Home > Articles > Programming > Ajax

This chapter is from the book

This chapter is from the book

Organizing Your Application Structure

When you generate an application using GWT's applicationCreator script, the script creates files and directories that follow a recommended structure. Each application that you create shares your Projects directory. Figure 4-31 shows how the directory looks for the HelloWorld generated application. Figure 4-32 shows the directory result after running the applicationCreator again and adding the new application, HelloWorld2, to the same Eclipse project used for HelloWorld. Notice that new scripts were created for the HelloWorld2 application. The applicationCreator script creates the application source files in the src directory, and shares this directory with the first HelloWorld application, as shown in Figure 4-33.

Figure 4-31

Figure 4-31 Directory structure for the HelloWorld application

Figure 4-32

Figure 4-32 Directory structure after adding a new application

Figure 4-33

Figure 4-33 Two applications sharing the same source directory

The source code is organized in standard Java package structure. Since we created the application as com.gwt.examples.HelloWorld2, the script generates the source files in the src/com/gwt/ examples directory. This directory structure technique is a nice way of organizing Java modules and applications. It allows you to add packages and give them a unique location in the source tree, avoiding overwriting other classes that may be in a different package but have the same name. It also gives you a unique way to refer to a class from Java code.

Each generated GWT application has a module file and other source files in the client subdirectory and public subdirectory. Figure 4-33 shows the module file for HelloWorld2, HelloWorld2.gwt.xml. This file specifies the application's configuration options for the GWT compiler. The generated module file looks like this:

   <!-- Inherit the core Web Toolkit stuff.                  -->
   <inherits name='com.google.gwt.user.User'/>
   <!-- Specify the app entry point class.                   -->
   <entry-point class='com.gwtapps.examples.client.HelloWorld2'/>

This is the minimum specification that the application needs to run. The GWT compiler needs to know the class that acts as the entry point to the application, specified with the entry-point tag, and it needs to use the com.google.gwt.user.User module for its user interface. When you need to use other modules in your application you specify their location here. The module file has many more configuration options, all of which are outlined on the GWT web site at http://code.google.com/webtoolkit.

Now let's look inside the public folder shown in Figure 4-34. For each generated application, the script creates a new HTML host file in the public directory. The GWT compiler considers files placed in the public directory to be part of the distribution. In other words, when you compile your application, GWT will copy all of the files in this directory to the www output directory. For example, we could move the CSS from inside the HTML host file to a separate CSS file and place it in this directory. Other common files you might place in this directory are images that are used in the application's user interface.

Figure 4-34

Figure 4-34 The public folder holding the static application files

The generated Java source file for the applications is found in the client directory, as shown in Figure 4-35. When the GWT compiler compiles the Java source to JavaScript, it compiles the Java files in this directory. Any files outside of this directory will not be compiled to JavaScript, and if you use them you will get an exception when compiling or running in hosted mode. However, using the inherits tag in your module file tells the GWT compiler to use another module.

Figure 4-35

Figure 4-35 The client directory holding the files that will be compiled to JavaScript

The GWT compile automatically includes subdirectories and packages in the client directory without inheriting a module. This is useful for organizing subcategories of code within your application. For example, many of the sample applications in this book use a model-view-controller (MVC) architecture and keep the model and view in subpackages. Figure 4-36 shows this type of organization for Chapter 7's Multi-Search sample application. You can use this to organize your client-side code into categories other than model and view.

Figure 4-36

Figure 4-36 MVC organization inside the client directory

There may be situations where you'll have application code that shouldn't be compiled to JavaScript and shouldn't be in the client directory; for example, when writing server-side code in Java, perhaps using a GWT RPC servlet. The common place to put this server-side code is in a server directory. For example, the Instant Messenger application in Chapter 9 places the servlet class in the server subdirectory, as shown in Figure 4-37. Since this is outside of the client directory, the GWT compile ignores the code when compiling the client. Typically the GWT compiler will not be able to compile server-side code since it usually uses packages that aren't emulated by GWT and would not be useful in a browser.

