Testing Custom Type Adapter Implementation in Google Gson

google/gson

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

            
/*
 * Copyright (C) 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.gson.functional;

import static com.google.common.truth.Truth.assertThat;

import com.google.common.base.Splitter;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.InstanceCreator;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import com.google.gson.common.TestTypes.BagOfPrimitives;
import com.google.gson.common.TestTypes.ClassWithCustomTypeConverter;
import com.google.gson.reflect.TypeToken;
import java.lang.reflect.Type;
import java.util.Date;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;
import java.util.Map;
import java.util.Set;
import org.junit.Before;
import org.junit.Ignore;
import org.junit.Test;

/**
 * Functional tests for the support of custom serializer and deserializers.
 *
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
public class CustomTypeAdaptersTest {
  private GsonBuilder builder;

  @Before
  public void setUp() throws Exception {
    builder = new GsonBuilder();
  }

  @Test
  public void testCustomSerializers() {
    Gson gson =
        builder
            .registerTypeAdapter(
                ClassWithCustomTypeConverter.class,
                (JsonSerializer<ClassWithCustomTypeConverter>)
                    (src, typeOfSrc, context) -> {
                      JsonObject json = new JsonObject();
                      json.addProperty("bag", 5);
                      json.addProperty("value", 25);
                      return json;
                    })
            .create();
    ClassWithCustomTypeConverter target = new ClassWithCustomTypeConverter();
    assertThat(gson.toJson(target)).isEqualTo("{\"bag\":5,\"value\":25}");
  }

  @Test
  public void testCustomDeserializers() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                ClassWithCustomTypeConverter.class,
                (JsonDeserializer<ClassWithCustomTypeConverter>)
                    (json, typeOfT, context) -> {
                      JsonObject jsonObject = json.getAsJsonObject();
                      int value = jsonObject.get("bag").getAsInt();
                      return new ClassWithCustomTypeConverter(
                          new BagOfPrimitives(value, value, false, ""), value);
                    })
            .create();
    String json = "{\"bag\":5,\"value\":25}";
    ClassWithCustomTypeConverter target = gson.fromJson(json, ClassWithCustomTypeConverter.class);
    assertThat(target.getBag().getIntValue()).isEqualTo(5);
  }

  @Test
  @Ignore
  public void disable_testCustomSerializersOfSelf() {
    Gson gson = createGsonObjectWithFooTypeAdapter();
    Gson basicGson = new Gson();
    Foo newFooObject = new Foo(1, 2L);
    String jsonFromCustomSerializer = gson.toJson(newFooObject);
    String jsonFromGson = basicGson.toJson(newFooObject);

    assertThat(jsonFromCustomSerializer).isEqualTo(jsonFromGson);
  }

  @Test
  @Ignore
  public void disable_testCustomDeserializersOfSelf() {
    Gson gson = createGsonObjectWithFooTypeAdapter();
    Gson basicGson = new Gson();
    Foo expectedFoo = new Foo(1, 2L);
    String json = basicGson.toJson(expectedFoo);
    Foo newFooObject = gson.fromJson(json, Foo.class);

    assertThat(newFooObject.key).isEqualTo(expectedFoo.key);
    assertThat(newFooObject.value).isEqualTo(expectedFoo.value);
  }

  @Test
  public void testCustomNestedSerializers() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                BagOfPrimitives.class,
                (JsonSerializer<BagOfPrimitives>) (src, typeOfSrc, context) -> new JsonPrimitive(6))
            .create();
    ClassWithCustomTypeConverter target = new ClassWithCustomTypeConverter();
    assertThat(gson.toJson(target)).isEqualTo("{\"bag\":6,\"value\":10}");
  }

  @Test
  public void testCustomNestedDeserializers() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                BagOfPrimitives.class,
                (JsonDeserializer<BagOfPrimitives>)
                    (json, typeOfT, context) -> {
                      int value = json.getAsInt();
                      return new BagOfPrimitives(value, value, false, "");
                    })
            .create();
    String json = "{\"bag\":7,\"value\":25}";
    ClassWithCustomTypeConverter target = gson.fromJson(json, ClassWithCustomTypeConverter.class);
    assertThat(target.getBag().getIntValue()).isEqualTo(7);
  }

