Java example source code file (RuntimeTypeAdapterFactoryFunctionalTest.java)

This example Java source code file (RuntimeTypeAdapterFactoryFunctionalTest.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

circle, class, jsonelement, jsonobject, jsonparseexception, linkedhashmap, map, override, runtimetypeadapterfactory, shape, square, string, typeadapter, util

The RuntimeTypeAdapterFactoryFunctionalTest.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 java.io.IOException;
import java.util.LinkedHashMap;
import java.util.Map;

import junit.framework.TestCase;

import com.google.gson.Gson;
import com.google.gson.JsonElement;
import com.google.gson.JsonObject;
import com.google.gson.JsonParseException;
import com.google.gson.JsonPrimitive;
import com.google.gson.TypeAdapter;
import com.google.gson.TypeAdapterFactory;
import com.google.gson.annotations.JsonAdapter;
import com.google.gson.internal.Streams;
import com.google.gson.reflect.TypeToken;
import com.google.gson.stream.JsonReader;
import com.google.gson.stream.JsonWriter;

/**
 * Functional tests for the RuntimeTypeAdapterFactory feature in extras.
 */
public final class RuntimeTypeAdapterFactoryFunctionalTest extends TestCase {

  private final Gson gson = new Gson();

  /**
   * This test also ensures that {@link TypeAdapterFactory} registered through {@link JsonAdapter}
   * work correctly for {@link Gson#getDelegateAdapter(TypeAdapterFactory, TypeToken)}.
   */
  public void testSubclassesAutomaticallySerialized() throws Exception {
    Shape shape = new Circle(25);
    String json = gson.toJson(shape);
    shape = gson.fromJson(json, Shape.class);
    assertEquals(25, ((Circle)shape).radius);

    shape = new Square(15);
    json = gson.toJson(shape);
    shape = gson.fromJson(json, Shape.class);
    assertEquals(15, ((Square)shape).side);
    assertEquals(ShapeType.SQUARE, shape.type);
  }

  @JsonAdapter(Shape.JsonAdapterFactory.class)
  static class Shape {
    final ShapeType type;
    Shape(ShapeType type) { this.type = type; }
    private static final class JsonAdapterFactory extends RuntimeTypeAdapterFactory<Shape> {
      public JsonAdapterFactory() {
        super(Shape.class, "type");
        registerSubtype(Circle.class, ShapeType.CIRCLE.toString());
        registerSubtype(Square.class, ShapeType.SQUARE.toString());
      }
    }
  }

  public enum ShapeType {
    SQUARE, CIRCLE
  }

  private static final class Circle extends Shape {
    final int radius;
    Circle(int radius) { super(ShapeType.CIRCLE); this.radius = radius; }
  }

  private static final class Square extends Shape {
    final int side;
    Square(int side) { super(ShapeType.SQUARE); this.side = side; }
  }

  // Copied from the extras package
  static class RuntimeTypeAdapterFactory<T> implements TypeAdapterFactory {
    private final Class<?> baseType;
    private final String typeFieldName;
    private final Map<String, Class labelToSubtype = new LinkedHashMap>();
    private final Map<Class subtypeToLabel = new LinkedHashMap, String>();

    protected RuntimeTypeAdapterFactory(Class<?> baseType, String typeFieldName) {
      if (typeFieldName == null || baseType == null) {
        throw new NullPointerException();
      }
      this.baseType = baseType;
      this.typeFieldName = typeFieldName;
    }

    /**
     * Creates a new runtime type adapter using for {@code baseType} using {@code
     * typeFieldName} as the type field name. Type field names are case sensitive.
     */
    public static <T> RuntimeTypeAdapterFactory of(Class baseType, String typeFieldName) {
      return new RuntimeTypeAdapterFactory<T>(baseType, typeFieldName);
    }

    /**
     * Creates a new runtime type adapter for {@code baseType} using {@code "type"} as
     * the type field name.
     */
    public static <T> RuntimeTypeAdapterFactory of(Class baseType) {
      return new RuntimeTypeAdapterFactory<T>(baseType, "type");
    }

    /**
     * Registers {@code type} identified by {@code label}. Labels are case
     * sensitive.
     *
     * @throws IllegalArgumentException if either {@code type} or {@code label}
     *     have already been registered on this type adapter.
     */
    public RuntimeTypeAdapterFactory<T> registerSubtype(Class type, String label) {
      if (type == null || label == null) {
        throw new NullPointerException();
      }
      if (subtypeToLabel.containsKey(type) || labelToSubtype.containsKey(label)) {
        throw new IllegalArgumentException("types and labels must be unique");
      }
      labelToSubtype.put(label, type);
      subtypeToLabel.put(type, label);
      return this;
    }

    /**
     * Registers {@code type} identified by its {@link Class#getSimpleName simple
     * name}. Labels are case sensitive.
     *
     * @throws IllegalArgumentException if either {@code type} or its simple name
     *     have already been registered on this type adapter.
     */
    public RuntimeTypeAdapterFactory<T> registerSubtype(Class type) {
      return registerSubtype(type, type.getSimpleName());
    }

    @Override public <R> TypeAdapter create(Gson gson, TypeToken type) {
      if (type.getRawType() != baseType) {
        return null;
      }

      final Map<String, TypeAdapter labelToDelegate
          = new LinkedHashMap<String, TypeAdapter();
      final Map<Class> subtypeToDelegate
          = new LinkedHashMap<Class>();
      for (Map.Entry<String, Class entry : labelToSubtype.entrySet()) {
        TypeAdapter<?> delegate = gson.getDelegateAdapter(this, TypeToken.get(entry.getValue()));
        labelToDelegate.put(entry.getKey(), delegate);
        subtypeToDelegate.put(entry.getValue(), delegate);
      }

      return new TypeAdapter<R>() {
        @Override public R read(JsonReader in) throws IOException {
          JsonElement jsonElement = Streams.parse(in);
          JsonElement labelJsonElement = jsonElement.getAsJsonObject().get(typeFieldName);
          if (labelJsonElement == null) {
            throw new JsonParseException("cannot deserialize " + baseType
                + " because it does not define a field named " + typeFieldName);
          }
          String label = labelJsonElement.getAsString();
          @SuppressWarnings("unchecked") // registration requires that subtype extends T
          TypeAdapter<R> delegate = (TypeAdapter) labelToDelegate.get(label);
          if (delegate == null) {
            throw new JsonParseException("cannot deserialize " + baseType + " subtype named "
                + label + "; did you forget to register a subtype?");
          }
          return delegate.fromJsonTree(jsonElement);
        }

        @Override public void write(JsonWriter out, R value) throws IOException {
          Class<?> srcType = value.getClass();
          String label = subtypeToLabel.get(srcType);
          @SuppressWarnings("unchecked") // registration requires that subtype extends T
          TypeAdapter<R> delegate = (TypeAdapter) subtypeToDelegate.get(srcType);
          if (delegate == null) {
            throw new JsonParseException("cannot serialize " + srcType.getName()
                + "; did you forget to register a subtype?");
          }
          JsonObject jsonObject = delegate.toJsonTree(value).getAsJsonObject();
          if (!jsonObject.has(typeFieldName)) {
            JsonObject clone = new JsonObject();
            clone.add(typeFieldName, new JsonPrimitive(label));
            for (Map.Entry<String, JsonElement> e : jsonObject.entrySet()) {
              clone.add(e.getKey(), e.getValue());
            }
            jsonObject = clone;
          }
          Streams.write(jsonObject, out);
        }
      };
    }
  }
}