jsp页面连接不上MySQL数据库的问题

迷南。 2023-02-24 07:53 1阅读 0赞

**jsp页面连接不上MySQL数据库**

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1284)
    	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1118)
    	at java.base/java.lang.Class.forName0(Native Method)
    	at java.base/java.lang.Class.forName(Class.java:332)
    	at Main.getConnection(Main.java:11)
    	at ServletLogin.doPost(ServletLogin.java:21)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:648)
    	at javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:230)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
    	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:192)
    	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:165)
    	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:198)
    	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:108)
    	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:522)
    	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:140)
    	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:79)
    	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:620)
    	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:87)
    	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:349)
    	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:1110)
    	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
    	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:785)
    	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1425)
    	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
    	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
    	at java.base/java.lang.Thread.run(Thread.java:835)

解决方法就是在WEB-INF下创建一个lib，并导入mysql-connector-java-5.1.37-bin.jar驱动jar包  
（自己真的菜，一切都做好了，就连导入jar包也是导入了，就是没有导入在WEB-INF目录下，自己还一直找错误在哪。。。。）  
**JDBC中的sql变量参数怎么写入String字符中**  
关键点就是处理好：’变量值‘ 变量值的外面有 ’ ‘是关键的，接下来就是字符串的拼接问题

String sql = "select * from user_table where username='"+name+"'"+"and password='"+password+"'";

不可以写成

String sql = "select * from user_table where username="+name+"and password="+password;

刚学习JDBC的菜鸟