Java example source code file (InstanceCreatorTest.java)

This example Java source code file (InstanceCreatorTest.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

base, classwithbasefield, gsonbuilder, instancecreator, instancecreatortest, override, reflection, sortedset, string, sub, subarraylist, subtreeset, suppresswarnings, type, typetoken, util

The InstanceCreatorTest.java Java example source code

/*
 * Copyright (C) 2009 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 com.google.gson.Gson;
import com.google.gson.GsonBuilder;
import com.google.gson.InstanceCreator;
import com.google.gson.common.TestTypes.Base;
import com.google.gson.common.TestTypes.ClassWithBaseField;
import com.google.gson.common.TestTypes.Sub;

import com.google.gson.reflect.TypeToken;
import java.util.ArrayList;
import java.util.List;
import junit.framework.TestCase;

import java.lang.reflect.Type;
import java.util.SortedSet;
import java.util.TreeSet;

/**
 * Functional Test exercising custom serialization only.  When test applies to both
 * serialization and deserialization then add it to CustomTypeAdapterTest.
 *
 * @author Inderjeet Singh
 */
public class InstanceCreatorTest extends TestCase {

  public void testInstanceCreatorReturnsBaseType() {
    Gson gson = new GsonBuilder()
      .registerTypeAdapter(Base.class, new InstanceCreator<Base>() {
        @Override public Base createInstance(Type type) {
         return new Base();
       }
      })
      .create();
    String json = "{baseName:'BaseRevised',subName:'Sub'}";
    Base base = gson.fromJson(json, Base.class);
    assertEquals("BaseRevised", base.baseName);
  }

  public void testInstanceCreatorReturnsSubTypeForTopLevelObject() {
    Gson gson = new GsonBuilder()
    .registerTypeAdapter(Base.class, new InstanceCreator<Base>() {
      @Override public Base createInstance(Type type) {
        return new Sub();
      }
    })
    .create();

    String json = "{baseName:'Base',subName:'SubRevised'}";
    Base base = gson.fromJson(json, Base.class);
    assertTrue(base instanceof Sub);

    Sub sub = (Sub) base;
    assertFalse("SubRevised".equals(sub.subName));
    assertEquals(Sub.SUB_NAME, sub.subName);
  }

  public void testInstanceCreatorReturnsSubTypeForField() {
    Gson gson = new GsonBuilder()
    .registerTypeAdapter(Base.class, new InstanceCreator<Base>() {
      @Override public Base createInstance(Type type) {
        return new Sub();
      }
    })
    .create();
    String json = "{base:{baseName:'Base',subName:'SubRevised'}}";
    ClassWithBaseField target = gson.fromJson(json, ClassWithBaseField.class);
    assertTrue(target.base instanceof Sub);
    assertEquals(Sub.SUB_NAME, ((Sub)target.base).subName);
  }

  // This regressed in Gson 2.0 and 2.1
  public void testInstanceCreatorForCollectionType() {
    @SuppressWarnings("serial")
    class SubArrayList<T> extends ArrayList {}
    InstanceCreator<List listCreator = new InstanceCreator>() {
      @Override public List<String> createInstance(Type type) {
        return new SubArrayList<String>();
      }
    };
    Type listOfStringType = new TypeToken<List() {}.getType();
    Gson gson = new GsonBuilder()
        .registerTypeAdapter(listOfStringType, listCreator)
        .create();
    List<String> list = gson.fromJson("[\"a\"]", listOfStringType);
    assertEquals(SubArrayList.class, list.getClass());
  }

  @SuppressWarnings({ "unchecked", "rawtypes" })
  public void testInstanceCreatorForParametrizedType() throws Exception {
    @SuppressWarnings("serial")
    class SubTreeSet<T> extends TreeSet {}
    InstanceCreator<SortedSet> sortedSetCreator = new InstanceCreator() {
      @Override public SortedSet createInstance(Type type) {
        return new SubTreeSet();
      }
    };
    Gson gson = new GsonBuilder()
        .registerTypeAdapter(SortedSet.class, sortedSetCreator)
        .create();

    Type sortedSetType = new TypeToken<SortedSet() {}.getType();
    SortedSet<String> set = gson.fromJson("[\"a\"]", sortedSetType);
    assertEquals(set.first(), "a");
    assertEquals(SubTreeSet.class, set.getClass());

    set = gson.fromJson("[\"b\"]", SortedSet.class);
    assertEquals(set.first(), "b");
    assertEquals(SubTreeSet.class, set.getClass());
  }
}