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Java example source code file (CustomDeserializerTest.java)

This example Java source code file (CustomDeserializerTest.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, dataholder, dataholderwrapper, gson, gsonbuilder, jsondeserializationcontext, jsondeserializer, jsonparseexception, mybase, override, reflection, string, suffix, suppresswarnings, type

The CustomDeserializerTest.java 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
 *
 * 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.JsonDeserializationContext;
import com.google.gson.JsonDeserializer;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.common.TestTypes.Base;
import com.google.gson.common.TestTypes.ClassWithBaseField;

import junit.framework.TestCase;

import java.lang.reflect.Type;

/**
 * Functional Test exercising custom deserialization only.  When test applies to both
 * serialization and deserialization then add it to CustomTypeAdapterTest.
 *
 * @author Joel Leitch
 */
public class CustomDeserializerTest extends TestCase {
  private static final String DEFAULT_VALUE = "test123";
  private static final String SUFFIX = "blah";

  private Gson gson;

  @Override
  protected void setUp() throws Exception {
    super.setUp();
    gson = new GsonBuilder().registerTypeAdapter(DataHolder.class, new DataHolderDeserializer()).create();
  }

  public void testDefaultConstructorNotCalledOnObject() throws Exception {
    DataHolder data = new DataHolder(DEFAULT_VALUE);
    String json = gson.toJson(data);

    DataHolder actual = gson.fromJson(json, DataHolder.class);
    assertEquals(DEFAULT_VALUE + SUFFIX, actual.getData());
  }

  public void testDefaultConstructorNotCalledOnField() throws Exception {
    DataHolderWrapper dataWrapper = new DataHolderWrapper(new DataHolder(DEFAULT_VALUE));
    String json = gson.toJson(dataWrapper);

    DataHolderWrapper actual = gson.fromJson(json, DataHolderWrapper.class);
    assertEquals(DEFAULT_VALUE + SUFFIX, actual.getWrappedData().getData());
  }

  private static class DataHolder {
    private final String data;

    // For use by Gson
    @SuppressWarnings("unused")
    private DataHolder() {
      throw new IllegalStateException();
    }

    public DataHolder(String data) {
      this.data = data;
    }

    public String getData() {
      return data;
    }
  }

  private static class DataHolderWrapper {
    private final DataHolder wrappedData;

    // For use by Gson
    @SuppressWarnings("unused")
    private DataHolderWrapper() {
      this(new DataHolder(DEFAULT_VALUE));
    }

    public DataHolderWrapper(DataHolder data) {
      this.wrappedData = data;
    }

    public DataHolder getWrappedData() {
      return wrappedData;
    }
  }

  private static class DataHolderDeserializer implements JsonDeserializer<DataHolder> {
    @Override
    public DataHolder deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
        throws JsonParseException {
      JsonObject jsonObj = json.getAsJsonObject();
      String dataString = jsonObj.get("data").getAsString();
      return new DataHolder(dataString + SUFFIX);
    }
  }

  public void testJsonTypeFieldBasedDeserialization() {
    String json = "{field1:'abc',field2:'def',__type__:'SUB_TYPE1'}";
    Gson gson = new GsonBuilder().registerTypeAdapter(MyBase.class, new JsonDeserializer<MyBase>() {
      @Override public MyBase deserialize(JsonElement json, Type pojoType,
          JsonDeserializationContext context) throws JsonParseException {
        String type = json.getAsJsonObject().get(MyBase.TYPE_ACCESS).getAsString();
        return context.deserialize(json, SubTypes.valueOf(type).getSubclass());
      }
    }).create();
    SubType1 target = (SubType1) gson.fromJson(json, MyBase.class);
    assertEquals("abc", target.field1);
  }

  private static class MyBase {
    static final String TYPE_ACCESS = "__type__";
  }

  private enum SubTypes {
    SUB_TYPE1(SubType1.class),
    SUB_TYPE2(SubType2.class);
    private final Type subClass;
    private SubTypes(Type subClass) {
      this.subClass = subClass;
    }
    public Type getSubclass() {
      return subClass;
    }
  }

  private static class SubType1 extends MyBase {
    String field1;
  }

  private static class SubType2 extends MyBase {
    @SuppressWarnings("unused")
    String field2;
  }

  public void testCustomDeserializerReturnsNullForTopLevelObject() {
    Gson gson = new GsonBuilder()
      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
        @Override
        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
          return null;
        }
      }).create();
    String json = "{baseName:'Base',subName:'SubRevised'}";
    Base target = gson.fromJson(json, Base.class);
    assertNull(target);
  }

  public void testCustomDeserializerReturnsNull() {
    Gson gson = new GsonBuilder()
      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
        @Override
        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
          return null;
        }
      }).create();
    String json = "{base:{baseName:'Base',subName:'SubRevised'}}";
    ClassWithBaseField target = gson.fromJson(json, ClassWithBaseField.class);
    assertNull(target.base);
  }

  public void testCustomDeserializerReturnsNullForArrayElements() {
    Gson gson = new GsonBuilder()
      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
        @Override
        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
          return null;
        }
      }).create();
    String json = "[{baseName:'Base'},{baseName:'Base'}]";
    Base[] target = gson.fromJson(json, Base[].class);
    assertNull(target[0]);
    assertNull(target[1]);
  }

  public void testCustomDeserializerReturnsNullForArrayElementsForArrayField() {
    Gson gson = new GsonBuilder()
      .registerTypeAdapter(Base.class, new JsonDeserializer<Base>() {
        @Override
        public Base deserialize(JsonElement json, Type typeOfT, JsonDeserializationContext context)
            throws JsonParseException {
          return null;
        }
      }).create();
    String json = "{bases:[{baseName:'Base'},{baseName:'Base'}]}";
    ClassWithBaseArray target = gson.fromJson(json, ClassWithBaseArray.class);
    assertNull(target.bases[0]);
    assertNull(target.bases[1]);
  }

  private static final class ClassWithBaseArray {
    Base[] bases;
  }
}

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