HTTP Status 500 - Servlet execution threw an exception

Java Web项目jdbc连接池异常错误信息：
type Exception report

message Servlet execution threw an exception

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

exception

javax.servlet.ServletException: Servlet execution threw an exception
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.NoClassDefFoundError: org/apache/commons/dbcp/BasicDataSource
com.grace.DBUtil2.(DBUtil2.java:35)
com.grace.Method.service(Method.java:37)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)
root cause

java.lang.ClassNotFoundException: org.apache.commons.dbcp.BasicDataSource
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1892)
org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1735)
com.grace.DBUtil2.(DBUtil2.java:35)
com.grace.Method.service(Method.java:37)
javax.servlet.http.HttpServlet.service(HttpServlet.java:731)
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/7.0.82 logs.

解决方案：到apache-tomcat/lib目录下，拷贝el-api.jar放到D:\Program Files\Java\jdk1.6.0\jre\lib\ext下即可.