Added a built-in update checker. See http://wiki.bukkit.org/Bukkit.yml#auto-updater for new bukkit.yml options.

src/main/java/org/bukkit/craftbukkit/updater/BukkitDLUpdaterService.java

@@ -0,0 +1,68 @@
+package org.bukkit.craftbukkit.updater;
+
+import com.google.gson.*;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.UnsupportedEncodingException;
+import java.lang.reflect.Type;
+import java.net.MalformedURLException;
+import java.net.URL;
+import java.net.URLEncoder;
+import java.text.DateFormat;
+import java.text.ParseException;
+import java.text.SimpleDateFormat;
+import java.util.Date;
+import java.util.logging.Level;
+import java.util.logging.Logger;
+
+public class BukkitDLUpdaterService {
+    private static final String API_PREFIX = "/api/1.0/downloads/projects/craftbukkit/view/";
+    private static final DateDeserializer dateDeserializer = new DateDeserializer();
+    private final String host;
+
+    public BukkitDLUpdaterService(String host) {
+        this.host = host;
+    }
+
+    public ArtifactDetails getArtifact(String slug) {
+        try {
+            return fetchArtifact(slug);
+        } catch (UnsupportedEncodingException ex) {
+            Logger.getLogger(BukkitDLUpdaterService.class.getName()).log(Level.WARNING, "Could not get Artifact details for the auto-updater", ex);
+        } catch (IOException ex) {
+            Logger.getLogger(BukkitDLUpdaterService.class.getName()).log(Level.WARNING, "Could not get Artifact details for the auto-updater", ex);
+        }
+
+        return null;
+    }
+
+    public ArtifactDetails fetchArtifact(String slug) throws UnsupportedEncodingException, IOException {
+        URL url = new URL("http", host, API_PREFIX + slug);
+        InputStreamReader reader = null;
+
+        try {
+            reader = new InputStreamReader(url.openStream());
+            Gson gson = new GsonBuilder().registerTypeAdapter(Date.class, dateDeserializer).setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES).create();
+            ArtifactDetails fromJson = gson.fromJson(reader, ArtifactDetails.class);
+
+            return fromJson;
+        } finally {
+            if (reader != null) {
+                reader.close();
+            }
+        }
+    }
+
+    static class DateDeserializer implements JsonDeserializer<Date> {
+        private static final SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
+
+        public Date deserialize(JsonElement je, Type type, JsonDeserializationContext jdc) throws JsonParseException {
+            try {
+                return format.parse(je.getAsString());
+            } catch (ParseException ex) {
+                throw new JsonParseException("Date is not formatted correctly", ex);
+            }
+        }
+    }
+}