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Mention that GsonBuilder.registerTypeAdapter makes (de-)serializers null-safe (#1704)

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Marcono1234 2022-08-22 15:55:31 +02:00 committed by GitHub
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6
gson/src/main/java/com/google/gson/GsonBuilder.java
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@ -534,6 +534,12 @@ public final class GsonBuilder {
* types! For example, applications registering {@code boolean.class} should also register {@code
* Boolean.class}.
*
* <p>{@link JsonSerializer} and {@link JsonDeserializer} are made "{@code null}-safe". This
* means when trying to serialize {@code null}, Gson will write a JSON {@code null} and the
* serializer is not called. Similarly when deserializing a JSON {@code null}, Gson will emit
* {@code null} without calling the deserializer. If it is desired to handle {@code null} values,
* a {@link TypeAdapter} should be used instead.
*
* @param type the type definition for the type adapter being registered
* @param typeAdapter This object must implement at least one of the {@link TypeAdapter},
* {@link InstanceCreator}, {@link JsonSerializer}, and a {@link JsonDeserializer} interfaces.

6
gson/src/test/java/com/google/gson/GsonTypeAdapterTest.java
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@ -53,10 +53,16 @@ public class GsonTypeAdapterTest extends TestCase {
fail("Type Adapter should have thrown an exception");
} catch (IllegalStateException expected) { }
// Verify that serializer is made null-safe, i.e. it is not called for null
assertEquals("null", gson.toJson(null, AtomicLong.class));
try {
gson.fromJson("123", AtomicLong.class);
fail("Type Adapter should have thrown an exception");
} catch (JsonParseException expected) { }
// Verify that deserializer is made null-safe, i.e. it is not called for null
assertNull(gson.fromJson(JsonNull.INSTANCE, AtomicLong.class));
}
public void testTypeAdapterProperlyConvertsTypes() throws Exception {