輸入形式的Input.jsp

<form class="form-horizontal" method="get" 
    action="${pageContext.request.contextPath}/FetchInfo" 
    enctype="multipart/form-data"> //using get method for servlet FetchInfo 
    <div class="form-group"> 
     <label for="reg no" class="col-sm-2 control-label">Application 
      number</label> 
     <div class="col-sm-6"> 
      <input type="number" class="form-control" name="appno" id="appno" 
       placeholder="Application number" max="9999"> 
     </div> 
    </div> 

    <div class="form-group"> 
     <div class="col-sm-offset-2 col-sm-10"> 
      <button type="submit" class="btn btn-default">Find</button> 
     </div> 
    </div> 
</form>

的Servlet FetchInfo.java

package com.ret; 

import java.io.IOException; 
import java.io.*; 

import javax.servlet.RequestDispatcher; 
import javax.servlet.ServletConfig; 
import javax.servlet.ServletException; 
import javax.servlet.annotation.WebServlet; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
import com.connection.JavaConnectDb; 
import com.mysql.jdbc.Connection; 

import java.sql.*; 

@WebServlet("/FetchInfo") 
public class FetchInfo extends HttpServlet { 
    private static final long serialVersionUID = 1L; 

private ServletConfig config; 
String page = "viewdoc.jsp"; 

public void init(ServletConfig config) throws ServletException { 
    this.config = config; 
} 

protected void doGet(HttpServletRequest request, HttpServletResponse response) 
     throws ServletException, IOException { 
    PrintWriter out = response.getWriter(); 
    String appno = request.getParameter("appno"); 
    int appnumber = Integer.parseInt(appno); 
    String app = null; 

    String name = null; 
    String address = null; 
    String qual = null; 
    String email = null; 
    String cate = null; 
    try { 
     Connection conn = (Connection) JavaConnectDb.connectDb(); 

     PreparedStatement ps = (PreparedStatement) conn.prepareStatement(
       "select Sr_no,Name,Address,Qualification,Email,Category from applications where Sr_no=?"); 
     ps.setInt(1, appnumber); 
     ResultSet resultSet = ps.executeQuery(); 
     app = resultSet.getString("Sr_no"); 
     name = resultSet.getString("Name"); 
     address = resultSet.getString("Address"); 
     qual = resultSet.getString("Qualification"); 
     email = resultSet.getString("Email"); 
     cate = resultSet.getString("Category"); 
     resultSet.close(); 
     ps.close(); 
    } catch (Exception e) { 
     System.out.println("Expection is;" + e); 
     out.print("expection e"); 
    } 
    request.setAttribute("Sr_no", app); 
    request.setAttribute("Name", name); 
    request.setAttribute("Address", address); 
    request.setAttribute("Qualification", qual); 
    request.setAttribute("Email", email); 
    request.setAttribute("Category", cate); 
    RequestDispatcher dispatcher = request.getRequestDispatcher(page); 
    if (dispatcher != null) { 
     dispatcher.forward(request, response); 
    } 

} 

}

jspfile viewdoc。 jsp

<%@ page language="java" import="java.util.*"%> 
    <!DOCTYPE html> 
<html> 
<head> 

<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> 
<link href="css/bootstrap.min.css" rel="stylesheet"> 
<title>view documents</title> 
</head> 
<body> 

    <% 
     String s1 = null; 
     String s2 = null; 
     String s3 = null; 
     String s4 = null; 
     String s5 = null; 
     String s6 = null; 
    %> 
    <div class="table-responsive"> 
     <table class="table table-bordered" align="center" cellpadding="5" 
      cellspacing="5"> 

      <tr bgcolor="#66cc66"> 
       <td><b>App no.</b></td> 
       <td><b>Name</b></td> 
       <td><b>Address</b></td> 
       <td><b>Qualification</b></td> 
       <td><b>Email</b></td> 
       <td><b>Category</b></td> 
       <td><b>Matriculation certificate</b></td> 
       <td><b>Qualification certificate</b></td> 
       <td><b>Category certificate</b></td> 
      </tr> 
      <% 
       s1 = request.getAttribute("Sr_no").toString(); 
       int s = Integer.parseInt(s1); 
       s2 = request.getAttribute("Name").toString(); 
       s3 = request.getAttribute("Address").toString(); 
       s4 = request.getAttribute("Qualification").toString(); 
       s5 = request.getAttribute("Email").toString(); 
       s6 = request.getAttribute("Category").toString(); 
      %> 
      <tr bgcolor="#DEB887"> 

       <td><%=s%></td> 
       <td><%=s2%></td> 
       <td><%=s3%></td> 
       <td><%=s4%></td> 
       <td><%=s5%></td> 
       <td><%=s6%></td> 

       <td><a href="${pageContext.request.contextPath}/Matric">view</a></td> 
       <td><a href="${pageContext.request.contextPath}/Qual">view</a></td> 
       <td><a href="${pageContext.request.contextPath}/Category">view</a></td> 

      </tr> 
     </table> 
    </div> 
    <script type="text/javascript" src="js/jquery1.11.3.min.js"></script> 
    <script type="text/javascript" src="js/bootstrap.min.js"></script> 
</body> 
</html>

*這些頁面顯示錯誤，當我使用「select * from應用程序，其中Sr_no =？」作爲PreparedStatement，用servlet FetchInfo.jsp編寫的代碼和？是從用戶輸入的jsp表單頁面input.jsp中請求的參數。請注意，我得到了瀏覽器的輸出，當我把preparestatement作爲「選擇*從應用程序」它不工作了我當我使用的地方cluase 我使用的數據庫是Mysql 請幫助...並提前感謝整理出來...... *

來源

2017-06-16 ashish_thakur

您不應該直接在servlet中使用準備好的語句。這是非常糟糕的軟件架構 – Jens

添加錯誤消息，請 – Jens

所以如何使用servlet中的preparedStatements –

-1

由於resultSet.getString("Sr_no")爲空或未執行，因此引發了NPE。

來源

2017-06-16 09:03:00

好吧，我得到它的感謝 –

順便說一句如何刪除它在上面的代碼 –

你應該添加空cckcks幾行你的代碼。 –

PreparedStatement的在servlet不是從數據庫的方式獲取數據，我想

輸入形式的Input.jsp

的Servlet FetchInfo.java

jspfile viewdoc。 jsp

回答

相關問題