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Getting Started With NetBeans Visual Web Pack 5.5

摘要: This tutorial gives you a whirlwind tour of the NetBeans Visual Web Pack. The tutorial shows you how to use the Visual Web Pack features to perform the typical phases of web application development

Contents

-  Software Needed for This Tutorial
-  Starting a Project
-  Creating Web Pages
-  Adding Components to a Web Page
-  Getting Help
-  Building and Testing a Web Application
-  Connecting Web Pages and Handling User Actions
-  Editing Java Code
-  Handling User Input
-  Storing and Passing Data
-  Connecting to Databases
-  Debugging a Web Application
  Content on this page applies to NetBeans 5.5 Visual Web Pack

This tutorial works with the following technologies and resources

JavaServer Faces Components/
Java EE Platform		 works with1.2 with Java EE 5*
works with1.1 with J2EE 1.4
Travel Database requiredRequired for some sections
BluePrints AJAX Component Library not requiredNot required

* As of the date this tutorial was published, only the Sun Java System Application Server supported Java EE 5.

This tutorial has been tailored for use with the Sun Java Application Server PE 9.0 Update Release 1 and with Tomcat 5.5.17. If you are using a different server, consult the Release Notes and FAQs for known problems and workarounds. For detailed information about the supported servers and Java EE platform, see the Release Notes.

Starting a Project

A project is the equivalent of your working environment for a web application. When you create a Visual Web Application project from the IDE, the IDE builds the foundation for a JavaServer Faces (JSF) web application. By default, the IDE creates a JSF 1.2 web application within a directory structure that conforms to the Java BluePrints project conventions for web applications.

Note: All the steps in this tutorial are based on the default Visual Web Pack project, which uses JSF 1.2 and Java EE 5.

You create a Visual Web Application project by choosing File > New Project from the main menu, selecting the Web category, and selecting the Visual Web Application project type.


Try It

  1. Start the IDE by using the appropriate step from the following list:

    • Windows. Double-click the NetBeans desktop icon.
    • Mac. Double-click the NetBeans icon in the installation folder.
    • Solaris Operating System (SPARC and x86 Platform Editions) and Linux. Navigate to the bin directory of your NetBeans installation, type ./netbeans, and press Enter.
  2. Click the Runtime header, or choose Window > Runtime from the main menu, to bring the Runtime window to the front.
  3. Create a project by choosing File > New Project from the main menu. In the categories pane, select Web, and in the Projects pane, select Visual Web Application.
  4. Click Next.
  5. Choose a server, and choose a Java EE Version.

  6. Click Finish to accept the default project name and location.

    The IDE creates the project directory web-application-name under your home directory by default.

  7. Explore the Projects window. As shown in the following figure, the Projects window groups items by category. Expand each of the nodes to see what type goes in each category. Notice the badge that appears next to the Application Bean node. This badge indicates that the file needs to be compiled. The IDE compiles the files automatically when you build the project.

    Figure 1: Projects Window
    Figure 1: Projects Window
  8. Under the Web Pages node is the Page1.jsp node. The IDE creates this page by default and makes it the start page. The arrow badge next to the node identifies the page as the start page. If you want to use a different page for the start page, right-click that page's node and choose Set as Start Page from the pop-up menu.

  9. Click the Files header, or choose Window > Files from the main menu, to bring the Files window to the front. This window organizes the items by their physical storage. Expand the nodes to see the structure.

    Figure 2: Files Window
    Figure 2: Files Window
  10. In Figure 2, notice the WebApplication1 > src > java > gettingstarted > Page1.java node. This Java class is the backing bean for the Page1.jsp file. Whenever you add a page to the project, the IDE creates both a .jsp file and a .java file for the page. You learn more about .jsp and .java files in the next section.

For More Information

Creating Web Pages

With Visual Web applications, you use JavaServer pages (JSP) and page beans (also known as backing beans) instead of HTML pages. The JSP page is a template from which the server generates the HTML response to be displayed in the browser (the client). The page bean contains the logic that the server executes when it generates the HTML response. The page bean also contains the logic that the server executes after a user submits the page.

When you add a web page in a Visual Web application, the IDE creates both a JSP file and a Java source file for you. You mostly use the Visual Designer and the Properties window to develop the web page. The IDE modifies the JSP code and Java code to implement what you design. Most of your work can be done from the Visual Designer and the Properties window.

Note: The JSP pages that the IDE generates are JSP documents. A JSP document is an XML document and, therefore, must be well-formed. While most JSP elements comply with XML syntax, there are some elements that are not XML compliant, such as comments, declarations, directives, expressions, and scriptlets. See the JavaServer Pages Syntax Reference for JSP document syntax.


