运行一个java程序的时候竟然报java.lang.ClassNotFoundException异常？怎么解决？_java.lang.classnotfoundexception: utf-8-优快云博客

本文详细介绍了在Tomcat 7.0环境下部署JavaWeb工程的过程，包括web.xml配置和MyFirstServlet实现细节。作者遇到的问题是访问Servlet时出现ClassNotFoundException，并提供了错误堆栈跟踪，寻求解决方法。

本人新建了一个javaWeb的工程，Tomcat版本7.0。

以下是我的web.xml文件：

<?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_2_5.xsd" id="WebApp_ID" version="2.5">
  <display-name>WEB12_http</display-name>
  
  <servlet>
  	<servlet-name>MyFirstServlet</servlet-name>
  	<servlet-class>itheima.servlet.MyFirstServlet</servlet-class>
  </servlet>
  
  <servlet-mapping>
  	<servlet-name>MyFirstServlet</servlet-name>
  	<url-pattern>/myFirstServlet</url-pattern>
  </servlet-mapping>
  
  <welcome-file-list>
    <welcome-file>index.html</welcome-file>
    <welcome-file>index.htm</welcome-file>
    <welcome-file>index.jsp</welcome-file>
    <welcome-file>default.html</welcome-file>
    <welcome-file>default.htm</welcome-file>
    <welcome-file>default.jsp</welcome-file>
  </welcome-file-list>
</web-app>

我写的java程序是

package itheima.servlet;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletResponse;

public class MyFirstServlet implements Servlet{

	public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {
		HttpServletResponse response=(HttpServletResponse) arg1;
		response.getWriter().write("This is my first servlet!!!");
	}
	
	public void destroy() {
		// TODO 自动生成的方法存根
		
	}

	public ServletConfig getServletConfig() {
		// TODO 自动生成的方法存根
		return null;
	}

	public String getServletInfo() {
		// TODO 自动生成的方法存根
		return null;
	}

	public void init(ServletConfig arg0) throws ServletException {
		// TODO 自动生成的方法存根
		
	}

}

以下是我的工程目录：

Tomcat服务器开启后，我想通过http://localhost:8080/WEB12_http/myFirstServlet这个方式访问我的页面，效果图应该如下：

但是一执行发现报了错：

java.lang.ClassNotFoundException: itheima.servlet.MyFirstServlet
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1718)
	at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1569)
	at org.apache.catalina.core.DefaultInstanceManager.loadClass(DefaultInstanceManager.java:529)
	at org.apache.catalina.core.DefaultInstanceManager.loadClassMaybePrivileged(DefaultInstanceManager.java:511)
	at org.apache.catalina.core.DefaultInstanceManager.newInstance(DefaultInstanceManager.java:139)
	at org.apache.catalina.core.StandardWrapper.loadServlet(StandardWrapper.java:1143)
	at org.apache.catalina.core.StandardWrapper.allocate(StandardWrapper.java:864)
	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:134)
	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
	at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
	at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
	at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
	at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:313)
	at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
	at java.lang.Thread.run(Unknown Source)

这是什么问题呢？求大神帮帮小白