  @Test
  public void testCustomTypeAdapterDoesNotAppliesToSubClasses() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                Base.class,
                (JsonSerializer<Base>)
                    (src, typeOfSrc, context) -> {
                      JsonObject json = new JsonObject();
                      json.addProperty("value", src.baseValue);
                      return json;
                    })
            .create();
    Base b = new Base();
    String json = gson.toJson(b);
    assertThat(json).contains("value");
    b = new Derived();
    json = gson.toJson(b);
    assertThat(json).contains("derivedValue");
  }

  @Test
  public void testCustomTypeAdapterAppliesToSubClassesSerializedAsBaseClass() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                Base.class,
                (JsonSerializer<Base>)
                    (src, typeOfSrc, context) -> {
                      JsonObject json = new JsonObject();
                      json.addProperty("value", src.baseValue);
                      return json;
                    })
            .create();
    Base b = new Base();
    String json = gson.toJson(b);
    assertThat(json).contains("value");
    b = new Derived();
    json = gson.toJson(b, Base.class);
    assertThat(json).contains("value");
    assertThat(json).doesNotContain("derivedValue");
  }

  private static class Base {
    int baseValue = 2;
  }

  private static class Derived extends Base {
    @SuppressWarnings("unused")
    int derivedValue = 3;
  }

  private Gson createGsonObjectWithFooTypeAdapter() {
    return new GsonBuilder().registerTypeAdapter(Foo.class, new FooTypeAdapter()).create();
  }

  public static class Foo {
    private final int key;
    private final long value;

    public Foo() {
      this(0, 0L);
    }

    public Foo(int key, long value) {
      this.key = key;
      this.value = value;
    }
  }

  public static final class FooTypeAdapter implements JsonSerializer<Foo>, JsonDeserializer<Foo> {
    @Override
    public Foo deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      return context.deserialize(json, typeOfT);
    }

    @Override
    public JsonElement serialize(Foo src, Type typeOfSrc, JsonSerializationContext context) {
      return context.serialize(src, typeOfSrc);
    }
  }

  @Test
  public void testCustomSerializerInvokedForPrimitives() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                boolean.class,
                (JsonSerializer<Boolean>)
                    (value, type, context) -> new JsonPrimitive(value ? 1 : 0))
            .create();
    assertThat(gson.toJson(true, boolean.class)).isEqualTo("1");
    assertThat(gson.toJson(true, Boolean.class)).isEqualTo("true");
  }

  @Test
  public void testCustomDeserializerInvokedForPrimitives() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                boolean.class,
                (JsonDeserializer<Boolean>) (json, type, context) -> json.getAsInt() != 0)
            .create();
    assertThat(gson.fromJson("1", boolean.class)).isEqualTo(Boolean.TRUE);
    assertThat(gson.fromJson("true", Boolean.class)).isEqualTo(Boolean.TRUE);
  }

  @Test
  public void testCustomByteArraySerializer() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                byte[].class,
                (JsonSerializer<byte[]>)
                    (src, typeOfSrc, context) -> {
                      StringBuilder sb = new StringBuilder(src.length);
                      for (byte b : src) {
                        sb.append(b);
                      }
                      return new JsonPrimitive(sb.toString());
                    })
            .create();
    byte[] data = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    String json = gson.toJson(data);
    assertThat(json).isEqualTo("\"0123456789\"");
  }

