如何發送servlet中的下拉列表項的值

我想從數據庫向網頁顯示各種類型（數學，物理，化學）的書籍細節。當我從下拉列表中選擇一個特定的項目時，其相應的書籍將顯示在網頁上。我JSP頁面看起來像：如何發送servlet中的下拉列表項的值

<%@ page contentType="text/html; charset=utf-8" language="java" import="java.sql.*" 
    errorPage="" %> 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org  
     /TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml"> 
<head> 
    <meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
    <title>Untitled Document</title> 
</head> 

<body> 
    <center> 
     <h1>Science Book</h1><br /><br /> 
     <hr color="#CC9999" size="5px" /><br /><br /> 

     <form action="Controller"> 
      <select name="book"> 
       <option value="Math">Math</option> 
       <option value="Phy">Physics</option> 
       <option value="Chem">Chemistry</option> 
      </select> 
      <input type="submit" value="Submit"/> 
     </form> 
    </center> 
</body>

這裏控制器是servlet名稱。我的servlet是這樣的：

package com.sayan.myservlet; 

import java.io.IOException; 
import java.io.PrintWriter; 
import java.sql.Connection; 
import java.sql.DriverManager; 
import java.sql.ResultSet; 
import java.sql.SQLException; 
import java.sql.Statement; 

import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 

public class Controller extends HttpServlet 
{ 
private static final long serialVersionUID = 1L; 

public Controller() 
{ 
    super(); 

} 


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


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


protected void doProcess(HttpServletRequest request, HttpServletResponse response) 
       throws ServletException, IOException 
{ 
    String booktype=null;   //set drowdownlist item value 
    PrintWriter out = response.getWriter(); 

    String drivername = "oracle.jdbc.OracleDriver"; 
    String url = "jdbc:oracle:thin:@172.16.0.30:1521:orcl"; 
    String username = "scott"; 
    String password = "tiger"; 

    Connection con = null; 
    Statement st = null; 
    ResultSet rs = null; 

    try{ 
     Class.forName(drivername); 
     con = DriverManager.getConnection(url,username,password); 
     st = con.createStatement(); 

     String sql = "select name,author,publisher,price from book where 
         type="+booktype; 
     System.out.println(sql); 
     rs = st.executeQuery(sql); 
     out.println("<html><body><table border=5>"); 
     out.println("<tr><th>name</th>"); 
     out.println("<th>author</th>"); 
     out.println("<th>publisher</th>"); 
     out.println("<th>price</th></tr><tr>"); 
     while(rs.next()){ 
      String name = rs.getString("name"); 
      String author = rs.getString("author"); 
      String publisher = rs.getString("publisher"); 
      String price = rs.getString("price"); 

      out.println("<td>" + name + "</td>"); 
      out.println("<td>" + author + "</td>"); 
      out.println("<td>" + publisher + "</td>"); 
      out.println("<td>" + price + "</td>"); 
     } 
     out.println("</tr></table></body></html"); 
    }catch(ClassNotFoundException cnfe){ 
     System.out.println("Exception caught : " + cnfe); 
    }catch(SQLException se){ 
     System.out.println("Exception caught : " + se); 
    }finally{ 
     try{ 
      con.close(); 
     }catch(SQLException se1){ 
      System.out.println("Exception caught : " + se1); 
     } 
    } 


}

}

我想設置在BOOKTYPE String.How的下拉列表項的值，我可以做到這一點？如果可能的話，請提及。

來源

2014-07-18 user3589907

使用轉發而不是在servlet中寫入響應。完成預期的結果比較容易。你可以在[StackOverflow Servlets wiki]（http://stackoverflow.com/tags/servlets/info）上找到關於它的更多信息。 –

如果我明白你的問題，然後

String booktype=request.getParameter("book");

此外，你應該使用PreparedStatement，因爲你發佈的代碼很容易受到SQL注入。最後，關閉您的Statement和ResultSet以及您的Connection，否則您可能會泄漏DB遊標。

Connection con = null; 
PreparedStatement st = null; 
ResultSet rs = null; 
String sql = "select name,author,publisher,price from book where " 
    + "type=?"; 

try { 
    // Class.forName(drivername); // <-- not needed since JDBC Version 4 
    // http://stackoverflow.com/a/8053125/2970947 
    con = DriverManager.getConnection(url, username, 
     password); 
    st = con.prepareStatement(sql); 
    st.setString(1, booktype); 

    System.out.println(sql); 
    rs = st.executeQuery(); 
    out.println("<html><body><table border=5>"); 
    out.println("<tr><th>name</th>"); 
    out.println("<th>author</th>"); 
    out.println("<th>publisher</th>"); 
    out.println("<th>price</th></tr><tr>"); 
    while (rs.next()) { 
    String name = rs.getString("name"); 
    String author = rs.getString("author"); 
    String publisher = rs.getString("publisher"); 
    String price = rs.getString("price"); 

    out.println("<td>" + name + "</td>"); 
    out.println("<td>" + author + "</td>"); 
    out.println("<td>" + publisher + "</td>"); 
    out.println("<td>" + price + "</td>"); 
    } 
    out.println("</tr></table></body></html"); 
} catch (ClassNotFoundException cnfe) { 
    System.out.println("Exception caught : " + cnfe); 
} catch (SQLException se) { 
    System.out.println("Exception caught : " + se); 
} finally { 
    try { 
    rs.close(); 
    } catch (SQLException se1) { 
    System.out 
     .println("Exception caught : " + se1); 
    } 
    try { 
    st.close(); 
    } catch (SQLException se1) { 
    System.out 
     .println("Exception caught : " + se1); 
    } 
    try { 
    con.close(); 
    } catch (SQLException se1) { 
    System.out 
     .println("Exception caught : " + se1); 
    } 
}

來源

2014-07-18 17:11:42

如何發送servlet中的下拉列表項的值

回答

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