Added prev/next and etag for caching of images

src/org/forkalsrud/album/exif/Entry.java

@@ -20,6 +20,9 @@ public class Entry {
     String caption;
     Date date;
     int orientation;
+    Entry next;
+    Entry prev;
+    String etag;
 
     
     /**
@@ -108,4 +111,25 @@ public class Entry {
     public void setOrientation(int orientation) {
         this.orientation = orientation;
     }
+
+    public Entry prev() {
+        return prev;
+    }
+    public Entry next() {
+        return next;
+    }
+
+
+    
+    public String getEtag() {
+        return etag;
+    }
+
+
+    
+    public void setEtag(String etag) {
+        this.etag = etag;
+    }
+
+
 }

src/org/forkalsrud/album/exif/EntryDao.java

@@ -5,6 +5,7 @@
 
 package org.forkalsrud.album.exif;
 
+import java.awt.image.BufferedImage;
 import java.io.File;
 import java.io.FileFilter;
 import java.io.FileInputStream;
@@ -24,6 +25,11 @@ import java.util.Iterator;
 import java.util.List;
 import java.util.Properties;
 
+import javax.imageio.ImageIO;
+import javax.imageio.ImageReadParam;
+import javax.imageio.ImageReader;
+import javax.imageio.stream.ImageInputStream;
+
 import com.drew.imaging.jpeg.JpegMetadataReader;
 import com.drew.imaging.jpeg.JpegProcessingException;
 import com.drew.metadata.Directory;
@@ -43,13 +49,18 @@ public class EntryDao {
     final static String CACHE_FILE = "cache.properties";
     final static String OVERRIDE_FILE = "album.properties";
 
+    boolean isCurrent(File directory) {
+
+        return directory.lastModified() <= new File(directory, CACHE_FILE).lastModified();
+    }
+
     public List<Entry> read(File directory) throws FileNotFoundException, IOException, JpegProcessingException, MetadataException, ParseException {
 
         List<Entry> entries = new ArrayList<Entry>();
 
         Properties cachedProps = new Properties();
         File cache = new File(directory, CACHE_FILE);
-        if (cache.exists() && cache.isFile() && cache.canRead())  {
+        if (cache.exists() && cache.isFile() && cache.canRead() && isCurrent(directory))  {
             cachedProps.load(new FileInputStream(cache));
         } else {
             generateEntries(directory, cachedProps);
@@ -80,9 +91,25 @@ public class EntryDao {
                 }
             }
         });
+        fillLinkedList(entries);
         return entries;
     }
 
+    void fillLinkedList(List<Entry> entries) {
+
+        Entry prev = null;
+        for (Entry e : entries) {
+            e.prev = prev;
+            if (prev != null) {
+                prev.next = e;
+            }
+            prev = e;
+        }
+        if (prev != null) {
+            prev.next = null;
+        }
+    }
+
 
     private void populate(Properties cachedProps, List<Entry> entries) throws ParseException {
 
@@ -100,6 +127,7 @@ public class EntryDao {
                     entry.setSize(new Dimension(cachedProps.getProperty("file." + name + ".dimensions")));
                     entry.setCaption(cachedProps.getProperty("file." + name + ".caption"));
                     entry.setOrientation(Integer.parseInt(cachedProps.getProperty("file." + name + ".orientation")));
+                    entry.setEtag(cachedProps.getProperty("file." + name + ".etag"));
                     entries.add(entry);
                 }
             }
@@ -137,6 +165,7 @@ public class EntryDao {
             String base = "file." + name + ".";
             boolean hasDate = false;
             boolean hasOrientation = false;
+            boolean hasDim = false;
 
