Servlet作为欢迎文件

Question

我想要一个servlet（称为Index，映射在/ Index）作为欢迎文件。通过JDBC Realm我保护这个资源，以便在访问它之前会显示一个登录表单。

我在应用启动时遇到的错误是404。

Index.java

@WebServlet("/Index")
public class Index extends HttpServlet {
    private static final long serialVersionUID = 1L;

    public Index() {
        super();
        // TODO Auto-generated constructor stub
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        request.getSession().setAttribute("isAdmin", request.isUserInRole("admin"));
        request.getSession().setAttribute("isLogged", isAuthenticated(request));
        DAO dao = (DAO) getServletContext().getAttribute("bd");
        try {
            request.getSession().setAttribute("id_user", dao.getUserByName(request.getUserPrincipal().getName()));
        } catch (SQLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        getServletContext().getRequestDispatcher("/index.jsp").forward(request, response);
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

    private boolean isAuthenticated(HttpServletRequest request) {
        return request.getUserPrincipal()!=null;
    }

}

的web.xml

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xmlns="http://java.sun.com/xml/ns/javaee"
    xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd"
    version="3.0">
    <display-name>MyApp</display-name>
    <welcome-file-list>
        <welcome-file>Index</welcome-file>
    </welcome-file-list>
    <login-config>
        <auth-method>FORM</auth-method>
        <realm-name>jdbcRealm</realm-name>
        <form-login-config>
            <form-login-page>/login.jsp</form-login-page>
            <form-error-page>/errorPage.jsp</form-error-page>
        </form-login-config>
    </login-config>
    <security-constraint>
        <web-resource-collection>
            <web-resource-name>Admin stuff</web-resource-name>
            <url-pattern>/admin/*</url-pattern>
            <http-method>GET</http-method>
            <http-method>POST</http-method>
        </web-resource-collection>
        <auth-constraint>
            <role-name>admin</role-name>
        </auth-constraint>
        <user-data-constraint>
            <transport-guarantee>CONFIDENTIAL</transport-guarantee>
        </user-data-constraint>
    </security-constraint>
    <security-constraint>
        <web-resource-collection>
            <web-resource-name>User stuff</web-resource-name>
            <url-pattern>/user/*</url-pattern>
            <http-method>GET</http-method>
            <http-method>POST</http-method>
        </web-resource-collection>
        <auth-constraint>
            <role-name>user</role-name>
        </auth-constraint>
        <user-data-constraint>
            <transport-guarantee>CONFIDENTIAL</transport-guarantee>
        </user-data-constraint>
    </security-constraint>
    <security-constraint>
        <web-resource-collection>
            <web-resource-name>All</web-resource-name>
            <url-pattern>/Index</url-pattern>
            <http-method>GET</http-method>
            <http-method>POST</http-method>
        </web-resource-collection>
        <auth-constraint>
            <role-name>admin</role-name>
            <role-name>user</role-name>
        </auth-constraint>
        <user-data-constraint>
            <transport-guarantee>CONFIDENTIAL</transport-guarantee>
        </user-data-constraint>
    </security-constraint>
    <security-role>
        <role-name>admin</role-name>
    </security-role>
    <security-role>
        <role-name>user</role-name>
    </security-role>
</web-app>