Question

我正在尝试使用Tomcat 7中的Servlet和JSP在MySQL数据库中插入图像。当我单击“保存”按钮时，它显示为null。我没有收到任何错误。

我还设置了commons-fileupload.jar文件和commons-io.jar文件。如果你有一些演示代码，请给我。

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"pageEncoding="ISO-8859-1"%>

<!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="FileUploadDBServlet" 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>

FileUploadDBServlet.java ：

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;

@WebServlet("/FileUploadDBServlet")
@MultipartConfig(maxFileSize = 16177215)    // upload file's size up to 16MB
public class FileUploadDBServlet extends HttpServlet {

    // database connection settings
    private String dbURL = "jdbc:mysql://localhost:3306/AppDB";
    private String dbUser = "root";
    private String dbPass = "root";

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

        // gets values of text fields
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");

        InputStream inputStream = null; // input stream of the upload file

        // obtains the upload file part in this multipart request
        Part filePart = request.getPart("photo");
        if (filePart != null) {
            // prints out some information for debugging
            System.out.println(filePart.getName());
            System.out.println(filePart.getSize());
            System.out.println(filePart.getContentType());

            // obtains input stream of the upload file
            inputStream = filePart.getInputStream();
        }

        Connection conn = null; // connection to the database
        String message = null;  // message will be sent back to client

        try {

              Class.forName("com.mysql.jdbc.Driver").newInstance();
            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) {
                // fetches input stream of the upload file for the blob column
                statement.setBlob(3, inputStream);
            }

            // sends the statement to the database server
            int row = statement.executeUpdate();
            if (row > 0) {
                message = "File uploaded and saved into database";
            }
        } catch (Exception  ex) {
            message = "ERROR: " + ex.getMessage();
             ex.printStackTrace();
        } finally {
            if (conn != null) {
                // closes the database connection
                try {
                    conn.close();
                } catch (SQLException ex) {
                    ex.printStackTrace();
                }
            }
            // sets the message in request scope
            request.setAttribute("Message", message);

            // forwards to the message page
            getServletContext().getRequestDispatcher("/Message.jsp").forward(request, response);
        }
    }
}

的web.xml ：

<web-app>
  <servlet>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <servlet-class>FileUploadDBServlet</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>FileUploadDBServlet</servlet-name>
    <url-pattern>/FileUploadDBServlet</url-pattern>
  </servlet-mapping>
</web-app>

Answer 1

以下代码说明了如何向/从db存储/检索图像。

首先使用以下代码在您的数据库中创建一个表

CREATE TABLE contacts (
    contact_id int PRIMARY KEY AUTO_INCREMENT,
    first_name varchar(45) DEFAULT NULL,
    last_name varchar(45) DEFAULT NULL,
    photo` mediumblob);

为输入参数创建一个jsp文件。

Upload.jsp：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
                    pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title>File Upload to Database</title>
    </head>
    <body>
        <h1>File Upload to Database</h1>
        <form name="fileform" method="post" action="uploadServlet" enctype="multipart/form-data">
            <label for="firstName">First Name:</label>
            <input type="text" name="firstName" size="50" placeholder="Enter Your FirstName" required/><br><br>
            <label for="lastName">Last Name: </label>
            <input type="text" name="lastName" size="50" placeholder="Enter Your LastName" required/><br><br>
            <label for="photo"> Portrait Photo:  </label>
            <input type="file" name="photo" size="50" placeholder="Upload Your Image" required/><br><br>
            <input type="submit" value="Save">
        </form>
    </body>
</html>

接下来创建用于上传图像的控制器。在这种情况下，我正在使用servlet。

FileUploadDbServlet.java：

package com.fileupload.attach;

import java.io.IOException;
import java.io.InputStream;
import java.io.FileOutputStream;
import java.io.OutputStream;
import java.sql.Blob;
import java.sql.ResultSet;
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.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.Part;

@MultipartConfig(maxFileSize = 16177215)
// upload file's size up to 16MB
public class FileUploadDBServlet extends HttpServlet {
    private static final int BUFFER_SIZE = 4096;
    // database connection settings
    private String dbURL = "jdbc:mysql://localhost:3306/mysql";
    private String dbUser = "root";
    private String dbPass = "arun";

