无法使用 Servlet 修改数据库

Question

消息：请求的资源[/AppDB/uploadServlet]不可用

描述：源服务器未找到目标资源的当前表示或不愿意公开表示存在。

我的代码（Servlet）是：

package net.codejava.upload;

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


/**
 * Servlet implementation class FileUploadDBServlet
 */
@WebServlet("/FileUploadDBServlet")
@MultipartConfig(maxFileSize = 16177215)    
public class FileUploadDBServlet extends HttpServlet {
    private static final long serialVersionUID = 1L;
    
     
    private String dbURL = "jdbc:mysql:///AppDB";
    private String dbUser = "root";
    private String dbPass = "Pa$$Word##";

       
    protected void doPost(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");
         
        InputStream inputStream = null;
         
        
        Part filePart = request.getPart("photo");
        if (filePart != null) {
            
            System.out.println(filePart.getName());
            System.out.println(filePart.getSize());
            System.out.println(filePart.getContentType());
             
            
            inputStream = filePart.getInputStream();
        }
         
        Connection conn = null; 
        String message = null;  
         
        try {
            
            DriverManager.registerDriver(new com.mysql.cj.jdbc.Driver());
            conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
 
            
            String sql = "INSERT INTO contacts (first_name, last_name, photo) values (?, ?, ?)";
            PreparedStatement statement = conn.prepareStatement(sql);
            statement.setString(1, firstName);
            statement.setString(2, lastName);
             
            if (inputStream != null) {
                
                statement.setBlob(3, inputStream);
            }
 
            int row = statement.executeUpdate();
            if (row > 0) {
                message = "File uploaded and saved into database";
            }
        } catch (SQLException ex) {
            message = "ERROR: " + ex.getMessage();
            ex.printStackTrace();
        } finally {
            if (conn != null) {
    
                try {
                    conn.close();
                } catch (SQLException ex) {
                    ex.printStackTrace();
                }
            }
            
            request.setAttribute("Message", message);
             
            
            getServletContext().getRequestDispatcher("/Message.jsp").forward(request, response);
        }
    }
}

我的 .JSP 是：

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
    "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
<title>File Upload to Database Demo</title>
</head>
<body>
    <center>
        <h1>File Upload to Database Demo</h1>
        <form method="post" action="uploadServlet" enctype="multipart/form-data">
            <table border="0">
                <tr>
                    <td>First Name: </td>
                    <td><input type="text" name="firstName" size="50"/></td>
                </tr>
                <tr>
                    <td>Last Name: </td>
                    <td><input type="text" name="lastName" size="50"/></td>
                </tr>
                <tr>
                    <td>Portrait Photo: </td>
                    <td><input type="file" name="photo" size="50"/></td>
                </tr>
                <tr>
                    <td colspan="2">
                        <input type="submit" value="Save">
                    </td>
                </tr>
            </table>
        </form>
    </center>
</body>
</html>

在 URL 栏上，我可以添加“Upload.jsp”，它将显示入口页面，但是（我可以通过运行加载 Upload.jsp 文件在服务器上）但是当我尝试通过尝试执行数据输入来填充我的数据库 table 时，它会重复显示上面的消息：

消息请求的资源[/AppDB/uploadServlet]不可用

描述源服务器未找到目标资源的当前表示或不愿意透露存在该表示。

Answer 1

在 JSP 表单标签中写入 *action="FileUploadDBServlet"* 而不是 *action="uploadServlet"*

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