Follow-up for `java.time` adapter changes #2972

Marcono1234 · 2026-01-13T12:07:19Z

Follow-up for #2948

internal Javadoc additions and changes
moved java.time tests to separate test class
added additional Maven Surefire Plugin execution which runs java.time test with --add-opens
some small code changes

(see also my GitHub review comments in the changed code below)

If you think some of this is not needed or want something changes, please let me know.

gson/src/main/java/com/google/gson/internal/bind/JavaTimeTypeAdapters.java

Marcono1234 · 2026-01-13T12:10:04Z

gson/src/main/java/com/google/gson/internal/bind/TypeAdapters.java

-  // TODO: update this when we are on at least Android API Level 24.
+  // TODO: switch to `Math#toIntExact` when we are on at least Android API Level 24.


Side note: Math#toIntExact throws ArithmeticException (a direct subclass of RuntimeException) instead of IllegalArgumentException which is currently used here.

Hmm, maybe we should throw ArithmeticException here too then.

gson/src/test/java/com/google/gson/functional/JavaTimeTest.java

Marcono1234 · 2026-01-13T12:15:20Z

gson/src/test/java/com/google/gson/functional/JavaTimeTest.java

+    // Print this to console to make troubleshooting Maven test execution easier
+    debugPrint("java.time fields are accessible: " + JAVA_TIME_FIELDS_ARE_ACCESSIBLE);


So that you see in the console for the java-time-test execution:

[INFO] Running com.google.gson.functional.JavaTimeTest java.time fields are accessible: true ...

and can be sure that it actually compared the results with the reflection-based adapter.

test-graal-native-image/src/test/java/com/google/gson/native_test/JavaTimeTest.java

Marcono1234 · 2026-01-13T12:18:38Z

README.md


 #### Minimum Android API level

+- Gson 2.14.0 and newer: API level 23


Only added this because the animal-sniffer-maven-plugin config had been changed to use the API Level 23 signatures.

But it seems we don't actually use any Android 23 API yet? So alternatively we could revert this here and used the API Level 21 signatures again?

Yes, I think that would make sense. Do you want to add it to this PR?

You mean revert to 21 API Level signatures again, right?

eamonnmcmanus

Thanks, this is great! Just a few small things.

eamonnmcmanus · 2026-01-13T15:35:57Z

README.md


 #### Minimum Android API level

+- Gson 2.14.0 and newer: API level 23


Yes, I think that would make sense. Do you want to add it to this PR?

eamonnmcmanus · 2026-01-13T15:37:44Z

gson/src/main/java/com/google/gson/internal/bind/IgnoreJRERequirement.java

@@ -1,10 +1,29 @@
+/*
+ * Copyright (C) 2026 Google Inc.


Thanks, I should have caught that. :-)

eamonnmcmanus · 2026-01-13T15:38:48Z

gson/src/main/java/com/google/gson/internal/bind/JavaTimeTypeAdapters.java

 * recent JDK versions. So here we freeze the representation that was current with JDK 21, in a way
 * that does not use reflection.
+ *
+ * <p>This class should not directly be used, instead the type adapter factory should be obtained


This is fair, since apparently the presence of .internal. in the package name is not enough to discourage people from reaching in and grabbing things.

My main concern was actually usage from within Gson (since TypeAdapters is internal as well), to avoid having other places directly access this class and forgetting to account for the potential reflection exceptions.

gson/src/main/java/com/google/gson/internal/bind/JavaTimeTypeAdapters.java

eamonnmcmanus · 2026-01-13T15:42:36Z

gson/src/main/java/com/google/gson/internal/bind/TypeAdapters.java

-  // TODO: update this when we are on at least Android API Level 24.
+  // TODO: switch to `Math#toIntExact` when we are on at least Android API Level 24.


Hmm, maybe we should throw ArithmeticException here too then.

gson/src/test/java/com/google/gson/functional/DefaultTypeAdaptersTest.java

eamonnmcmanus · 2026-01-13T15:44:29Z

gson/src/test/java/com/google/gson/functional/JavaTimeTest.java

+ * Test for {@code java.time} classes.
+ *
+ * <p>If reflective access to JDK classes is possible, this test also verifies that the custom
+ * adapters behave identical to the reflection-based approach (to ensure backward compatibility),


Nit: s/identical/identically/.

gson/src/test/java/com/google/gson/functional/JavaTimeTest.java

test-graal-native-image/src/test/java/com/google/gson/native_test/JavaTimeTest.java

Marcono1234 · 2026-01-13T20:52:19Z

gson/src/main/java/com/google/gson/internal/bind/TypeAdapters.java

+  /**
+   * Adapter factory for {@code java.time} classes. Returns {@code null} if not supported by the
+   * current environment (e.g. too old Android version, without desugaring).
+   */


Actually, maybe this comment I added is incorrect? When java.time is unavailable, I am not sure if trying to load JavaTimeTypeAdapters and accessing the factory would really trigger reflection exceptions. Maybe those would only occur on usage of the factory (which would be bad) or for all non-java.time classes the getName().startsWith("java.time.") would not succeed and the factory returns null (which would be fine).

Do you have an internal test which covers this, and know how this behaves?
(I will see if I can also test this with a dummy Android project)

Follow-up for java.time adapter changes

9489c93

Marcono1234 commented Jan 13, 2026

View reviewed changes

Fix Gson subset build

2ce5629

eamonnmcmanus requested changes Jan 13, 2026

View reviewed changes

Marcono1234 commented Jan 13, 2026

View reviewed changes

		// TODO: update this when we are on at least Android API Level 24.
		// TODO: switch to `Math#toIntExact` when we are on at least Android API Level 24.

		// Print this to console to make troubleshooting Maven test execution easier
		debugPrint("java.time fields are accessible: " + JAVA_TIME_FIELDS_ARE_ACCESSIBLE);


		#### Minimum Android API level

		- Gson 2.14.0 and newer: API level 23

Follow-up for java.time adapter changes #2972

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Follow-up for java.time adapter changes #2972

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Marcono1234 Jan 13, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Follow-up for `java.time` adapter changes #2972

Follow-up for `java.time` adapter changes #2972

Marcono1234 Jan 13, 2026 •

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