gson-comments/gson/src/test/java/com/google/gson/GsonTest.java

/*
 * Copyright (C) 2016 The Gson Authors
 *
 * 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;

import static com.google.common.truth.Truth.assertThat;
import static org.junit.Assert.assertThrows;

import com.google.gson.Gson.FutureTypeAdapter;
import com.google.gson.internal.Excluder;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;
import com.google.gson.stream.MalformedJsonException;
import java.io.IOException;
import java.io.StringReader;
import java.io.StringWriter;
import java.lang.reflect.Field;
import java.lang.reflect.Type;
import java.text.DateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.concurrent.CountDownLatch;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicReference;
import org.junit.Test;

/**
 * Unit tests for {@link Gson}.
 *
 * @author Ryan Harter
 */
public final class GsonTest {

  private static final Excluder CUSTOM_EXCLUDER =
      Excluder.DEFAULT.excludeFieldsWithoutExposeAnnotation().disableInnerClassSerialization();

  private static final FieldNamingStrategy CUSTOM_FIELD_NAMING_STRATEGY =
      new FieldNamingStrategy() {
        @Override
        public String translateName(Field f) {
          return "foo";
        }
      };

  private static final ToNumberStrategy CUSTOM_OBJECT_TO_NUMBER_STRATEGY = ToNumberPolicy.DOUBLE;
  private static final ToNumberStrategy CUSTOM_NUMBER_TO_NUMBER_STRATEGY =
      ToNumberPolicy.LAZILY_PARSED_NUMBER;

  @Test
  public void testStrictnessDefault() {
    assertThat(new Gson().strictness).isEqualTo(Strictness.LENIENT);
  }

  @Test
  public void testOverridesDefaultExcluder() {
    Gson gson =
        new Gson(
            CUSTOM_EXCLUDER,
            CUSTOM_FIELD_NAMING_STRATEGY,
            new HashMap<Type, InstanceCreator<?>>(),
            true,
            false,
            true,
            false,
            false,
            FormattingStyle.PRETTY,
            Strictness.LENIENT,
            false,
            false,
            true,
            LongSerializationPolicy.DEFAULT,
            null,
            DateFormat.DEFAULT,
            DateFormat.DEFAULT,
            new ArrayList<TypeAdapterFactory>(),
            new ArrayList<TypeAdapterFactory>(),
            new ArrayList<TypeAdapterFactory>(),
            CUSTOM_OBJECT_TO_NUMBER_STRATEGY,
            CUSTOM_NUMBER_TO_NUMBER_STRATEGY,
            Collections.<ReflectionAccessFilter>emptyList());

    assertThat(gson.excluder).isEqualTo(CUSTOM_EXCLUDER);
    assertThat(gson.fieldNamingStrategy()).isEqualTo(CUSTOM_FIELD_NAMING_STRATEGY);
    assertThat(gson.serializeNulls()).isTrue();
    assertThat(gson.htmlSafe()).isFalse();
  }

  @Test
  public void testClonedTypeAdapterFactoryListsAreIndependent() {
    Gson original =
        new Gson(
            CUSTOM_EXCLUDER,
            CUSTOM_FIELD_NAMING_STRATEGY,
            new HashMap<Type, InstanceCreator<?>>(),
            true,
            false,
            true,
            false,
            false,
            FormattingStyle.PRETTY,
            Strictness.LENIENT,
            false,
            false,
            true,
            LongSerializationPolicy.DEFAULT,
            null,
            DateFormat.DEFAULT,
            DateFormat.DEFAULT,
            new ArrayList<TypeAdapterFactory>(),
            new ArrayList<TypeAdapterFactory>(),
            new ArrayList<TypeAdapterFactory>(),
            CUSTOM_OBJECT_TO_NUMBER_STRATEGY,
            CUSTOM_NUMBER_TO_NUMBER_STRATEGY,
            Collections.<ReflectionAccessFilter>emptyList());

    Gson clone =
        original.newBuilder().registerTypeAdapter(int.class, new TestTypeAdapter()).create();

    assertThat(clone.factories).hasSize(original.factories.size() + 1);
  }

  private static final class TestTypeAdapter extends TypeAdapter<Object> {
    @Override
    public void write(JsonWriter out, Object value) {
      // Test stub.
    }

    @Override
    public Object read(JsonReader in) {
      return null;
    }
  }

  @Test
  public void testGetAdapter_Null() {
    Gson gson = new Gson();
    NullPointerException e =
        assertThrows(NullPointerException.class, () -> gson.getAdapter((TypeToken<?>) null));
    assertThat(e).hasMessageThat().isEqualTo("type must not be null");
  }

