我有 Eclipse 作为我的 IDE、tomcat 服务器 9.0、MySQL 都在 Windows 10 中运行。
我创建了一个简单的项目来连接MySQL中的简单数据库，当我创建JAVA项目时代码运行完美，但是当我在Dynamic Web下创建servlet时，相同的代码失败项目。
这是代码，问题是Class.forName
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
Connection conn = null;
try {
Class.forName("com.mysql.jdbc.Driver");
conn = DriverManager.getConnection("jdbc:mysql://localhost/amir","root","1234");
} catch (SQLException e) {
e.printStackTrace();
} catch (ClassNotFoundException e) {
e.printStackTrace();
}
response.setContentType("text/html");
PrintWriter p = response.getWriter();
p.println ("<html><body><h3>Hi</h3></body></html>");
}
这是StackTrace:
java.lang.ClassNotFoundException: com.mysql.jdbc.Driver at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1275) at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1109) at java.lang.Class.forName0(Native Method) at java.lang.Class.forName(Unknown Source) at myServlet.DynamicWeb.doGet(DynamicWeb.java:36) at javax.servlet.http.HttpServlet.service(HttpServlet.java:635) at javax.servlet.http.HttpServlet.service(HttpServlet.java:742) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53) at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193) at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166) at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:199) at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96) at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:475) at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140) at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:80) at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:624) at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87) at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:342) at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:498) at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66) at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:796) at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1368) at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49) 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)
最佳答案
您收到类未找到异常，因为包中的这些类不存在于 WEB-INF/lib 文件夹中。
您必须将项目中使用/包含的所有库或 jar 手动复制到 WEB-INF/lib 文件夹。
在这种情况下，将连接 db 所需的所有 jar 或库文件复制到动态 Web 项目的 WEB-INF/lib 文件夹中，它一定可以正常工作。
关于java - MySQL 与 Java (Servlet) 连接的 ClassNotFoundException，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/43718248/