Uses the "Last-Modified" header for "If-Modified-Since"

Uses the "Last-Modified" header for "If-Modified-Since"
see http://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html#sec13.3.4

Change-Id: I0f5e9b45f4f79d7c1b286e465f9750dcd71b6bfd
Signed-off-by: Ralph Bergmann <ralph@the4thfloor.eu>

4 files changed, 25 insertions, 2 deletions

diff --git a/src/main/java/com/android/volley/Cache.java b/src/main/java/com/android/volley/Cache.java
index eafd118..f1ec757 100644
--- a/src/main/java/com/android/volley/Cache.java
+++ b/src/main/java/com/android/volley/Cache.java
@@ -74,6 +74,9 @@ public interface Cache {
         /** Date of this response as reported by the server. */
         public long serverDate;
 
+        /** The last modified date for the requested object. */
+        public long lastModified;
+
         /** TTL for this record. */
         public long ttl;
 
diff --git a/src/main/java/com/android/volley/toolbox/BasicNetwork.java b/src/main/java/com/android/volley/toolbox/BasicNetwork.java
index bc1cfdb..4b1603b 100644
--- a/src/main/java/com/android/volley/toolbox/BasicNetwork.java
+++ b/src/main/java/com/android/volley/toolbox/BasicNetwork.java
@@ -212,8 +212,8 @@ public class BasicNetwork implements Network {
             headers.put("If-None-Match", entry.etag);
         }
 
-        if (entry.serverDate > 0) {
-            Date refTime = new Date(entry.serverDate);
+        if (entry.lastModified > 0) {
+            Date refTime = new Date(entry.lastModified);
             headers.put("If-Modified-Since", DateUtils.formatDate(refTime));
         }
     }
diff --git a/src/main/java/com/android/volley/toolbox/DiskBasedCache.java b/src/main/java/com/android/volley/toolbox/DiskBasedCache.java
index b283788..036b55a 100644
--- a/src/main/java/com/android/volley/toolbox/DiskBasedCache.java
+++ b/src/main/java/com/android/volley/toolbox/DiskBasedCache.java
@@ -349,6 +349,9 @@ public class DiskBasedCache implements Cache {
         /** Date of this response as reported by the server. */
         public long serverDate;
 
+        /** The last modified date for the requested object. */
+        public long lastModified;
+
         /** TTL for this record. */
         public long ttl;
 
@@ -370,6 +373,7 @@ public class DiskBasedCache implements Cache {
             this.size = entry.data.length;
             this.etag = entry.etag;
             this.serverDate = entry.serverDate;
+            this.lastModified = entry.lastModified;
             this.ttl = entry.ttl;
             this.softTtl = entry.softTtl;
             this.responseHeaders = entry.responseHeaders;
@@ -396,6 +400,13 @@ public class DiskBasedCache implements Cache {
             entry.ttl = readLong(is);
             entry.softTtl = readLong(is);
             entry.responseHeaders = readStringStringMap(is);
+
+            try {
+                entry.lastModified = readLong(is);
+            } catch (EOFException e) {
+                // the old cache entry format doesn't know lastModified
+            }
+
             return entry;
         }
 
@@ -407,6 +418,7 @@ public class DiskBasedCache implements Cache {
             e.data = data;
             e.etag = etag;
             e.serverDate = serverDate;
+            e.lastModified = lastModified;
             e.ttl = ttl;
             e.softTtl = softTtl;
             e.responseHeaders = responseHeaders;
@@ -426,6 +438,7 @@ public class DiskBasedCache implements Cache {
                 writeLong(os, ttl);
                 writeLong(os, softTtl);
                 writeStringStringMap(responseHeaders, os);
+                writeLong(os, lastModified);
                 os.flush();
                 return true;
             } catch (IOException e) {
diff --git a/src/main/java/com/android/volley/toolbox/HttpHeaderParser.java b/src/main/java/com/android/volley/toolbox/HttpHeaderParser.java
index cb08432..e342c9e 100644
--- a/src/main/java/com/android/volley/toolbox/HttpHeaderParser.java
+++ b/src/main/java/com/android/volley/toolbox/HttpHeaderParser.java
@@ -42,6 +42,7 @@ public class HttpHeaderParser {
         Map<String, String> headers = response.headers;
 
         long serverDate = 0;
+        long lastModified = 0;
         long serverExpires = 0;
         long softExpire = 0;
         long maxAge = 0;
@@ -79,6 +80,11 @@ public class HttpHeaderParser {
             serverExpires = parseDateAsEpoch(headerValue);
         }
 
+        headerValue = headers.get("Last-Modified");
+        if (headerValue != null) {
+            lastModified = parseDateAsEpoch(headerValue);
+        }
+
         serverEtag = headers.get("ETag");
 
         // Cache-Control takes precedence over an Expires header, even if both exist and Expires
@@ -96,6 +102,7 @@ public class HttpHeaderParser {
         entry.softTtl = softExpire;
         entry.ttl = entry.softTtl;
         entry.serverDate = serverDate;
+        entry.lastModified = lastModified;
         entry.responseHeaders = headers;
 
         return entry;