tomcat中的Filter实现
// 责任链的调度器
public interface FilterChain {
public void initFilters(List<Filter> filters);
public void doFilter (Object params);
}
// 过滤器 责任链上的一个零件
public interface Filter {
public void doFilter (Object params , FilterChain filterChain);
}
public class DefaultFilterChain implements {
private List<Filter> filters;
private Iterator<Filter> iterator;
public void initFilters(List<Filter> filters) {
// 这里可以对 filter 进行排序， 通过Ordered 接口排序
this.filters = filters ;
iterator = filters.iterator;
}
public void doFilter (Object params) {
// 这里可以进行判空操作
if (iterator.hasNext()) {
iterator.next().doFilter(params , this);
}
}
}
具体过滤器 1. 2. 3. 测试用
/**
* Created by zhuangjiesen on 2017/10/26.
*/
public class CommonFilter1 implements Filter {
@Override
public void doFilter(Object params, FilterChain filterChain) {
System.out.println("i am CommonFilter1 doFilter ....");
filterChain.doFilter(params);
}
}
/**
* Created by zhuangjiesen on 2017/10/26.
*/
public class CommonFilter2 implements Filter {
@Override
public void doFilter(Object params, FilterChain filterChain) {
System.out.println("i am CommonFilter2 doFilter ....");
}
}
/**
* Created by zhuangjiesen on 2017/10/26.
*/
public class CommonFilter3 implements Filter {
@Override
public void doFilter(Object params, FilterChain filterChain) {
System.out.println("i am CommonFilter3 doFilter ....");
}
}
调用 filterChain.doFilter(params); 责任链才能继续工作
调用示例：
/**
* Created by zhuangjiesen on 2017/10/25.
*/
public class DesignTest {
public static void main(String[] args) {
System.out.println("设计模式...");
FilterChain filterChain = new DefaultFilterChain();
List<Filter> filters = new ArrayList<>();
filters.add(new CommonFilter1());
filters.add(new CommonFilter2());
filters.add(new CommonFilter3());
// 初始化
filterChain.initFilters(filters);
// 调用过滤器
filterChain.doFilter("zhuangjiesen");
}
}
// 责任链模式就是你只要实现 Filter 接口加入到队列中
如果需要下滤，可以调用 filterChain.doFilter(params);
如果不需要下滤， 不调用就可以，就停在当前过滤器中
