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Java example source code file (ParameterizedTypeFixtures.java)

This example Java source code file (ParameterizedTypeFixtures.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

class, jsonelement, jsonobject, myparameterizedtype, myparameterizedtypeinstancecreator, override, parameterizedtypefixtures, primitivetypeadapter, reflection, runtimeexception, securityexception, string, stringbuilder, suppresswarnings

The ParameterizedTypeFixtures.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;

import com.google.gson.internal.$Gson$Types;

import com.google.gson.internal.Primitives;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;


/**
 * This class contains some test fixtures for Parameterized types. These classes should ideally
 * belong either in the common or functional package, but they are placed here because they need
 * access to package protected elements of com.google.gson.
 *
 * @author Inderjeet Singh
 * @author Joel Leitch
 */
public class ParameterizedTypeFixtures {

  public static class MyParameterizedType<T> {
    public final T value;
    public MyParameterizedType(T value) {
      this.value = value;
    }
    public T getValue() {
      return value;
    }

    public String getExpectedJson() {
      String valueAsJson = getExpectedJson(value);
      return String.format("{\"value\":%s}", valueAsJson);
    }

    private String getExpectedJson(Object obj) {
      Class<?> clazz = obj.getClass();
      if (Primitives.isWrapperType(Primitives.wrap(clazz))) {
        return obj.toString();
      } else if (obj.getClass().equals(String.class)) {
        return "\"" + obj.toString() + "\"";
      } else {
        // Try invoking a getExpectedJson() method if it exists
        try {
          Method method = clazz.getMethod("getExpectedJson");
          Object results = method.invoke(obj);
          return (String) results;
        } catch (SecurityException e) {
          throw new RuntimeException(e);
        } catch (NoSuchMethodException e) {
          throw new RuntimeException(e);
        } catch (IllegalArgumentException e) {
          throw new RuntimeException(e);
        } catch (IllegalAccessException e) {
          throw new RuntimeException(e);
        } catch (InvocationTargetException e) {
          throw new RuntimeException(e);
        }
      }
    }

    @Override
    public int hashCode() {
      return value == null ? 0 : value.hashCode();
    }

    @SuppressWarnings("unchecked")
    @Override
    public boolean equals(Object obj) {
      if (this == obj) {
        return true;
      }
      if (obj == null) {
        return false;
      }
      if (getClass() != obj.getClass()) {
        return false;
      }
      MyParameterizedType<T> other = (MyParameterizedType) obj;
      if (value == null) {
        if (other.value != null) {
          return false;
        }
      } else if (!value.equals(other.value)) {
        return false;
      }
      return true;
    }
  }

  public static class MyParameterizedTypeInstanceCreator<T>
      implements InstanceCreator<MyParameterizedType{
    private final T instanceOfT;
    /**
     * Caution the specified instance is reused by the instance creator for each call.
     * This means that the fields of the same objects will be overwritten by Gson.
     * This is usually fine in tests since there we deserialize just once, but quite
     * dangerous in practice.
     *
     * @param instanceOfT
     */
    public MyParameterizedTypeInstanceCreator(T instanceOfT) {
      this.instanceOfT = instanceOfT;
    }
    @Override public MyParameterizedType<T> createInstance(Type type) {
      return new MyParameterizedType<T>(instanceOfT);
    }
  }

  public static final class MyParameterizedTypeAdapter<T>
  implements JsonSerializer<MyParameterizedType, JsonDeserializer> {
    @SuppressWarnings("unchecked")
    public static<T> String getExpectedJson(MyParameterizedType obj) {
      Class<T> clazz = (Class) obj.value.getClass();
      boolean addQuotes = !clazz.isArray() && !Primitives.unwrap(clazz).isPrimitive();
      StringBuilder sb = new StringBuilder("{\"");
      sb.append(obj.value.getClass().getSimpleName()).append("\":");
      if (addQuotes) {
        sb.append("\"");
      }
      sb.append(obj.value.toString());
      if (addQuotes) {
        sb.append("\"");
      }
      sb.append("}");
      return sb.toString();
    }

    @Override public JsonElement serialize(MyParameterizedType<T> src, Type classOfSrc,
        JsonSerializationContext context) {
      JsonObject json = new JsonObject();
      T value = src.getValue();
      json.add(value.getClass().getSimpleName(), context.serialize(value));
      return json;
    }

    @SuppressWarnings("unchecked")
    @Override public MyParameterizedType<T> deserialize(JsonElement json, Type typeOfT,
        JsonDeserializationContext context) throws JsonParseException {
      Type genericClass = ((ParameterizedType) typeOfT).getActualTypeArguments()[0];
      Class<?> rawType = $Gson$Types.getRawType(genericClass);
      String className = rawType.getSimpleName();
      JsonElement jsonElement = json.getAsJsonObject().get(className);

      T value;
      if (genericClass == Integer.class) {
        value = (T) Integer.valueOf(jsonElement.getAsInt());
      } else if (genericClass == String.class) {
        value = (T) jsonElement.getAsString();
      } else {
        value = (T) jsonElement;
      }

      if (Primitives.isPrimitive(genericClass)) {
        PrimitiveTypeAdapter typeAdapter = new PrimitiveTypeAdapter();
        value = (T) typeAdapter.adaptType(value, rawType);
      }
      return new MyParameterizedType<T>(value);
    }
  }
}

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