Apress bắt đầu ứng dụng với java google - p 7 docx

If you’re using Eclipse and the Google Eclipse Plugin, you can launch your application locally by selecting Debug As ➤ Web Application from the Run menu.. Deploying Your Sample Applicati

■Note Google Suggest, AdSense for Content, and Orkut are among the many products created through

the “20 percent time” perk

Figure 3-8 The Google App Engine launcher for Mac

You don’t have to use the launcher to start your development projects on the local development server If you’re using Eclipse and the Google Eclipse Plugin, you can launch your application locally by selecting Debug As ➤ Web Application from the Run menu

For more control or to script the launch of your applications locally, you can launch the development web server from the command line You should execute this command from the SDK’s appengine-java-sdk/bin directory

If you are using Windows, run the following command:

appengine-java-sdk\bin\dev_appserver.cmd [options] war-location

If you are using Mac OS X or Linux, run the following command:

These commands are OS-specific wrapper scripts that run the Java class com.google

appengine.tools.KickStart in appengine-java-sdk/lib/appengine-tools-api.jar For

details on the available command options reference the online documentation

■Note To stop the development server, press Control + C (on Windows, Mac, or Linux)

Deploying Your Sample Application

It’s time to deploy your application to App Engine where you can browse it

publicly and share it with the world There’s a small Jet Engine icon in your

Eclipse tool bar that was created when you installed the Google Eclipse Plugin

Click that icon while making sure that your ChapterThree sample application is

selected in the Package Explorer It’s important to note that, at the time of this

writing, you get 10 applications per account You may consider choosing generic application IDs for the examples in this book and reusing them for each chapter You’ll be presented with a Deploy Project to Google App Engine dialog like the

one shown in Figure 3-9 The project name should have been defaulted to the project you had selected in Eclipse If it’s blank or doesn’t look quite right, click cancel, select the ChapterThree project in Eclipse, and click the Jet Engine button again

Figure 3-9 The Deploy Project to Google App Engine dialog

the bottom of the dialog window You’ll see something similar to Figure 3-10

Figure 3-10 The App Engine project settings dialog

Note that the Application ID field of your dialog isn’t populated You first have to create the application in your Google App Engine console to move past this point in the deployment process Use the My applications… link to open the Application Registration form for your App Engine account Figures 3-11 and 3-12 follow the process for your account You’ll have to create a unique Application identifier, which must be unique across the appspot.com domain Use the Check Availability feature

to verify that your application ID is available

Figure 3-11 Registering kylechapterthree.appspot.com (use a unique name)

Figure 3-12 Confirming that the application was registered

Now that you’ve deployed your application you have a few options for production

use You can browse to your application live on appspot.com by navigating to your

application’s unique domain on appspot In the example case (shown in Figures 3-11 and 3-12), the application lives at http://kylechapterthree.appspot.com, as shown in

your App Engine application We’ll look at that later in the book

Figure 3-13 The application live on appspot.com

Summary

In this chapter you built your first Google App Engine for Java application using the Guestbook demo application that comes with the SDK You set up and configured the SDK and Google Plugin for Eclipse and even deployed your application to appspot.com We’re going to dive a little deeper into some development

technologies and application components in Chapter 4, where you’ll look at

different approaches to constructing a user interface in an App Engine application and review some libraries and development frameworks

■ ■ ■

Servlet Container and Frameworks

Now that you’ve set up your development environment and configured the SDK, it's

time to look at the design of your application Out of the box, App Engine uses the

Java Servlet standard for web applications, but you may be able to use your favorite

framework as well In this chapter we’ll look at different libraries and frameworks that run in App Engine You’ll build a small application with servlets and JavaServer (JSP)

pages as well as applications using Spring MVC and Adobe Flex with GraniteDS

Choosing a Framework

Choosing the best application framework almost always generates a heated debate

There are pros and cons for each framework, and every developer has an opinion Some developers may prefer a robust Enterprise JavaBeans (EJB) framework while others

prefer a lightweight, agile approach To ensure that your application will run within the App Engine server runtime environment, App Engine imposes some constraints that

enable applications to run “nicely” together and be scalable across multiple distributed runtime instances

While Google doesn't officially support the libraries or frameworks that run on App Engine, it does take a community-oriented approach to compatibility While many

frameworks will run seamlessly on App Engine, others will not Some frameworks will require modifications, and there is an active and vibrant community dedicated to

interoperability

Popular Java libraries and frameworks are listed in Table 4-1 Frameworks marked

as compatible should work out-of-the-box with some minor configuration changes or code tweaks Ones marked “Semi-compatible” typically include some features that

will not operate properly due to App Engine restrictions (for example, writing to the

file system, multithreading) Most incompatible frameworks fail to run due to their

reliance on classes not supported by App Engine

page

Direct Web Remoting (DWR) 2.0.5, 3.0 RC1 Compatible

Google Data (GData) client library for

Java

All Compatible

Framework Version(s) Status

OpenSocial client library for Java 20090402 Compatible

framework You can certainly develop feature-rich, scalable applications for

App Engine using servlets and JSPs We are going to take a quick peek at some

applications built using the Java Servlet standard, Swing MVC, and Adobe Flex with GraniteDS

Servlets and JavaServer Pages

For web applications, the Java Servlet standard is one of the major foundations of the server stack By default App Engine utilizes this tried-and-true standard for web applications as well As with most servlet containers, App Engine serves up servlets, JSPs, static files, and other data files from the web archive (WAR) directory based

on the configuration in the deployment descriptor Gone are the days of manually configuring and load-balancing your servers based on traffic A major advantage of App Engine is that it automatically scales your application for you Applications run

on multiple web servers simultaneously and Google automatically adjusts the server pool based on the load

As with most multitenant environments, App Engine runs the JVM in a secured

“sandbox” environment to isolate applications from one another for security and service availability The sandbox ensures that applications don’t step on one another, hog server resources, or perform actions that they shouldn’t These restrictions can be great for ensuring scalability but can make you want to pull your hair out sometimes For instance, applications don’t have access to the local file system for write operations, cannot spawn threads, cannot leverage JNI or other native code, and cannot make ad hoc network connections Most of the time it’s not an issue, but

in certain cases you’ll find yourself wanting to write to the local file system or spawn a new thread to perform operations more efficiently

To get started with App Engine, you’re going to build a small application

that incorporates some basic functionality The application is a simple telesales application that sales representatives can use to field inbound sales calls Users will

be able to search for existing accounts or create new accounts They can view existing sales opportunities for the account or create new opportunities that other sales reps can follow up on Your application will contain a single servlet and a number of JSPs You’ll persist your data to Bigtable (We’ll just skim over the functionality here, as we’ll dig into Bigtable in detail in Chapter 7.)

Views

Starting with the views for your application, the servlet container serves a welcome page (Figure 4-1 and Listing 4-1), a simple form that allows the user to perform a

keyword search for existing accounts in Bigtable Users can also choose to create a

new account for sales opportunities

Figure 4-1 The default welcome web page

Listing 4-1 The code for index.html

<html>

<head>

<title>Google App Engine Servlet Example with Bigtable</title>

<link rel="stylesheet" type="text/css"

href="/stylesheets/styles.css"/>

</head>

<body>

<span class="title">Google App Engine Servlet Example with

Bigtable</span>

<p>Before creating a new Opportunity, ensure that the Account does

not already exist You can also <a

href="telesales?action=accountCreate"/>create a new account</a>.</p>

<p/>