TaskExecutor and TaskScheduler being picked up by Spring as same type

Question

I have the following configuration: ``` @org.springframework.context.annotation.Configuration @EnableJpaRepositories @EnableAsync @EnableScheduling public class MyConfiguration { @Bean public TaskExecutor taskExecutor() { ThreadPoolTaskExecutor executor = new ThreadPoolTaskExecutor(); executor.setCorePoolSize(10); executor.setMaxPoolSize(20); executor.setQueueCapacity(50); return executor; } @Bean public TaskScheduler taskScheduler() { ThreadPoolTaskScheduler scheduler = new ThreadPoolTaskScheduler(); scheduler.setPoolSize(10); return scheduler; } } ``` Then I have a class listening for ContextRefreshEvents, like: ``` @Component public class ScreenerScheduler implements ApplicationListener<ContextRefreshedEvent> { @Inject private TaskScheduler scheduler; @Inject private ApplicationContext context; @Override public void onApplicationEvent(ContextRefreshedEvent event) { } ``` When I run the application (web) I get: ``` Error creating bean with name 'screenerJobExecutor': Injection of au…

Accepted Answer

This `@Bean` method

```
@Bean
public TaskScheduler taskScheduler() {
```

returns an object of type `ThreadPoolTaskScheduler` which is

```
public class ThreadPoolTaskScheduler extends ExecutorConfigurationSupport
    implements TaskScheduler, SchedulingTaskExecutor {
```

so it fits both interfaces, `TaskScheduler` and `TaskExecutor` (super type of `SchedulingTaskExecutor`).

If you try to inject a field of type `TaskExecutor` like your stack trace says

```
Could not autowire field: private org.springframework.core.task.TaskExecutor...
```

Spring won't be able to choose which one.

This will only happen if the `ApplicationContext` from where you are trying to pull the beans has already initialized the beans, for example, in a Web application where your root context would register `MyConfiguration` and where the servlet context would declare your `screenerJobExecutor` bean that needs to be injected with a bean of type `TaskExecutor`.

You can indeed use

```
@Qualifier(value = "taskExecutor")
```

to fix this particular situation as Spring will use the bean name and not the bean type to satisfy the injection target.

TaskExecutor and TaskScheduler being picked up by Spring as same type

Solution

Problem