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Add (de-)serialization support for Iterable
This adds only support for (de-)serializing Iterable, but not any of its subtypes since it would not be possible to properly deserialize them again.
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80 changes: 80 additions & 0 deletions
80
gson/src/main/java/com/google/gson/internal/bind/IterableTypeAdapterFactory.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,80 @@ | ||
| package com.google.gson.internal.bind; | ||
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| import com.google.gson.Gson; | ||
| import com.google.gson.TypeAdapter; | ||
| import com.google.gson.TypeAdapterFactory; | ||
| import com.google.gson.internal.$Gson$Types; | ||
| import com.google.gson.reflect.TypeToken; | ||
| import com.google.gson.stream.JsonReader; | ||
| import com.google.gson.stream.JsonToken; | ||
| import com.google.gson.stream.JsonWriter; | ||
| import java.io.IOException; | ||
| import java.lang.reflect.Type; | ||
| import java.util.ArrayList; | ||
| import java.util.List; | ||
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| public final class IterableTypeAdapterFactory implements TypeAdapterFactory { | ||
| public static final IterableTypeAdapterFactory INSTANCE = new IterableTypeAdapterFactory(); | ||
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| private IterableTypeAdapterFactory() { | ||
| } | ||
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| @Override | ||
| public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> typeToken) { | ||
| Type type = typeToken.getType(); | ||
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| Class<? super T> rawType = typeToken.getRawType(); | ||
| /* | ||
| * Only support Iterable, but not subtypes | ||
| * This allows freely choosing Iterable implementation on deserialization | ||
| */ | ||
| if (rawType != Iterable.class) { | ||
| return null; | ||
| } | ||
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| Type elementType = $Gson$Types.getIterableElementType(type, rawType); | ||
| TypeAdapter<?> elementTypeAdapter = gson.getAdapter(TypeToken.get(elementType)); | ||
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| @SuppressWarnings({"unchecked", "rawtypes"}) // create() doesn't define a type parameter | ||
| TypeAdapter<T> result = new Adapter(gson, elementType, elementTypeAdapter); | ||
| return result; | ||
| } | ||
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| private static final class Adapter<E> extends TypeAdapter<Iterable<E>> { | ||
| private final TypeAdapter<E> elementTypeAdapter; | ||
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| public Adapter(Gson context, Type elementType, TypeAdapter<E> elementTypeAdapter) { | ||
| this.elementTypeAdapter = | ||
| new TypeAdapterRuntimeTypeWrapper<E>(context, elementTypeAdapter, elementType); | ||
| } | ||
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| @Override public Iterable<E> read(JsonReader in) throws IOException { | ||
| if (in.peek() == JsonToken.NULL) { | ||
| in.nextNull(); | ||
| return null; | ||
| } | ||
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| List<E> list = new ArrayList<E>(); | ||
| in.beginArray(); | ||
| while (in.hasNext()) { | ||
| E instance = elementTypeAdapter.read(in); | ||
| list.add(instance); | ||
| } | ||
| in.endArray(); | ||
| return list; | ||
| } | ||
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| @Override public void write(JsonWriter out, Iterable<E> iterable) throws IOException { | ||
| if (iterable == null) { | ||
| out.nullValue(); | ||
| return; | ||
| } | ||
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| out.beginArray(); | ||
| for (E element : iterable) { | ||
| elementTypeAdapter.write(out, element); | ||
| } | ||
| out.endArray(); | ||
| } | ||
| } | ||
| } |
91 changes: 91 additions & 0 deletions
91
gson/src/test/java/com/google/gson/functional/IterableTest.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,91 @@ | ||
| package com.google.gson.functional; | ||
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| import java.io.IOException; | ||
| import java.util.ArrayList; | ||
| import java.util.Arrays; | ||
| import java.util.Iterator; | ||
| import java.util.List; | ||
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| import com.google.gson.Gson; | ||
| import com.google.gson.GsonBuilder; | ||
| import com.google.gson.TypeAdapter; | ||
| import com.google.gson.reflect.TypeToken; | ||
| import com.google.gson.stream.JsonReader; | ||
| import com.google.gson.stream.JsonWriter; | ||
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| import junit.framework.TestCase; | ||
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| public class IterableTest extends TestCase { | ||
| private static class CustomIterable implements Iterable<Integer> { | ||
| final int base; | ||
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| public CustomIterable(int base) { | ||
| this.base = base; | ||
| } | ||
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| @Override | ||
| public Iterator<Integer> iterator() { | ||
| return Arrays.asList(base + 1, base + 2).iterator(); | ||
| } | ||
| } | ||
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| public void testSerialize() { | ||
| CustomIterable iterable = new CustomIterable(0); | ||
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| Gson gson = new Gson(); | ||
| // Serializing specific Iterable subtype should use reflection-based approach | ||
| assertEquals("{\"base\":0}", gson.toJson(iterable)); | ||
| // But serializing as Iterable should use adapter | ||
| assertEquals("[1,2]", gson.toJson(iterable, Iterable.class)); | ||
| } | ||
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| public void testDeserialize() { | ||
| Gson gson = new Gson(); | ||
| // Deserializing as specific Iterable subtype should use reflection-based approach | ||
| // i.e. must not choose any (potentially incompatible) class implementing `Iterable` | ||
| // See also https://github.com/google/gson/issues/1708 | ||
| assertEquals(1, gson.fromJson("{\"base\":1}", CustomIterable.class).base); | ||
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| // But deserializing as Iterable should use adapter | ||
| Iterable<Integer> deserialized = gson.fromJson("[1,2]", new TypeToken<Iterable<Integer>>() {}.getType()); | ||
| // Collect elements and then compare them to not make any assumptions about | ||
| // type of `deserialized` | ||
| ArrayList<Integer> elements = new ArrayList<>(); | ||
| for (Integer element : deserialized) { | ||
| elements.add(element); | ||
| } | ||
| assertEquals(Arrays.asList(1, 2), elements); | ||
| } | ||
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| private static class CustomIterableTypeAdapter extends TypeAdapter<Iterable<?>> { | ||
| private static final int SERIALIZED = 5; | ||
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| private static List<Integer> getDeserialized() { | ||
| return Arrays.asList(1, 2); | ||
| } | ||
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| @Override public void write(JsonWriter out, Iterable<?> value) throws IOException { | ||
| out.value(SERIALIZED); | ||
| } | ||
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| @Override public Iterable<?> read(JsonReader in) throws IOException { | ||
| in.skipValue(); | ||
| return getDeserialized(); | ||
| } | ||
| } | ||
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| /** | ||
| * Verify that overwriting built-in {@link Iterable} adapter is possible. | ||
| */ | ||
| public void testCustomAdapter() { | ||
| Gson gson = new GsonBuilder() | ||
| .registerTypeAdapter(Iterable.class, new CustomIterableTypeAdapter()) | ||
| .create(); | ||
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| String expectedJson = String.valueOf(CustomIterableTypeAdapter.SERIALIZED); | ||
| assertEquals(expectedJson, gson.toJson(new ArrayList<>(), Iterable.class)); | ||
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| List<Integer> expectedDeserialized = CustomIterableTypeAdapter.getDeserialized(); | ||
| assertEquals(expectedDeserialized, gson.fromJson("[]", Iterable.class)); | ||
| } | ||
| } |