• Google App Engine - Host your applications
• Google Compute Engine - Host your Virtual Machines
• Google Cloud Storage - Host your files
• Google Cloud SQL - Host your databases
• Google BigQuery - Analyze data
• New! Cloud Datastore
• Details at cloud.google.com

• A web application platform
  • Create applications in Java, Python, Go or PHP
  • Store data in the cloud
• A set of APIs, including
  • Data Storage
  • Task Queues
  • Users
• Easy to
  • Build and Deploy
  • Manage
  • Scale
• Great for startups: start free and scale as you need it
• Details at developers.google.com/appengine

Step 1: Get the Google App Engine SDK

• Provides libraries for APIs and utilities for deploying

Step 2: Write code

• Handling requests
• Managing data

Step 3: Test locally

Step 4: Deploy to App Engine

Always remember: developers.google.com/appengine

First

• Install Eclipse for Java
• Install the Google Plugin for Eclipse (App Engine SDK Plugin)
• Details at https://developers.google.com/appengine (Getting Started)

Then

• Develop your web application
• Run and test locally
• Deploy to App Engine

• Open Eclipse
• Click File -> New -> Other -> Google -> Web Application Project
• Provide a name, package and select "Generate project sample code"
• Click Finish
• Right-click your project -> Run As -> Web Application
• Visit http://localhost:8888/ in your web browser

• Project Root
• • src/
    • Source code goes here
  • war/
    • Static files go here
    • index.html
    • style/
    • js/
    • WEB-INF/
      • web.xml - Servlet configuration
      • appengine-web.xml - App Engine configuration

Step 1: make sure your web.xml is updated

<welcome-file-list>
  <welcome-file>index.html</welcome-file>
</welcome-file-list>
      

Step 2: Define your servlet(s)

<servlet>
  <servlet-name>Exercise2</servlet-name>
  <servlet-class>com.samples.exercises.Exercise2Servlet</servlet-class>
</servlet>
      

Step 3: Map your servlet to a url

<servlet-mapping>
  <servlet-name>Exercise2</servlet-name>
  <url-pattern>/exercise2</url-pattern>
</servlet-mapping>
      

Step 4: Write servlet code

public class Exercise2Servlet extends HttpServlet {
  public void doGet(HttpServletRequest req, HttpServletResponse resp)
      throws IOException {
    resp.setContentType("text/html");
    resp.getWriter().println("<p>This is another servlet</p>");
  }
}
      

• Right-click your project -> New -> Class
• Provide a package name and class name
• Superclass is javax.servlet.http.HttpServlet
• Create doGet(...) method (or doPost, etc.)
• Add servlet to web.xml
• Map servlet to /exercise2 in web.xml
• Run your web application
• Visit http://localhost:8888/exercise2 in your web browser

• Schemaless NoSQL database
• Object/Entity persistence
• Entity has kind, identifier and optional ancestor path

DatastoreService datastore = DatastoreServiceFactory.getDatastoreService();
// Kind is Person, Identifier is danacton
Entity dan = new Entity("Person", "danacton");
dan.setProperty("name", "Dan");
dan.setProperty("hairColour", "brown");
datastore.put(dan);

Entity danChild = new Entity("Person", "danchild1", dan.getKey());
danChild.setProperty("name", "Dan Child");
danChild.setProperty("hairColour", "brown");
datastore.put(danChild);
      

Update

Entity dan = datastore.get(KeyFactory.stringToKey(...));
dan.setProperty("name", "Daniel");
datastore.put(dan);
// key from datastore viewer for now
      

Delete

datastore.delete(KeyFactory.stringToKey(...));
// key from datastore viewer for now
      

Filter nameFilter = new FilterPredicate("hairColour", FilterOperator.EQUAL, "brown");
Query q = new Query("Person").setFilter(nameFilter);
resp.setContentType("text/html");

PreparedQuery pq = datastore.prepare(q);
for (Entity result : pq.asIterable()) {
  String name = (String) result.getProperty("name");
  resp.getWriter().println("Person <b>" + name + "</b> has brown hair<br/>");
}
      

• Create 4 new servlets
  • CreateServlet - servlet path /create
  • ListServlet - servlet path /list
  • UpdateServlet - servlet path /update
  • DeleteServlet - servlet path /delete


• 1. Create 2 entities of type Person
• 2. List the entities
• 3. Note the keys (can use Datastore viewer)
• 4. Update 1 of the entities
• 5. Delete 1 of the entities

PersistenceManager pm = PMF.get().getPersistenceManager();

Person dan = new Person();
dan.setName("Dan");
dan.setHairColour("brown");

Person danChild = new Person();
danChild.setName("Dan Child");
danChild.setHairColour("brown");

try {
  pm.makePersistent(dan);
  pm.makePersistent(danChild);
} finally {
  pm.close();
}
      

Update

PersistenceManager pm = PMF.get().getPersistenceManager();
Person dan = pm.getObjectById(Person.class, ...);
dan.setName("Daniel");
pm.makePersistent(dan);
// id from datastore viewer for now
      

Delete

PersistenceManager pm = PMF.get().getPersistenceManager();
Person dan = pm.getObjectById(Person.class, ...);
pm.deletePersistent(dan);
// id from datastore viewer for now
      

PersistenceManager pm = PMF.get().getPersistenceManager();
Query q = pm.newQuery(Person.class, "hairColour == 'brown' order by name desc");

resp.setContentType("text/html");
List<Person> results = (List<Person>) q.execute();
for (Person p : results) {
  String name = p.getName();
  resp.getWriter().println("Person <b>" + name + "</b> has brown hair<br/>");
}
      

• Update the 4 servlets from Exercise 3 to use JDO
• You'll need a class and a PMF
• 1. Create 2 entities of type Person
• 2. List the entities
• 3. Note the keys (can use Datastore viewer)
• 4. Update 1 of the entities
• 5. Delete 1 of the entities

• Dynamic server-side coding of HTML pages
• An HTML page with Java code in it
• Whereas a servlet is Java code that prints some HTML
• Presentation layer for your data
• Extension .jsp
• In the war directory

Start by denoting this is a JSP page

<%@page language="java" contentType="text/html; charset=UTF-8"
            pageEncoding="UTF-8"%>
      

Import required classes

<%@page import="java.util.Date" %>
      

Add Java code to your JSP pages

<b><% out.println(new Date()); %></b>
      

<%@page language="java" contentType="text/html; charset=UTF-8"
           pageEncoding="UTF-8"%>
<%@page import="java.util.Date" %>

<!DOCTYPE html>
<html>
  <head>
    <title>A simple example</title>
  </head>
  <body>
    <p>
      The date is: <b><% out.println(new Date()); %></b>
    </p>
  </body>
</html>
    

Before, we hard-coded keys. Now, we pass them around.

Using HTTP GET

http://localhost:8888/update?id=4
      

Using HTTP POST with a form

<form action="/update" method="POST">
  <input type="hidden" name="id" value="4">
</form>
      

In your code

<%
  String val = "nothing";
  if (request.getParameter("id") != null) {
    val = request.getParameter("id");
  }
%>
The id you passed is <b><%=val%></b>
      

• Create a web app that manages people
• These operations are required
  • Create a Person
  • Update a Person
  • Delete a Person

• Use servlets to do the work (e.g. deleting a Person)
• Use JSP for presentation/data capture (e.g. showing all Person objects)
• Servlets: create, delete, update
• JSPs: home, update entry, create entry

• Google App Engine documentation
• Google App Engine code tutorials
• These slides