ClassNotFoundException：com.mysql.jdbc.Driver。 用于Web应用程序的JDBC MySQL驱动程序

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

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：

 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文件的方式。 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。

Answer 1

您错过了类路径中的mysql-connector-j jar文件。 使用“java -cp。：mysql.jar …”。 欧。 这是一个webapp！ 然后将mysql jar文件放到WEB-INF / lib文件夹中。

Answer 2

右键单击Libraries – > Add JAR / Folder并选择mysql-connector-java.jar文件

Answer 3

如果您使用的是Apache Tomcat，则可能必须使用Java选项卡中的“配置Tomcat”将驱动程序添加到路径中。