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

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

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CHAPTER 3 ■ GETTING STARTED WITH GOOGLE APP ENGINE FOR JAVA 38 ■ 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: appengine-java-sdk/bin/dev_appserver.sh [options] war-location CHAPTER 3 ■ GETTING STARTED WITH GOOGLE APP ENGINE FOR JAVA 39 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 CHAPTER 3 ■ GETTING STARTED WITH GOOGLE APP ENGINE FOR JAVA 40 Once you’re ready to move forward click the App Engine project settings… link at 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. CHAPTER 3 ■ GETTING STARTED WITH GOOGLE APP ENGINE FOR JAVA 41 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 CHAPTER 3 ■ GETTING STARTED WITH GOOGLE APP ENGINE FOR JAVA 42 Figure 3-13. If you’re using Google Apps you can create a unique domain name for 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. C H A P T E R 4 ■ ■ ■ 43 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. CHAPTER 4 ■ SERVLET CONTAINER AND FRAMEWORKS 44 Table 4-1. Java libraries and frameworks from Google’s “Will it play in App Engine” page Framework Version(s) Status Apache Commons FileUpload 1.2.1 Semi-Compatible Apache POI ? Incompatible BlazeDS 3.2.0 Compatible Compass ? Semi-Compatible Direct Web Remoting (DWR) 2.0.5, 3.0 RC1 Compatible dyuproject ? Compatible Ehcache 1.6.0 Compatible Facelets 1.1.14 Compatible Google Data (GData) client library for Java All Compatible Grails 1.1.1 Compatible GraniteDS ? Compatible Guice ? Semi-Compatible Hibernate All Incompatible iText ? Incompatible Java Topology Suite (JTS) 1.10 Compatible JBoss Seam ? Semi-Compatible Jersey 1.0.2 Semi-Compatible log4j ? Compatible CHAPTER 4 ■ SERVLET CONTAINER AND FRAMEWORKS 45 Framework Version(s) Status MyFaces 1.1.6 Compatible OpenSocial client library for Java 20090402 Compatible OSGi ? Semi-Compatible Restlet ? Compatible RichFaces 3.1.6 Incompatible SiteMesh 2.4.2 + Compatible Spring MVC 2.5.6 Compatible Spring ORM 2.5.6 Compatible Spring Security ? Semi-Compatible Stripes Framework ? Compatible Struts 1 1.2.28 Compatible Struts 2 ? Compatible Tapestry 5.0.18 Compatible Tapestry 5.1 Incompatible Tiles 2.0.7 Compatible Vaadin ? Semi-Compatible VRaptor 2 ? Compatible WebORB ? Compatible Wicket ? Semi-Compatible ZK 3.6.2 + Compatible CHAPTER 4 ■ SERVLET CONTAINER AND FRAMEWORKS 46 Depending on your application’s needs, you may or may not choose to use a 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 CHAPTER 4 ■ SERVLET CONTAINER AND FRAMEWORKS 47 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/> <form method="post" action="telesales"> . WITH GOOGLE APP ENGINE FOR JAVA 39 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 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. to your application’s unique domain on appspot. In the example case (shown in Figures 3-1 1 and 3-1 2), the application lives at http://kylechapterthree.appspot.com, as shown in CHAPTER 3 ■ GETTING

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