How to retrieve and display images from a database in a JSP page?

Question

How can I retrieve and display images from a database in a JSP page?

Answer 1

Let's see in steps what should happen:

• JSP is basically a view technology which is supposed to generate HTML output.
• To display an image in HTML, you need the HTML element.
• To let it locate an image, you need to specify its src attribute.
• The src attribute needs to point to a valid http:// URL and thus not a local disk file system path file:// as that would never work when the server and client run at physically different machines.
• The image URL needs to have the image identifier in either the request path (e.g. http://example.com/context/images/foo.png) or as request parameter (e.g. http://example.com/context/images?id=1).
• In JSP/Servlet world, you can let a Servlet listen on a certain URL pattern like /images/*, so that you can just execute some Java code on specific URL's.
• Images are binary data and are to be obtained as either a byte[] or InputStream from the DB, the JDBC API offers the ResultSet#getBytes() and ResultSet#getBinaryStream() for this, and JPA API offers @Lob for this.
• In the Servlet you can just write this byte[] or InputStream to the OutputStream of the response the usual Java IO way.
• The client side needs to be instructed that the data should be handled as an image, thus at least the Content-Type response header needs to be set as well. You can obtain the right one via ServletContext#getMimeType() based on image file extension which you can extend and/or override via in web.xml.

That should be it. It almost writes code itself. Let's start with HTML (in JSP):

You can if necessary also dynamically set src with EL while iterating using JSTL:

Then define/create a servlet which listens on GET requests on URL pattern of /images/*, the below example uses plain vanilla JDBC for the job:

@WebServlet("/images/*")
public class ImageServlet extends HttpServlet {

    // content=blob, name=varchar(255) UNIQUE.
    private static final String SQL_FIND = "SELECT content FROM Image WHERE name = ?";

    @Resource(name="jdbc/yourDB") // For Tomcat, define as  in context.xml and declare as  in web.xml.
    private DataSource dataSource;
    
    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        String imageName = request.getPathInfo().substring(1); // Returns "foo.png".

        try (Connection connection = dataSource.getConnection(); PreparedStatement statement = connection.prepareStatement(SQL_FIND)) {
            statement.setString(1, imageName);
            
            try (ResultSet resultSet = statement.executeQuery()) {
                if (resultSet.next()) {
                    byte[] content = resultSet.getBytes("content");
                    response.setContentType(getServletContext().getMimeType(imageName));
                    response.setContentLength(content.length);
                    response.getOutputStream().write(content);
                } else {
                    response.sendError(HttpServletResponse.SC_NOT_FOUND); // 404.
                }
            }
        } catch (SQLException e) {
            throw new ServletException("Something failed at SQL/DB level.", e);
        }
    }

}

That's it. In case you worry about HEAD and caching headers and properly responding on those requests, use this abstract template for static resource servlet.

See also:

• How should I connect to JDBC database / datasource in a servlet based application?
• How to upload an image and save it in database?
• Simplest way to serve static data from outside the application server in a Java web application