登录案例，登陆成功之后跳转到一个个人主页，欢迎您 xxx

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本文介绍了一种使用cookie和session实现登录验证的方法。通过示例代码展示了如何设置和读取cookie及session来实现用户登录后的状态保持，并跳转到个人主页。

登录案例，登陆成功之后跳转到一个个人主页，欢迎您 xxx

1.通过cookie实现
2.通过session实现（关闭浏览器仍然可以访问到session中的数据功能）

1.通过cookie实现

结构：
在这里插入图片描述

代码：
login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/app/loginz" method="post">
        <input type="text" name="username"><br>
        <input type="password" name="password"><br>
        <input type="submit">
    </form>
</body>
</html>

LoginServlet.java

@WebServlet("/loginz")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //不做任何校验，只要输入就当作登录成功
        Cookie cookie = new Cookie("username", username);
        cookie.setMaxAge(180);
        cookie.setPath(request.getContextPath() + "/infog");
        response.addCookie(cookie);
        response.getWriter().println("登录成功，即将跳转至个人主页....");
        response.setHeader("refresh", "2;url=" + request.getContextPath() + "/infog");
        //Context域不可以
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
}

InfoServlet.java

@WebServlet("/infog")
public class InfoServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //
        String username = "";
        Cookie[] cookies = request.getCookies();
        if(cookies != null){
            for (Cookie cookie : cookies) {
                if("username".equals(cookie.getName())){
                    username = cookie.getValue();
                    cookie.setMaxAge(0);
                    cookie.setPath(request.getContextPath() + "/info");
                    response.addCookie(cookie);
                }
            }
        }
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().println("<!DOCTYPE html>\n" +
                "<html lang=\"en\">\n" +
                "<head>\n" +
                "    <meta charset=\"UTF-8\">\n" +
                "    <title>Title</title>\n" +
                "</head>\n" +
                "<body>");

        response.getWriter().println("欢迎您，" + username);

        response.getWriter().println("</body>\n" +
                "</html>");
    }
}

结果：
在这里插入图片描述

从另一浏览器直接访问：
在这里插入图片描述

DelCookieServlet.java(删除cookie)

@WebServlet("/dell")
public class DelCookieServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //通过访问该servlet，将cookie信息删除
        Cookie[] cookies = request.getCookies();
        if(cookies != null){
            for (Cookie cookie : cookies) {
                if("username".equals(cookie.getName())){
                    cookie.setMaxAge(0);
                    //需要把这个告诉给浏览器
                    response.addCookie(cookie);
                }
            }
        }
    }
}

结果：
在这里插入图片描述

在这里插入图片描述

2.通过session实现（关闭浏览器仍然可以访问到session中的数据功能）

结构：
在这里插入图片描述
代码：
login.html

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <form action="/app/loginz" method="post">
        <input type="text" name="username"><br>
        <input type="password" name="password"><br>
        <input type="submit">
    </form>
</body>
</html>

LoginServlet.java

@WebServlet("/loginz")
public class LoginServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        response.setContentType("text/html;charset=utf-8");
        String username = request.getParameter("username");
        String password = request.getParameter("password");
        //不做任何校验，只要输入就当作登录成功
        Cookie cookie = new Cookie("username", username);
        cookie.setMaxAge(180);
        cookie.setPath(request.getContextPath() + "/infog");
        response.addCookie(cookie);
        response.getWriter().println("登录成功，即将跳转至个人主页....");
        response.setHeader("refresh", "2;url=" + request.getContextPath() + "/infog");
        //Context域不可以
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }
}

InfoServletSession.java

@WebServlet("/infos")
public class InfoServletSession extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //
        String username = (String) request.getSession().getAttribute("username");
        if (username==null){
            username="";
        }
        response.setContentType("text/html;charset=utf-8");
        response.getWriter().println("<!DOCTYPE html>\n" +
                "<html lang=\"en\">\n" +
                "<head>\n" +
                "    <meta charset=\"UTF-8\">\n" +
                "    <title>Title</title>\n" +
                "</head>\n" +
                "<body>");

        response.getWriter().println("欢迎您，" + username);

        response.getWriter().println("</body>\n" +
                "</html>");
    }
}