Question

我编写了一个简单的JSP代码，将PDF文件上传到Mysql BLOB数据库

我的HTML代码是

<form method="post" action="uploadfile.jsp" enctype="multipart/form-data">
        <center>
            <table border="1" width="25%" cellpadding="5">
                <thead> 
                        <th colspan="3">Upload File</th>        
                </thead>
                <tbody>
                    <tr>    
                        <td>Title : </td>
                        <td><input type="text" name="title" size="30"></td>
                    </tr>
                    <tr>
                        <td>Choose File : </td>
                        <td><input type="file" name="file_uploaded" /></td>
                    </tr>
                    <tr>
                        <td colspan="3"><center><input type="submit" value="Upload"></center></td>
                    </tr>
                </tbody>             
            </table>
        </center>
    </form>

我的JSP代码是

<%@page import="java.io.*" %>
<%@page import="java.sql.*" %>
<% 
            response.setContentType("text/html;charset=UTF-8");


            InputStream inputStream = null;

           Connection conn=null;
           PreparedStatement st=null;
           ResultSet rs=null;

            String title=(request.getParameter("title"));
            Part filePart = request.getPart("file_uploaded");

            if (filePart != null) 
            {
                out.println(filePart.getName());
                out.println(filePart.getSize());
                out.println(filePart.getContentType());

                inputStream = filePart.getInputStream();
            }

            try 
            {
                String idTemp="1";
                 Class.forName("com.mysql.jdbc.Driver");

  conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/fileupload","root","password");

                String sql = "INSERT INTO files (id, title, file) values (?, ?, ?)";
                st = conn.prepareStatement(sql);
                st.setString(1, idTemp);
                st.setString(2, title);

                if (inputStream != null) 
                {
                    st.setBinaryStream(3, inputStream, (int) filePart.getSize());
                }

                int row = st.executeUpdate();
                if (row > 0) 
                {
                    out.println("File uploaded!!!");

                    conn.close();

                    RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
                    rd.include(request, response);
                }
                else
                {
                    out.println("Couldn't upload your file!!!");

                    conn.close();

                    RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
                    rd.include(request, response);
                }    

            }catch(Exception e){out.print(e);}     
%>

执行此代码后。我收到错误“ java.sql.SQLException：没有为参数3指定值”

此代码有什么问题。我的数据库表为空，我无法上传任何pdf数据

我的数据库SQL是

create table files(id int(4),title varchar(20),file mediumblob,primary key(id)) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Answer 1

您在本节中遇到错误。

String sql = "INSERT INTO files (id, title, file) values (?, ?, ?)";
                st = conn.prepareStatement(sql);
                st.setString(1, idTemp);
                st.setString(2, title);

在这里您需要添加另一个参数。您仅添加了两个参数，但是在查询中您通过values (?, ?, ?)声明了三个参数

Answer 2

我刚刚创建了一个Servlet代码，现在可以正常工作了

import java.io.IOException;
import java.io.InputStream;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import javax.servlet.ServletException;
import javax.servlet.annotation.MultipartConfig;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpSession;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;
import java.io.PrintWriter;
import javax.servlet.RequestDispatcher;

@WebServlet("/uploadServlet")
@MultipartConfig(maxFileSize = 16177215)

public class UploadFileController extends HttpServlet 
{
    /**
     * 
     */
private static final long serialVersionUID = 1L;

@Override
protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException 
{
            response.setContentType("text/html;charset=UTF-8");
            PrintWriter out = response.getWriter();

            InputStream inputStream = null;
            Connection conn=null;
            PreparedStatement st=null;
            ResultSet rs=null;
            String idTemp=request.getParameter("id");
            String title=(request.getParameter("title"));
            String site=request.getParameter("site");
            Part filePart = request.getPart("file_uploaded");

            HttpSession hs=request.getSession(true);
            hs.setAttribute("site", site);

            if (filePart != null) 
            {
                System.out.println(filePart.getName());
                System.out.println(filePart.getSize());
                System.out.println(filePart.getContentType());

                inputStream = filePart.getInputStream();
            }

            try 
            {
                 Class.forName("com.mysql.jdbc.Driver");

                 conn = DriverManager.getConnection("jdbc:mysql://localhost:3306/database","root","password");
                String sql = "INSERT INTO files (id, title,file) values (?, ?, ?)";
                st = conn.prepareStatement(sql);
                st.setString(1, idTemp);
                st.setString(2, title);
                //st.setString(3, site);

                if (inputStream != null) 
                {
                    st.setBinaryStream(3, inputStream, (int) filePart.getSize());
                }

                int row = st.executeUpdate();
                if (row > 0) 
                {
                    String fileuploaded="fileuploaded";
                    out.println("<script> alert("+fileuploaded+")</script>");

                    conn.close();

                    RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
                    rd.include(request, response);
                }
                else
                {
                    out.println("Couldn't upload your file!!!");

                    conn.close();

                    RequestDispatcher rd = request.getRequestDispatcher("index.jsp");
                    rd.include(request, response);
                }    

            }catch(Exception e){out.println(e);}
}

}

java.sql.SQLException：未为参数3

2 个答案: