Question

我不知道为什么这会出现在404，但我在同一个包中的其他servlet工作得很好。我必须在这里遗漏一些简单的东西。如果您发现任何错误，请告诉我。我正在阅读Murach java servlets一书并开始讨论这个问题，我不知道我做错了什么

当我尝试通过映射/ AE访问AddEmailListServlet时，我收到404错误。如果我尝试访问/ Emailsss，servlet加载就好了。不明白为什么??

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.0" xmlns="http://java.sun.com/xml/ns/javaee"xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd">
<servlet>
    <servlet-name>AddEmailListServlet</servlet-name>
    <servlet-class>email.AddEmailListServlet</servlet-class>
</servlet>
<servlet>
    <servlet-name>EmailServlet</servlet-name>
    <servlet-class>email.EmailServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>AddEmailListServlet</servlet-name>
    <url-pattern>/AE</url-pattern>
</servlet-mapping>
<servlet-mapping>
    <servlet-name>EmailServlet</servlet-name>
    <url-pattern>/Emailsss</url-pattern>
</servlet-mapping>
<session-config>
    <session-timeout>
        30
    </session-timeout>
</session-config>
<error-page>
    <error-code>404</error-code>
    <location>/error_404.jsp</location>
</error-page>
<error-page>
    <exception-type>java.lang.Throwable</exception-type>
    <location>/error_java.jsp</location>
</error-page>
</web-app>

AE映射不希望对AddEmailListServlet起作用。这是servlet代码：

package email;

import business.User;
import data.UserIO;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

import java.util.Date;
import java.util.ArrayList;
import java.util.HashMap;

public class AddEmailListServlet extends HttpServlet {

/**
 * Processes requests for both HTTP
 * <code>GET</code> and
 * <code>POST</code> methods.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
protected void processRequest(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    response.setContentType("text/html;charset=UTF-8");
    PrintWriter out = response.getWriter();
    try {
        /* TODO output your page here. You may use following sample code. */
        out.println("<!DOCTYPE html>");
        out.println("<html>");
        out.println("<head>");
        out.println("<title>Servlet AddToEmailListServlet</title>");            
        out.println("</head>");
        out.println("<body>");
        out.println("<h1>Servlet AddToEmailListServlet at " + request.getContextPath() + "</h1>");
        out.println("</body>");
        out.println("</html>");
    } finally {            
        out.close();
    }
}

// <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code.">
/**
 * Handles the HTTP
 * <code>GET</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
    this.doPost(request, response);
    PrintWriter out = response.getWriter();
    out.println("Hello from AddEmailListServlet.java");
}

/**
 * Handles the HTTP
 * <code>POST</code> method.
 *
 * @param request servlet request
 * @param response servlet response
 * @throws ServletException if a servlet-specific error occurs
 * @throws IOException if an I/O error occurs
 */
@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {

    String firstName = request.getParameter("firstName");
    String lastName = request.getParameter("lastName");
    String emailAddress = request.getParameter("emailAddress");

    ServletContext sc = request.getServletContext();
    String path = sc.getRealPath("/WEB-INF/EmailList.txt");

    User user = new User(firstName, lastName, emailAddress);
    UserIO.add(user, path);

    HttpSession session = request.getSession();
    session.setAttribute("user", user);

    String url = "/ch09/dispay_email_entry.jsp";
    RequestDispatcher dispatcher = 
            request.getServletContext().getRequestDispatcher(url);
    dispatcher.forward(request, response);

    //processRequest(request, response);
}

/**
 * Returns a short description of the servlet.
 *
 * @return a String containing servlet description
 */
@Override
public String getServletInfo() {
    return "Short description";
}// </editor-fold>
}

Answer 1

您的servlet不是servlet。它没有扩展HttpServlet。我甚至感到惊讶的是，由于这个错误，webapp部署没有错误。检查日志。

当您的意图是覆盖超类或接口方法时，始终使用@Override注释您的方法。如果您已经这样做，编译器会生成错误，警告您该方法没有覆盖任何内容。

404未找到加载在web.xml中映射的servlet

1 个答案: