基本使用

//@WebFilter("/*")  *表示拦截所有请求
@WebFilter("/servletDemo1")
public class FilterDemo implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("对象初始化。。。");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        System.out.println("filter执行了。。。");
        servletResponse.setContentType("text/html;charset=utf-8");
        filterChain.doFilter(servletRequest, servletResponse);
    }

    @Override
    public void destroy() {
        System.out.println("对象销毁。。。");
    }

}