GAE/JのLow-Level APIで複数値プロパティを扱う例

MultiValuesTestServlet.java

package org.koherent.appengine.test;

import java.io.IOException;
import java.io.PrintWriter;
import java.util.ArrayList;
import java.util.List;
import java.util.Set;
import java.util.TreeSet;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.google.appengine.api.datastore.DatastoreService;
import com.google.appengine.api.datastore.DatastoreServiceFactory;
import com.google.appengine.api.datastore.Entity;
import com.google.appengine.api.datastore.EntityNotFoundException;
import com.google.appengine.api.datastore.KeyFactory;

@SuppressWarnings("serial")
public class MultiValuesTestServlet extends HttpServlet {
	@SuppressWarnings("unchecked")
	@Override
	protected void doGet(HttpServletRequest request,
			HttpServletResponse response) throws ServletException, IOException {
		DatastoreService service = DatastoreServiceFactory
				.getDatastoreService();
		response.setContentType("text/plain");

		// put
		{
			Entity entity = new Entity("kind", "name");

			Set<Integer> values = new TreeSet<Integer>();
			values.add(1);
			values.add(2);
			values.add(3);

			entity.setProperty("propertyName", values);
			service.put(entity);
		}

		// get
		try {
			Entity entity = service.get(KeyFactory.createKey("kind", "name"));

			// SetはArrayListに、IntegerはLongに変換されていることに注意
			List<Long> values = (ArrayList<Long>) entity
					.getProperty("propertyName");

			PrintWriter out = response.getWriter();
			for (Long value : values) {
				out.println(value);
			}
		} catch (EntityNotFoundException e) {
			e.printStackTrace();
		}
	}
}