登录页面时出错如下，请问如何解决？还有上传附件的截图，登录框特别小，如何修改？

HTTP Status 500 - javax.servlet.ServletException: java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null'

type Exception report

message javax.servlet.ServletException: java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null'

description The server encountered an internal error that prevented it from fulfilling this request.

exception

org.apache.jasper.JasperException: javax.servlet.ServletException: java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null'
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:548)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:454)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

javax.servlet.ServletException: java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null'
org.apache.jasper.runtime.PageContextImpl.doHandlePageException(PageContextImpl.java:908)
org.apache.jasper.runtime.PageContextImpl.handlePageException(PageContextImpl.java:837)
org.apache.jsp.check_jsp._jspService(check_jsp.java:177)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:431)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.sql.SQLException: Cannot create JDBC driver of class '' for connect URL 'null'
org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createConnectionFactory(BasicDataSource.java:2065)
org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createDataSource(BasicDataSource.java:1939)
org.apache.tomcat.dbcp.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:1412)
com.zh.conpool.Condata.getConnection(Condata.java:15)
com.zh.util.login.<init>(login.java:15)
org.apache.jsp.check_jsp._jspService(check_jsp.java:119)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:431)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.sql.SQLException: No suitable driver
java.sql.DriverManager.getDriver(DriverManager.java:315)
org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createConnectionFactory(BasicDataSource.java:2049)
org.apache.tomcat.dbcp.dbcp2.BasicDataSource.createDataSource(BasicDataSource.java:1939)
org.apache.tomcat.dbcp.dbcp2.BasicDataSource.getConnection(BasicDataSource.java:1412)
com.zh.conpool.Condata.getConnection(Condata.java:15)
com.zh.util.login.<init>(login.java:15)
org.apache.jsp.check_jsp._jspService(check_jsp.java:119)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:431)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:396)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:340)
javax.servlet.http.HttpServlet.service(HttpServlet.java:725)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
note The full stack trace of the root cause is available in the Apache Tomcat/8.0.18 logs.