JSP & servlet ：javax.servlet.ServletException
新手刚开始学习JSP与servlet，不知道为什么总是报这个异常
javax.servlet.ServletException: Error instantiating servlet class com.soft.whdx.servlet.LoginSerlvet
下面是详细错误报告：
type Exception report

message Error instantiating servlet class com.soft.whdx.servlet.LoginSerlvet

description The server encountered an internal error that prevented it from fulfilling this request.

exception

javax.servlet.ServletException: Error instantiating servlet class com.soft.whdx.servlet.LoginSerlvet
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2441)
org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2430)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
java.lang.Thread.run(Thread.java:619)
root cause

java.lang.ClassNotFoundException: com.soft.whdx.servlet.LoginSerlvet
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:501)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1040)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:607)
org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.doRun(AprEndpoint.java:2441)
org.apache.tomcat.util.net.AprEndpoint$SocketProcessor.run(AprEndpoint.java:2430)
java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
java.lang.Thread.run(Thread.java:619)
note The full stack trace of the root cause is available in the Apache Tomcat/7.0.53 logs.

其中servlet源代码如下：
package com.soft.MyFirstWebProject.servlet;

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

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

import