本文執行個體講述了Java實現JSP使用Servelt串連Oracle資料庫的方法。為了實現在Servlet 中串連資料庫，必須編寫Servlet 的類程式。將Servlet 類程式放到WEB 伺服器的servlets 或者classes 目錄下面，為調用Servlet，需要建立發送Servlet 請求的HTML 文檔。本例通過(Driver)Class.forName(driverName).newInstance()方法來實現載入驅動程式，建立與資料庫連接。
具體程式碼為：
1．Database 類繼承了HttpServlet 類，共有兩個方法：doGet()和displayResult()，代碼如下：
public class Database extends HttpServlet{public void doGet()；public void displayResult(ResultSet results,PrintWriter out);}
2．在doGet()方法中建立與資料庫的串連並執行查詢：
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/ndb@192.168.1.6:1521: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()方法顯示查詢結果:
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．因為程式使用了JDBC 類、servlet 類和使用控制台輸出，所以需要引入如下的包：
import java.sql.*;import java.io.*;import javax.servlet.*;import javax.servlet.http.*;
5．編譯Database.java，產生Database.class 檔案，將Database.class 放到WEB 伺服器的servlets 目錄下，本例採用Java Web Server 作為WEB 伺服器。配置好WEB 伺服器，添加database.class，指定名稱為database。
6．編寫調用Servlet 的database.html 檔案。代碼如下：
<html><head><title>Jsp使用Servlet串連資料庫</title></head><body><center><form action="/servlet/database" method="get"><input name="action" type="submit" value="串連資料庫"></form></center></body></html>
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