After this I thought well how can we make use of these from a web application. In this post I'll take a look at how to serve up images through a servlet so that we can display them in a web page. I was more interested in the perceived speed of such a technique over storing the file on the file system and I must say it actually didn't feel that slow.
The code is as follows:
public class GetImage extends HttpServlet {
private static final long serialVersionUID = -3505939293849012116L;
protected void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
String beerId = com.google.common.base.Preconditions.checkNotNull(request.getParameter("id"));
InitialContext ctx;
DataSource ds = null;
Connection connection = null;
PreparedStatement stmt = null;
try {
ctx = new InitialContext();
ds = (DataSource) ctx.lookup("java:/beerDS");
connection = ds.getConnection();
String sql = "select image1, image1_content_type " +
"from beer where id = ? and rownum() = 1";
stmt = connection.prepareStatement(sql);
stmt.setInt(1, Integer.valueOf(beerId));
stmt.execute();
ResultSet rs = stmt.getResultSet();
while (rs.next()) {
byte[] bytes = rs.getBytes("image1");
String contentType = rs.getString("image1_content_type");
int length = bytes.length;
response.setContentType(contentType);
response.setContentLength(length);
response.getOutputStream().write(bytes);
}
response.getOutputStream().flush();
response.getOutputStream().close();
} catch (NamingException e) {
e.printStackTrace();
} catch (SQLException e) {
e.printStackTrace();
} catch (NullPointerException npe) {
return;
} finally {
if (connection != null)
try {
connection.close();
} catch (SQLException e) {
e.printStackTrace();
}
if (stmt != null)
try {
stmt.close();
} catch (SQLException e) {
e.printStackTrace();
}
}
}
}
A few things to note include:
- You can't write multiple images to the response, not if you wan't something that can be understood by a browser. You refer to the servlet like any other file when using the url html or dynamic content. To access the image in a html page you would use a standard img tag as follows, like in the following example :
