Testing Tree-Based Type Adapter Implementation in Google GSON

google/gson

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

            
/*
 * Copyright (C) 2011 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.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.reflect.TypeToken;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;
import org.junit.Before;
import org.junit.Test;

/** Collection of functional tests for DOM tree based type adapters. */
public class TreeTypeAdaptersTest {
  private static final Id<Student> STUDENT1_ID = new Id<>("5", Student.class);
  private static final Id<Student> STUDENT2_ID = new Id<>("6", Student.class);
  private static final Student STUDENT1 = new Student(STUDENT1_ID, "first");
  private static final Student STUDENT2 = new Student(STUDENT2_ID, "second");
  private static final Type TYPE_COURSE_HISTORY =
      new TypeToken<Course<HistoryCourse>>() {}.getType();
  private static final Id<Course<HistoryCourse>> COURSE_ID = new Id<>("10", TYPE_COURSE_HISTORY);

  private Gson gson;
  private Course<HistoryCourse> course;

  @Before
  public void setUp() {
    gson = new GsonBuilder().registerTypeAdapter(Id.class, new IdTreeTypeAdapter()).create();
    course =
        new Course<>(
            COURSE_ID,
            4,
            new Assignment<HistoryCourse>(null, null),
            Arrays.asList(STUDENT1, STUDENT2));
  }

  @Test
  public void testSerializeId() {
    String json = gson.toJson(course, TYPE_COURSE_HISTORY);
    assertThat(json).contains(String.valueOf(COURSE_ID.getValue()));
    assertThat(json).contains(String.valueOf(STUDENT1_ID.getValue()));
    assertThat(json).contains(String.valueOf(STUDENT2_ID.getValue()));
  }

  @Test
  public void testDeserializeId() {
    String json =
        "{courseId:1,students:[{id:1,name:'first'},{id:6,name:'second'}],"
            + "numAssignments:4,assignment:{}}";
    Course<HistoryCourse> target = gson.fromJson(json, TYPE_COURSE_HISTORY);
    assertThat(target.getStudents().get(0).id.getValue()).isEqualTo("1");
    assertThat(target.getStudents().get(1).id.getValue()).isEqualTo("6");
    assertThat(target.getId().getValue()).isEqualTo("1");
  }

  @SuppressWarnings("UnusedTypeParameter")
  private static final class Id<R> {
    final String value;

    @SuppressWarnings("unused")
    final Type typeOfId;

    private Id(String value, Type typeOfId) {
      this.value = value;
      this.typeOfId = typeOfId;
    }

    public String getValue() {
      return value;
    }
  }

  private static final class IdTreeTypeAdapter
      implements JsonSerializer<Id<?>>, JsonDeserializer<Id<?>> {

    @Override
    public Id<?> deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      if (!(typeOfT instanceof ParameterizedType)) {
        throw new JsonParseException("Id of unknown type: " + typeOfT);
      }
      ParameterizedType parameterizedType = (ParameterizedType) typeOfT;
      // Since Id takes only one TypeVariable, the actual type corresponding to the first
      // TypeVariable is the Type we are looking for
      Type typeOfId = parameterizedType.getActualTypeArguments()[0];
      return new Id<>(json.getAsString(), typeOfId);
    }

    @Override
    public JsonElement serialize(Id<?> src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive(src.getValue());
    }
  }

  @SuppressWarnings("unused")
  private static class Student {
    Id<Student> id;
    String name;

    private Student() {
      this(null, null);
    }

    public Student(Id<Student> id, String name) {
      this.id = id;
      this.name = name;
    }
  }

  @SuppressWarnings("unused")
  private static class Course<T> {
    final List<Student> students;
    private final Id<Course<T>> courseId;
    private final int numAssignments;
    private final Assignment<T> assignment;

    private Course() {
      this(null, 0, null, new ArrayList<>());
    }

    public Course(
        Id<Course<T>> courseId,
        int numAssignments,
        Assignment<T> assignment,
        List<Student> players) {
      this.courseId = courseId;
      this.numAssignments = numAssignments;
      this.assignment = assignment;
      this.students = players;
    }

    public Id<Course<T>> getId() {
      return courseId;
    }

    List<Student> getStudents() {
      return students;
    }
  }

  @SuppressWarnings("unused")
  private static class Assignment<T> {
    private final Id<Assignment<T>> id;
    private final T data;

    private Assignment() {
      this(null, null);
    }

    public Assignment(Id<Assignment<T>> id, T data) {
      this.id = id;
      this.data = data;
    }
  }

  @SuppressWarnings("unused")
  private static class HistoryCourse {
    int numClasses;
  }
}