如何实现Spring Event(异步事件)

<!-- https://mvnrepository.com/artifact/org.springframework/org.springframework.context -->
<dependency>
    <groupId>org.springframework</groupId>
    <artifactId>org.springframework.context</artifactId>
    <version>3.1.2.RELEASE</version>
</dependency>

import com.hrm.dto.ExamAnswer;
import org.springframework.context.ApplicationEvent;


public class AnswerEvent extends ApplicationEvent {
    private static final long serialVersionUID = 1L;
    public AnswerEvent(ExamAnswer answer) {
        super(answer);
    }
}

import com.hrm.dto.ExamAnswer;
import com.hrm.service.event.AnswerEvent;
import org.springframework.context.ApplicationListener;
import org.springframework.scheduling.annotation.EnableAsync;
import org.springframework.stereotype.Component;


@Component
@EnableAsync
public class AnswerEventListener implements ApplicationListener<ExamAnswer> {
    @Override
    public void onApplicationEvent(AnswerEvent answerEvent) {
        ExamAnswer answer = (ExamAnswer) answerEvent.getSource();
        if(answer != null) {
            super.save(answer);
        }
    }
}

import com.hrm.dto.ExamAnswer;
import com.hrm.service.event.AnswerEvent;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.context.ApplicationContext;
import org.springframework.stereotype.Repository;

@Repository
public class ExamAnswerDaoImpl implements ExamAnswerDao {
    @Autowired
    private ApplicationContext applicationContext;
    
	private void putAnswerToSpringEvent(ExamAnswer examAnswer) {
		发送Spring Event 事件
        applicationContext.publishEvent(new AnswerEvent(examAnswer));
    }
}