设计模式-ChainOfResponsibility责任链

定义：责任链模式(Iterator Pattern), 是行为型设计模式之一。这种模型结构有点类似现实生活中铁链，由一个个铁环首尾相接构成一条链，如果这种结构用在编程领域，则每个节点可以看做一个对象，每个对象有不同的处理逻辑，将一个请求从链的首端发出，沿着链的路径依次传递每个节点对象，直到有对象处理这个请求为止，我们将这样一种模式称为责任链模式
 

场景：多个对象可以处理同一个请求，但具体由哪个对象处理则在运行时动态决定

下面是模拟filter的处理逻辑代码

interface Filter {
    void doFilter(Request request, Response response, FilterChain chain);
}

class HTMLFilter implements Filter {
    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        request.str = request.str.replaceAll("<", "[").replaceAll(">", "]") + "HTMLFilter()";
        chain.doFilter(request, response);
        response.str += "--HTMLFilter()";

    }
}

class Request {
    String str;
}

class Response {
    String str;
}

class SensitiveFilter implements Filter {
    @Override
    public void doFilter(Request request, Response response, FilterChain chain) {
        request.str = request.str.replaceAll("996", "955") + " SensitiveFilter()";
        chain.doFilter(request, response);
        response.str += "--SensitiveFilter()";

    }
}


class FilterChain {
    List filters = new ArrayList<>();
    int index = 0;

    public FilterChain add(Filter f) {
        filters.add(f);
        return this;
    }

    public void doFilter(Request request, Response response) {
        if(index == filters.size()) return;
        Filter f = filters.get(index);
        index ++;

        f.doFilter(request, response, this);
    }

//测试类
public class Servlet_Main {
    public static void main(String[] args) {
        Request request = new Request();
        request.str = "大家好:)，