Servlet 过滤器Filter判断用户是否登陆（jsp页面）

最新推荐文章于 2022-05-10 18:09:29 发布

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#java #servlet #jsp #Filter

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本文介绍了一个简单的登录过滤器实现方式，通过Servlet过滤器拦截访问，判断用户是否已登录，并进行相应的处理。

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过滤器Servlet类：

package servlet;

import java.io.IOException;
//import java.io.PrintWriter;

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
//import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


	public class LoginFilter implements Filter {

		 private static final String LOGON_URI = "LOGON_URI";

		 private static final String REGISTER_URI = "REGISTER_URI";

		 private String logon_page;

		 private String register_page;

		 public void destroy() {
		 }

		 public void doFilter(ServletRequest request, ServletResponse response,
		   FilterChain chain) throws IOException, ServletException {
		  HttpServletRequest req = (HttpServletRequest) request;
		  HttpServletResponse resp = (HttpServletResponse) response;
		  resp.setContentType("text/html;");
		  resp.setCharacterEncoding("utf-8");
		  HttpSession session = req.getSession();
		 // PrintWriter out = resp.getWriter();
		  // 得到用户请求的URI
		  String request_uri = req.getRequestURI();
		  // 得到web应用程序的上下文路径
		  String ctxPath = req.getContextPath();
		  // 去除上下文路径，得到剩余部分的路径
		  String uri = request_uri.substring(ctxPath.length());
		  // 判断用户访问的是否是登录页面
		  if (uri.equals(logon_page) || uri.equals(register_page)) {
		   chain.doFilter(request, response);
		   return;
		  } else {
		   // 如果访问的不是登录页面，则判断用户是否已经登录
		   if (null != session.getAttribute("curUser")
		     && "" != session.getAttribute("curUser"))

		{
		    chain.doFilter(request, response);
		    return;
		   } 
		   else {
			   String   msg = "您未登录！";
	           String  url = "Errorer";
	             req.setAttribute("err", msg);
	             RequestDispatcher dis = req.getRequestDispatcher(url);
	  		     dis.forward(req, resp);
		   }
		    //out.println("<script language=/"javaScript/">"
		     // + "parent.location.href='" +

		//ctxPath + logon_page + "'"
		    //  + "</script>");
		   // return;
		  // }
		  }
		 }

		 public void init(FilterConfig config) throws ServletException {
		  // TODO Auto-generated method stub
		  // 从部署描述符中获取登录页面和首页的URI
		  logon_page = config.getInitParameter(LOGON_URI);
		  register_page = config.getInitParameter(REGISTER_URI);
		  // System.out.println(logon_page);
		  if (null == logon_page || null == register_page) {
		   throw new ServletException("没有找到登录页面或主页");
		  }
		 }

	}

修改Web核心配置文件：

注：保存后需要重启tomcat服务器

 <filter>
    <filter-name>loginFilter</filter-name>
    <filter-class>servlet.LoginFilter</filter-class>
    <init-param>
          <param-name>LOGON_URI</param-name>
          <param-value>/login.jsp</param-value>
    </init-param>
    <init-param>
          <param-name>REGISTER_URI</param-name>
          <param-value>/register.jsp</param-value>
    </init-param>
  </filter>
<filter-mapping>
	<filter-name>charseterEncodingFilter</filter-name>
	<url-pattern>/*</url-pattern>
</filter-mapping>
 <filter-mapping>
   <filter-name>loginFilter</filter-name>
   <url-pattern>*.jsp</url-pattern>
  </filter-mapping>

Errorer错误信息处理类：

package servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.RequestDispatcher;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

/**
 * Servlet implementation class Error
 */
public class Errorer extends HttpServlet {

	private static final long serialVersionUID = 1L;

	protected void processRequest(HttpServletRequest request, HttpServletResponse response)
			    throws ServletException, IOException {
			        response.setContentType("text/html;charset=UTF-8");
			        PrintWriter out = response.getWriter();
			        String url="login.jsp";
			        try {

			            out.println("<html>");
			            out.println("<head>");
			            out.println("<title>Servlet Error</title>");
			            out.println("</head>");
			            out.println("<body>");
			            out.println("<h2 align=center>" + request.getAttribute("err") + "</h2>");
			            response.setHeader("refresh", "2;url='login.jsp'");
			            response.setContentType("text/html;charset=UTF-8");
			            response.getWriter().write("请登录！页面将在3秒后自动跳转，如果没有，请点击<a href='login.jsp'>回到登录页面</a>");
			            out.println("</body>");
			            out.println("</html>");

			        } finally {
			            out.close();
			 		   RequestDispatcher dis = request.getRequestDispatcher(url);
					   dis.forward(request, response);
			        }
			    }

			    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
			    /** 
			     * Handles the HTTP <code>GET</code> method.
			     * @param request servlet request
			     * @param response servlet response
			     * @throws ServletException if a servlet-specific error occurs
			     * @throws IOException if an I/O error occurs
			     */
			    @Override
			    protected void doGet(HttpServletRequest request, HttpServletResponse response)
			    throws ServletException, IOException {
			        processRequest(request, response);
			    } 

			    /** 
			     * Handles the HTTP <code>POST</code> method.
			     * @param request servlet request
			     * @param response servlet response
			     * @throws ServletException if a servlet-specific error occurs
			     * @throws IOException if an I/O error occurs
			     */
			    @Override
			    protected void doPost(HttpServletRequest request, HttpServletResponse response)
			    throws ServletException, IOException {
			        processRequest(request, response);
			    }

			    /** 
			     * Returns a short description of the servlet.
			     * @return a String containing servlet description
			     */
			    @Override
			    public String getServletInfo() {
			        return "Short description";
			    }// </editor-fold>
}

效果展示：