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This tutorial shows how to implement a Java web application that uploads files to server and save the files into database.

Table of content:

The application applies the following technologies:

- Servlet 3.0: Using Servlet 3.0 we can write code to handle file upload easily. For detailed explanation of how to upload file with Servlet 3.0, read the tutorial: How to write upload file servlet with Servlet 3.0 API.
- MySQL database 5.5: We will store uploaded files in MySQL database. For more details about how to store files in MySQL database, read the article: Insert file data into MySQL database using JDBC.

The application will consist of the following source files:

- Upload.jsp: presents a form which allows users entering some information (first name and last name), and picking up a file (a portrait image).
- FileUploadDBServlet: captures input from the upload form, saves the upload file into database, and forwards the users to a message page.
- Message.jsp: shows either successful or error message.

Now, let’s go through each part of the application in details.

1. Creating MySQL database table

First, let’s create a database and a table in MySQL. Execute the following script using either MySQL Command Line Client or MySQL Workbench:

 create database AppDB;
 
use AppDB;
 
CREATE TABLE `contacts` (
  `contact_id` int(11) NOT NULL AUTO_INCREMENT,
  `first_name` varchar(45) DEFAULT NULL,
  `last_name` varchar(45) DEFAULT NULL,
  `photo` mediumblob,
  PRIMARY KEY (`contact_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1

 

The script will create a database named AppDB and a table named contacts. File will be stored in the column photo which is of type mediumblob which can store up to 16 MB of binary data. For larger files, use longblob (up to 4 GB).

2. Coding upload form page

Write code for the upload form as follows (Upload.jsp):

 <%@ 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="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>

 

This page shows two text fields (first name and last name) and a file field which allows the users choosing a file to upload. The action attribute of this form is set to uploadServlet which is URL mapping of the servlet we will create in the next section.

3. Coding file upload servlet

Create a servlet class named FileUploadDBServlet.java with the following code:

 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;
 
@WebServlet("/uploadServlet")
@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 = "secret";
     
    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 {
            // connects to the database
            DriverManager.registerDriver(new org.mariadb.jdbc.Driver());
            conn = DriverManager.getConnection(dbURL, dbUser, dbPass);
 
            // constructs SQL statement
            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 (SQLException 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);
        }
    }
}

 

In this servlet, we use two annotations:

- @WebServlet: marks this servlet so that the servlet container will load it at startup, and map it to the URL pattern /uploadServlet.
- @MultipartConfig: indicates this servlet will handle multipart request. We restrict maximum size of the upload file up to 16 MB.

The doPost() method carries out all the details. Here, there are three noticeable points:

Obtaining the part of upload file in the request:

1
Part filePart = request.getPart("photo");

The name “photo” is name of the file input field in the Upload.jsp page.
Obtaining input stream of the upload file:

1
inputStream = filePart.getInputStream();
And pass the input stream into the prepared statement:

1	`statement.setBlob(3, inputStream);`

Recommended Book: Java Database Best Practices￥3,949, 2ndHand;￥1,981～

4. Coding message page

Create a JSP page named as Message.jsp with the following code:

<%@ 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>Message</title>
</head>
<body>
    <center>
        <h3><%=request.getAttribute("Message")%></h3>
    </center>
</body>
</html>

This page simply displays value of the variable “Message” in the request scope.

5. Testing the application and verifying file stored in database

Supposing the application is deployed on localhost at port 8080, under the context root /FileUploadDatabase, type the following URL:

http://localhost:8080/FileUploadDatabase/Upload.jsp

The following upload form is displayed:

Type first name, last name, and pick up an image file. Click Save button, if everything is going well, this message appears:

To verify that the file is stored successfully in the database, open a new SQL Editor in MySQL Workbench and execute the following query:

1	`select * from contacts;`

The query would return the newly inserted record, right click on the BLOB cell of the column photo, and select Open Value in Editor from the context menu:

A dialog appears and we can see the image in the Image tab:

If you want to retrieve the stored file programmatically, read the tutorial: Read file data from database using JDBC.

NOTE: By default, MySQL restricts the size of data packet can be sent in a query to only 1 MB. So you may get an error if trying to upload a file bigger than this limit. To increase this size limit, set the max_allowed_packet variable in MySQL, as discussed in the tutorial Insert file data into MySQL database using JDBC.

Attachments:
FileUploadDatabase.zip	[Eclipse project]	676 kB

Upload files to database (Servlet + JSP + MySQL)

1. Creating MySQL database table

2. Coding upload form page

3. Coding file upload servlet

4. Coding message page

5. Testing the application and verifying file stored in database