Filter拦截器(过滤器)

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我是靠谱客的博主无奈花瓣，这篇文章主要介绍Filter拦截器(过滤器)，现在分享给大家，希望可以做个参考。

不让浏览器直接访问我们的web资源需要加一层拦截器来过滤比如没有登录就直接访问我的购物车等一些不合理操作

和servlet同样是三大组件之一

所以和servlet的创建方式差不多同样是实现一个接口不过是filter的接口

测试在不加filter拦截器的情况下访问web资源

下面加上拦截器实现Filter接口注意是哪个包下面的

复制代码

1
import javax.servlet.*;

页面同样访问就会拦截下来

接下来是放行拦截器

访问页面

复制代码

@WebFilter("/*")
public class FilterLogin implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
        //强转 把ServletRequest request 转行从HttpServletRequest request
        HttpServletRequest req = (HttpServletRequest) request;

//判断是否和登录注册相关的请求
        String[] urls = {"/login.jsp", "/register.jsp", "/ServletLogin","/ServletRegister","/ServletCheckCode","/imgs/","/css/"};

String url = req.getRequestURL().toString();
        //把相关的请求全部放在urls中 然后给放行
//循环判断urls中的url是否和url相等
        for (String s : urls) {
            if (url.contains(s)){
                //找到了就放行
                chain.doFilter(request, response);
                //结束
               return;
            }
        }
        //得到session
        User user = (User) req.getSession().getAttribute("user");
        if (user == null) {
            //没有登录 跳转到登录页面 提示信息
            req.setAttribute("filter_msg", "请先登录");
            //跳转到登录页面
            req.getRequestDispatcher("/login.jsp").forward(request, response);
        }else {
            chain.doFilter(request, response);
        }

}
    public void init(FilterConfig config) throws ServletException {
    }

public void destroy() {
    }

}

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@WebFilter("/*")
public class FilterLogin implements Filter {
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws ServletException, IOException {
        //强转 把ServletRequest request 转行从HttpServletRequest request
        HttpServletRequest req = (HttpServletRequest) request;

        //判断是否和登录注册相关的请求
        String[] urls = {"/login.jsp", "/register.jsp", "/ServletLogin","/ServletRegister","/ServletCheckCode","/imgs/","/css/"};

        String url = req.getRequestURL().toString();
        //把相关的请求全部放在urls中 然后给放行
//循环判断urls中的url是否和url相等
        for (String s : urls) {
            if (url.contains(s)){
                //找到了就放行
                chain.doFilter(request, response);
                //结束
               return;
            }
        }
        //得到session
        User user = (User) req.getSession().getAttribute("user");
        if (user == null) {
            //没有登录 跳转到登录页面 提示信息
            req.setAttribute("filter_msg", "请先登录");
            //跳转到登录页面
            req.getRequestDispatcher("/login.jsp").forward(request, response);
        }else {
            chain.doFilter(request, response);
        }


    }
    public void init(FilterConfig config) throws ServletException {
    }


    public void destroy() {
    }

}