为什么我为Class.forName（" com.mysql.jdbc.Driver"）获取类找不到异常; [英] Why I am getting class not found exception for Class.forName("com.mysql.jdbc.Driver");
问题描述
我正在开发一个Web应用程序使用：eclipse IDE（Marse），Java 8，Apache tomcat 8，MySQL。
我的用户注册代码如下：
I am developing an web app Using : eclipse IDE(Marse), Java 8, Apache tomcat 8, MySQL. My code for user registration is as follows:
System.out.println("Connecting....");
Class.forName("com.mysql.jdbc.Driver");
System.out.println("Class found....");
String url="jdbc:mysql://localhost:3306/db";
String user="root";
String password="root";
System.out.println("success");
Connection conn = DriverManager.getConnection(url,user,password);
String query = "insert into login (username,password,emailid,country,city) values (?,?,?,?,?)";
PreparedStatement ps = conn.prepareStatement(query);
ps.setString(1,b.getUsername());
ps.setString(2,b.getPassword());
ps.setString(3,b.getEmailid());
ps.setString(4,b.getCountry());
ps.setString(5,b.getCity());
int count=ps.executeUpdate();
ps.close();
conn.close();
我的代码也正确我也添加了mysql-connector-java-5.1.36 在eclipse中使用 Build path> add_external_jar 选项。但仍然为什么它给我这样的例外呢？
My code is also correct and also I added mysql-connector-java-5.1.36 by using Build path>add_external_jar option in eclipse. But still why it gives me such a exception ?
连接....
java.lang.ClassNotFoundException：com.mysql .gdbc.Driver
org.apache.catalina.loader.WebappClassLoaderBase.loadClass（WebappClassLoaderBase.java:1332）
at org.apache.catalina.loader.WebappClassLoaderBase.loadClass（WebappClassLoaderBase.java:1166）
at java.lang.Class.forName0（Native Method）
at java.lang.Class.forName（Unknown Source）
at model.InfoModel.SaveInfo（InfoModel.java:14）
at controller.Register_user.doGet（Register_user.java:35）
at javax.servlet.http.HttpServlet.service（HttpServlet.java:622)
at javax.servlet.http.HttpServlet。 service（HttpServlet.java:729）
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:291）
at org.apache.catalina.core.ApplicationFilterChain.doFilter（ApplicationFilterChain。 java：206）
at org.apache.to mcat.websocket.server.WsFilter.doFilter（WsFilter.java:52）
at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter（ApplicationFilterChain.java:239）
at org.apache.catalina。 core.ApplicationFilterChain.doFilter（ApplicationFilterChain.java:206）
at org.apache.catalina.core.StandardWrapperValve.invoke（StandardWrapperValve.java:219）
at org.apache.catalina.core.StandardContextValve。在org.apache.catalina.authenticator.AuthenticatorBase.invoke（AuthenticatorBase.java:502）上调用（StandardContextValve.java:106）
org.apache.catalina.core.StandardHostValve.invoke（StandardHostValve。 java：142）
at org.apache.catalina.valves.ErrorReportValve.invoke（ErrorReportValve.java:79）
at org.apache.catalina.valves.AbstractAccessLogValve.invoke（AbstractAccessLogValve.java:616）
at org.apache.catalina.core.StandardEngineValve.invoke（StandardEngineValve.java:88）
at org.apache.catalina.connector.Coy oteAdapter.service（CoyoteAdapter.java:518）
at org.apache.coyote.http11.AbstractHttp11Processor.process（AbstractHttp11Processor.java:1091）
at org.apache.coyote.AbstractProtocol $ AbstractConnectionHandler.process（ AbstractProtocol.java:673）
at org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.doRun（NioEndpoint.java:1526）
at org.apache.tomcat.util.net.NioEndpoint $ SocketProcessor.run（NioEndpoint.java:1482）
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）
Connecting.... java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1332) at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1166) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at model.InfoModel.SaveInfo(InfoModel.java:14) at controller.Register_user.doGet(Register_user.java:35) at javax.servlet.http.HttpServlet.service(HttpServlet.java:622) at javax.servlet.http.HttpServlet.service(HttpServlet.java:729) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:291) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:239) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:206) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:219) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:106) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:142) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:616) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:88) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:518) at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1091) at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:673) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1526) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1482) at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source) at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Unknown Source)
推荐答案
右键单击项目，转到属性。从左窗格中选择部署程序集（如果未找到，请阅读更新部分）。检查是否提供了 Java构建路径条目。如果没有，请单击添加并包含它。如果已经存在，请单击添加以将连接器jar包含为存档。执行项目> 清理，重新启动服务器。
Right click on the Project, go to Properties. Choose Deployment Assembly (if not found, read the update part) from the left pane. Check if Java Build Path Entries are provided. If not, click on Add and include it. If it is already present, click Add to include your connector jar as Archive. Do a Project>Clean, restart your Server.
如果项目没有分面，您将找不到此选项。您可以单击 Project Facets ，转换为分面结构并添加动态Web模块和相关的依赖项。
If the Project is not being Faceted, you will not find this option. You can click on Project Facets, convert to faceted structure and add Dynamic Web Module and related dependencies.
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