创建一个简单的注册登录页面涉及以下步骤：

1. 创建一个带有doGet方法的Servlet来显示注册登录页面。

2. 创建另一个Servlet来处理注册和登录逻辑。

以下是简单的示例代码：
RegistrationLoginServlet.java (显示页面)

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
 
public class RegistrationLoginServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html");
        PrintWriter out = response.getWriter();
        out.println("");
        out.println("");
        out.println("");
        out.println("
Registration Login Page
");
        out.println("
");
        out.println("Username:");
        out.println("
");
        out.println("Password:");
        out.println("
");
        out.println("");
        out.println(""
);
        out.println("");
        out.println("");
    }
}

RegisterLoginActionServlet.java (处理注册登录)

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
 
public class RegisterLoginActionServlet extends HttpServlet {
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        String username = request.getParameter("username");
        String password = request.getParameter("password");
 
        // 这里可以添加逻辑来验证用户名和密码，比如查询数据库等
 
        // 假设用户名和密码正确
        boolean isAuthenticated = username.equals("admin") && password.equals("password");
 
        if (isAuthenticated) {
            response.sendRedirect("welcome.jsp"); // 重定向到欢迎页面
        } else {
            PrintWriter out = response.getWriter();
            out.println("");
            out.println("");
            out.println("");
            out.println("
Login Failed
");
            out.println("Invalid username or password.");
            out.println("");
            out.println("");
        }
    }
}

在web.xml中注册这两个Servlet：

<servlet>
    <servlet-name>registrationLoginservlet-name>
    <servlet-class>RegistrationLoginServletservlet-class>
servlet>
<servlet-mapping>
    <servlet-name>registrationLoginservlet-name>
    <url-pattern>/register.jspurl-pattern>
servlet-mapping>
 
<servlet>
    <servlet-name>registerLoginActionservlet-name>
    <servlet-class>RegisterLoginActionServletservlet-class>
servlet>
<servlet-mapping>
    <servlet-name>registerLoginActionservlet-name>
    <url-pattern>/RegisterLoginActionurl-pattern>
servlet-mapping>

这个例子中，register.jsp是显示注册登录页面的URL，用户填写表单后提交到RegisterLoginAction，由RegisterLoginActionServlet处理。在实际应用中，你需要将逻辑扩展为包括数据库交互以验证用户凭据。