“HTTP状态404请求的资源不可用”

时间：2017-07-16 17:08:01

标签： java servlets

我是servlet编程的新手。我已经检查了有关Http 404错误的各种其他链接，但没有任何帮助。所以我在这里发布我的代码。

我在WebContent/文件夹form1.html，form2.html，form3.html中有三个html表单，所有这些表单都具有相同的url模式，因为在同一个Http会话中访问三种不同的表单

form1.html 

<html>
<head>
<title>Adhar Registration Form</title>
</head>
<body style="background-color:orange">
<h1>FORM 1</h1>
<form action="./reg" method="get">

<table>
<tr><td>NAME:</td><td><input type="text" name="id"/></td></tr>
<tr><td>F_NAME:</td><td><input type="text" name="name"/></td></tr>
<tr><td>M_NAME:</td><td><input type="text" name="email"/></td></tr>

<tr><td><input type="submit" name= "NEXT"> </td></tr>
</table>
<input type="hidden" name="fno" value="1">

</form>

</body>
</html>

form2.html 

<html>
<head>
<title>Adhar Registration Form</title>
</head>
<body style="background-color:orange">
<h1>FORM 2</h1>

<form action="./reg" method="get">

<table>
<tr><td>CONTACT:</td><td><input type="text" name="id"/></td></tr>
<tr><td>EMAIL:</td><td><input type="text" name="name"/></td></tr>
<tr><td>ADDRESS:</td><td><textarea rows ="10" cols="5" name="address"></textarea></td></tr>

<tr><td><input type="submit" name= "NEXT"> </td></tr>
</table>
<input type="hidden" name="fno" value="2">

</form>

</body>
</html>

<html>
<head>

<title>Adhar Registration Form</title>
</head>
<body style="background-color:orange">
<h1>FORM 3</h1>
<form action="./reg" method="get">

<table>
<tr><td>QUALIFICATION:</td><td><input type="text" name="id"/></td></tr>
<tr><td>PAN NO:</td><td><input type="text" name="name"/></td></tr>

<tr><td><input type="submit" name= "Register"> </td></tr>
</table>
<input type="hidden" name="fno" value="3">

</form>
</body>
</html>

的web.xml 

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>Adhar</display-name>
  <welcome-file-list>
    <welcome-file>form1.html</welcome-file>
  </welcome-file-list>
  
  <servlet>
    <servlet-name>login</servlet-name>
    <servlet-class>container.RegistrationServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>login</servlet-name>
    <url-pattern>/reg</url-pattern>
</servlet-mapping>
</web-app>

RegistrationServlet.java 

package container;

import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;

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;

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

    public static final String URL = "jdbc:mysql://localhost/db";
    public static final String USER = "root";
    public static final String PASSWORD = "12345";
    public static final String DRIVER_CLASS = "com.mysql.jdbc.Driver";

    /**
     * @see HttpServlet#HttpServlet()
     */
    public RegistrationServlet() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        PrintWriter out = response.getWriter();

        HttpSession hs = request.getSession();
        String fno = request.getParameter("fno");

        if(fno.equals("1")){
            String name = request.getParameter("name");
            String f_name = request.getParameter("f_name");
            String m_name = request.getParameter("m_name");

            hs.setAttribute("name", name);
            hs.setAttribute("f_name", f_name);
            hs.setAttribute("m_name", m_name);

            response.sendRedirect("./Form2.html");
        }
        if(fno.equals("2")){

            String contact = request.getParameter("contact");
            String email = request.getParameter("email");
            String address = request.getParameter("address");

            hs.setAttribute("contact", contact);
            hs.setAttribute("email", email);
            hs.setAttribute("address", address);

            response.sendRedirect("./Form3.html");
        }
        if(fno.equals("3")){

            String qual = request.getParameter("qual");
            String pan = request.getParameter("pan");

            String name = (String)hs.getAttribute("name");
            String f_name = (String)hs.getAttribute("f_name");
            String m_name = (String)hs.getAttribute("m_name");

            String contact = (String)hs.getAttribute("contact");
            String email = (String)hs.getAttribute("email");
            String address = (String)hs.getAttribute("address");

            try {
                Class.forName(DRIVER_CLASS);
                System.out.println("Loaded the driver");

                Connection con = DriverManager.getConnection(URL,USER,PASSWORD);
                PreparedStatement ps = con.prepareStatement("INSERT into adharReg values(?,?,?,?,?,?,?,?)");

                ps.setString(1, name);
                ps.setString(2, f_name);
                ps.setString(3, m_name);
                ps.setString(4, contact);
                ps.setString(5, email);
                ps.setString(6, address);
                ps.setString(7, qual);
                ps.setString(8, pan);

                int i = ps.executeUpdate();

                if(i!=0){
                    out.println("<h1>REGISTRATION SUCCESS</h1>");
                }
                else{
                    out.println("<h1>REGISTRATION FAILED</h1>");
                }

            } catch (Exception e) {
                // TODO: handle exception
                out.println("<h1>REGISTRATION FAILED" + e.getMessage() + " </h1>");
            }

        }
    }

}

我正在使用tomcat服务器8.0。我检查了这个Link，我的tomcat服务器具有完全相同的设置。并且this link跟随任何可能的错误但是，我不知道为什么我得到Http 404错误的确切原因。帮帮我解决为什么我收到此错误。

感谢。

2 个答案:

答案 0 :(得分：0)

检查web.xml是否存在于WEB-INF文件夹中。

并使用servlet映射到web.xml

并在web.xml中注册servlet，如下所示：

<servlet>
<servlet-name>yourServlet</servlet-name>
<servlet-class>com.example.YourServlet</servlet-class>
</servlet>

<servlet-mapping>
<servlet-name>yourServlet</servlet-name>
<url-pattern>/servlet</url-pattern>  
</servlet-mapping>

更多参考下面的链接： -

http://www.beingjavaguys.com/2013/08/jsp-servlet-hello-world-example.html

https://www.javatpoint.com/servlet-with-annotation

答案 1 :(得分：0)

该问题是由web.xml配置与WebServlet批注之间的冲突引起的。 web.xml是一个名为login的servlet，它目标是/ reg url，但是在RegistrationServlet中，还有一个@WebServlet注释的声明引用了同一个url / reg。

一种可能的解决方案是从web.xml中删除servlet声明，这意味着web.xml内容应该是这样的。

的web.xml 

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>Adhar</display-name>
  <welcome-file-list>
    <welcome-file>form1.html</welcome-file>
  </welcome-file-list>

</web-app>

只允许通过注释声明Servlet。希望这会有所帮助。

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