    //naive way to obtain a connection to database
    //this MUST be improved, shown for 
    private Connection getConnection() {
        Connection conn = null;
        try {
            DriverManager.registerDriver(new com.mysql.jdbc.Driver());
            conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
        } catch (Exception e) {
            //wrapping any exception and rethrowing it
            //inside a RuntimeException
            //so the method is silent to exceptions
            throw new RuntimeException("Failed to obtain database connection.", e);
        }
        return conn;
    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response)
        throws ServletException, IOException {
        //get values of text fields
        String firstName = request.getParameter("firstName");
        String lastName = request.getParameter("lastName");
        InputStream inputStream = null; // input stream of the upload file
        // obtains the upload file part in this multipart request
        Part filePart = request.getPart("photo");
        if (filePart != null) {
            // prints out some information for debugging
            System.out.println(filePart.getName());
            System.out.println(filePart.getSize());
            System.out.println(filePart.getContentType());

            //obtains input stream of the upload file
            //the InputStream will point to a stream that contains
            //the contents of the file
            inputStream = filePart.getInputStream();
        }

        Connection conn = null; // connection to the database
        String message = null; // message will be sent back to client
        try {
            // connects to the database
            conn = getConnection();
            // constructs SQL statement
            String sql = "INSERT INTO contacts (first_name, last_name, photo) values (?, ?, ?)";
            //Using a PreparedStatement to save the file
            PreparedStatement pstmtSave = conn.prepareStatement(sql);
            pstmtSave.setString(1, firstName);
            pstmtSave.setString(2, lastName);

            if (inputStream != null) {
                //files are treated as BLOB objects in database
                //here we're letting the JDBC driver
                //create a blob object based on the
                //input stream that contains the data of the file
                pstmtSave.setBlob(3, inputStream);
            }
            //sends the statement to the database server
            int row = pstmtSave.executeUpdate();
            if (row > 0) {
                message = "File uploaded and saved into database";
            }

            String filepath = "D:/Dev/JavaWorkSpaceNew/FileUploadDatabase/WebContent/FromDb.jpg";
            //Obtaining the file from database
            //Using a second statement
            String sql1 = "SELECT photo FROM contacts WHERE first_name=? AND last_name=?";
            PreparedStatement pstmtSelect = conn.prepareStatement(sql1);
            pstmtSelect.setString(1, firstName);
            pstmtSelect.setString(2, lastName);
            ResultSet result = statement1.executeQuery();
            if (result.next()) {
                Blob blob = result.getBlob("photo");
                InputStream inputStream1 = blob.getBinaryStream();
                OutputStream outputStream = new FileOutputStream(filepath);
                int bytesRead = -1;
                byte[] buffer = new byte[BUFFER_SIZE];
                while ((bytesRead = inputStream1.read(buffer)) != -1) {
                    outputStream.write(buffer, 0, bytesRead);
                }
                inputStream1.close();
                outputStream.close();
                System.out.println("File saved");
            }
        } catch (SQLException ex) {
            message = "ERROR: " + ex.getMessage();
            ex.printStackTrace();
        } finally {
            if (conn != null) {
                // closes the database connection
                try {
                    conn.close();
                } catch (SQLException ex) {
                    //silent
                }
            }
            // sets the message in request scope
            request.setAttribute("message", message);

            // forwards to the message page
            getServletContext().getRequestDispatcher("/Message.jsp")
                .include(request, response);
        }
    }
}

的web.xml：

<?xml version="1.0" encoding="UTF-8"?>
<web-app>
    <display-name>servletFileUpload</display-name>
    <welcome-file-list>
        <welcome-file>Upload.jsp</welcome-file>
    </welcome-file-list>
    <servlet>
        <description></description>
        <display-name>FileUploadDBServlet</display-name>
        <servlet-name>FileUploadDBServlet</servlet-name>
    <servlet-class>com.fileupload.attach.FileUploadDBServlet</servlet-class>
    </servlet>
    <servlet-mapping>
        <servlet-name>FileUploadDBServlet</servlet-name>
        <url-pattern>/uploadServlet</url-pattern>
    </servlet-mapping>
</web-app>

