SpringMVC适配器模式代码示例

if(mappedHandler.getHandler() instanceof MultiActionController){ 
  ((MultiActionController)mappedHandler.getHandler()).xxx 
}else if(mappedHandler.getHandler() instanceof XXX){ 
  ... 
}else if(...){ 
  ... 
}

//定义一个Adapter接口 
public interface HandlerAdapter {
	public Boolean supports(Object handler);
	public void handle(Object handler);
}
//以下是三种Controller实现 
public interface Controller {
}
public class HttpController implements Controller{
	public void doHttpHandler(){
		System.out.println("http...");
	}
}
public class SimpleController implements Controller{
	public void doSimplerHandler(){
		System.out.println("simple...");
	}
}
public class AnnotationController implements Controller{
	public void doAnnotationHandler(){
		System.out.println("annotation...");
	}
}
//下面编写适配器类 
public class SimpleHandlerAdapter implements HandlerAdapter {
	public void handle(Object handler) {
		((SimpleController)handler).doSimplerHandler();
	}
	public Boolean supports(Object handler) {
		return (handler instanceof SimpleController);
	}
}
public class HttpHandlerAdapter implements HandlerAdapter {
	public void handle(Object handler) {
		((HttpController)handler).doHttpHandler();
	}
	public Boolean supports(Object handler) {
		return (handler instanceof HttpController);
	}
}
public class AnnotationHandlerAdapter implements HandlerAdapter {
	public void handle(Object handler) {
		((AnnotationController)handler).doAnnotationHandler();
	}
	public Boolean supports(Object handler) {
		return (handler instanceof AnnotationController);
	}
}
//模拟一个DispatcherServlet 
import java.util.ArrayList;
import java.util.List;
public class DispatchServlet {
	public static List<HandlerAdapter> handlerAdapters = new ArrayList<HandlerAdapter>();
	public DispatchServlet(){
		handlerAdapters.add(new AnnotationHandlerAdapter());
		handlerAdapters.add(new HttpHandlerAdapter());
		handlerAdapters.add(new SimpleHandlerAdapter());
	}
	public void doDispatch(){
		//此处模拟SpringMVC从request取handler的对象，仅仅new出，可以出，        
		//不论实现何种Controller，适配器总能经过适配以后得到想要的结果 
		//   HttpController controller = new HttpController(); 
		//   AnnotationController controller = new AnnotationController(); 
		SimpleController controller = new SimpleController();
		//得到对应适配器 
		HandlerAdapter adapter = getHandler(controller);
		//通过适配器执行对应的controller对应方法 
		adapter.handle(controller);
	}
	public HandlerAdapter getHandler(Controller controller){
		for (HandlerAdapter adapter: this.handlerAdapters){
			if(adapter.supports(controller)){
				return adapter;
			}
		}
		return null;
	}
	public static void main(String[] args){
		new DispatchServlet().doDispatch();
	}
}