servlet拦截器

我不是女神ヾ 2023-10-05 09:54 8阅读 0赞

### servlet拦截器配置教程 ###

**一、创建拦截器类，实现Filter 接口**，重写拦截器方法  
destroy(),doFilter(),init()；

拦截器要做的事情，在doFilter()方法里写；

拦截做完后，调用FilterChain.doFilter(request, response)，将信息传递给下一个拦截器，如过只有一个拦截器，并且拦截通过，则跳到该跳的页面。

public class LoginFilter implements Filter {
        
    
    	public void destroy() {
        
    	}
    
    	public void doFilter(ServletRequest req, ServletResponse res,
    			FilterChain chain) throws IOException, ServletException {
        
    		req.setCharacterEncoding("utf-8");
    		res.setCharacterEncoding("utf-8");
    		res.setContentType("utf-8");
    		HttpServletRequest request=(HttpServletRequest)req;
    		HttpServletResponse response=(HttpServletResponse)res;
    		HttpSession session = request.getSession();
    		if(session.getAttribute("flag")==null){
        
    			PrintWriter out = response.getWriter();
    			out.print("<script type='text/javascript'>alert('非法访问，请登录！');" +
    					"location='/filter/index.jsp'; chartset='utf-8';</script>");
    			
    		}else{
        
    			chain.doFilter(request, response);
    		}
    		
    
    	}
    	public void init(FilterConfig arg0) throws ServletException {
        
    
    	}
    
    }

**二、配置web.xml拦截器信息**。

<?xml version="1.0" encoding="UTF-8"?>
    <web-app version="2.5" 
    	xmlns="http://java.sun.com/xml/ns/javaee" 
    	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
    	xsi:schemaLocation="http://java.sun.com/xml/ns/javaee 
    	http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
      <welcome-file-list>
        <welcome-file>index.jsp</welcome-file>
      </welcome-file-list>
      
      
      <filter>
      	<filter-name>LoginFilter</filter-name>  
      	<filter-class>filter.LoginFilter</filter-class>
      </filter>
      
      
      <filter-mapping>
      	<filter-name>LoginFilter</filter-name>	
      	<url-pattern>/user/*</url-pattern>	
      </filter-mapping>
    </web-app>