ClassNotFoundException:com.mysql.jdbc.Driver。 JDBC MySQL驱动程序用于Web应用程序 [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.jar文件的MySQL JDBC驱动程序,它在我的库源文件夹下,我有以下代码:

  public static Connection getConnection()throws SQLException {
Connection conn = null;
尝试{
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:服务器启动在645 ms 
java.lang.ClassNotFoundException:com.mysql.jdbc.Driver
at org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1678)
在org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523)
在java.lang。 Class.forName0(Native Method)
在java.lang.Class.forName(Class.java:169)
在gbook.DbHelper.getConnection(DbHelper.java:14)
在gbook。 DbHelper.getGuestBook(DbHelper.java:51)
在org.apache.jsp.index_jsp._jspService(index_jsp.java:83)
在org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase。 java:70)
在javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
在org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:433)
在org.apache.jasper.servlet.JspServlet.serviceJspFile(J spServlet.java:389)
在org.apache.jasper.servlet.JspServlet.service(JspServlet.java:333)
在javax.servlet.http.HttpServlet.service(HttpServlet.java:722)
在org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:304)
在org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
在org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:224)
在org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:169)
在org.apache .catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)
在org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)
在org.apache.catalina.valves .ErrorReportValve.invoke(ErrorReportValve.java:100)
在org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:929)
在org.apache.catalina.core.StandardEngineValve.inv oke(StandardEngineValve.java:118)
在org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:405)
在org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor。 java:964)
在org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process(AbstractProtocol.java:515)
在org.apache.tomcat.util.net.JIoEndpoint $ SocketProcessor.run(JIoEndpoint。 java:302)
在java.util.concurrent.ThreadPoolExecutor $ Worker.runTask(ThreadPoolExecutor.java:886)
在java.util.concurrent.ThreadPoolExecutor $ Worker.run(ThreadPoolExecutor.java:908)
在java.lang.Thread.run(Thread.java:680)
2011年12月1日下午1:41:05 org.apache.catalina.core.StandardWrapperValve调用
SEVERE:Servlet .service()用于在路径[/ JDBC-MySQL]的上下文中使用servlet [jsp] [root]引发异常[javax.servlet.ServletException:java.lang.NoClassDefFoundError:com / mysql / jdbc / Connection]
java .lang.ClassNotFoundException:com.mysq l org.apache.catalina.loader.WebappClassLoader.loadClass(WebappClassLoader.java:1523 )
在gbook.DbHelper.getGuestBook(DbHelper.java:52)
在org.apache.jsp.index_jsp._jspService(index_jsp.java:83)
在org.apache.jasper。 runtime.jsp >

这是我如何添加jar文件。我创建了一个lib文件夹,将jar放在里面,然后我去配置eclipse中的构建路径,并将lib文件夹中的jar添加到项目中。

解决方案你错过了你的类路径中的mysql-connector-j jar文件。使用java -cp。:mysql.jar ...。欧。这是一个webapp!然后把mysql jar文件放到WEB-INF / lib文件夹中。


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;

    }

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)

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.

解决方案

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.

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