2 files changed, 12 insertions, 5 deletions

diff --git a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/FileSender.java b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/FileSender.java
index 05510a05b0..946fb15a3d 100644
--- a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/FileSender.java
+++ b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/FileSender.java
@@ -58,12 +58,14 @@ import java.io.IOException;
 import java.io.OutputStream;
 import java.io.RandomAccessFile;
 import java.text.MessageFormat;
+import java.time.Instant;
 import java.util.Enumeration;
 
 import javax.servlet.http.HttpServletRequest;
 import javax.servlet.http.HttpServletResponse;
 
 import org.eclipse.jgit.lib.ObjectId;
+import org.eclipse.jgit.util.FS;
 
 /**
  * Dumps a file over HTTP GET (or its information via HEAD).
@@ -76,7 +78,7 @@ final class FileSender {
 
 	private final RandomAccessFile source;
 
-	private final long lastModified;
+	private final Instant lastModified;
 
 	private final long fileLen;
 
@@ -89,7 +91,7 @@ final class FileSender {
 		this.source = new RandomAccessFile(path, "r");
 
 		try {
-			this.lastModified = path.lastModified();
+			this.lastModified = FS.DETECTED.lastModifiedInstant(path);
 			this.fileLen = source.getChannel().size();
 			this.end = fileLen;
 		} catch (IOException e) {
@@ -114,7 +116,7 @@ final class FileSender {
 		}
 	}
 
-	long getLastModified() {
+	Instant getLastModified() {
 		return lastModified;
 	}
 
diff --git a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ObjectFileServlet.java b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ObjectFileServlet.java
index 62f075c73c..5a27be6430 100644
--- a/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ObjectFileServlet.java
+++ b/org.eclipse.jgit.http.server/src/org/eclipse/jgit/http/server/ObjectFileServlet.java
@@ -54,6 +54,7 @@ import static org.eclipse.jgit.util.HttpSupport.HDR_LAST_MODIFIED;
 import java.io.File;
 import java.io.FileNotFoundException;
 import java.io.IOException;
+import java.time.Instant;
 
 import javax.servlet.ServletException;
 import javax.servlet.http.HttpServlet;
@@ -76,7 +77,9 @@ abstract class ObjectFileServlet extends HttpServlet {
 
 		@Override
 		String etag(FileSender sender) throws IOException {
-			return Long.toHexString(sender.getLastModified());
+			Instant lastModified = sender.getLastModified();
+			return Long.toHexString(lastModified.getEpochSecond())
+					+ Long.toHexString(lastModified.getNano());
 		}
 	}
 
@@ -145,7 +148,9 @@ abstract class ObjectFileServlet extends HttpServlet {
 
 		try {
 			final String etag = etag(sender);
-			final long lastModified = (sender.getLastModified() / 1000) * 1000;
+			// HTTP header Last-Modified header has a resolution of 1 sec, see
+			// https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html#sec14.29
+			final long lastModified = sender.getLastModified().getEpochSecond();
 
 			String ifNoneMatch = req.getHeader(HDR_IF_NONE_MATCH);
 			if (etag != null && etag.equals(ifNoneMatch)) {