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Google API Client Library for Java. Supports Java 5 (or higher) desktop (SE) and web (EE), Android, and Google App Engine.

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/*
 * Copyright (c) 2010 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.api.client.googleapis.json;

import com.google.api.client.http.HttpResponse;
import com.google.api.client.json.Json;
import com.google.api.client.util.ClassInfo;
import com.google.api.client.util.FieldInfo;

import org.codehaus.jackson.JsonParser;

import java.io.IOException;
import java.lang.reflect.Field;
import java.util.HashMap;

/**
 * Google JSON-C feed parser when the item class can be computed from the kind.
 * 
 * @since 1.0
 * @author Yaniv Inbar
 */
public final class JsonMultiKindFeedParser extends AbstractJsonFeedParser {

  private final HashMap> kindToItemClassMap =
      new HashMap>();

  public JsonMultiKindFeedParser(JsonParser parser, Class feedClass,
      Class... itemClasses) {
    super(parser, feedClass);
    int numItems = itemClasses.length;
    HashMap> kindToItemClassMap = this.kindToItemClassMap;
    for (int i = 0; i < numItems; i++) {
      Class itemClass = itemClasses[i];
      ClassInfo classInfo = ClassInfo.of(itemClass);
      Field field = classInfo.getField("kind");
      if (field == null) {
        throw new IllegalArgumentException("missing kind field for "
            + itemClass.getName());
      }
      Object item = ClassInfo.newInstance(itemClass);
      String kind = (String) FieldInfo.getFieldValue(field, item);
      if (kind == null) {
        throw new IllegalArgumentException("missing value for kind field in "
            + itemClass.getName());
      }
      kindToItemClassMap.put(kind, itemClass);
    }
  }

  @Override
  Object parseItemInternal() throws IOException {
    parser.nextToken();
    String key = parser.getCurrentName();
    if (key != "kind") {
      throw new IllegalArgumentException("expected kind field: " + key);
    }
    parser.nextToken();
    String kind = parser.getText();
    Class itemClass = kindToItemClassMap.get(kind);
    if (itemClass == null) {
      throw new IllegalArgumentException("unrecognized kind: " + kind);
    }
    return Json.parse(parser, itemClass, null);
  }

  public static  JsonMultiKindFeedParser use(HttpResponse response,
      Class feedClass, Class... itemClasses) throws IOException {
    return new JsonMultiKindFeedParser(JsonCParser
        .parserForResponse(response), feedClass, itemClasses);
  }
}