RandomImageServlet.java

package info.freelibrary.djatoka.view;

import gov.lanl.adore.djatoka.util.IOUtils;

import info.freelibrary.djatoka.Constants;
import info.freelibrary.util.FileUtils;
import info.freelibrary.util.RegexFileFilter;

import java.io.File;
import java.io.FilenameFilter;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Properties;
import java.util.Random;

import javax.servlet.ServletContext;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

public class RandomImageServlet extends HttpServlet implements Constants {

    private static final long serialVersionUID = -7221546341356013641L;

    private static final Logger LOGGER = LoggerFactory
	    .getLogger(RandomImageServlet.class);

    private Properties myProps;

    @SuppressWarnings("unchecked")
    @Override
    protected void doGet(HttpServletRequest aRequest,
	    HttpServletResponse aResponse) throws ServletException, IOException {
	FilenameFilter jp2Filter = new RegexFileFilter(JP2_FILE_PATTERN);
	File jp2Dir = new File(myProps.getProperty(JP2_DATA_DIR));
	ServletContext context = getServletContext();
	Object object = context.getAttribute("djin");
	Random random = new Random();
	List<String> files;
	String image;
	
	// As a first pass, do this from the file system
	if (object == null) {
	    File[] jp2Files = FileUtils.listFiles(jp2Dir, jp2Filter, true);

	    files = new ArrayList<String>();

	    for (int index = 0; index < jp2Files.length; index++) {
		files.add(stripExt(jp2Files[index].getName()));
	    }
	    
	    files = Collections.synchronizedList(files);
	    context.setAttribute("djin", files);
	}
	else {
	    files = (List<String>) object;
	}

	image = files.get(random.nextInt((files.size() - 2) + 1));
	image = aRequest.getRequestURI().replace("random", image);
	aRequest.getRequestDispatcher(image).forward(aRequest, aResponse);
    }

    @Override
    public void init() throws ServletException {
	String dir = getServletContext().getRealPath("/WEB-INF/classes") + "/";
	String propertiesFile = dir + PROPERTIES_FILE;

	try {
	    myProps = IOUtils.loadConfigByPath(propertiesFile);

	    if (LOGGER.isDebugEnabled()) {
		LOGGER.debug("Loaded properties file: {}", propertiesFile);
	    }
	}
	catch (Exception details) {
	    throw new ServletException(details);
	}
    }

    private String stripExt(String aFileName) {
	int index = aFileName.lastIndexOf('.');
	return index != -1 ? aFileName.substring(0, index) : aFileName;
    }
}