import java.io.ByteArrayOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.InputStream;
import java.security.DigestInputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Collections;
import java.util.logging.Logger;
import java.util.zip.ZipEntry;
import java.util.zip.ZipInputStream;
import javax.cache.CacheException;
import javax.cache.CacheManager;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public class ScServlet extends HttpServlet {
private static final Logger log = Logger.getLogger(ScServlet.class.getName());
private static String identifier;
/**
* This servlet receives all '/sc/*' requests according to a rule defined in
* 'web.xml'. It looks for the necessary resource in 'sc.zip' which should
* be present in the application classpath.
*/
public void doGet(HttpServletRequest req, HttpServletResponse resp) throws IOException {
// Sometimes the request URI begins with '/sc' and other times with
// '/myappname/sc', so we always remove '/myappname' from the request URI
String requestedURI = req.getRequestURI().replaceFirst("/myappname", "");
// At this point requestedURI begins with '/sc/...' but the zip file entries
// begin with 'sc/...', so we remove the first '/'
requestedURI = requestedURI.substring(1);
requestedURI = requestedURI.replaceAll("//", "/");
log.info("Requested URI '" + req.getRequestURI() + "' converted to '" + requestedURI + "'");
try {
// Client side caching
resp.setHeader("ETag", getIdentifier());
resp.setHeader("Cache-Control", "public, max-age=2592000"); // Client cache age 30 days
// Load from server side cache
resp.getOutputStream().write(getResourceFromCache(resp,requestedURI));
} catch (CacheException e) {
resp.getOutputStream().write(getResourceFromZip(resp,requestedURI));
}
}
/**
*
* @return md5 string for current sc.zip
*/
private String getIdentifier()
{
if (identifier == null)
{
InputStream is = null;
try {
// Generate md5 digest from file
MessageDigest md = MessageDigest.getInstance("MD5");
is = new FileInputStream("sc.zip");
int buffersize = is.available();
byte[] buffer = new byte[buffersize];
is = new DigestInputStream(is, md);
while (is.read(buffer) > 0);
byte[] digest = md.digest();
identifier = new String(digest);
} catch (FileNotFoundException e)
{
e.printStackTrace();
} catch (NoSuchAlgorithmException e)
{
e.printStackTrace();
} catch (IOException e)
{
e.printStackTrace();
} finally
{
try
{
is.close();
} catch (Exception e)
{
e.printStackTrace();
}
}
}
return identifier;
}
private byte[] getResourceFromCache(HttpServletResponse resp,String key)
throws CacheException, IOException {
javax.cache.Cache cache = CacheManager.getInstance().getCacheFactory().createCache(Collections.emptyMap());
byte[] resource = (byte[]) cache.get(key);
if (resource == null) {
resource = getResourceFromZip(resp,key);
cache.put(key, resource);
}
return resource;
}
private byte[] getResourceFromZip(HttpServletResponse resp,String requestedURI) throws FileNotFoundException, IOException {
// search for resource
ZipInputStream in = new ZipInputStream(new FileInputStream("sc.zip"));
ZipEntry entry;
while ((entry = in.getNextEntry()) != null) {
if (requestedURI.equals(entry.getName())) {
// resource found
// redirect it to output stream
ByteArrayOutputStream out = new ByteArrayOutputStream();
byte[] buf = new byte[1024];
int len;
while ((len = in.read(buf)) > 0) {
out.write(buf, 0, len);
}
in.close();
out.close();
log.info("Requested '" + requestedURI + "' found in zip file entry: " + entry.getName());
return out.toByteArray();
}
}
log.severe("Requested '" + requestedURI + "' not found in zip file!");
return null;
}
}
Comment