HTTP状态404-请求的资源不可用

Question

几个月前我为我的大学（一个问答游戏）做过这个项目，一切都很好！现在我重新打开了eclipse项目，但我不知道为什么，它不起作用！我已经搜索了旧话题，因为我知道这是一个经常出现的问题，但我不知道如何解决它！我认为这只是一个配置问题，因为我已经在另一个工作站上编写了整个项目，而且一切都很好。现在我正在尝试使用Eclipse Mars和tomcat 8.0在我的Mac上运行servlet。

这里我报告了我的一个servlet和xml文件的代码。

package servlet;

import java.io.IOException;
import java.sql.SQLException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletContext;
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;

import database.DbHelper;

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

private DbHelper dbHelper = null;

@Override
public void init(ServletConfig config) throws ServletException {
    super.init(config);
    ServletContext context = config.getServletContext();
    String driver = context.getInitParameter("dbDriver");
    String path = context.getInitParameter("dbUrl");
    String user = context.getInitParameter("dbUser");
    String pass = context.getInitParameter("dbPassword");

    try {
        dbHelper = new DbHelper(driver, path, user, pass);
    } catch (ClassNotFoundException | SQLException e) {
        e.printStackTrace();
    }

}

@Override
public void destroy() {
    super.destroy();
    if(dbHelper!=null){
        try {
            dbHelper.destroy();
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    HttpSession session=request.getSession();

    String username=request.getParameter("username");
    String password=request.getParameter("password");


    try {if (dbHelper.isPlayer(username, password)){
        session.setAttribute("username",username);
        response.sendRedirect("Player");

    } else
        if (dbHelper.isAuthor(username, password)){ 
            session.setAttribute("username",username);
            response.sendRedirect("Author");

        }else{
            request.setAttribute("error", 1);
            request.getRequestDispatcher("jsp/login.jsp").forward(request, response);
        }
    } catch (SQLException e) {
        e.printStackTrace();
        response.sendRedirect("html/error.html");
    }
}

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
    doPost(req, resp);
}

}

XML文件：

<?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"
metadata-complete="true">

<display-name>CheckMyBrain</display-name>
<welcome-file-list>
<welcome-file>index.html</welcome-file>
<welcome-file>index.htm</welcome-file>
<welcome-file>index.jsp</welcome-file>
<welcome-file>default.html</welcome-file>
<welcome-file>default.htm</welcome-file>
<welcome-file>default.jsp</welcome-file>
</welcome-file-list>

<context-param>
<description>Database URL</description>
<param-name>dbUrl</param-name>
<param-value>jdbc:mysql://localhost:3306/Quiz</param-value>
</context-param>
<context-param>
<description>Database user</description>
<param-name>dbUser</param-name>
<param-value>root</param-value>
</context-param>
<context-param>
<description>Database password</description>
<param-name>dbPassword</param-name>
<param-value>root</param-value>
</context-param>
<context-param>
<description>Database driver</description>
<param-name>dbDriver</param-name>
<param-value>com.mysql.jdbc.Driver</param-value>
</context-param>
<context-param>
<param-name>smtpHost</param-name>
<param-value>smtp.gmail.com</param-value>
</context-param>
<context-param>
<param-name>smtpPort</param-name>
<param-value>587</param-value>
</context-param>
<context-param>
 <param-name>smtpUser</param-name>
<param-value>checkmybrain37@gmail.com</param-value>
</context-param>
<context-param>
<param-name>smtpPass</param-name>
<param-value>stosultomcat</param-value>
</context-param>
</web-app>

folders here

Tomcat位置不在工作区元数据上。

When i run the Servlet