HTTP狀態500-由DeploymentDescriptorLoadException引起的實例化Servlet類錯誤

Question

我試圖自學servlet和Tomcat等。我在線上學習了一些教程，並嘗試使用maven構建我的第一個servlet，然后出現此錯誤：

type Exception report

message Error instantiating servlet class com.perficient.servlets.HelloWorld

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

exception

javax.servlet.ServletException: Error instantiating servlet class com.perficient.servlets.HelloWorld
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    org.apache.tomcat.util.net.JIoEndpoint$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.perficient.servlets.HelloWorld
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1858)
    org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1709)
    org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:956)
    org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:625)
    org.apache.tomcat.util.net.JIoEndpoint$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/7.0.64 logs.

我在網上做了一些研究，但沒有一個答案能解決我的問題。 我的項目樹如下所示： 項目樹

問題說：

Description Resource    Path    Location    Type
CHKJ3000E: WAR Validation Failed: org.eclipse.jst.j2ee.commonarchivecore.internal.exception.DeploymentDescriptorLoadException: WEB-INF/web.xml  FirstWebapp     Unknown Validation Message

因此，我認為web.xml一定有問題，但我不熟悉此錯誤消息。 這是我的web.xml：

<!DOCTYPE web-app PUBLIC
 "-//Sun Microsystems, Inc.//DTD Web Application 2.3//EN"
 "http://java.sun.com/dtd/web-app_2_3.dtd" >

<web-app>
    <display-name>Archetype Created Web Application</display-name>

    <servlet>
        <servlet-name>HelloWorld</servlet-name>
        <servlet-class>com.perficient.servlets.HelloWorld</servlet-class>
    </servlet>

    <servlet-mapping>
        <servlet-name>HelloWorld</servlet-name>
        <url-pattern>/HelloWorld</url-pattern>
    </servlet-mapping>
</web-app>

有人知道我的web.xml出了什么問題嗎？ 非常感謝！

Answer 1

ClassNotFoundException：com.perficient.servlets.HelloWorld

1. Tomcat無法找到您的HelloWorld類。 確保在WEB-INF / classes中添加了com.perficient.servlets.HelloWorld。

2. 將映射更改為：

    <servlet-mapping> <servlet-name>HelloWorld</servlet-name> <url-pattern>/servlet/HelloWorld</url-pattern> </servlet-mapping>