  @Test
  public void testGetAdapter_Concurrency() {
    class DummyAdapter<T> extends TypeAdapter<T> {
      @Override
      public void write(JsonWriter out, T value) throws IOException {
        throw new AssertionError("not needed for this test");
      }

      @Override
      public T read(JsonReader in) throws IOException {
        throw new AssertionError("not needed for this test");
      }
    }

    final AtomicInteger adapterInstancesCreated = new AtomicInteger(0);
    final AtomicReference<TypeAdapter<?>> threadAdapter = new AtomicReference<>();
    final Class<?> requestedType = Number.class;

    Gson gson =
        new GsonBuilder()
            .registerTypeAdapterFactory(
                new TypeAdapterFactory() {
                  private volatile boolean isFirstCall = true;

                  @Override
                  public <T> TypeAdapter<T> create(final Gson gson, TypeToken<T> type) {
                    if (isFirstCall) {
                      isFirstCall = false;

                      // Create a separate thread which requests an adapter for the same type
                      // This will cause this factory to return a different adapter instance than
                      // the one it is currently creating
                      Thread thread =
                          new Thread() {
                            @Override
                            public void run() {
                              threadAdapter.set(gson.getAdapter(requestedType));
                            }
                          };
                      thread.start();
                      try {
                        thread.join();
                      } catch (InterruptedException e) {
                        throw new RuntimeException(e);
                      }
                    }

                    // Create a new dummy adapter instance
                    adapterInstancesCreated.incrementAndGet();
                    return new DummyAdapter<>();
                  }
                })
            .create();

    TypeAdapter<?> adapter = gson.getAdapter(requestedType);
    assertThat(adapterInstancesCreated.get()).isEqualTo(2);
    assertThat(adapter).isInstanceOf(DummyAdapter.class);
    assertThat(threadAdapter.get()).isInstanceOf(DummyAdapter.class);
  }

  /**
   * Verifies that two threads calling {@link Gson#getAdapter(TypeToken)} do not see the same
   * unresolved {@link FutureTypeAdapter} instance, since that would not be thread-safe.
   *
   * <p>This test constructs the cyclic dependency {@literal CustomClass1 -> CustomClass2 ->
   * CustomClass1} and lets one thread wait after the adapter for CustomClass2 has been obtained
   * (which still refers to the nested unresolved FutureTypeAdapter for CustomClass1).
   */
  @Test
  public void testGetAdapter_FutureAdapterConcurrency() throws Exception {
    /**
     * Adapter which wraps another adapter. Can be imagined as a simplified version of the {@code
     * ReflectiveTypeAdapterFactory$Adapter}.
     */
    class WrappingAdapter<T> extends TypeAdapter<T> {
      final TypeAdapter<?> wrapped;
      boolean isFirstCall = true;

      WrappingAdapter(TypeAdapter<?> wrapped) {
        this.wrapped = wrapped;
      }

      @Override
      public void write(JsonWriter out, T value) throws IOException {
        // Due to how this test is set up there is infinite recursion, therefore
        // need to track how deeply nested this call is
        if (isFirstCall) {
          isFirstCall = false;
          out.beginArray();
          wrapped.write(out, null);
          out.endArray();
          isFirstCall = true;
        } else {
          out.value("wrapped-nested");
        }
      }

      @Override
      public T read(JsonReader in) throws IOException {
        throw new AssertionError("not needed for this test");
      }
    }

    final CountDownLatch isThreadWaiting = new CountDownLatch(1);
    final CountDownLatch canThreadProceed = new CountDownLatch(1);

    final Gson gson =
        new GsonBuilder()
            .registerTypeAdapterFactory(
                new TypeAdapterFactory() {
                  // volatile instead of AtomicBoolean is safe here because CountDownLatch prevents
                  // "true" concurrency
                  volatile boolean isFirstCaller = true;

                  @Override
                  public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
                    Class<?> raw = type.getRawType();

                    if (raw == CustomClass1.class) {
                      // Retrieves a WrappingAdapter containing a nested FutureAdapter for
                      // CustomClass1
                      TypeAdapter<?> adapter = gson.getAdapter(CustomClass2.class);

                      // Let thread wait so the FutureAdapter for CustomClass1 nested in the adapter
                      // for CustomClass2 is not resolved yet
                      if (isFirstCaller) {
                        isFirstCaller = false;
                        isThreadWaiting.countDown();

