如何将sql查询的结果发布到servlet中？

这里是我的servlet：

package HWpackage; 

import java.io.*; 

import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
import java.sql.Statement; 
import javax.servlet.*; 
import javax.servlet.http.*; 

public class DemoData extends HttpServlet { 

    protected void processRequest(HttpServletRequest request, HttpServletResponse response) 
    throws ServletException, IOException { 
     response.setContentType("text/html;charset=UTF-8"); 
     PrintWriter out = response.getWriter(); 
     try { 
      out.println("<html>"); 
      out.println("<head>"); 
      out.println("<title>Demo of Data Persistence</title>"); 
      out.println("</head>"); 
      out.println("<body>"); 

     try { 
       String driver = "oracle.jdbc.driver.OracleDriver"; 
       String url = "jdbc:oracle:thin:@coit-ora01.uncc.edu:1521:class"; 
       String username = "johnR"; 
       String password = "lAylko0K"; 

       // Load database driver if it's not already loaded. 
       Class.forName(driver); 
       // Establish network connection to database. 
       Connection connection = 
       DriverManager.getConnection(url, username, password); 
       // Create a statement for executing queries. 
       Statement statement = connection.createStatement(); 
       String query = 
       "SELECT sum(cost) FROM stocks where username = 'Bora'"; 
       // Send query to database and store results. 
       ResultSet resultSet = statement.executeQuery(query); 

       while(resultSet.next()) { 


       out.println("Your total cost is"); 


       } 
       connection.close(); 
      } catch(ClassNotFoundException cnfe) { 
       System.err.println("Error loading driver: " + cnfe); 
       // Useful when you debug your program on the coit server 
       // where System.out.println("") becomes futile 
       out.println("<tr> Error loading driver: " + cnfe); 
       out.println("</tr>"); 
      } catch(SQLException sqle) { 
       System.err.println("Error with connection: " + sqle); 
       // Again, for debug purpose 
       out.println("<tr> Error with connection: " + sqle); 
       out.println("</tr>"); 
      } 

      out.println("</table>"); 
      out.println("</body>"); 
      out.println("</html>"); 
     } finally { 
      out.close(); 
     } 
    } 

    // <editor-fold defaultstate="collapsed" desc="HttpServlet methods. Click on the + sign on the left to edit the code."> 
    /** 
    * Handles the HTTP <code>GET</code> method. 
    * @param request servlet request 
    * @param response servlet response 
    * @throws ServletException if a servlet-specific error occurs 
    * @throws IOException if an I/O error occurs 
    */ 

    protected void doGet(HttpServletRequest request, HttpServletResponse response) 
    throws ServletException, IOException { 
     processRequest(request, response); 
    } 

    /** 
    * Handles the HTTP <code>POST</code> method. 
    * @param request servlet request 
    * @param response servlet response 
    * @throws ServletException if a servlet-specific error occurs 
    * @throws IOException if an I/O error occurs 
    */ 

    protected void doPost(HttpServletRequest request, HttpServletResponse response) 
    throws ServletException, IOException { 
     processRequest(request, response); 
    } 

    /** 
    * Returns a short description of the servlet. 
    * @return a String containing servlet description 
    */ 

    public String getServletInfo() { 
     return "Short description"; 
    }// </editor-fold> 

}

我想知道发布此查询在servlet的结果正确的方法：

String query = 
       "SELECT sum(cost) FROM stocks where username = 'Bora'";

后是

out.println("Your total cost is");

如果有人可以提供给我的信息，你会认真做我的夜晚。感谢大家。

来源

2011-04-11 Turk

我不明白是什么问题，请您详细说明一下吧？你是什么意思'将SQL查询的结果发布到servlet'？ – 2011-04-11 00:42:35

的方式之一，就是要做到这一点： -

SELECT sum(cost) AS COST FROM stocks where username = 'Bora'
在这个代码块修改于：

而（结果集。下一个（））{

  Double cost = resultSet.getDouble("COST"); 
      out.println("Your total cost is" + cost);

}

旁注：

不要硬代码的SQL参数这种方式。您很容易受到SQL injection攻击。使用参数标记即。 `SELECT sum(cost) AS COST FROM stocks where username = ?和JDBC PreparedStatement来执行它。
创建一个单独的DAO类来处理所有数据库工作。这将促进代码中的解耦。

来源

2011-04-11 00:41:32 CoolBeans

完美！谢谢！ – Turk 2011-04-19 14:07:02

欢迎 – CoolBeans 2011-04-19 14:12:10

下面是一个额外的问题...我设置了一个DAO，但我一直试图弄清楚如何将DAO中的ResultSet从另一个servlet中提取出来。我将如何调用该ResultSet并将其设置为字符串？ – Turk 2011-04-19 15:40:56

out.println("Your total cost is "+resultSet.getString("sum(cost)"));

来源

2011-04-11 00:40:28 bdares

如何将sql查询的结果发布到servlet中？

回答

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