java.lang.ClassNotFoundException：at jdbc.DatabaseAccess.doGet（DatabaseAccess.java:25）

时间：2015-05-04 12:58:06

标签： java mysql servlets jdbc

我正在尝试使用servlet和jdbc连接到MySQL数据库的简单登录身份验证。在tomcat服务器上执行后，我收到以下错误： 

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at jdbc.DatabaseAccess.doGet(DatabaseAccess.java:25)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)
May 04, 2015 6:06:29 PM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/servelt] has started
May 04, 2015 6:06:29 PM org.apache.catalina.core.StandardContext reload
INFO: Reloading Context with name [/servelt] is completed
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1720)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1571)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Unknown Source)
    at jdbc.DatabaseAccess.doGet(DatabaseAccess.java:25)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:624)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:303)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:241)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:208)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:220)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:122)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:505)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:170)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:103)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:950)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:116)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:423)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1079)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:620)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:316)
    at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)
    at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    at java.lang.Thread.run(Unknown Source)

我正在分享所有文件的内容： DatabaseAccess.java 

package jdbc;
import java.io.*;
import javax.servlet.*;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.*;
import java.sql.*;
@WebServlet("/DatabaseAccess") 
public class DatabaseAccess extends HttpServlet
{
    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp)
            throws ServletException, IOException 
    {
            resp.setContentType("text/html");
            PrintWriter out = resp.getWriter();
            String title = "Database connect";
            String docType ="<!doctype html>\n";
            out.println(docType +"<html>\n" +"<head><title>" + title + "</title></head>\n" +"<body>\n" +
                 "<h1 align=\"center\">" + title + "</h1>\n");
            try 
            {
            Class.forName("com.mysql.jdbc.Driver");
            Connection con=DriverManager.getConnection("jdbc:mysql://localhost:3306/test","root","root");  
            Statement stmt=con.createStatement();  
            ResultSet rs=stmt.executeQuery("select * from student");
            while(rs.next()){
                int id  = rs.getInt("id");
                int marks = rs.getInt("marks");
                String name = rs.getString("name");
                out.println("ID: " + id + "<br>");
                out.println(", name: " + name + "<br>");
                out.println(", marks: " + marks + "<br>");
             }
             out.println("</body></html>");
             rs.close();
             stmt.close();
             con.close();
        } 
        catch (Exception e) 
        {
            e.printStackTrace();
        }  

    }

}

WEB.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>servelt</display-name>
  <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>

   <servlet>
     <servlet-name>DatabaseAccess</servlet-name>
     <servlet-class>jdbc.DatabaseAccess</servlet-class>
 </servlet>
 <servlet-mapping>
     <servlet-name>DatabaseAccess</servlet-name>
     <url-pattern>/DatabaseAccess</url-pattern>
  </servlet-mapping>


</web-app>

请帮我解决这个问题。

3 个答案:

答案 0 :(得分：0)

将您的mysql连接器jar添加到要由tomcat

加载的WEB-INF \ lib文件夹中

答案 1 :(得分：0)

异常是java.lang.ClassNotFoundException:在lib文件夹或类路径中添加相应的jar

答案 2 :(得分：0)

您的源代码是正确的。例外情况表明，mysql连接器不在您的库中。您必须将mysql jdbc连接器添加到您的应用程序 classpath 和 WEB-INF / lib 类路径并单独运行任何方法，则不会发生异常，但是如果调用此方法，则会从servlet或jsp发生错误。对于解决方案，您还必须添加mysql jdbc连接器jar到 WEB-INF / lib

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