                        try {
                          canThreadProceed.await();
                        } catch (InterruptedException e) {
                          throw new RuntimeException(e);
                        }
                      }

                      return new WrappingAdapter<>(adapter);
                    } else if (raw == CustomClass2.class) {
                      TypeAdapter<?> adapter = gson.getAdapter(CustomClass1.class);
                      assertThat(adapter).isInstanceOf(FutureTypeAdapter.class);
                      return new WrappingAdapter<>(adapter);
                    } else {
                      throw new AssertionError("Adapter for unexpected type requested: " + raw);
                    }
                  }
                })
            .create();

    final AtomicReference<TypeAdapter<?>> otherThreadAdapter = new AtomicReference<>();
    Thread thread =
        new Thread() {
          @Override
          public void run() {
            otherThreadAdapter.set(gson.getAdapter(CustomClass1.class));
          }
        };
    thread.start();

    // Wait until other thread has obtained FutureAdapter
    isThreadWaiting.await();
    TypeAdapter<?> adapter = gson.getAdapter(CustomClass1.class);
    // Should not fail due to referring to unresolved FutureTypeAdapter
    assertThat(adapter.toJson(null)).isEqualTo("[[\"wrapped-nested\"]]");

    // Let other thread proceed and have it resolve its FutureTypeAdapter
    canThreadProceed.countDown();
    thread.join();
    assertThat(otherThreadAdapter.get().toJson(null)).isEqualTo("[[\"wrapped-nested\"]]");
  }

  @Test
  public void testGetDelegateAdapter() {
    class DummyAdapter extends TypeAdapter<Number> {
      private final int number;

      DummyAdapter(int number) {
        this.number = number;
      }

      @Override
      public Number read(JsonReader in) throws IOException {
        throw new AssertionError("not needed for test");
      }

      @Override
      public void write(JsonWriter out, Number value) throws IOException {
        throw new AssertionError("not needed for test");
      }

      // Override toString() for better assertion error messages
      @Override
      public String toString() {
        return "adapter-" + number;
      }
    }

    class DummyFactory implements TypeAdapterFactory {
      private final DummyAdapter adapter;

      DummyFactory(DummyAdapter adapter) {
        this.adapter = adapter;
      }

      @SuppressWarnings("unchecked")
      @Override
      public <T> TypeAdapter<T> create(Gson gson, TypeToken<T> type) {
        return (TypeAdapter<T>) adapter;
      }

      // Override equals to verify that reference equality check is performed by Gson,
      // and this method is ignored
      @Override
      public boolean equals(Object obj) {
        return obj instanceof DummyFactory && ((DummyFactory) obj).adapter.equals(adapter);
      }

      @Override
      public int hashCode() {
        return adapter.hashCode();
      }
    }

    DummyAdapter adapter1 = new DummyAdapter(1);
    DummyFactory factory1 = new DummyFactory(adapter1);
    DummyAdapter adapter2 = new DummyAdapter(2);
    DummyFactory factory2 = new DummyFactory(adapter2);

    Gson gson =
        new GsonBuilder()
            // Note: This is 'last in, first out' order; Gson will first use factory2, then factory1
            .registerTypeAdapterFactory(factory1)
            .registerTypeAdapterFactory(factory2)
            .create();

    TypeToken<?> type = TypeToken.get(Number.class);

    assertThrows(NullPointerException.class, () -> gson.getDelegateAdapter(null, type));
    assertThrows(NullPointerException.class, () -> gson.getDelegateAdapter(factory1, null));

    // For unknown factory the first adapter for that type should be returned
    assertThat(gson.getDelegateAdapter(new DummyFactory(new DummyAdapter(0)), type))
        .isEqualTo(adapter2);

    assertThat(gson.getDelegateAdapter(factory2, type)).isEqualTo(adapter1);
    // Default Gson adapter should be returned
    assertThat(gson.getDelegateAdapter(factory1, type)).isNotInstanceOf(DummyAdapter.class);

    DummyFactory factory1Eq = new DummyFactory(adapter1);
    // Verify that test setup is correct
    assertThat(factory1.equals(factory1Eq)).isTrue();
    // Should only consider reference equality and ignore that custom `equals` method considers
    // factories to be equal, therefore returning `adapter2` which came from `factory2` instead
    // of skipping past `factory1`
    assertThat(gson.getDelegateAdapter(factory1Eq, type)).isEqualTo(adapter2);
  }

