登录页面：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<html>
<head>
</head>
<body>
<form action="servlet/LoginServlet" method="post">
<input type="text" name="username"/><br/>
<input type="password" name="password"/><br/>
<input type="submit" value="登录"/>
</form>
</body>
</html>
登录成功页面：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<html>
<head>
</head>
<body>登录成功!
</body>
</html>
web.xml
<filter>
<filter-name>LoginFilter</filter-name>
<filter-class>filter.LoginFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>LoginFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>
<servlet>
<servlet-name>LoginServlet</servlet-name>
<servlet-class>servlet.LoginServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>LoginServlet</servlet-name>
<url-pattern>/servlet/LoginServlet</url-pattern>
</servlet-mapping>
LoginServlet
public class LoginServlet extends HttpServlet {
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doPost(request, response);
}
public String notNull(String param) {
return param == null ? "" : param;
}
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
HttpSession session = request.getSession();
String username = request.getParameter("username");
String password = request.getParameter("password");
System.out.println("username:"+username);
System.out.println("password:"+password);
if (username.equals("douya0808") && password.equals("123456")) {// 直接给xxxxLoginTest/servlet/LoginServlet会由于没传值而报出NullPointer
System.out.println("信息正确，跳转页面中...");
session.setAttribute("login", "LoginSuccess!");
response.sendRedirect(request.getContextPath() + "/success.jsp");
} else {
response.sendRedirect(request.getContextPath() + "/login.jsp");
}
}
}
LoginFilter
public class LoginFilter implements Filter {
public void init(FilterConfig filterConfig) throws ServletException {
System.out.println("过滤器初始化中...");
}
public void destroy() {
}
public void doFilter(ServletRequest request, ServletResponse response,
FilterChain chain) throws IOException, ServletException {
HttpServletRequest httpServletRequest = (HttpServletRequest) request;
HttpServletResponse httpServletResponse = (HttpServletResponse) response;
HttpSession session = httpServletRequest.getSession();
System.out.println("开始过滤....");
if (httpServletRequest.getServletPath().indexOf("login.jsp") > 0 || httpServletRequest.getServletPath().indexOf("servlet/LoginServlet") > 0) {
System.out.println("放过该请求...");
chain.doFilter(request, response);
} else {
String user = (String) session.getAttribute("login");
if (user != null) {
System.out.println("已登录，取消过滤...");
chain.doFilter(request, response);
} else {
System.out.println("未登录，跳转到登录页面...");
httpServletResponse.sendRedirect(httpServletRequest.getContextPath() + "/login.jsp");
}
}
System.out.println("完成过滤....");
}
}
请前辈们帮我看下我这里有什么需要改进的地方吗？以为小弟刚学就是凭着记忆写的，而且我看网上的很多例子都是只放开login.jsp，但是我这里需要放开login.jsp还需要放开表单的请求路径servlet/LoginServlet，不然就会一直卡在login.jsp，是不是我写的哪里有问题呢？300分奉上！
------解决方案--------------------
你肯定要放开login.jsp页面和它请求的servlet，如果有注销页面的话，还要把注销页面和相应的注销的servlet一并放过，如果你只放过了login.jsp，你点击登陆后就会请求相应的servlet.，由于每一个请求都会经过过滤器过滤，当你请求servlet的时候，不满足你过滤器中的条件，直接就跳转到login.jsp，希望能帮到你
------解决方案--------------------
正解，不累赘陈述了
------解决方案--------------------