Message.jsp：

<%@ page language="java" contentType="text/html; charset=ISO-8859-1"
        pageEncoding="ISO-8859-1"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1">
        <title>Message</title>
    </head>
    <body>
        <h3>Result of the operation: ${message}</h3>
    </body>
</html>

Answer 2

Jsp Page

Save this page with any name


<%@page contentType="text/html" pageEncoding="UTF-8"%>
<!DOCTYPE html>
<html>
    <head>
        <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
        <title>JSP Page</title>
    </head>
    <body>
        <form action="abc" method="post" enctype="multipart/form-data"> <br><br>
            <table>
                <tr>
                    <td>UserName:  </td>
                    <td width='10px'></td>
                    <td><input type="text" name="name"/></td>
                </tr>

                <tr>
                    <td>Upload: </td>
                    <td width='10px'></td>
                    <td><input type="file" name="file" value="Upload"/></td>
                </tr>
                <tr>
                    <td><input type="submit" value="submit"></td>
                </tr>
            </table>
        </form>
    </body>
</html>




Servlet page and save this page as abc.java


source code


import java.io.File;
import java.io.IOException;
import java.io.PrintWriter;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
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;

@WebServlet(urlPatterns = {"/abc"})
@MultipartConfig(fileSizeThreshold = 1024 * 1024 * 10, maxFileSize = 1024 * 1024 * 50, maxRequestSize = 1024 * 1024 * 100)
public class abc extends HttpServlet {

//    this if directory name where the file will be uploaded and saved
    private static final String SAVE_DIR = "images";

//    this is the method which is created by system it self
    protected void processRequest(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        response.setContentType("text/html;charset=UTF-8");
        try (PrintWriter out = response.getWriter()) {

//            this tyr is created by me for the connection of database
            try {

//                this is the path provide by me to save the image 
                String savePath = "C:" + File.separator + SAVE_DIR; 
/*in place of C: you can place a path wher you need to save the image*/

//                this comment will picup the image file and have convert it into file type
                File fileSaveDir = new File(savePath);
                if (!fileSaveDir.exists()) {
                    fileSaveDir.mkdir();
                }

//                this two comment will take the name and image form web page
                String name = request.getParameter("name");
                Part part = request.getPart("file");

//                this comment will extract the file name of image
                String fileName = extractFileName(part);

//                this will print the image name and user provide name
                out.println(fileName);
                out.println("\n" + name);

                /*if you may have more than one files with same name then you can calculate 
  some random characters and append that characters in fileName so that it will 
  make your each image name identical.*/
                part.write(savePath + File.separator + fileName);

                /* 
                You need this loop if you submitted more than one file
                for (Part part : request.getParts()) {
                String fileName = extractFileName(part);
                part.write(savePath + File.separator + fileName);
            }*/
//            connectio to database
                Class.forName("com.mysql.jdbc.Driver");
                Connection con = DriverManager.getConnection("url", "host -name", "password");

//                query to insert name and image name
                String query = "INSERT INTO image_link (name,photourl) values (?, ?)";

                PreparedStatement pst;
                pst = con.prepareStatement(query);
                pst.setString(1, name);
                String filePath = savePath + File.separator + fileName;
                pst.setString(2, filePath);
                pst.executeUpdate();

            } catch (Exception ex) {
                out.println("error" + ex);
            }

        }
    }

//    the extractFileName() is method used to extract the file name
    private String extractFileName(Part part) {
        String contentDisp = part.getHeader("content-disposition");
        String[] items = contentDisp.split(";");
        for (String s : items) {
            if (s.trim().startsWith("filename")) {
                return s.substring(s.indexOf("=") + 2, s.length() - 1);
            }
        }
        return "";
    }

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

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

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

}

如何在Tomcat 7中使用Servlet和JSP在MySQL数据库中插入图像

2 个答案: