java观察者模式的三种实现方式代码实例

public interface Observer {
    public void update(Object o);
}

public class ObserverImpl implements Observer{
    private Object str;
    @Override
    public void update(Object o) {
        this.str = o;
        System.out.println(this.str);
    }
}

    @Autowired
    private List<Observer> observers;
    @GetMapping("impl/{str}")
    public void impl(@PathVariable("str")  String str){
        for (Observer observer : observers){
            observer.update(str);
        }
    }

public class CustEvent extends ApplicationEvent  {

    public String msg;

    public CustEvent(Object source, String msg) {
        super(source);
        this.msg = msg;
    }
}

@Component
public class CustEventListener {

    @EventListener()
    public void eventListen(ApplicationEvent applicationEvent){
        if(applicationEvent instanceof CustEvent){
            CustEvent custEvent = (CustEvent)applicationEvent;
            System.out.println(custEvent.msg);
        }
    }
}

    @GetMapping("event/{str}")
    public void event(@PathVariable("str")  String str){
        context.publishEvent(new CustEvent(this,str));
    }

public class JavaObserverA implements Observer {

    private int myState;
    @Override
    public void update(Observable o, Object arg) {
        myState = ((JavaConcreteSubject)o).getState();
        System.out.println(myState);
    }
}

public class JavaConcreteSubject extends Observable {

    private int state;

    public void set(int s){
        state = s;  //目标对象的状态发生了改变
        setChanged();  //表示目标对象已经做了更改
        notifyObservers(state);  //通知所有的观察者
    }

    public int getState() {
        return state;
    }

}

    private JavaConcreteSubject subject = new JavaConcreteSubject();
    public testController(){
        subject.addObserver(new JavaObserverA());
    }
    @GetMapping("util/{str}")
    public void util(@PathVariable("str")  String str){
        subject.set(1);
    }