  @Test
  public void testNewJsonWriter_Default() throws IOException {
    StringWriter writer = new StringWriter();
    JsonWriter jsonWriter = new GsonBuilder().create().newJsonWriter(writer);
    jsonWriter.beginObject();
    jsonWriter.name("test");
    jsonWriter.nullValue();
    jsonWriter.name("<test2");
    jsonWriter.value(true);
    jsonWriter.endObject();

    // Additional top-level value
    IllegalStateException e = assertThrows(IllegalStateException.class, () -> jsonWriter.value(1));
    assertThat(e).hasMessageThat().isEqualTo("JSON must have only one top-level value.");

    jsonWriter.close();
    assertThat(writer.toString()).isEqualTo("{\"\\u003ctest2\":true}");
  }

  @SuppressWarnings({"deprecation", "InlineMeInliner"}) // for GsonBuilder.setLenient
  @Test
  public void testNewJsonWriter_Custom() throws IOException {
    StringWriter writer = new StringWriter();
    JsonWriter jsonWriter =
        new GsonBuilder()
            .disableHtmlEscaping()
            .generateNonExecutableJson()
            .setPrettyPrinting()
            .serializeNulls()
            .setLenient()
            .create()
            .newJsonWriter(writer);
    jsonWriter.beginObject();
    jsonWriter.name("test");
    jsonWriter.nullValue();
    jsonWriter.name("<test2");
    jsonWriter.value(true);
    jsonWriter.endObject();

    // Additional top-level value
    jsonWriter.value(1);

    jsonWriter.close();
    assertThat(writer.toString()).isEqualTo(")]}'\n{\n  \"test\": null,\n  \"<test2\": true\n}1");
  }

  @Test
  public void testNewJsonReader_Default() throws IOException {
    String json = "test"; // String without quotes
    JsonReader jsonReader = new GsonBuilder().create().newJsonReader(new StringReader(json));
    assertThrows(MalformedJsonException.class, jsonReader::nextString);
    jsonReader.close();
  }

  @SuppressWarnings({"deprecation", "InlineMeInliner"}) // for GsonBuilder.setLenient
  @Test
  public void testNewJsonReader_Custom() throws IOException {
    String json = "test"; // String without quotes
    JsonReader jsonReader =
        new GsonBuilder().setLenient().create().newJsonReader(new StringReader(json));
    assertThat(jsonReader.nextString()).isEqualTo("test");
    jsonReader.close();
  }

  /**
   * Modifying a GsonBuilder obtained from {@link Gson#newBuilder()} of a {@code new Gson()} should
   * not affect the Gson instance it came from.
   */
  @Test
  public void testDefaultGsonNewBuilderModification() {
    Gson gson = new Gson();
    GsonBuilder gsonBuilder = gson.newBuilder();

    // Modifications of `gsonBuilder` should not affect `gson` object
    gsonBuilder.registerTypeAdapter(
        CustomClass1.class,
        new TypeAdapter<CustomClass1>() {
          @Override
          public CustomClass1 read(JsonReader in) throws IOException {
            throw new UnsupportedOperationException();
          }

          @Override
          public void write(JsonWriter out, CustomClass1 value) throws IOException {
            out.value("custom-adapter");
          }
        });
    gsonBuilder.registerTypeHierarchyAdapter(
        CustomClass2.class,
        new JsonSerializer<CustomClass2>() {
          @Override
          public JsonElement serialize(
              CustomClass2 src, Type typeOfSrc, JsonSerializationContext context) {
            return new JsonPrimitive("custom-hierarchy-adapter");
          }
        });
    gsonBuilder.registerTypeAdapter(
        CustomClass3.class,
        new InstanceCreator<CustomClass3>() {
          @Override
          public CustomClass3 createInstance(Type type) {
            return new CustomClass3("custom-instance");
          }
        });

    assertDefaultGson(gson);
    // New GsonBuilder created from `gson` should not have been affected by changes either
    assertDefaultGson(gson.newBuilder().create());

    // But new Gson instance from `gsonBuilder` should use custom adapters
    assertCustomGson(gsonBuilder.create());
  }

  private static void assertDefaultGson(Gson gson) {
    // Should use default reflective adapter
    String json1 = gson.toJson(new CustomClass1());
    assertThat(json1).isEqualTo("{}");

    // Should use default reflective adapter
    String json2 = gson.toJson(new CustomClass2());
    assertThat(json2).isEqualTo("{}");