Figure 4-37

Figure 4-37 Server-side code is placed outside the client directory

The reverse is possible, however. The server classes can use classes in the client directory as long as they don't rely on browser features. The Instant Messenger application does this to share the Java classes that are used to transmit data over RPC between the client and the server.

Finally, when you're ready to deploy your application, you run the generated compile script. GWT copies all of the files used for distribution, including the generated JavaScript files and all of the files in the public directory, to the applications directory inside the www directory. The compiler names the application's directory with the full module name, as shown in Figure 4-38.

Figure 4-38

Figure 4-38 The GWT writes the compiled and static files to the www directory

InformIT Promotional Mailings & Special Offers

I would like to receive exclusive offers and hear about products from InformIT and its family of brands. I can unsubscribe at any time.


Pearson Education, Inc., 221 River Street, Hoboken, New Jersey 07030, (Pearson) presents this site to provide information about products and services that can be purchased through this site.

This privacy notice provides an overview of our commitment to privacy and describes how we collect, protect, use and share personal information collected through this site. Please note that other Pearson websites and online products and services have their own separate privacy policies.

Collection and Use of Information

To conduct business and deliver products and services, Pearson collects and uses personal information in several ways in connection with this site, including:

Questions and Inquiries

For inquiries and questions, we collect the inquiry or question, together with name, contact details (email address, phone number and mailing address) and any other additional information voluntarily submitted to us through a Contact Us form or an email. We use this information to address the inquiry and respond to the question.

Online Store

For orders and purchases placed through our online store on this site, we collect order details, name, institution name and address (if applicable), email address, phone number, shipping and billing addresses, credit/debit card information, shipping options and any instructions. We use this information to complete transactions, fulfill orders, communicate with individuals placing orders or visiting the online store, and for related purposes.


Pearson may offer opportunities to provide feedback or participate in surveys, including surveys evaluating Pearson products, services or sites. Participation is voluntary. Pearson collects information requested in the survey questions and uses the information to evaluate, support, maintain and improve products, services or sites, develop new products and services, conduct educational research and for other purposes specified in the survey.

Contests and Drawings

Occasionally, we may sponsor a contest or drawing. Participation is optional. Pearson collects name, contact information and other information specified on the entry form for the contest or drawing to conduct the contest or drawing. Pearson may collect additional personal information from the winners of a contest or drawing in order to award the prize and for tax reporting purposes, as required by law.


If you have elected to receive email newsletters or promotional mailings and special offers but want to unsubscribe, simply email information@informit.com.

Service Announcements

On rare occasions it is necessary to send out a strictly service related announcement. For instance, if our service is temporarily suspended for maintenance we might send users an email. Generally, users may not opt-out of these communications, though they can deactivate their account information. However, these communications are not promotional in nature.

Customer Service

We communicate with users on a regular basis to provide requested services and in regard to issues relating to their account we reply via email or phone in accordance with the users' wishes when a user submits their information through our Contact Us form.

Other Collection and Use of Information

Application and System Logs

Pearson automatically collects log data to help ensure the delivery, availability and security of this site. Log data may include technical information about how a user or visitor connected to this site, such as browser type, type of computer/device, operating system, internet service provider and IP address. We use this information for support purposes and to monitor the health of the site, identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents and appropriately scale computing resources.

Web Analytics

Pearson may use third party web trend analytical services, including Google Analytics, to collect visitor information, such as IP addresses, browser types, referring pages, pages visited and time spent on a particular site. While these analytical services collect and report information on an anonymous basis, they may use cookies to gather web trend information. The information gathered may enable Pearson (but not the third party web trend services) to link information with application and system log data. Pearson uses this information for system administration and to identify problems, improve service, detect unauthorized access and fraudulent activity, prevent and respond to security incidents, appropriately scale computing resources and otherwise support and deliver this site and its services.

