8-22Filter过滤器_22 filter-优快云博客

本文详细介绍了如何使用web.xml配置文件和注解的方式在Java Web应用中设置过滤器，以控制对特定资源的访问。通过LoginFilter和JspFilter两个示例，展示了如何检查用户会话状态并重定向未登录用户。

相关课件：https://download.youkuaiyun.com/download/crystallf/11593606

配置web.xml来设置过滤器

    <filter>
        <filter-name>LoginFilter</filter-name>
        <filter-class>com.pactrea.config.LoginFilter</filter-class>
    </filter>
    <filter-mapping>
        <filter-name>LoginFilter</filter-name>
        <url-pattern>*.do</url-pattern>
    </filter-mapping>

package com.pactrea.config;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

public class LoginFilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("通过了登录过滤器");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse,
                         FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        if ((request.getServletPath().equals("/login.do"))) {
            filterChain.doFilter(request, response);
        } else {
            if ((request.getSession().getAttribute("currUser") == null)) {
                response.sendRedirect(request.getContextPath() + "/");
            } else {
                filterChain.doFilter(request, response);
            }
        }
//        String currentUrl = request.getRequestURL().toString();
//        System.out.println(currentUrl);
//
//        int a = currentUrl.indexOf("goodsList.jsp");
////        System.out.println(a);
//
//        if (a != -1) {
//            response.sendRedirect("jsp/login.jsp");
//        }


    }

    @Override
    public void destroy() {

    }
}

注解配置过滤器

package com.pactrea.config;

import javax.servlet.*;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;

@WebFilter(urlPatterns = "*.jsp")
public class JspFilter implements Filter {
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        System.out.println("通过了JSP过滤器");
    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {

        HttpServletRequest request = (HttpServletRequest) servletRequest;
        HttpServletResponse response = (HttpServletResponse) servletResponse;

        if ((request.getServletPath().equals("/jsp/login.jsp"))) {
            filterChain.doFilter(request, response);
        } else {
            if ((request.getSession().getAttribute("currUser") == null)) {
                response.sendRedirect(request.getContextPath() + "/jsp/login.jsp");
            } else {
                filterChain.doFilter(request, response);
            }
        }
    }

    @Override
    public void destroy() {

    }
}