    // Should use default instance creator
    CustomClass3 customClass3 = gson.fromJson("{}", CustomClass3.class);
    assertThat(customClass3.s).isEqualTo(CustomClass3.NO_ARG_CONSTRUCTOR_VALUE);
  }

  /**
   * Modifying a GsonBuilder obtained from {@link Gson#newBuilder()} of a custom Gson instance
   * (created using a GsonBuilder) should not affect the Gson instance it came from.
   */
  @Test
  public void testNewBuilderModification() {
    Gson gson =
        new GsonBuilder()
            .registerTypeAdapter(
                CustomClass1.class,
                new TypeAdapter<CustomClass1>() {
                  @Override
                  public CustomClass1 read(JsonReader in) throws IOException {
                    throw new UnsupportedOperationException();
                  }

                  @Override
                  public void write(JsonWriter out, CustomClass1 value) throws IOException {
                    out.value("custom-adapter");
                  }
                })
            .registerTypeHierarchyAdapter(
                CustomClass2.class,
                new JsonSerializer<CustomClass2>() {
                  @Override
                  public JsonElement serialize(
                      CustomClass2 src, Type typeOfSrc, JsonSerializationContext context) {
                    return new JsonPrimitive("custom-hierarchy-adapter");
                  }
                })
            .registerTypeAdapter(
                CustomClass3.class,
                new InstanceCreator<CustomClass3>() {
                  @Override
                  public CustomClass3 createInstance(Type type) {
                    return new CustomClass3("custom-instance");
                  }
                })
            .create();

    assertCustomGson(gson);

    // Modify `gson.newBuilder()`
    GsonBuilder gsonBuilder = gson.newBuilder();
    gsonBuilder.registerTypeAdapter(
        CustomClass1.class,
        new TypeAdapter<CustomClass1>() {
          @Override
          public CustomClass1 read(JsonReader in) throws IOException {
            throw new UnsupportedOperationException();
          }

          @Override
          public void write(JsonWriter out, CustomClass1 value) throws IOException {
            out.value("overwritten custom-adapter");
          }
        });
    gsonBuilder.registerTypeHierarchyAdapter(
        CustomClass2.class,
        new JsonSerializer<CustomClass2>() {
          @Override
          public JsonElement serialize(
              CustomClass2 src, Type typeOfSrc, JsonSerializationContext context) {
            return new JsonPrimitive("overwritten custom-hierarchy-adapter");
          }
        });
    gsonBuilder.registerTypeAdapter(
        CustomClass3.class,
        new InstanceCreator<CustomClass3>() {
          @Override
          public CustomClass3 createInstance(Type type) {
            return new CustomClass3("overwritten custom-instance");
          }
        });

    // `gson` object should not have been affected by changes to new GsonBuilder
    assertCustomGson(gson);
    // New GsonBuilder based on `gson` should not have been affected either
    assertCustomGson(gson.newBuilder().create());

    // But new Gson instance from `gsonBuilder` should be affected by changes
    Gson otherGson = gsonBuilder.create();
    String json1 = otherGson.toJson(new CustomClass1());
    assertThat(json1).isEqualTo("\"overwritten custom-adapter\"");

    String json2 = otherGson.toJson(new CustomClass2());
    assertThat(json2).isEqualTo("\"overwritten custom-hierarchy-adapter\"");

    CustomClass3 customClass3 = otherGson.fromJson("{}", CustomClass3.class);
    assertThat(customClass3.s).isEqualTo("overwritten custom-instance");
  }

  private static void assertCustomGson(Gson gson) {
    String json1 = gson.toJson(new CustomClass1());
    assertThat(json1).isEqualTo("\"custom-adapter\"");

    String json2 = gson.toJson(new CustomClass2());
    assertThat(json2).isEqualTo("\"custom-hierarchy-adapter\"");

    CustomClass3 customClass3 = gson.fromJson("{}", CustomClass3.class);
    assertThat(customClass3.s).isEqualTo("custom-instance");
  }

  private static class CustomClass1 {}

  private static class CustomClass2 {}

  private static class CustomClass3 {
    static final String NO_ARG_CONSTRUCTOR_VALUE = "default instance";

    final String s;

    public CustomClass3(String s) {
      this.s = s;
    }

    @SuppressWarnings("unused") // called by Gson
    public CustomClass3() {
      this(NO_ARG_CONSTRUCTOR_VALUE);
    }
  }
}