Filter总结

 

1、多个Filter的执行顺序

Fileter的执行顺序与在web.xml中声明的顺序一致，先声明的先执行。

<filter>
        <filter-name>MyServlet1filter-name>
        <filter-class>com.alibaba.exchange.MyServlet1filter-class>
    filter>
    <filter-mapping>
        <filter-name>MyServlet1filter-name>
        <url-pattern>/*url-pattern>
    filter-mapping>
    <filter>
        <filter-name>MyServlet2filter-name>
        <filter-class>com.alibaba.exchange.MyServlet2filter-class>
    filter>
    <filter-mapping>
        <filter-name>MyServlet2filter-name>
        <url-pattern>/*url-pattern>
    filter-mapping>

在Filter中代码如下：

@Override
public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain chain) throws IOException, ServletException {
    // TODO Auto-generated method stub
    System.out.println("MyServlet1 doFilter before");
    chain.doFilter(request, response);
    System.out.println("MyServlet1 doFilter after");
}

过滤链执行结果如下：
MyServlet1 doFilter before
MyServlet2 doFilter before
zhangsan, hello123
MyServlet2 doFilter after
MyServlet1 doFilter after