Java Servlet，http 状态 404，请求的资源不可用

Question

我正在尝试使用 Eclipse IDE 和 Tomcat7 服务器在 java 中创建一个 servlet。当我运行服务器中的 HelloForm 时，它会显示表单，但在输入数字并单击提交后，它会显示：

HTTP Status 404 - /Test2/HelloWorld

type Status report

message /Test2/HelloWorld

description The requested resource is not available.

Apache Tomcat/7.0.47

HelloForm.html

的代码

<!DOCTYPE html>
<html>
<body>
    <form action="HelloWorld" method="post">
        Enter 1st number : <input type="text" name="num1"> <br>
        Enter 2st number : <input type="text" name="num2"> <br> <input
            type="submit">
    </form>
</body>
</html>

HelloWorld.java

的代码

package mypkg;

public class HelloWorld extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        int num1 = Integer.parseInt(request.getParameter("num1"));
        int num2 = Integer.parseInt(request.getParameter("num2"));
        int sum = num1 + num2;
        System.out.println(sum);
        PrintWriter out = response.getWriter();
        out.println("Addition : " + sum);
    }
}

代码 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">

    <servlet>
        <servlet-name>HelloWorldServlet</servlet-name>
        <servlet-class>mypkg.HelloWorld</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloWorldServlet</servlet-name>
        <url-pattern>/sayhello</url-pattern>
    </servlet-mapping>

</web-app>

Answer 1

您错过了 @WebServlet("/HelloWorld")。下面是完整的代码：

package mypkg;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

@WebServlet("/sayhello")
public class HelloWorld extends HttpServlet {

    protected void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {

        int num1 = Integer.parseInt(request.getParameter("num1"));
        int num2 = Integer.parseInt(request.getParameter("num2"));
        int sum = num1 + num2;
        System.out.println(sum);
        PrintWriter out = response.getWriter();
        out.println("Addition : " + sum);
    }
}

确保您的 web.xml 具有以下根声明，否则它将不会被解释为支持 @WebServlet 注释的 Servlet 3.0。

<web-app 
    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"
    version="3.0">

更新：

我看到您现在已经在问题中添加了您的 web.xml 的内容。根据此更新，您的 HTML form action 应如下所示：

<form action="sayhello" method="post">

Java Servlet，http 状态 404，请求的资源不可用

Java Servlet, http status 404, The requested resource is not available

servlets

http-status-code-404