> The commit in this PR implements the proposal for enhancement that was 
> discussed in the core-libs-dev mailing list recently[1], for 
> https://bugs.openjdk.java.net/browse/JDK-8231640
> 
> At a high level - the `store()` APIs in `Properties` have been modified to 
> now look for the `SOURCE_DATE_EPOCH` environment variable[2]. If that env 
> variable is set, then instead of writing out the current date time as a date 
> comment, the `store()` APIs instead will use the value set for this env 
> variable to parse it to a `Date` and write out the string form of such a 
> date. The implementation here uses the `d MMM yyyy HH:mm:ss 'GMT'` date 
> format and `Locale.ROOT` to format and write out such a date. This should 
> provide reproducibility whenever the `SOURCE_DATE_EPOCH` is set. Furthermore, 
> intentionally, no changes in the date format of the "current date" have been 
> done.
> 
> These  modified `store()` APIs work in the presence of the `SecurityManager` 
> too. The caller is expected to have a read permission on the 
> `SOURCE_DATE_EPOCH` environment variable. If the caller doesn't have that 
> permission, then the implementation of these `store()` APIs will write out 
> the "current date" and will ignore any value that has been set for the 
> `SOURCE_DATE_EPOCH` env variable. This should allow for backward 
> compatibility of existing applications, where, when they run under a 
> `SecurityManager` and perhaps with an existing restrictive policy file, the 
> presence of `SOURCE_DATE_EPOCH` shouldn't impact their calls to the `store()` 
> APIs.
> 
> The modified `store()` APIs will also ignore any value for 
> `SOURCE_DATE_EPOCH` that  cannot be parsed to an `long` value. In such cases, 
> the `store()` APIs will write out the "current date" and ignore the value set 
> for this environment variable. No exceptions will be thrown for such invalid 
> values. This is an additional backward compatibility precaution to prevent 
> any rogue value for `SOURCE_DATE_EPOCH` from breaking applications.
> 
> An additional change in the implementation of these `store()` APIs and 
> unrelated to the date comment, is that these APIs will now write out the 
> property keys in a deterministic order. The keys will be written out in the 
> natural ordering as specified by `java.lang.String#compareTo()` API.
> 
> The combination of the ordering of the property keys when written out and the 
> usage of `SOURCE_DATE_EPOCH` environment value to determine the date comment 
> should together allow for reproducibility of the output generated by these 
> `store()` APIs.
> 
> New jtreg test classes have been introduced to verify these changes. The 
> primary focus of `PropertiesStoreTest` is the ordering aspects of the 
> property keys that are written out. On the other hand 
> `StoreReproducibilityTest` focuses on the reproducibility of the output 
> generated by these APIs.  The `StoreReproducibilityTest` runs these tests 
> both in the presence and absence of `SecurityManager`. Plus, in the presence 
> of SecurityManager, it tests both the scenarios where the caller is granted 
> the requisite permission and in other case not granted that permission.
> 
> These new tests and existing tests under `test/jdk/java/util/Properties/` 
> pass with these changes.
> 
> [1] 
> https://mail.openjdk.java.net/pipermail/core-libs-dev/2021-August/080758.html
> [2] https://reproducible-builds.org/specs/source-date-epoch/

Jaikiran Pai has updated the pull request incrementally with one additional 
commit since the last revision:

  Implement Mark's suggestion in CSR to include the java.properties.date in the 
list of system properties listed in System::getProperties()

-------------

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/5372/files
  - new: https://git.openjdk.java.net/jdk/pull/5372/files/eb31d287..458c1fd3

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=5372&range=19
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=5372&range=18-19

  Stats: 3 lines in 1 file changed: 3 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/5372.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/5372/head:pull/5372

PR: https://git.openjdk.java.net/jdk/pull/5372

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