BatchWrapper.java

import java.io.IOException;
import java.util.List;

import com.google.api.client.googleapis.batch.BatchRequest;
import com.google.api.client.googleapis.batch.json.JsonBatchCallback;
import com.google.api.client.googleapis.json.GoogleJsonError;
import com.google.api.client.googleapis.json.GoogleJsonErrorContainer;
import com.google.api.client.http.HttpHeaders;
import com.google.api.services.admin.directory.Directory;
import com.google.api.services.admin.directory.DirectoryRequest;
import com.google.common.collect.Lists;

/**
 * Wrapper for com.google.api.client.googleapis.batch.BatchRequest.
 * 
 * <p>Sample code</p>
 * 
 * <pre>
 * List&lt;DirectoryRequest&lt;User&gt;&gt; requests =
 * 	Lists.newArrayListWithCapacity(userEmails.size());
 * for (String email : Arrays.asList("user1@example.com", "user2@example.com")) {
 * 	requests.add(api.users().get(email));
 * }
 * List&lt;BatchResult&lt;DirectoryRequest&lt;User&gt;, User&gt;&gt; results =
 * 	new BatchWrapper&lt;User&gt;(api).execute(requests);
 * for (BatchResult&lt;DirectoryRequest&lt;User&gt;, User&gt; result : results) {
 * 	Object key = result.getKey().get("userKey");
 * 	if (result.getError() != null) {
 * 		System.out.println("[!]" + key + ":" + result.getError());
 * 	} else {
 * 		System.out.println(key + ":" + result.getValue());
 * 	}
 * }
 * </pre>
 * 
 * <p>add dependency for Admin SDK.</p>
 * 
 * <pre>
 * &lt;dependency&gt;
 * 	 &lt;groupId&gt;com.google.apis&lt;/groupId&gt;
 * 	 &lt;artifactId&gt;google-api-services-admin-directory&lt;/artifactId&gt;
 * 	 &lt;version&gt;directory_v1-rev28-1.17.0-rc&lt;/version&gt;
 * &lt;/dependency&gt;
 * </pre>
 * @author shin1ogawa
 * @param <T> destination class type
 */
public class BatchWrapper<T> {

	final Directory api;

	final Class<T> dataClass;


	/**
	 * the constructor.
	 * @param api Directory API
	 * @param clazzes
	 * @category constructor
	 */
	@SuppressWarnings("unchecked")
	public BatchWrapper(Directory api, T... clazzes) {
		this.api = api;
		this.dataClass = (Class<T>) clazzes.getClass().getComponentType();
	}

	/**
	 * @param requests
	 * @return list of {@link BatchResult}
	 * @throws IOException
	 * @author shin1ogawa
	 */
	public List<BatchResult<DirectoryRequest<T>, T>> execute(List<DirectoryRequest<T>> requests)
			throws IOException {
		List<BatchResult<DirectoryRequest<T>, T>> results =
				Lists.newArrayListWithCapacity(requests.size());
		BatchRequest batch = api.batch();
		for (DirectoryRequest<T> request : requests) {
			BatchResult<DirectoryRequest<T>, T> callback =
					new BatchResult<DirectoryRequest<T>, T>(request);
			results.add(callback);
			batch.queue(request.buildHttpRequest(), this.dataClass, GoogleJsonErrorContainer.class,
					callback);
		}
		batch.execute();
		return results;
	}


	/**
	 * @author shin1ogawa
	 * @param <K> Type of key
	 * @param <V> Type of value
	 */
	public static class BatchResult<K, V> extends JsonBatchCallback<V> {

		final K key;

		V value;

		HttpHeaders responseHeaders;

		GoogleJsonError error;


		/**
		 * the constructor.
		 * @param key
		 * @category constructor
		 */
		public BatchResult(K key) {
			this.key = key;
		}

		@Override
		public void onSuccess(V value, HttpHeaders responseHeaders) {
			this.value = value;
			this.responseHeaders = responseHeaders;
		}

		@Override
		public void onFailure(GoogleJsonError error, HttpHeaders responseHeaders) {
			this.error = error;
			this.responseHeaders = responseHeaders;
		}

		/**
		 * @return the value
		 * @category accessor
		 */
		public V getValue() {
			return value;
		}

		/**
		 * @return the responseHeaders
		 * @category accessor
		 */
		public HttpHeaders getResponseHeaders() {
			return responseHeaders;
		}

		/**
		 * @return the error
		 * @category accessor
		 */
		public GoogleJsonError getError() {
			return error;
		}

		/**
		 * @return the key
		 * @category accessor
		 */
		public K getKey() {
			return key;
		}
	}
}