Filter的使用

╰半橙微兮° 2022-05-17 06:13 180阅读 0赞

### Filter ###

必须实现javax.Servlet.Filter接口  
必须定义以下三个方法

init()，初始化  
doFilter()，处理请求  
destory()，销毁

### 配置 ###

web.xml配置过滤器

<filter>
      <filter-name>SessionFilter</filter-name>
      
      <filter-class>com.service.SessionFilter</filter-class>
    </filter>
    <filter-mapping>
      <filter-name>SessionFilter</filter-name>
      
      <url-pattern>/home/*</url-pattern>
      
    </filter-mapping>

实现代码

package cn.com.hwasunsoft.lims.web.filter;
    
    import cn.com.hwasunsoft.lims.web.controller.admin.MessageController;
    import org.springframework.beans.factory.annotation.Autowired;
    import org.springframework.stereotype.Component;
    import org.springframework.ui.Model;
    import org.springframework.web.context.WebApplicationContext;
    
    import javax.servlet.*;
    import javax.servlet.http.HttpServletRequest;
    import java.io.IOException;
    import java.util.HashMap;
    import java.util.Map;
    
    /** * Created by ali on 2018/5/25. */
    public class MessageFilter implements Filter { 
    
        private WebApplicationContext wac;
    
        @Override
        public void init(FilterConfig arg0) throws ServletException {
            wac = (WebApplicationContext)arg0.getServletContext().getAttribute(WebApplicationContext.ROOT_WEB_APPLICATION_CONTEXT_ATTRIBUTE);
        }
    
        @Override
        public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
            try {
                if (servletRequest!=null){
                    MessageController messageController = wac.getBean(MessageController.class);
                    servletRequest.setAttribute("messageList", messageController.selectMessageList());
                }
            } catch (Exception e) {
                throw e;
            } finally {
                 filterChain.doFilter(servletRequest, servletResponse);
            }
        }
    
        @Override
        public void destroy() {
    
        }
    }