我刚刚开始为Web开发人员学习Java。我正在阅读第2章的教程。我已经逐行检查了它,一切都是一样的。我还不知道它还没有弄清楚问题。这是我的错误:
exception
javax.servlet.ServletException: Error instantiating servlet class apress.helloworld.HelloWorld
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:526)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:655)
org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Unknown Source)
root cause
java.lang.ClassNotFoundException: apress.helloworld.HelloWorld
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1324)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1177)
org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:503)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:610)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:526)
org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1078)
org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:655)
org.apache.coyote.http11.Http11NioProtocol$Http11ConnectionHandler.process(Http11NioProtocol.java:222)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1566)
org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1523)
java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
java.lang.Thread.run(Unknown Source)
这是我的代码:
package apress.helloworld;
import java.io.IOException;
import java.io.PrintWriter;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class HellowWorld extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) {
try {
response.setContentType("text/html");
PrintWriter printWriter = response.getWriter();
printWriter.println("<h2>");
printWriter.println("hello World!");
printWriter.println("</h2>");
} catch (IOException ioException) {
ioException.printStackTrace();
}
}
}
和web.xml(不确定是否相关)
<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
<display-name>helloworld</display-name>
<servlet>
<servlet-name>HelloWorld</servlet-name>
<servlet-class>apress.helloworld.HelloWorld</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>HelloWorld</servlet-name>
<url-pattern>/hello</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>
任何人都可以帮助我,所以我可以学习java ??
答案 0 :(得分:2)
你的班级名称中有拼写错误(附加'w')。修复,重新编译,世界将再次美丽。请记住更改文件名以匹配类名。 ;)
public class HellowWorld extends HttpServlet
答案 1 :(得分:1)
在您收到的错误消息中,第一部分的底线显示“未知来源”,这可能是因为找不到您的课程。这是因为你在“apress.helloworld”包下面有它,但是把你的类名称拼写为“HellowWorld”。修复类名,所有内容都应该正常运行。