextRefreshedEvent event) {

        if (event.getApplicationContext().getParent() == null) {
            System.out.println("\nThread Started");
            taskExecutor.execute(ctx.getBean(MyThread.class));
        }
    }
}

This will give you a pre-configured, fresh instance of MyThread and execute it on a Thread selected by the TaskExecutor at hand.