将servlet部署到Glassfish后的Java - 404

<servlet>
    <servlet-name>MyServlet</servlet-name>
    <servlet-class>com.example.MyServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>MyServlet</servlet-name>
    <url-pattern>/myServlet</url-pattern>
</servlet-mapping>

package com.example;

import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class MyServlet extends HttpServlet {
    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.getWriter().println("Hello, World!");
    }
}

myapp.war
├── WEB-INF
│   ├── classes
│   │   └── com
│   │       └── example
│   │           └── MyServlet.class
│   └── web.xml