JavaWeb中的filter链

过滤器链(配置多个过滤器)

1. 执行顺序：如果有两个过滤器：过滤器1和过滤器2
   1. 过滤器1
   2. 过滤器2
   3. 资源执行
   4. 过滤器2
   5. 过滤器1
2. 过滤器先后顺序问题：
   1. 注解配置：按照类名的字符串比较规则比较，值小的先执行
      如： AFilter 和 BFilter，AFilter就先执行了。
   2. web.xml配置： 谁定义在上边，谁先执行

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

//过滤器链
@WebFilter("/*")
public class FilterDemo6 implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        System.out.println("demo6....go...");
        chain.doFilter(req, resp);
        System.out.println("demo6....back...");
    }

    public void init(FilterConfig config) throws ServletException {

    }

}

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import java.io.IOException;

@WebFilter("/*")
public class FilterDemo7 implements Filter {
    public void destroy() {
    }

    public void doFilter(ServletRequest req, ServletResponse resp, FilterChain chain) throws ServletException, IOException {
        System.out.println("demo7....go...");
        chain.doFilter(req, resp);
        System.out.println("demo7....back...");
    }

    public void init(FilterConfig config) throws ServletException {

    }

}