openjdk team mailing list archive

[Emmanuel Bourg <ebourg@xxxxxxxxxx>]

Source: openjdk-11
Severity: normal
User: reproducible-builds@xxxxxxxxxxxxxxxxxxxxxxx
Usertags: timestamps toolchain

When writing a properties file using the java.util.Properties class, a header
containing the current date is automatically added. This renders the output non
reproducible.

Here is a patch for java.util.Properties checking if the SOURCE_DATE_EPOCH
environment variable is specified and using it instead of the current date
for the timestamp.

Description: Makes the timestamp in the properties files header reproducible when SOURCE_DATE_EPOCH is specified
Author: Emmanuel Bourg <ebourg@xxxxxxxxxx>
Forwarded: no
--- a/src/java.base/share/classes/java/util/Properties.java
+++ b/src/java.base/share/classes/java/util/Properties.java
@@ -905,7 +905,7 @@
         if (comments != null) {
             writeComments(bw, comments);
         }
-        bw.write("#" + new Date().toString());
+        bw.write("#" + getFormattedTimestamp());
         bw.newLine();
         synchronized (this) {
             for (Map.Entry<Object, Object> e : entrySet()) {
@@ -1555,4 +1555,22 @@
         }
         this.map = map;
     }
+
+    /**
+     * Returns a formatted timestamp to be used in the properties file header.
+     * The date used is the current date, unless the SOURCE_DATE_EPOCH
+     * environment variable is specified. In this case the format used is
+     * locale and timezone insensitive to ensure the output is reproducible.
+     */
+    private String getFormattedTimestamp() {
+        if (System.getenv("SOURCE_DATE_EPOCH") == null) {
+            return new Date().toString();
+        } else {
+            // Use the SOURCE_DATE_EPOCH timestamp and make the format locale/timezone insensitive
+            java.text.SimpleDateFormat fmt = new java.text.SimpleDateFormat("yyyy-MM-dd HH:mm:ss z", java.util.Locale.ENGLISH);
+            fmt.setTimeZone(java.util.TimeZone.getTimeZone("UTC"));
+            Date date = new Date(1000 * Long.parseLong(System.getenv("SOURCE_DATE_EPOCH")));
+            return fmt.format(date);
+        }
+    }
 }