gson-comments/gson/src/test/java/com/google/gson/functional/JsonAdapterSerializerDeserializerTest.java

/*
 * Copyright (C) 2016 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.errorprone.annotations.Keep;
import com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.JsonSerializationContext;
import com.google.gson.JsonSerializer;
import com.google.gson.TypeAdapter;
import com.google.gson.annotations.JsonAdapter;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import java.io.IOException;
import java.lang.reflect.Type;
import org.junit.Test;

/**
 * Functional tests for the {@link JsonAdapter} annotation on fields where the value is of type
 * {@link JsonSerializer} or {@link JsonDeserializer}.
 */
public final class JsonAdapterSerializerDeserializerTest {

  @Test
  public void testJsonSerializerDeserializerBasedJsonAdapterOnFields() {
    Gson gson = new Gson();
    String json =
        gson.toJson(new Computer(new User("Inderjeet Singh"), null, new User("Jesse Wilson")));
    assertThat(json)
        .isEqualTo("{\"user1\":\"UserSerializer\",\"user3\":\"UserSerializerDeserializer\"}");
    Computer computer =
        gson.fromJson("{'user2':'Jesse Wilson','user3':'Jake Wharton'}", Computer.class);
    assertThat(computer.user2.name).isEqualTo("UserDeserializer");
    assertThat(computer.user3.name).isEqualTo("UserSerializerDeserializer");
  }

  private static final class Computer {
    @JsonAdapter(UserSerializer.class)
    @Keep
    final User user1;

    @JsonAdapter(UserDeserializer.class)
    @Keep
    final User user2;

    @JsonAdapter(UserSerializerDeserializer.class)
    @Keep
    final User user3;

    Computer(User user1, User user2, User user3) {
      this.user1 = user1;
      this.user2 = user2;
      this.user3 = user3;
    }
  }

  private static final class User {
    public final String name;

    private User(String name) {
      this.name = name;
    }
  }

  private static final class UserSerializer implements JsonSerializer<User> {
    @Override
    public JsonElement serialize(User src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive("UserSerializer");
    }
  }

  private static final class UserDeserializer implements JsonDeserializer<User> {
    @Override
    public User deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      return new User("UserDeserializer");
    }
  }

  private static final class UserSerializerDeserializer
      implements JsonSerializer<User>, JsonDeserializer<User> {
    @Override
    public JsonElement serialize(User src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive("UserSerializerDeserializer");
    }

    @Override
    public User deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      return new User("UserSerializerDeserializer");
    }
  }

  @Test
  public void testJsonSerializerDeserializerBasedJsonAdapterOnClass() {
    Gson gson = new Gson();
    String json = gson.toJson(new Computer2(new User2("Inderjeet Singh")));
    assertThat(json).isEqualTo("{\"user\":\"UserSerializerDeserializer2\"}");
    Computer2 computer = gson.fromJson("{'user':'Inderjeet Singh'}", Computer2.class);
    assertThat(computer.user.name).isEqualTo("UserSerializerDeserializer2");
  }

  private static final class Computer2 {
    final User2 user;

    Computer2(User2 user) {
      this.user = user;
    }
  }

  @JsonAdapter(UserSerializerDeserializer2.class)
  private static final class User2 {
    public final String name;

    private User2(String name) {
      this.name = name;
    }
  }

  private static final class UserSerializerDeserializer2
      implements JsonSerializer<User2>, JsonDeserializer<User2> {
    @Override
    public JsonElement serialize(User2 src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive("UserSerializerDeserializer2");
    }

    @Override
    public User2 deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      return new User2("UserSerializerDeserializer2");
    }
  }

  @Test
  public void testDifferentJsonAdaptersForGenericFieldsOfSameRawType() {
    Container c = new Container("Foo", 10);
    Gson gson = new Gson();
    String json = gson.toJson(c);
    assertThat(json).contains("\"a\":\"BaseStringAdapter\"");
    assertThat(json).contains("\"b\":\"BaseIntegerAdapter\"");
  }

  private static final class Container {
    @JsonAdapter(BaseStringAdapter.class)
    @Keep
    Base<String> a;

    @JsonAdapter(BaseIntegerAdapter.class)
    @Keep
    Base<Integer> b;

    Container(String a, int b) {
      this.a = new Base<>(a);
      this.b = new Base<>(b);
    }
  }

  private static final class Base<T> {
    @SuppressWarnings("unused")
    T value;

    Base(T value) {
      this.value = value;
    }
  }

  private static final class BaseStringAdapter implements JsonSerializer<Base<String>> {
    @Override
    public JsonElement serialize(
        Base<String> src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive("BaseStringAdapter");
    }
  }

  private static final class BaseIntegerAdapter implements JsonSerializer<Base<Integer>> {
    @Override
    public JsonElement serialize(
        Base<Integer> src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive("BaseIntegerAdapter");
    }
  }

  @Test
  public void testJsonAdapterNullSafe() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                User.class,
                new TypeAdapter<User>() {
                  @Override
                  public User read(JsonReader in) throws IOException {
                    in.nextNull();
                    return new User("fallback-read");
                  }

                  @Override
                  public void write(JsonWriter out, User value) throws IOException {
                    assertThat(value).isNull();
                    out.value("fallback-write");
                  }
                })
            .serializeNulls()
            .create();

    String json = gson.toJson(new WithNullSafe(null, null, null, null));
    // Only nullSafe=true serializer writes null; for @JsonAdapter with deserializer nullSafe is
    // ignored when serializing
    assertThat(json)
        .isEqualTo(
            "{\"userS\":\"UserSerializer\",\"userSN\":null,\"userD\":\"fallback-write\",\"userDN\":\"fallback-write\"}");

    WithNullSafe deserialized =
        gson.fromJson(
            "{\"userS\":null,\"userSN\":null,\"userD\":null,\"userDN\":null}", WithNullSafe.class);
    // For @JsonAdapter with serializer nullSafe is ignored when deserializing
    assertThat(deserialized.userS.name).isEqualTo("fallback-read");
    assertThat(deserialized.userSN.name).isEqualTo("fallback-read");
    assertThat(deserialized.userD.name).isEqualTo("UserDeserializer");
    assertThat(deserialized.userDN).isNull();
  }

  @SuppressWarnings("MemberName")
  private static final class WithNullSafe {
    // "userS..." uses JsonSerializer
    @JsonAdapter(value = UserSerializer.class, nullSafe = false)
    final User userS;

    @JsonAdapter(value = UserSerializer.class, nullSafe = true)
    final User userSN;

    // "userD..." uses JsonDeserializer
    @JsonAdapter(value = UserDeserializer.class, nullSafe = false)
    final User userD;

    @JsonAdapter(value = UserDeserializer.class, nullSafe = true)
    final User userDN;

    WithNullSafe(User userS, User userSN, User userD, User userDN) {
      this.userS = userS;
      this.userSN = userSN;
      this.userD = userD;
      this.userDN = userDN;
    }
  }
}