ClassNotFoundException: com.mysql.jdbc.Driver.用于 Web 应用程序的 JDBC MySQL 驱动程序 [英] ClassNotFoundException: com.mysql.jdbc.Driver. JDBC MySQL driver for web application

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问题描述

所以我有一个 MySQL JDBC 驱动程序的 .jar 文件,它在我的库源文件夹下,我有以下代码:

So I have a .jar file for the MySQL JDBC driver, it is under my libraries source folder and I have the following code:

public static Connection getConnection() throws SQLException {
        Connection conn = null;
        try{
            Class.forName("com.mysql.jdbc.Driver").newInstance();
            String url = "jdbc:mysql://50.56.81.42:3306/GUEST_BOOK";
            String user = "user";
            String password = "pass";

            conn = (Connection) DriverManager.getConnection(url, user, password);
        }catch(ClassNotFoundException e){
            e.printStackTrace();
        }catch(InstantiationException e){
            e.printStackTrace();
        }catch(IllegalAccessException e){
            e.printStackTrace();
        }
            return conn;

    }

但是,它总是给我这个错误:

However, it always gives me this error:

INFO: Server startup in 645 ms
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
    at java.lang.Class.forName0(Native Method)
    at java.lang.Class.forName(Class.java:169)
    at gbook.DbHelper.getConnection(DbHelper.java:14)
    at gbook.DbHelper.getGuestBook(DbHelper.java:51)
    at org.apache.jsp.index_jsp._jspService(index_jsp.java:83)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:433)
    at org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:389)
    at org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:100)
    at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:964)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:515)
    at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:302)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:680)
Dec 1, 2011 1:41:05 PM org.apache.catalina.core.StandardWrapperValve invoke
SEVERE: Servlet.service() for servlet [jsp] in context with path [/JDBC-MySQL] threw exception [javax.servlet.ServletException: java.lang.NoClassDefFoundError: com/mysql/jdbc/Connection] with root cause
java.lang.ClassNotFoundException: com.mysql.jdbc.Connection
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
    at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
    at gbook.DbHelper.getGuestBook(DbHelper.java:52)
    at org.apache.jsp.index_jsp._jspService(index_jsp.java:83)
    at org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)

这是我添加 jar 文件的方法.我创建了一个lib文件夹并将jar放入其中,然后我在eclipse中配置构建路径并将lib文件夹中的jar添加到项目中.

Here's how I added the jar file. I created a lib folder and put the jar inside and then I go to configure build path in eclipse and added the jar inside the lib folder to the project.

推荐答案

您在类路径中遗漏了 mysql-connector-j jar 文件.使用java -cp .:mysql.jar...".欧.这是一个网络应用程序!然后将mysql jar文件放到WEB-INF/lib文件夹下.

You missed mysql-connector-j jar file in your classpath. Use "java -cp .:mysql.jar...". Ou. It's a webapp! Then put mysql jar file to WEB-INF/lib folder.

这篇关于ClassNotFoundException: com.mysql.jdbc.Driver.用于 Web 应用程序的 JDBC MySQL 驱动程序的文章就介绍到这了,希望我们推荐的答案对大家有所帮助,也希望大家多多支持IT屋!

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