設計模式—鏈路模式（實例）

第一步：設置參數dto

/**
 * 請求DTO
 */
public class RequestDTO {

}

第二步：設置父類handler

public abstract class ParentHandler {
        protected ParentHandler nextHandler;

        protected ApplicationContext context = SpringContextUtil.getApplicationContext();

        protected abstract boolean needHandler(RequestDTO request);

        /**
         * 子類handler需重寫該handler()方法
         * @param request
         */
        protected void handler(RequestDTO request){
                ParentHandler handler =this.nextHandler;
                while (handler !=null){
                        if(handler.needHandler(request)){
                                handler.handler(request);
                        }
                        handler =handler.nextHandler;
                }
        }
        /**
         * 設置nextHandler
         * @param nextHandler
         * @return
         */
        protected ParentHandler setNextHandler(ParentHandler nextHandler){
                this.nextHandler =nextHandler;
                return this.nextHandler;
        }
}

第三步：設置子類handler

第一個子類handler

public class FirstHandler extends ParentHandler{
        @Override
        protected boolean needHandler(RequestDTO request) {
                return true;
        }

        @Override
        protected void handler(RequestDTO request){
                System.out.println("FirstHandler.handler");
                //此處只有在firstHandler中添加，其他的子類handler不能添加
                super.handler(request);
        }
}

第二個子類handler

public class SecondHandler extends ParentHandler {
        @Override
        protected boolean needHandler(RequestDTO request) {
                return true;
        }

        @Override
        protected void handler(RequestDTO request){
                System.out.println("SecondHandler.handler");
        }
}

第三個子類handler

public class ThirdHandler extends ParentHandler {
        @Override
        protected boolean needHandler(RequestDTO request) {
                return true;
        }

        @Override
        protected void handler(RequestDTO request){
                System.out.println("ThirdHandler.handler");
        }
}

子類handler按需添加 。。。。。

第四步：設置handler工廠類，main方法測試

public class HandlerFactroy {
        private static ParentHandler handlerLinked =new FirstHandler();
        static {
                handlerLinked
                        .setNextHandler(new SecondHandler())
                        .setNextHandler(new ThirdHandler());
        }

        public static ParentHandler getHandlerLinked(){
                return handlerLinked;
        }

        public static void main(String[] args){
                RequestDTO requestDTO =new RequestDTO();
                HandlerFactroy.getHandlerLinked().handler(requestDTO);
        }

}