java部分代码（java代码部分已经测试过，单独运行没有问题。）：
package db;
import java.sql.*;
public class DBmanage {
public Connection con=null;
public Statement stmt=null;
public ResultSet rs=null;
private static String dbDriver="com.microsoft.sqlserver.jdbc.SQLServerDriver";
private static String dburl="jdbc:sqlserver://localhost:1433;DatabaseName=student";
private static String dbname="sa";
private static String dbpassword="12345";
public static Connection getConnection(){
Connection conn=null;
try {
Class.forName(dbDriver);
conn=DriverManager.getConnection(dburl, dbname, dbpassword);
System.out.println("连接成功");
} catch (Exception e) {
// TODO: handle exception
System.err.println("连接失败");
}
return conn;
}
public ResultSet doQuery(String sql){
try {
con=DBmanage.getConnection();
stmt=con.createStatement();
rs=stmt.executeQuery(sql);
} catch (SQLException e) {
// TODO: handle exception
e.printStackTrace();
System.out.println("连接失败"+e.getMessage());
}
return rs;
}
public void closeConnection(){
try {
if(rs==null){
rs.close();
}
} catch (Exception e) {
// TODO: handle exception
}
try {
if(stmt==null){
stmt.close();
}
} catch (Exception e) {
// TODO: handle exception
}
try {
if(con==null){
con.close();
}
} catch (Exception e) {
// TODO: handle exception
}
}
public static void main(String[] args) {
DBmanage cc=new DBmanage();
String sql01="select * from admin01";
ResultSet rss=null;
getConnection();
rss=cc.doQuery(sql01);
try {
while(rss.next()){
System.out.print(rss.getString("id")+" ");
System.out.print(rss.getString("name")+" ");
System.out.println(rss.getString("sex"));
}
} catch (SQLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
jsp代码部分：
<%@page import="java.sql.SQLException"%>
<%@page import="java.sql.ResultSet"%>
<%@page import="db.DBmanage"%>
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<%
request.setCharacterEncoding("utf-8");
while (rs.next()) {
System.out.print(rs.getString("id") + " ");
System.out.print(rs.getString("name") + " ");
System.out.println(rs.getString("sex"));
}
DB.closeConnection();
} catch (SQLException e) {
out.println("conn:" + e.getMessage());
}
%>
报错部分：
org.apache.jasper.JasperException: An exception occurred processing JSP page /index.jsp at line 21
18: try {
19: DBmanage DB = new DBmanage();
20: String sql = "select top 3 * from admin";
21: ResultSet rs = DB.doQuery(sql);
22: %>
23:
24:
Stacktrace:
org.apache.jasper.servlet.JspServletWrapper.handleJspException(JspServletWrapper.java:588)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:481)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
root cause
java.lang.NullPointerException
db.DBmanage.doQuery(DBmanage.java:32)
org.apache.jsp.index_jsp._jspService(index_jsp.java:140)
org.apache.jasper.runtime.HttpJspBase.service(HttpJspBase.java:70)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.jasper.servlet.JspServletWrapper.service(JspServletWrapper.java:443)
org.apache.jasper.servlet.JspServlet.serviceJspFile(JspServlet.java:385)
org.apache.jasper.servlet.JspServlet.service(JspServlet.java:329)
javax.servlet.http.HttpServlet.service(HttpServlet.java:729)
org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
采用纯JDBC方式连接数据库，java部分已经测试通过。
