Java 执行servlet程序时出错

在练习servlet程序时，我遇到了这个问题。现在我在我创建的任何项目中都面临着同样的问题。不知道我做错了什么。我正在使用netbeans 8.1和glass fish服务器。错误是：-

HTTP Status 500 - Internal Server Error
type Exception report
messageInternal Server Error
descriptionThe server encountered an internal error that prevented it from      
fulfilling this request.
exception javax.servlet.ServletException: Error instantiating servlet class calc
root cause
com.sun.enterprise.container.common.spi.util.InjectionException: Error creating managed object for class: class calc

root cause

java.lang.NoSuchMethodException: calc.<init>()

note The full stack traces of the exception and its root causes are available in the   
GlassFish Server Open Source Edition 4.1 logs.
GlassFish Server Open Source Edition 4.1 

xml代码：-

<?xml version="1.0" encoding="UTF-8"?>
<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">
    <servlet>
       <servlet-name>calc</servlet-name>
       <servlet-class>calc</servlet-class>
    </servlet>
    <servlet-mapping>
       <servlet-name>calc</servlet-name>
       <url-pattern>/calc</url-pattern>
    </servlet-mapping>
    <session-config>
       <session-timeout>
           30
       </session-timeout>
    </session-config>
    <welcome-file-list>
       <welcome-file>index.html</welcome-file>
    </welcome-file-list>
</web-app>

计算
计算
计算
/计算
30
index.html

您的serlvet类必须扩展javax.servlet.http.HttpServlet类

public class calc extends the javax.servlet.http.HttpServlet
{
    public void doGet(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException
    {
    .....

对于第二个错误，我不确定为什么会出现此错误，可能是inject对象的另一个配置，但要解决此问题，必须创建一个没有参数的公共构造函数

public class calc extends the javax.servlet.http.HttpServlet
    {
        public calc() {}
        public void doGet(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException
        {
    .....

---

你想点击的网址是什么？对于index.html，它与参数一起完美运行，参数根据action=“”进入servlet是愚蠢的错误。我纠正了它，但现在它是一个完全不同的错误。我更新了post@augustushill你能把错误日志部分贴在日志部分吗？我是这个网站的新手，这是某种错误发布约定吗？只需复制并通过glassfish日志中的文本，您会发现java.lang.NoSuchMethodException问题。没有为类指定访问说明符。这是个错误。谢谢。：）

public class calc extends the javax.servlet.http.HttpServlet
{
    public void doGet(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException
    {
    .....

public class calc extends the javax.servlet.http.HttpServlet
    {
        public calc() {}
        public void doGet(HttpServletRequest req,HttpServletResponse res) throws IOException,ServletException
        {
    .....