  @Test
  public void testCustomByteArrayDeserializerAndInstanceCreator() {
    GsonBuilder gsonBuilder =
        new GsonBuilder()
            .registerTypeAdapter(
                byte[].class,
                (JsonDeserializer<byte[]>)
                    (json, typeOfT, context) -> {
                      String str = json.getAsString();
                      byte[] data = new byte[str.length()];
                      for (int i = 0; i < data.length; ++i) {
                        data[i] = Byte.parseByte("" + str.charAt(i));
                      }
                      return data;
                    });
    Gson gson = gsonBuilder.create();
    String json = "'0123456789'";
    byte[] actual = gson.fromJson(json, byte[].class);
    byte[] expected = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
    for (int i = 0; i < actual.length; ++i) {
      assertThat(actual[i]).isEqualTo(expected[i]);
    }
  }

  private static final class StringHolder {
    String part1;
    String part2;

    public StringHolder(String string) {
      List<String> parts = Splitter.on(':').splitToList(string);
      part1 = parts.get(0);
      part2 = parts.get(1);
    }

    public StringHolder(String part1, String part2) {
      this.part1 = part1;
      this.part2 = part2;
    }
  }

  private static class StringHolderTypeAdapter
      implements JsonSerializer<StringHolder>,
          JsonDeserializer<StringHolder>,
          InstanceCreator<StringHolder> {

    @Override
    public StringHolder createInstance(Type type) {
      // Fill up with objects that will be thrown away
      return new StringHolder("unknown:thing");
    }

    @Override
    public StringHolder deserialize(
        JsonElement src, Type type, JsonDeserializationContext context) {
      return new StringHolder(src.getAsString());
    }

    @Override
    public JsonElement serialize(
        StringHolder src, Type typeOfSrc, JsonSerializationContext context) {
      String contents = src.part1 + ':' + src.part2;
      return new JsonPrimitive(contents);
    }
  }

  // Test created from Issue 70
  @Test
  public void testCustomAdapterInvokedForCollectionElementSerializationWithType() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(StringHolder.class, new StringHolderTypeAdapter())
            .create();
    Type setType = new TypeToken<Set<StringHolder>>() {}.getType();
    StringHolder holder = new StringHolder("Jacob", "Tomaw");
    Set<StringHolder> setOfHolders = new HashSet<>();
    setOfHolders.add(holder);
    String json = gson.toJson(setOfHolders, setType);
    assertThat(json).contains("Jacob:Tomaw");
  }

  // Test created from Issue 70
  @Test
  public void testCustomAdapterInvokedForCollectionElementSerialization() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(StringHolder.class, new StringHolderTypeAdapter())
            .create();
    StringHolder holder = new StringHolder("Jacob", "Tomaw");
    Set<StringHolder> setOfHolders = new HashSet<>();
    setOfHolders.add(holder);
    String json = gson.toJson(setOfHolders);
    assertThat(json).contains("Jacob:Tomaw");
  }

  // Test created from Issue 70
  @Test
  public void testCustomAdapterInvokedForCollectionElementDeserialization() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(StringHolder.class, new StringHolderTypeAdapter())
            .create();
    Type setType = new TypeToken<Set<StringHolder>>() {}.getType();
    Set<StringHolder> setOfHolders = gson.fromJson("['Jacob:Tomaw']", setType);
    assertThat(setOfHolders.size()).isEqualTo(1);
    StringHolder foo = setOfHolders.iterator().next();
    assertThat(foo.part1).isEqualTo("Jacob");
    assertThat(foo.part2).isEqualTo("Tomaw");
  }

  // Test created from Issue 70
  @Test
  public void testCustomAdapterInvokedForMapElementSerializationWithType() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(StringHolder.class, new StringHolderTypeAdapter())
            .create();
    Type mapType = new TypeToken<Map<String, StringHolder>>() {}.getType();
    StringHolder holder = new StringHolder("Jacob", "Tomaw");
    Map<String, StringHolder> mapOfHolders = new HashMap<>();
    mapOfHolders.put("foo", holder);
    String json = gson.toJson(mapOfHolders, mapType);
    assertThat(json).contains("\"foo\":\"Jacob:Tomaw\"");
  }

