简单回调机制的Java实现

原理图：

代码

//首先是接口部分：

package mechanism;
public interface ICallBack {

	public abstract void doSomething();
}

package mechanism;

public interface ICallee {
	public abstract String askforCallback();

	public abstract void setCallback(ICallBack callback);
}

//然后是实现部分：

package mechanism;

public class CallBack implements ICallBack{

	@Override
	public void doSomething() {
		System.out.println("do something useful in callback");
		
	}

}

package mechanism;

public class Callee1 implements ICallee {

	private ICallBack callback;
	
	@Override
	public void setCallback(ICallBack callback) {
		this.callback = callback;
	}

	@Override
	public String askforCallback() {
		System.out.println("pre operations before invoke callback");
		callback.doSomething();
		System.out.println("post operations after invoke callback");
		String result = "function execute success, ruturn result";
		return result;
	}
}

package mechanism;

public class Caller {
	private ICallee callee;
	
	public void setCallee(ICallee callee) {
		this.callee = callee;
	}

	public void bindCallBacktoCallee(ICallBack callback) {
		callee.setCallback(callback);
	}
	public void executeTask() {
		System.out.println("pre task analysis");
		System.out.println("doing part of task");
		//excute one function
		String result = callee.askforCallback();
		System.out.println("post operation as respond to callee's result");
		System.out.println("complete the task");
	}
}

//测试：

package mechanism;

public class Test {

	public static void main(String[] args) {
		System.out.println("main flow : some operations before using Caller");
		
		ICallee callee1 = new Callee1();		
		//由Caller完成Callback与Callee的绑定，从而将Callback的执行
		//委托给Callee
		//先分配资源
		Caller caller = new Caller();	
		ICallBack callback = new CallBack();
		//再完成配置工作
		caller.setCallee(callee1);	
		caller.bindCallBacktoCallee(callback);
		//然后就可以运行了
		caller.executeTask();
	}
}