java过滤器原理并实现一个过滤器
web中的过滤器,将所有请求进行拦截过滤,并能够再过滤前处理和过滤后处理。
下面我手动实现一个过滤器,使用到了递归的思路:
1、先定义一个过滤器接口,很标准,没的说。
/**
* @author lingkang
* Created by 2022/12/7
*/
public interface Filter {
void doFilter(Object req,Object res,FilterChain filterChain)throws Exception;
}
2、编写一个过滤连作为递归操作
/**
* @author lingkang
* Created by 2022/12/7
*/
public class FilterChain {
public Filter[] filters;
public int length = 0, current = 0;
public FilterChain(Filter[] filters) {
this.filters = filters;
length = filters.length;
}
void doFilter(Object req, Object res) throws Exception {
if (current < length) {
current++;// 自增
filters[current - 1].doFilter(req, res, this);
} else {
current=0;//reset
// 在此处调用处理逻辑方法
System.out.println("finish");
}
}
}
3、执行过滤器
/**
* @author lingkang
* Created by 2022/12/7
* 过滤器实现原理,递归实现
*/
public class Main {
public static void main(String[] args) throws Exception {
Filter[] filters = new Filter[2];// 自定义过滤
filters[0] = new F1();
filters[1] = new F2();
FilterChain filterChain = new FilterChain(filters);
Object req = null, res = null;
filterChain.doFilter(req, res);// 模拟过滤
System.out.println("OK");
}
static class F1 implements Filter {
@Override
public void doFilter(Object req, Object res, FilterChain filterChain) throws Exception {
System.out.println("F1 前");
filterChain.doFilter(req, res);
System.out.println("F1 后");
}
}
static class F2 implements Filter {
@Override
public void doFilter(Object req, Object res, FilterChain filterChain) throws Exception {
System.out.println("F2 前");
filterChain.doFilter(req, res);
System.out.println("F2 后");
}
}
}
效果输出如下:
F1 前
F2 前
finish
F2 后
F1 后
OK