要创建可滚动、可更新的ResultSet对象，必须使用Connection对象的带两个参数的createStatement()方法创建的Statement，第一个参数用下面两个常量之一：
ResultSet.TYPE_SCROLL_SENSITIVE
ResultSet.TYPE_SCROLL_INSENSITIVE
第二个参数使用下面常量：
ResultSet.CONCUR_UPDATABLE
6. 参考程序如下：
package com.control;
import java.io.*;
import java.sql.*;
import javax.servlet.*;
import javax.servlet.http.*;
public class BookQueryServlet extends HttpServlet{
沈泽刚 秦玉平主编清华大学出版社
Connection dbconn;
public void init() {
String driver = "org.postgresql.Driver";
String dburl = "jdbc:postgresql://127.0.0.1:5432/bookstore";
String username = "bookstore";
String password = "bookstore";
try{
Class.forName(driver);
dbconn = DriverManager.getConnection(
dburl,username,password);
}catch(ClassNotFoundException e1){
}catch(SQLException e2){}
}
public void doGet(HttpServletRequest request,
HttpServletResponse response)
throws ServletException,IOException{
response.setContentType("text/html;charset=gb2312");
PrintWriter out = response.getWriter();
out.println("<html><body>");
out.println("<table>");
try{
String sql="SELECT * FROM books";
Statement stmt = dbconn.createStatement();
ResultSet rst = stmt.executeQuery(sql);
while(rst.next()){
out.println("<tr><td>"+rst.getString(1)+"</td>");
out.println("<td>"+rst.getString(2)+"</td>");
out.println("<td>"+rst.getString(3)+"</td>");
out.println("<td>"+rst.getString(4)+"</td>");
out.println("<td>"+rst.getDouble(5)+"</td></tr>");
}
}catch(SQLException e){
e.printStackTrace();
}
out.println("</table>");
out.println("</body></html>");
}
public void destroy(){
try {
dbconn.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
沈泽刚 秦玉平主编清华大学出版社
try{
Class.forName(driver);
Connection dbconn = DriverManager.getConnection(
dburl,username,password);
DatabaseMetaData dbmd = dbconn.getMetaData();
out.println("数据库名："+dbmd.getDatabaseProductName()+"</br>");
out.println("数据库版本："+dbmd.getDatabaseProductVersion()+"</br>"); out.println("连接的用户："+dbmd.getUserName()+"</br>");
out.println("数据库URL："+dbmd.getURL()+"</br>");
out.println("驱动程序名："+dbmd.getDriverName()+"</br>");
out.println("驱动程序版本："+dbmd.getDriverVersion()+"</br>");
}catch(ClassNotFoundException e1){
out.println(e1);
}catch(SQLException e2){
out.println(e2);
}
%>
</body></html> 8. JSP页面如下：
<%@ page contentType="text/html;charset=gb2312" %>
<%@ page import="java.sql.*,java.io.*"%>
<html><body>
<%
String driver = "org.postgresql.Driver";
String dburl = "jdbc:postgresql://127.0.0.1:5432/bookstore";
String username = "bookstore";
String password = "bookstore";
try{
Class.forName(driver);
Connection dbconn = DriverManager.getConnection(
dburl,username,password);
String sql="SELECT * FROM public.books";
Statement stmt = dbconn.createStatement();
ResultSet rst = stmt.executeQuery(sql);
ResultSetMetaData rstmd = rst.getMetaData();
out.println("结果集列数："+rstmd.getColumnCount()+"</br>");
out.println("第3列标题："+rstmd.getColumnLabel(3)+"</br>");
out.println("第3列名："+rstmd.getColumnName(3)+"</br>");
out.println("第3列类型："+rstmd.getColumnType(3)+"</br>");
out.println("第3列类型名："+rstmd.getColumnTypeName(3)+"</br>"); }catch(ClassNotFoundException e1){
out.println(e1);
}catch(SQLException e2){
out.println(e2);
沈泽刚 秦玉平主编清华大学出版社
}
%>
</body></html>
9. 按教材7.7.2节建立局部或全局数据源sampleDS。创建程序7.9的CustomerBean.java程序和程序7.10的SampleDAO.java程序。
SelectCustomerServlet.java代码如下：
package com.control;
import java.io.*;
import java.sql.*;
import java.util.*;
import javax.servlet.*;
import javax.servlet.http.*;
import com.model.CustomerBean;