Spring在Bean中注入任务执行器

Question

I'm using Spring Boot and I'm not able to inject a task executor in a service bean. Here's some code:

@Service
public class ClassA {
 @Autowired
    private ThreadPoolTaskExecutor taskExecutor;

 public void doSht(){
     for(int i = 0; i<this.taskExecutor.getMaxPoolSize(); i++){
         this.taskExecutor.execute(new ClassB());
     }
 }
}

Class B:

public class ClassB implements Runnable {

    @Override
    public void run() {
        System.out.println("Class B running");
    }

}

Controller:

@Controller
public class IndexController {
    @Autowired
    ClassA ca;

    @RequestMapping("/")
    public String index(){
        return "index";
    }

    @RequestMapping("test")
    public String test(ClassA ca){
        ca.doSht();
        return "test";
    }
}

And here's the task executor configuration:

@SpringBootApplication
public class App{
    @Bean
    public ThreadPoolTaskExecutor taskExecutor() {
        ThreadPoolTaskExecutor taskExecutor = new ThreadPoolTaskExecutor();
        taskExecutor.setCorePoolSize(5);
        taskExecutor.setMaxPoolSize(10);
        taskExecutor.setQueueCapacity(30);
        return taskExecutor;
    }


    public static void main(String[] args) throws Exception{
        SpringApplication app = new SpringApplication(App.class);
        app.run(args);
    }
}

I want the ClassB instances being executed when a request comes to /test, but I get a NullPointerException because the task executor being not autowired into ClassA bean.

What am I doing wrong?

Answer 1

To fix the error please see the following instructions:

1. Go to IndexController class

2. Go to public String test(ClassA ca) method

3. Remove Class ca input parameter form test method

4. test method should be like this

test method changed:

   @RequestMapping("test")
    public String test(){
        ca.doSht();
        return "test";
    }

The null pointer exception is caused because test method is using ca method argument instead of ca object that comes from @Autowired annotation

Answer 2

As your using @SpringBootApplication in App class , it is registering your custom bean definition to IOC and also it is autowiring the bean correctly. Otherwise you'll get error on autowiring class.

So its not the issue with autowiring. You can set a debug point to check that. Now in your controller you messed up your instance variable with method argument by using same name. Moreover @RequestMapping not supplying your custom class objects. So it is coming as null and you're get the exception.

Hope you understand the issue.