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Java example source code file (

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Java - Java tags/keywords

abstract, atomicinteger, atomiclong, concrete, exception, gsonbuilder, illegalstateexception, jsondeserializationcontext, jsondeserializer, jsonelement, jsonparseexception, math, override, reflection, string, type

The Java example source code

 * 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
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * See the License for the specific language governing permissions and
 * limitations under the License.


import java.lang.reflect.Type;
import java.math.BigInteger;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.atomic.AtomicLong;
import junit.framework.TestCase;

 * Contains numerous tests involving registered type converters with a Gson instance.
 * @author Inderjeet Singh
 * @author Joel Leitch
public class GsonTypeAdapterTest extends TestCase {
  private Gson gson;

  protected void setUp() throws Exception {
    gson = new GsonBuilder()
        .registerTypeAdapter(AtomicLong.class, new ExceptionTypeAdapter())
        .registerTypeAdapter(AtomicInteger.class, new AtomicIntegerTypeAdapter())

  public void testDefaultTypeAdapterThrowsParseException() throws Exception {
    try {
      gson.fromJson("{\"abc\":123}", BigInteger.class);
      fail("Should have thrown a JsonParseException");
    } catch (JsonParseException expected) { }

  public void testTypeAdapterThrowsException() throws Exception {
    try {
      gson.toJson(new AtomicLong(0));
      fail("Type Adapter should have thrown an exception");
    } catch (IllegalStateException expected) { }

    try {
      gson.fromJson("123", AtomicLong.class);
      fail("Type Adapter should have thrown an exception");
    } catch (JsonParseException expected) { }

  public void testTypeAdapterProperlyConvertsTypes() throws Exception {
    int intialValue = 1;
    AtomicInteger atomicInt = new AtomicInteger(intialValue);
    String json = gson.toJson(atomicInt);
    assertEquals(intialValue + 1, Integer.parseInt(json));

    atomicInt = gson.fromJson(json, AtomicInteger.class);
    assertEquals(intialValue, atomicInt.get());

  public void testTypeAdapterDoesNotAffectNonAdaptedTypes() throws Exception {
    String expected = "blah";
    String actual = gson.toJson(expected);
    assertEquals("\"" + expected + "\"", actual);

    actual = gson.fromJson(actual, String.class);
    assertEquals(expected, actual);

  private static class ExceptionTypeAdapter
      implements JsonSerializer<AtomicLong>, JsonDeserializer {
    @Override public JsonElement serialize(
        AtomicLong src, Type typeOfSrc, JsonSerializationContext context) {
      throw new IllegalStateException();
    @Override public AtomicLong deserialize(
        JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      throw new IllegalStateException();

  private static class AtomicIntegerTypeAdapter
      implements JsonSerializer<AtomicInteger>, JsonDeserializer {
    @Override public JsonElement serialize(AtomicInteger src, Type typeOfSrc, JsonSerializationContext context) {
      return new JsonPrimitive(src.incrementAndGet());

    @Override public AtomicInteger deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      int intValue = json.getAsInt();
      return new AtomicInteger(--intValue);

  static abstract class Abstract {
    String a;

  static class Concrete extends Abstract {
    String b;

  public void testDeserializerForAbstractClass() {
    Concrete instance = new Concrete();
    instance.a = "android";
    instance.b = "beep";
    assertSerialized("{\"a\":\"android\"}", Abstract.class, true, true, instance);
    assertSerialized("{\"a\":\"android\"}", Abstract.class, true, false, instance);
    assertSerialized("{\"a\":\"android\"}", Abstract.class, false, true, instance);
    assertSerialized("{\"a\":\"android\"}", Abstract.class, false, false, instance);
    assertSerialized("{\"b\":\"beep\",\"a\":\"android\"}", Concrete.class, true, true, instance);
    assertSerialized("{\"b\":\"beep\",\"a\":\"android\"}", Concrete.class, true, false, instance);
    assertSerialized("{\"b\":\"beep\",\"a\":\"android\"}", Concrete.class, false, true, instance);
    assertSerialized("{\"b\":\"beep\",\"a\":\"android\"}", Concrete.class, false, false, instance);

  private void assertSerialized(String expected, Class<?> instanceType, boolean registerAbstractDeserializer,
      boolean registerAbstractHierarchyDeserializer, Object instance) {
    JsonDeserializer<Abstract> deserializer = new JsonDeserializer() {
      public Abstract deserialize(JsonElement json, Type typeOfT,
          JsonDeserializationContext context) throws JsonParseException {
        throw new AssertionError();
    GsonBuilder builder = new GsonBuilder();
    if (registerAbstractDeserializer) {
      builder.registerTypeAdapter(Abstract.class, deserializer);
    if (registerAbstractHierarchyDeserializer) {
      builder.registerTypeHierarchyAdapter(Abstract.class, deserializer);
    Gson gson = builder.create();
    assertEquals(expected, gson.toJson(instance, instanceType));

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