  // Test created from Issue 70
  @Test
  public void testCustomAdapterInvokedForMapElementSerialization() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(StringHolder.class, new StringHolderTypeAdapter())
            .create();
    StringHolder holder = new StringHolder("Jacob", "Tomaw");
    Map<String, StringHolder> mapOfHolders = new HashMap<>();
    mapOfHolders.put("foo", holder);
    String json = gson.toJson(mapOfHolders);
    assertThat(json).contains("\"foo\":\"Jacob:Tomaw\"");
  }

  // Test created from Issue 70
  @Test
  public void testCustomAdapterInvokedForMapElementDeserialization() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(StringHolder.class, new StringHolderTypeAdapter())
            .create();
    Type mapType = new TypeToken<Map<String, StringHolder>>() {}.getType();
    Map<String, StringHolder> mapOfFoo = gson.fromJson("{'foo':'Jacob:Tomaw'}", mapType);
    assertThat(mapOfFoo.size()).isEqualTo(1);
    StringHolder foo = mapOfFoo.get("foo");
    assertThat(foo.part1).isEqualTo("Jacob");
    assertThat(foo.part2).isEqualTo("Tomaw");
  }

  @Test
  public void testEnsureCustomSerializerNotInvokedForNullValues() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(DataHolder.class, new DataHolderSerializer())
            .create();
    DataHolderWrapper target = new DataHolderWrapper(new DataHolder("abc"));
    String json = gson.toJson(target);
    assertThat(json).isEqualTo("{\"wrappedData\":{\"myData\":\"abc\"}}");
  }

  @Test
  public void testEnsureCustomDeserializerNotInvokedForNullValues() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(DataHolder.class, new DataHolderDeserializer())
            .create();
    String json = "{wrappedData:null}";
    DataHolderWrapper actual = gson.fromJson(json, DataHolderWrapper.class);
    assertThat(actual.wrappedData).isNull();
  }

  // Test created from Issue 352
  @Test
  @SuppressWarnings({"JavaUtilDate", "UndefinedEquals"})
  public void testRegisterHierarchyAdapterForDate() {
    Gson gson =
        new GsonBuilder().registerTypeHierarchyAdapter(Date.class, new DateTypeAdapter()).create();
    assertThat(gson.toJson(new Date(0))).isEqualTo("0");
    assertThat(gson.toJson(new java.sql.Date(0))).isEqualTo("0");
    assertThat(gson.fromJson("0", Date.class)).isEqualTo(new Date(0));
    assertThat(gson.fromJson("0", java.sql.Date.class)).isEqualTo(new java.sql.Date(0));
  }

  private static class DataHolder {
    final String data;

    public DataHolder(String data) {
      this.data = data;
    }
  }

  private static class DataHolderWrapper {
    final DataHolder wrappedData;

    public DataHolderWrapper(DataHolder data) {
      this.wrappedData = data;
    }
  }

  private static class DataHolderSerializer implements JsonSerializer<DataHolder> {
    @Override
    public JsonElement serialize(DataHolder src, Type typeOfSrc, JsonSerializationContext context) {
      JsonObject obj = new JsonObject();
      obj.addProperty("myData", src.data);
      return obj;
    }
  }

  private static class DataHolderDeserializer implements JsonDeserializer<DataHolder> {
    @Override
    public DataHolder deserialize(
        JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      JsonObject jsonObj = json.getAsJsonObject();
      JsonElement jsonElement = jsonObj.get("data");
      if (jsonElement == null || jsonElement.isJsonNull()) {
        return new DataHolder(null);
      }
      return new DataHolder(jsonElement.getAsString());
    }
  }

  @SuppressWarnings("JavaUtilDate")
  private static class DateTypeAdapter implements JsonSerializer<Date>, JsonDeserializer<Date> {
    @Override
    public Date deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context) {
      return typeOfT == Date.class
          ? new Date(json.getAsLong())
          : new java.sql.Date(json.getAsLong());
    }

    @Override
    public JsonElement serialize(Date src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive(src.getTime());
    }
  }
}