Java 学习笔记 Filter过滤器

Filter过滤器为客户端和服务器之间的过滤器，两端之间进行信息交互的时候需要这个过滤器来进行信息过滤

示例：

登陆页面

点击登陆后跳转到登陆成功页面
为了防止不通过登陆页面直接进入登陆成功页面，需要增加一个防止直接使用http://localhost:8080/ssm/logsucess.jsp进行登陆，需要增加一个过滤器

过滤器代码如下
Logfilter.java

package com.filter;


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

public class Logfilter implements Filter {

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
        HttpServletRequest httpServletRequest = (HttpServletRequest) servletRequest;
        HttpServletResponse httpServletResponse = (HttpServletResponse) servletResponse;
        HttpSession session = httpServletRequest.getSession();
        String name = (String) session.getAttribute("name");
        System.out.println("filter:"+name);
        if (name == null){
            //不是登陆状态
            httpServletResponse.sendRedirect("/ssm/log.jsp");
        }else {
            filterChain.doFilter(servletRequest,servletResponse);
        }

    }

    @Override
    public void destroy() {

    }
}

web.xml中加入

<!--过滤器  -->
  <filter>
    <filter-name>logfilter</filter-name>
    <filter-class>com.filter.Logfilter</filter-class>
  </filter>
  <filter-mapping>
    <filter-name>logfilter</filter-name>
    <!-- 是去除项目名称之后的url   -->
    <url-pattern>/logsucess.jsp</url-pattern>
  </filter-mapping>

SpringBoot使用filter

filter类中加入注解

@WebFilter("/*")

然后在启动类中加入该注解

@ServletComponentScan

相关函数使用

1. httpServletResponse.sendRedirect("/…")
   重定向到一个地址
2. httpServletrequest.getRequestDispatcher("/…").forward(request,resp)
   转发到一个地址