本文实例讲述了Java实现JSP使用Servelt连接Oracle数据库的方法。为了实现在Servlet 中连接数据库，必须编写Servlet 的类程序。将Servlet 类程序放到WEB 服务器的servlets 或者classes 目录下面，为调用Servlet，需要创建发送Servlet 请求的HTML 文档。本例通过(Driver)Class.forName(driverName).newInstance()方法来实现加载驱动程序，建立与数据库连接。
具体程序代码为：
1．Database 类继承了HttpServlet 类，共有两个方法：doGet()和displayResult()，代码如下：
public class Database extends HttpServlet{public void doGet()；public void displayResult(ResultSet results,PrintWriter out);}2．在doGet()方法中建立与数据库的连接并执行查询：
public void doGet(){HttpServletRequest request,HttpServletResponse response}throws ServletException, IOException{PrintWriter out;String title = "Simple Servlet connecting to Oracle DB";response.setContentType("text/html;charset=GB2312");out = response.getWriter();out.println("<HTML><HEAD><TITLE>");out.println(title);out.println("</TITLE></HEAD><BODY>");out.println("<H1>" + title + "</H1>");out.println("<P>This is output from SimpleServlet.");String driverName = "oracle.jdbc.driver.OracleDriver";Driver d;Connection con;Statement stmt;ResultSet results;try{d = (Driver)Class.forName(driverName).newInstance();con = DiverManager.getConnection("jdbc:oracle:thin:ndb/[email protected]:1521:PC6");stmt = con.createStatement();String sqlstr = "select * from data";results = stmt.executeQuery(sqlstr);displayResult(results,out);stmt.close();con.close();}catch (Exception e){out.println("error: " + e.toString());}out.println("</BODY></HTML>");out.close();}3．DisplayResult()方法显示查询结果:
public void displayResult(ResultSet results,PrintWriter out){StringBuffer buf = new StringBuffer();String temp;try{ResultSetMetaData rsmd = results.getMetaData();int numCols = rsmd.getColumnCount();int i, rowcount = 0;for (i=1; i <= numCols; i++){if (i > 1) buf.append(",");buf.append(rsmd.getColumnLabel(i));}buf.append("");while (results.next() && rowcount < 100){for (i=1; i <= numCols; i++){if (i > 1) buf.append(",");buf.append((results.getString(i)));}buf.append("<br>");rowcount++;}out.println("<br>");out.println(buf.toString());results.close();}catch (Exception e){out.println("error: " + e.toString());return;}}4．因为程序使用了JDBC 类、servlet 类和使用控制台输出，所以需要引入如下的包：
import java.sql.*;import java.io.*;import javax.servlet.*;import javax.servlet.http.*;
5．编译Database.java，产生Database.class 文件，将Database.class 放到WEB 服务器的servlets 目录下，本例采用Java Web Server 作为WEB 服务器。配置好WEB 服务器，添加database.class，指定名称为database。
6．编写调用Servlet 的database.html 文件。代码如下：
<html><head><title>Jsp使用Servlet连接数据库</title></head><body><center><form action="/servlet/database" method="get"><input name="action" type="submit" value="连接数据库"></form></center></body></html>