Using NoSQL in the Cloud - Professional NoSQL

Databases Reference

In-Depth Information

Tersely Exploring the Java App Engine SDK

To get started, read the introductory tutorial, available online at http://code.google.com/

appengine/docs/java/gettingstarted/ . Programs written in Java to run on the app engine are

web applications that leverage the standard Java specifi cation like Java Servlets. The app engine

run time hosts a Java application server. The container itself is a customized implementation of the

Webtide Jetty application server.

The fundamentals of the app engine remain the same whether they are accessed from Python or Java

so repeating what has already been described would be futile. Therefore, this section jumps right in

to show a few bits about accessing the data store using the Java standards like JDO and JPA.

The DataNucleus ( www.datanucleus.org/ ) open-source app engine plug-in bridges the gap

between the Java standard persistence frameworks (in particular JDO and JPA) and the Google

Bigtable-based data store.

To set up and confi gure JDO read the online documentation at http://code.google.com/

appengine/docs/java/datastore/jdo/ . For JPA confi guration look at http://code.google

.com/appengine/docs/java/datastore/jpa/ .

The Task class from the Python example can be created as a JDO-aware plain old Java object

(POJO) like so:

package taskmanager;

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import com.google.appengine.api.datastore.Key;

import java.util.Date;

import javax.jdo.annotations.IdGeneratorStrategy;

import javax.jdo.annotations.PersistenceCapable;

import javax.jdo.annotations.Persistent;

import javax.jdo.annotations.PrimaryKey;

@PersistenceCapable

public class Task {

@PrimaryKey

@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)

private Key key;

@Persistent

private String name;

@Persistent

private String description;

@Persistent

private Date startDate;

@Persistent

private String status;

public Greeting(String name, String description, Date startDate,

String status) {

this.name = name;

this.description = description;