想了好久，还是不知道在哪出问题了,驱动包也重新下载了好几次，用户密码没问题

Question

没导入？右击项目【Build Path】-->【Configure Build Path...】-->【Libraries】-->【add JARs...】 选到jdbc包

Answer 1

将 jsp 页面 贴全一下 article  这个 jsp

Answer 2

报错的jsp代码贴出来

Answer 3

对于web开发,导进来的jar包,不会打包到Tomcat服务器上去,需要手动向jar包放入WEB-INF的lib文件夹中,

Answer 4

检查下tomcat容器中项目下web-inf 下 的lib中有没有包

Answer 5

jsp页面头上没写 import需要的东西。

Answer 6

org.apache.jasper.JasperException: An exception occurred processing JSP page /article.jsp at line 74: <%!
5: private void tree(List<Article> articles, Connection conn, int id, int grade) {
6:  String sql = "select * from article where pid = " + id;
7:  Statement stmt = DB.createStmt(conn);
8:  ResultSet rs = DB.executeQuery(stmt, sql); 
9:  try {
10:  while(rs.next()) {
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)root cause 
java.lang.NullPointerException
com.bjsxt.bbs.DB.createStmt(DB.java:29)
org.apache.jsp.article_jsp.tree(article_jsp.java:24)
org.apache.jsp.article_jsp._jspService(article_jsp.java:96)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter

Answer 7

<%@ page import="java.sql.*,com.bbs.*, java.util.*"%>

Answer 8

org.apache.jasper.JasperException: An exception occurred processing JSP page /article.jsp at line 74: <%!
5: private void tree(List<Article> articles, Connection conn, int id, int grade) {
6:  String sql = "select * from article where pid = " + id;
7:  Statement stmt = DB.createStmt(conn);
8:  ResultSet rs = DB.executeQuery(stmt, sql); 
9:  try {
10:  while(rs.next()) {
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:568)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:470)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:52)root cause 
java.lang.NullPointerException
com.bjsxt.bbs.DB.createStmt(DB.java:29)
org.apache.jsp.article_jsp.tree(article_jsp.java:24)
org.apache.jsp.article_jsp._jspService(article_jsp.java:96)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:432)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:395)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:339)
javax.servlet.http.HttpServlet.service(HttpServlet.java:727)
org.apache.tomcat.websocket.server.WsFilter.doFilter
org.apache.jsp.article_jsp.tree(article_jsp.java:24) 24行空指针，数据库没连接成功？jsp文件的代码贴出来