java HttpServlet 的 Tomcat ClassNotFoundException
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原文地址: http://stackoverflow.com/questions/15803082/
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StackOverFlow
Tomcat ClassNotFoundException for HttpServlet
提问by Steve Robinson
We are getting a java.lang.ClassNotFoundException: HttpServletwith a JSP project running on the Apache Tomcat server (v5.5) in Eclipse. The lib folder under Web-inf does have the servelt-api jar. And furthermore we have imported the javax.servlet.http.* library. But still we are getting this exception.
我们正在java.lang.ClassNotFoundException: HttpServletEclipse中获得一个在 Apache Tomcat 服务器 (v5.5) 上运行的 JSP 项目。Web-inf 下的 lib 文件夹确实有 servelt-api jar。此外，我们还导入了 javax.servlet.http.* 库。但是我们仍然收到此异常。
package com.bean;
import java.io.*;
import java.util.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class AdminLogin extends HttpServlet{
ArrayList list=new ArrayList();
public void doGet(HttpServletRequest request,HttpServletResponse response) throws ServletException,IOException{
try{
response.setContentType("text/html");
PrintWriter out=response.getWriter();
String id=request.getParameter("user");
String pass=request.getParameter("pass");
System.out.println("ID==================>>"+id+"PASS========>>"+pass);
if(id.equalsIgnoreCase("admin")&&pass.equalsIgnoreCase("admin"))
{
response.sendRedirect("AdminPage.jsp");
}
else
{
response.sendRedirect("Failure.html");
}
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
Error Stack Trace:
错误堆栈跟踪：
java.lang.NoClassDefFoundError: HttpServlet
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClassCond(Unknown Source)
java.lang.ClassLoader.defineClass(Unknown Source)
java.security.SecureClassLoader.defineClass(Unknown Source)
org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1847)
org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:873)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1326)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
java.lang.Thread.run(Unknown Source)
root cause
java.lang.ClassNotFoundException: HttpServlet
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1359)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
java.lang.ClassLoader.defineClass1(Native Method)
java.lang.ClassLoader.defineClassCond(Unknown Source)
java.lang.ClassLoader.defineClass(Unknown Source)
java.security.SecureClassLoader.defineClass(Unknown Source)
org.apache.catalina.loader.WebappClassLoader.findClassInternal(WebappClassLoader.java:1847)
org.apache.catalina.loader.WebappClassLoader.findClass(WebappClassLoader.java:873)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1326)
org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1205)
org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:117)
org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:151)
org.apache.coyote.http11.Http11Processor.process(Http11Processor.java:870)
org.apache.coyote.http11.Http11BaseProtocol$Http11ConnectionHandler.processConnection(Http11BaseProtocol.java:665)
org.apache.tomcat.util.net.PoolTcpEndpoint.processSocket(PoolTcpEndpoint.java:528)
org.apache.tomcat.util.net.LeaderFollowerWorkerThread.runIt(LeaderFollowerWorkerThread.java:81)
org.apache.tomcat.util.threads.ThreadPool$ControlRunnable.run(ThreadPool.java:685)
java.lang.Thread.run(Unknown Source)
Web.xml:
网页.xml：
<?xml version="1.0" encoding="UTF-8"?>
<web-app id="WebApp_ID" version="2.4" xmlns="http://java.sun.com/xml/ns/j2ee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://java.sun.com/xml/ns/j2ee http://java.sun.com/xml/ns/j2ee/web-app_2_4.xsd">
<display-name>CarPooling</display-name>
<servlet>
<description>
</description>
<display-name>AdminLogin</display-name>
<servlet-name>AdminLogin</servlet-name>
<servlet-class>com.bean.AdminLogin</servlet-class>
</servlet>
<servlet>
<servlet-name>employee</servlet-name>
<servlet-class>com.bean.UserLogin</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>AdminLogin</servlet-name>
<url-pattern>/demo</url-pattern>
</servlet-mapping>
<servlet-mapping>
<servlet-name>employee</servlet-name>
<url-pattern>/login</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-list>
</web-app>
project folder structure:
项目文件夹结构：
回答by Hardik Mishra
The lib folder under Web-inf does have the servelt-api jar.
Web-inf 下的 lib 文件夹确实有 servelt-api jar。
There is no need to add servlet-api.jar to Classpath. IDE takes care of that.
不需要将 servlet-api.jar 添加到 Classpath。IDE 负责解决这个问题。
Check whether you Build Path contains Tomcat libraries.
检查您的构建路径是否包含 Tomcat 库。
Right click on Project --> Properties.
右键单击项目 --> 属性。
Sample Screen
示例屏幕
回答by Bhanu Hoysala
1: Right Click on your Project -> 2: Build path -> 3: Add Libraries -> 4: User Libraries -> 5: click on user libraries -> 6: click on new -> 7: Give an library name you like -> 8: click on "Add External Jars" -> 9: browse and select any of the jar file you need.
1：右键单击您的项目-> 2：构建路径-> 3：添加库-> 4：用户库-> 5：单击用户库-> 6：单击新建-> 7：给出您喜欢的库名称-> 8：单击“添加外部罐子”-> 9：浏览并选择您需要的任何 jar 文件。
but in your case if you need servlet-api.jarit is located at TomcatX.X/lib/*.jar
但在你的情况下，如果你需要servlet-api.jar它位于 TomcatX.X/lib/*.jar
Consider this solution if you are missing only that .jar file. It is not a best practice at all for the core libraries.
如果您只缺少该 .jar 文件，请考虑使用此解决方案。对于核心库来说，这根本不是最佳实践。
If your PC is properly configured these library files are automatically loaded to your project by eclipse.
如果您的 PC 配置正确，这些库文件会通过 eclipse 自动加载到您的项目中。
