一个jsp登录注册页面，在连接到数据库验证时tomcat服务器500报错。

Question

HTTP状态 500 - 内部服务器错误
类型 异常报告

消息 An exception occurred processing [/check-login.jsp] at line [8]

描述 服务器遇到一个意外的情况，阻止它完成请求。

例外情况

org.apache.jasper.JasperException: An exception occurred processing [/check-login.jsp] at line [8]

Connection conn = null;
PreparedStatement ps = null;
ResultSet rs = null;
Class.forName("com.mysql.jdbc.Driver");
String url = "此处省略，源代码是填写了的";
String username = "此处省略，源代码是填写了的";

Stacktrace:
    org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:610)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:489)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:379)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:327)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)

根本原因。

javax.servlet.ServletException: java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:657)
    org.apache.jsp.check_002dlogin_jsp._jspService(check_002dlogin_jsp.java:155)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:466)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:379)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:327)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
        

java.lang.ClassNotFoundException: com.mysql.jdbc.Driver
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1407)
    org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1215)
    org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:122)
    org.apache.jasper.servlet.JasperLoader.loadClass(JasperLoader.java:58)
    java.lang.Class.forName0(Native Method)
    java.lang.Class.forName(Class.java:264)
    org.apache.jsp.check_002dlogin_jsp._jspService(check_002dlogin_jsp.java:124)
    org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:466)
    org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:379)
    org.apache.jasper.servlet.JspServlet.service(JspServlet.java:327)
    javax.servlet.http.HttpServlet.service(HttpServlet.java:764)
    org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)