web development helpdesk

When using JTST to access a request parameter we typically use something like this:

${param.xyz}

If the parameter name contains a . then this becomes

${param.xyz.abc}

Problem is that JSTL interprets this as being the abc property of the xyz bean which is not what we want.

In this case we instead need to use the more long winded JSTL syntax for specifying the property name of interest:

${param['xyz.abc']}

This now correctly returns the value of the request paramater with name ‘xyz.abc’.

written by objects \\ tags: jstl, param, parameter, request, syntax

If you require multiple imports then you can either use multiple import page directives, or specify them all in one page directive which each import commas separated

Multiple import directives

<%@ import="java.util.*" %>
<%@ import="java.io.*" %>
<%@ import="java.net.*" %>

One import directive (comma separated)

<%@ import="java.util.*, java.io.*, java.net.*" %>

written by objects \\ tags: import, page directive

Sometimes you need the path of a file in your web application, for example if you need to open a file for reading. You could hard code where your web application is deployed but that will break if you ever move where your application is deployed.

Luckily the ServletContext class provides a getRealPath() method to determine the path of any file contained within your web application.

public class ImageServlet extends HttpServlet
{
   public void doGet(HttpServletRequest req,
      HttpServletResponse resp) throws IOException
   {
    	ServletContext application = getServletContext();

    	// Get the absolute path to file that lives in this application

        String filepath = application.getRealPath("WEB-INF/images/a.gif");
        File file = new File(filepath);
        FileInputStream in = new FileInputStream(file);

written by objects \\ tags: file, getRealPath, path, ServletContext, webapp