本文实例为大家分享了jsp实现登录验证的过滤器，供大家参考，具体内容如下
1.新建一个Dynamic Web Project项目，里面新建1个filter文件、1个servlet文件和2个jsp文件，整体的框架如图所示：
2.LoginFilter.java里面的代码如下所示：
package filter;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.annotation.WebFilter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebFilter(filterName = "loginFilter", urlPatterns = { "/*" })
public class LoginFilter implements Filter {
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
HttpServletResponse resp = (HttpServletResponse) response;
HttpSession session = req.getSession(true);
resp.setContentType("text/html;");
resp.setCharacterEncoding("utf-8");
PrintWriter out = resp.getWriter();
String request_uri = req.getRequestURI();
String ctxPath = req.getContextPath();
String uri = request_uri.substring(ctxPath.length());
if (uri.contains("login.jsp") || uri.contains("loginServlet")) {
chain.doFilter(request, response);
} else {
if (session.getAttribute("user") != null) {
chain.doFilter(request, response);
} else {
out.println("您没有登录，请先登录！3秒后回到登录页面。");
resp.setHeader("refresh", "3;url=" + ctxPath + "/login.jsp");
return;
}
}
}
public void init(FilterConfig fConfig) throws ServletException {
}
}
3.LoginServlet.java里面的代码如下所示：
package servlet;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@WebServlet(name = "loginServlet", urlPatterns = { "/loginServlet" })
public class LoginServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
protected void doGet(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
doPost(request, response);
}
protected void doPost(HttpServletRequest request,
HttpServletResponse response) throws ServletException, IOException {
String username = request.getParameter("name");
String password = request.getParameter("pwd");
if ("filter".equals(username) && "filter".equals(password)) {
HttpSession session = request.getSession(true);
session.setAttribute("user", username);
response.sendRedirect("loginSuccess.jsp");
} else {
response.sendRedirect("login.jsp");
}
}
}
4.login.jsp里面的代码如下所示：
<%@page import="java.util.Date"%> <%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>example</title> </head> <body bgcolor="lightPink"> <form action="loginServlet" method="post"> <table> <tr> <td>用户名：</td> <td><input type="text" name="name" /></td> </tr> <tr> <td>密码：</td> <td><input type="password" name="pwd" /> </tr> <tr> <td><input type="submit" value="提交" /></td> <td><input type="reset" value="重置" /></td> </tr> </table> </form> </body> </html>
5.loginSuccess.jsp里面的代码如下所示：
<%@page import="java.util.Date"%>
<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>example</title>
</head>
<body>
<%
String username = (String) session.getAttribute("user");
%>
恭喜<%=username%>登录成功！
</body>
</html>
6.在浏览器里面输入http://localhost:8080/Servlet/login.jsp运行之后得到的结果如下所示：
