Java 无法在tomcat服务器上运行简单Servlet。获取HTTP状态500-实例化servlet类com.main.Hello时出错

当我试图在Tomcat服务器上运行一个简单的servlet类时，它给出了这个错误

HTTP Status 500 - Error instantiating servlet class com.main.Hello

type Exception report
message Error instantiating servlet class com.main.Hello
description The server encountered an internal error that prevented it 
from fulfilling this request.

exception

javax.servlet.ServletException: Error instantiating servlet class com.main.Hello
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)

root cause

java.lang.ClassNotFoundException: com.main.Hello
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1892)
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1735)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:506)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:962)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:452)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1087)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:637)
org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Thread.java:745)

note The full stack trace of the root cause is available in the Apache Tomcat/7.0.75 logs.
Apache Tomcat/7.0.75

我不明白出了什么问题。我查过我知道的一切。在XML中正确映射。下面是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" id="WebApp_ID" version="3.0">
<display-name>Web_Application</display-name>
  <servlet>
    <servlet-name>Hello</servlet-name>
    <servlet-class>com.main.Hello</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>Hello</servlet-name>
    <url-pattern>/hello</url-pattern>
  </servlet-mapping>
</web-app>

网络应用
你好
你好
你好
/你好

如果需要更多信息，请告诉我。请帮我解决这个问题

---

谢谢。

请正确检查您的类路径，并确保

web.xml

存在于

web-INF

文件夹中。然后清理项目并运行它。

您是否确实在com.main.Hello.java上编写了servlet文件？

java.lang.ClassNotFoundException:com.main.Hello

此消息表明WAR文件和/或部署过程存在问题

Tomcat

找不到.class文件。