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/*
 * Copyright 2013 the original author or authors.
 *
 * 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 ratpack.render;

import com.google.common.reflect.TypeToken;
import ratpack.handling.Context;

/**
 * A {@link Renderer} super class that provides a {@link #getType()} implementation based on the generic type of the impl.
 * 
 * Implementations need only to declare the type they render as the value for type variable {@code T} and implement {@link #render(ratpack.handling.Context, Object)}.
 * 
 * import ratpack.handling.Context;
 * import ratpack.render.RendererSupport;
 *
 * // A type of thing to be rendered
 * public class Thing {
 *   private final String name;
 *
 *   public Thing(String name) {
 *     this.name = name;
 *   }
 *
 *   public String getName() {
 *     return this.name;
 *   }
 * }
 *
 * // Renderer implementation
 * public class ThingRenderer extends RendererSupport<Thing> {
 *   public void render(Context context, Thing thing) {
 *     context.render("Thing: " + thing.getName());
 *   }
 * }
 * 
 *
 * @param  The type of object this renderer renders
 */
public abstract class RendererSupport implements Renderer {

  private final Class type;

  protected RendererSupport() {
    TypeToken typeToken = new TypeToken(getClass()) {
    };

    if (typeToken.getType() instanceof Class) {
      @SuppressWarnings("unchecked") Class rawType = (Class) typeToken.getRawType();
      this.type = rawType;
    } else {
      throw new IllegalArgumentException("Type parameter T of RendererSupport must be a Class");
    }
  }

  /**
   * The type of object that this renderer can render (the type for {@code T}).
   *
   * @return The type of object that this renderer can render.
   */
  @Override
  public Class getType() {
    return type;
  }

  /**
   * {@inheritDoc}
   */
  abstract public void render(Context context, T t) throws Exception;

}