Cookies and Related Technologies

This site uses cookies and similar technologies to personalize content, measure traffic patterns, control security, track use and access of information on this site, and provide interest-based messages and advertising. Users can manage and block the use of cookies through their browser. Disabling or blocking certain cookies may limit the functionality of this site.

Do Not Track

This site currently does not respond to Do Not Track signals.


Pearson uses appropriate physical, administrative and technical security measures to protect personal information from unauthorized access, use and disclosure.


This site is not directed to children under the age of 13.


Pearson may send or direct marketing communications to users, provided that

  • Pearson will not use personal information collected or processed as a K-12 school service provider for the purpose of directed or targeted advertising.
  • Such marketing is consistent with applicable law and Pearson's legal obligations.
  • Pearson will not knowingly direct or send marketing communications to an individual who has expressed a preference not to receive marketing.
  • Where required by applicable law, express or implied consent to marketing exists and has not been withdrawn.

Pearson may provide personal information to a third party service provider on a restricted basis to provide marketing solely on behalf of Pearson or an affiliate or customer for whom Pearson is a service provider. Marketing preferences may be changed at any time.

Correcting/Updating Personal Information

If a user's personally identifiable information changes (such as your postal address or email address), we provide a way to correct or update that user's personal data provided to us. This can be done on the Account page. If a user no longer desires our service and desires to delete his or her account, please contact us at customer-service@informit.com and we will process the deletion of a user's account.


Users can always make an informed choice as to whether they should proceed with certain services offered by InformIT. If you choose to remove yourself from our mailing list(s) simply visit the following page and uncheck any communication you no longer want to receive: www.informit.com/u.aspx.

Sale of Personal Information

Pearson does not rent or sell personal information in exchange for any payment of money.

While Pearson does not sell personal information, as defined in Nevada law, Nevada residents may email a request for no sale of their personal information to NevadaDesignatedRequest@pearson.com.

Supplemental Privacy Statement for California Residents

California residents should read our Supplemental privacy statement for California residents in conjunction with this Privacy Notice. The Supplemental privacy statement for California residents explains Pearson's commitment to comply with California law and applies to personal information of California residents collected in connection with this site and the Services.

Sharing and Disclosure

Pearson may disclose personal information, as follows:

  • As required by law.
  • With the consent of the individual (or their parent, if the individual is a minor)
  • In response to a subpoena, court order or legal process, to the extent permitted or required by law
  • To protect the security and safety of individuals, data, assets and systems, consistent with applicable law
  • In connection the sale, joint venture or other transfer of some or all of its company or assets, subject to the provisions of this Privacy Notice
  • To investigate or address actual or suspected fraud or other illegal activities
  • To exercise its legal rights, including enforcement of the Terms of Use for this site or another contract
  • To affiliated Pearson companies and other companies and organizations who perform work for Pearson and are obligated to protect the privacy of personal information consistent with this Privacy Notice
  • To a school, organization, company or government agency, where Pearson collects or processes the personal information in a school setting or on behalf of such organization, company or government agency.


This web site contains links to other sites. Please be aware that we are not responsible for the privacy practices of such other sites. We encourage our users to be aware when they leave our site and to read the privacy statements of each and every web site that collects Personal Information. This privacy statement applies solely to information collected by this web site.

Requests and Contact

Please contact us about this Privacy Notice or if you have any requests or questions relating to the privacy of your personal information.

Changes to this Privacy Notice

We may revise this Privacy Notice through an updated posting. We will identify the effective date of the revision in the posting. Often, updates are made to provide greater clarity or to comply with changes in regulatory requirements. If the updates involve material changes to the collection, protection, use or disclosure of Personal Information, Pearson will provide notice of the change through a conspicuous notice on this site or other appropriate way. Continued use of the site after the effective date of a posted revision evidences acceptance. Please contact us if you have questions or concerns about the Privacy Notice or any objection to any revisions.

Last Update: November 17, 2020