Transcript School Supply System on Google App Engine

By: Devesh Sharma

Why Cloud Computing?
◦ Traditional Business Applications
 Expensive
 Complicated
 Difficult to manage

Idea behind Cloud Computing
◦ Instead of organizations running their business
applications by themselves in-house, run them on
shared data centers.

1. Ease of use

2. Lower costs

3. Unlimited storage capacity

4. Highly automated

5. Allows IT to shift focus

6. Scalability

Actors: Parents and Teacher

Features:
◦ Application and database hosted on Google App
Engine
◦ Developed Front End using Servlets and JSP’s
◦ Developed Back End using Google App Engine (non
relational) datastore

Demo

Advantages:
◦ Easy to get started
◦ Automatic Scalability
◦ Reliability, performance and security of Google’s
infrastructure
◦ Cost efficient hosting
◦ Risk free trial period

The Mail Java API

The Users Java API

Other services:
◦ App Engine applications can send and receive email
messages
◦ The Mail Service Java API supports the JavaMail interface
for sending email messages
◦ Example
◦ App Engine applications can authenticate users who
have Google Accounts
◦ Example
◦ Image manipulation, URL fetch, OAuth, etc

Not a relational database, Object Oriented
database instead

Datastore stores and performs queries over
data objects, known as entities

An entity has one or more properties

App Engine Java SDK includes
implementations of the Java Data Objects
(JDO) and Java Persistence API (JPA) interfaces


Interaction with the datastore using a
PersistenceManager object, obtained from
PersistenceManagerFactory object
Setting up a PersistenceManagerFactory instance
takes time to initialize. Therefore, an app should
reuse a single instance.

An easy way: wrap it in singleton class, PMF.java

Demo – PMF.java on Eclipse

Defining Data classes
◦ Annotations:
 @PersistenceCapable
 @Persistent
◦ Relationships:
 One to One
 One to Many
◦ Show Users.java data class in Eclipse

Creating data/Making Objects Persistent
◦ Example:
 PersistenceManager pm =
PMF.get().getPersistenceManager();
Users user = new Users(“Devesh”, “Sharma”,..);
try{
pm.makePersistent(user);
}finally{
pm.close();
}

Queries in App Engine:
◦ JDO includes a query language (JDOQL) for retrieving objects that meet a
set of criteria.
◦
Query query = pm.newQuery(Users.class);
query.setFilter("lastName == lastNameParam");
query.declareParameters("String lastNameParam");
try {
List<Users> results = (List<Users>) query.execute(“Sharma");
if (results.iterator().hasNext()) {
for (Users u : results) {
// ...
}
} else {
// ... no results ...
}
} finally {
query.closeAll();
}

Updating an Object
◦ Users u = pm.getObjectByID(Users.class, key);
U.setFirstName(newFirstName);

Deleting an object
◦ pm.deletePersistent(user);

Use admin console to:
Create a new application
Add other people as developers
View error logs and analyze traffic
Blacklist IP addresses or subnets – DoS protection
service
◦ Browse your application’s datastore and manage
indexes
◦ Test new versions of your application, and switch
the version that users see
◦
◦
◦
◦

My Admin Console



http://code.google.com/appengine/
http://code.google.com/appengine/docs/jav
a/overview.html
What is Cloud computing?. (n.d.). Retrieved
from
http://www.salesforce.com/cloudcomputing/