责任链和装饰者设计模式

• 前言
• 一、责任链模式
• • 1.1 类图
  • 1.2 代码
• 二、装饰者模式
• • 2.1 类图
  • 2.2 代码

工作中实际遇到最多的是责任链模式，相对而言装饰者模式用的较少。
责任链模式比较常见就是各种filter和各种intercepet。还比如activiti流程引擎框架中也使用了责任链+命名的设计模式

责任链负责将把所有处理类方法串联起来，挨个进行处理
下面举例子：

举个例子，按照如下类图进行开发

IInterceptor

public interface IInterceptor {

    boolean process(String msg);

}

TokenInterceptor

public class TokenInterceptor implements IInterceptor {

    @Override
    public boolean process(String msg) {
        if (msg.contains("token")) {
            System.out.println("拦截处理token");
            return true;
        }

        return false;
    }

}

ParamInterceptor

public class ParamInterceptor implements IInterceptor {
    @Override
    public boolean process(String msg) {
        if (msg.contains("非法字符")) {
            System.out.println("拦截处理非法字符");
            return true;
        }
        return false;
    }
}

ChainInterceptor
后面还可以将这个chain传如另一个ChainInterceptor进行迭代，因为ChainInterceptor本身也是IInterceptor

public class ChainInterceptor implements IInterceptor {
    LinkedList list = new LinkedList<>();

    public ChainInterceptor() {
        list.add(new TokenInterceptor());
        list.add(new ParamInterceptor());
    }

    @Override
    public boolean process(String msg) {
        for (IInterceptor interceptor : list) {
            if (interceptor.process(msg)) {
                //中间有一个处理拦截了；
                //后面就不需要在遍历处理
                return true;
            }
        }

        return false;
    }
}

测试：Main

public class Main {

    public static void main(String[] args) {
        ChainInterceptor chain = new ChainInterceptor();
        String msg = "反倒是token都is哈佛了";
        chain.process(msg);

    }

}

装饰者模式，见名知义，给某个物体增加修饰。比如要给汽车加上翅膀，再加上炮弹

Vehicle

public abstract class Vehicle {

    abstract void run();

}

Car

public class Car extends Vehicle {
    @Override
    void run() {
        System.out.println("汽车四个轮子 go~~~");
    }
}

VehicleDecorator

public abstract class VehicleDecorator extends Vehicle {

    public Vehicle vehicle;

    public VehicleDecorator(Vehicle vehicle) {
        this.vehicle = vehicle;
    }
    
}

CarWingDecorator

public class CarWingDecorator extends VehicleDecorator {

    public CarWingDecorator(Vehicle vehicle) {
        super(vehicle);
    }

    @Override
    void run() {
        super.vehicle.run();
        System.out.println("car加上理想的翅膀  sososo~~~~");
    }
}

CarGanDecorator

public class CarGanDecorator extends VehicleDecorator {

    public CarGanDecorator(Vehicle vehicle) {
        super(vehicle);
    }

    @Override
    void run() {
        super.vehicle.run();
        System.out.println("car加上炮弹hong hong~~~~~");

    }
}

测试
Main

public class Main {

    public static void main(String[] args) {
        CarGanDecorator decorator = new CarGanDecorator(new CarWingDecorator(new Car()));
        decorator.run();
    }

}