设计模式之责任链模式

责任链模式的核心思想是让请求对象(Request)沿着链(chain)按照一定顺序(ordered)依次传递下去，链上的每个处理器(Filter)都有机会去处理请求(request)。 客户端只需把请求传递给链(chain)上的第一个处理器(filter)即可，至于被谁处理，客户端不care。

/** * Test.java * * @author zhanghui * */public class Test {    public static void main(String[] args) {        FilterManager.service(new Request(), new Response());    }}class Request {}class Response {}class FilterManager {        private static Filter firstFilter = null;        static {        // 可以把所有的filter放到配置文件中，然后这里从配置文件中初始化所有filter        Filter f1 = new MyFilter1();        Filter f2 = new MyFilter2();        Filter f3 = new MyFilter3();        f1.setNextFilter(f2);        f2.setNextFilter(f3);        f3.setNextFilter(new NullFilter());                firstFilter = f1;    }        public static void service(Request req, Response resp) {        if (firstFilter != null) {            firstFilter.process(req, resp);        }    }}interface Filter {    void setNextFilter(Filter filter);    void process(Request req, Response resp);}abstract class AbstractFilter implements Filter {    protected Filter next;        public void setNextFilter(Filter next) {        this.next = next;    }}class MyFilter1 extends AbstractFilter {    public void process(Request req, Response resp) {        System.out.println("before MyFilter1...");        next.process(req, resp);        System.out.println("after MyFilter1...");    }}class MyFilter2 extends AbstractFilter {    public void process(Request req, Response resp) {        System.out.println("before MyFilter2...");        next.process(req, resp);        System.out.println("after MyFilter2...");    }}class MyFilter3 extends AbstractFilter {    public void process(Request req, Response resp) {        System.out.println("before MyFilter3...");        next.process(req, resp);        System.out.println("after MyFilter3...");    }}class NullFilter extends AbstractFilter {    public void process(Request req, Response resp) {        // do nothing    }}

 

运行结果：

before MyFilter1...
before MyFilter2...
before MyFilter3...
after MyFilter3...
after MyFilter2...
after MyFilter1...