             Metadata metadata = JpegMetadataReader.readMetadata(f);
             Directory exifDirectory = metadata.getDirectory(ExifDirectory.class);
@@ -150,6 +179,7 @@ public class EntryDao {
                 int width = exifDirectory.getInt(ExifDirectory.TAG_EXIF_IMAGE_WIDTH);
                 int height = exifDirectory.getInt(ExifDirectory.TAG_EXIF_IMAGE_HEIGHT);
                 cachedProps.setProperty(base + "dimensions", new Dimension(width, height).toString());
+                hasDim = true;
             }
             if (exifDirectory.containsTag(ExifDirectory.TAG_DATETIME_ORIGINAL)) {
                 Date captureDate = exifDirectory.getDate(ExifDirectory.TAG_DATETIME_ORIGINAL);
@@ -166,13 +196,22 @@ public class EntryDao {
                 int width = jpegDirectory.getInt(JpegDirectory.TAG_JPEG_IMAGE_WIDTH);
                 int height = jpegDirectory.getInt(JpegDirectory.TAG_JPEG_IMAGE_HEIGHT);
                 cachedProps.setProperty(base + "dimensions", new Dimension(width, height).toString());
+                hasDim = true;
             }
+            cachedProps.setProperty(base + "etag", Integer.toHexString(name.hashCode() + Long.valueOf(f.lastModified()).hashCode()));
             if (!hasDate) {
                 cachedProps.setProperty(base + "captureDate", sdf.format(new Date(f.lastModified())));
             }
             if (!hasOrientation) {
                 cachedProps.setProperty(base + "orientation", "1");
             }
+            if (!hasDim) {
+                Dimension dim = decodeImageForDimensions(f);
+                if (dim != null) {
+                    cachedProps.setProperty(base + "dimensions", dim.toString());
+                    hasDim = true;
+                }
+            }
         }
         File dst = new File(directory, CACHE_FILE);
         if (directory.canWrite()) {
@@ -180,5 +219,24 @@ public class EntryDao {
         }
     }
 
+    Dimension decodeImageForDimensions(File file) throws IOException {
+
+        String suffix = null;
+        String name = file.getName();
+        if (name.indexOf('.') > 0) {
+            suffix = name.substring(name.lastIndexOf('.') + 1);
+        }
+        Iterator<ImageReader> readers = ImageIO.getImageReadersBySuffix(suffix);
+        if (!readers.hasNext()) { 
+            return null;
+        }
+        ImageReader reader = readers.next();
+        ImageInputStream iis = ImageIO.createImageInputStream(file);
+        reader.setInput(iis, true);
+        ImageReadParam param = reader.getDefaultReadParam();
+        BufferedImage img = reader.read(0, param);
+        return new Dimension(img.getWidth(), img.getHeight());
+    }
+
 
 }

src/org/forkalsrud/album/web/AlbumServlet.java

@@ -94,6 +94,8 @@ public class AlbumServlet
             try {
                 Entry e = dao.readFile(file);
                 req.setAttribute("entry", e);
+                req.setAttribute("prev", e.prev());
+                req.setAttribute("next", e.next());
                 RequestDispatcher rd = req.getRequestDispatcher("/WEB-INF/velocity/photo.vm");
                 rd.forward(req, res);
             } catch (Exception e) {
@@ -104,17 +106,22 @@ public class AlbumServlet
         }            
     }
 
+    boolean etagMatches(HttpServletRequest req, HttpServletResponse res, Entry entry, String size) {
+        String reqEtag = req.getHeader("If-None-Match");
+        String fileEtag = entry.getEtag() + "-" + size;
+        if (reqEtag != null) {
+            return reqEtag.equals(fileEtag);
+        }
+        res.setHeader("ETag", fileEtag);
+        return false;
+    }
 
     void scaleImage(HttpServletRequest req, HttpServletResponse res, File file, String size) throws IOException, JpegProcessingException, MetadataException, ParseException {
 
-        List<Entry> entries = dao.read(file.getParentFile());
+        Entry entry = dao.readFile(file);
-        Entry entry = null;
+        if (etagMatches(req, res, entry, size)) {
-        String myName = file.getName();
+            res.setStatus(HttpServletResponse.SC_NOT_MODIFIED);
-        for (Entry e : entries) {
+            return;
-            if (myName.equals(e.getName())) {
-                entry = e;
-                break;
-            }
         }
         Dimension orig = entry.getSize();
         Dimension outd;
@@ -134,7 +141,7 @@ public class AlbumServlet
         ImageInputStream iis = ImageIO.createImageInputStream(file);
         reader.setInput(iis, true);
         ImageReadParam param = reader.getDefaultReadParam();
-        if (true /* subsampling */) {
+        if (false /* subsampling */) {
             double subSampleScale = (double)outd.getWidth() / orig.getWidth();
             int subSampling = (int)Math.floor(0.25d/subSampleScale);
             if (subSampling > 1) {

webapp/WEB-INF/velocity/photo.vm

@@ -34,6 +34,15 @@
 
 </head>
 <body>
+<center>
+#if($prev)
+  <a href="${prev.name}.photo">&lt;--</a>
+#end
+#if($next)
+  <a href="${next.name}.photo">--&gt;</a>
+#end
+</center>
+
 #set($thmb = 480)
 #set($dim = $entry.size.scaled($thmb))
   <div class="photo">