Try It

  1. In the Projects window, right-click the Web Pages node and choose New > Page, as shown in the following figure.

    Figure 3: Right-Clicking the Web Pages Node
    Figure 3: Right-Clicking the Web Pages Node

  2. Accept the default name of Page2 and click Finish. The IDE opens Page2 in the Visual Editor, which is in the editing area, as shown in the following figure.

    Figure 4: Visual Designer
    Figure 4: Visual Designer

  3. Click the Java button in the editing toolbar to see the source code for the page bean, as shown in the following figure. When the editing area shows the Java source, the Navigator window appears. This window lists all the member fields and methods. Notice that the page's source code has methods to access the Application Bean, Session Bean, and Request Bean. See the Storing and Passing Data section in this tutorial for an explanation of these three types of beans.

    Figure 5: Java Source for Page Bean
    Figure 5: Java Source for Page Bean

  4. The source also has methods that get invoked during certain lifecycle events between the time the page is requested and the time the page rendering is complete.

    Tip: Double-clicking a member in the Navigator window positions the source code in the editing area on that member's declaration. You can also click in the Navigator window and start typing the first few characters of a member's name to raise a Quick Search dialog box. Continue typing until the IDE highlights the desired entry in the list, and press Enter to position the source code at the matching member's declaration, as shown in the following figure.

    Figure 6: Quick Search in the Navigator Window
    Figure 6: Quick Search in the Navigator Window

  5. Click the JSP button in the editing toolbar to see the JSP code for the page, as shown in the following figure. Notice how the JSP page uses JSP document syntax.

    Figure 7: JSP View
    Figure 7: JSP View

  6. Click Design in the editing toolbar to switch to the Visual Designer and to display the representation of the page in the Outline window, which is shown in the following figure. Note how the tags in the JSP file are represented as nodes in the Outline window.

    Figure 8: Outline Window
    Figure 8: Outline Window

For More Information

Adding Components to a Web Page

You design a web page by dragging components from the Palette window and dropping them on the web page in the Visual Designer. The following figure shows Page2 with the Button, Text Field, Message, Drop Down List, and Radio Button Group components. All of these components are available from the Basic section of the Palette. The components have been customized by changing the component properties. You learn about properties later in this section.

Figure 9: Components in the Visual Designer
Figure 9: Components in the Visual Designer

Note: The components that are available from the Palette are JSF components, which have been enhanced according to the Design Time API so that their properties are available for the Visual Designer and the Properties window. You can use other components in the web applications that you build using the IDE, but you will not be able to use the interactive design-time features of the IDE on these components unless they have been customized according to requirements of the Design Time API. If the Java EE version is set to Java EE 5 (the default), the Palette offers JSF 1.2 components. If, when you create the project, you set the Java EE version to 1.3 or 1.4, the Palette offers JSF 1.1 components.

Most of the components that you use are in the Basic, Layout, and Composite sections of the Palette window. The following tables show some of the most commonly used components.

Table 1: Input Components

Component Description Palette Section
Text Field An input field for a single line of text. Basic
Text Area An input field for multiple lines of text. Basic
Password Field An input field that echoes the input characters with a replacement character to mask the input. Basic
Calendar An input field with a pop-up calendar that allows the user to select a date. Basic
Drop Down List A drop-down menu, also referred to as a combo box. Basic
Listbox A list from which the user can select either one item or multiple items, depending on how the component is configured. Basic
Checkbox A single-character box that the user can either select (check) or clear. Basic
Radio Button A single radio button that the user can select (check). Basic
Add Remove List Two lists (one for available options, one for selected options) with buttons to move the options between the lists, and to order the selected options. Composite
File Upload A component with a text input field and a Browse button that displays a file chooser for specifying a file to upload. The application uploads the specified file when the user submits the page. Basic
 

Table 2: Display Components

Component Description Palette Section
Static Text Field for displaying text. Basic
Label Text field that can be associated with an input field and for which you can specify a weak, medium, or strong font style. Basic
Image Inline image. Basic
Message Text field that is linked to a specific component for displaying validation errors and other messages about that component. Basic
Message Group Text field for displaying runtime error messages, program generated error messages, and, optionally, validation errors and other messages about components that are on the page. Basic
Alert Displays an icon and informational text such as a warning, an error, or the successful completion of some event. Composite
Page Alert Similar to an Alert component, but is intended for displaying the icon and information on a separate page. Layout
 

Table 3: Grouping Components

Component Description Palette Section
Checkbox Group Displays two or more check boxes in a grid layout. Basic
Radio Button Group Displays two or more radio buttons in a grid layout and ensures that only one button can be selected at a time. Basic
Table, Table Row Group, and Table Column Displays data from a composite data type such as a database table or an array. Basic
Tree and Tree Node Renders an expandable list in a tree structure. Basic
Tab Set and Tab Displays different layouts on the same page. Also can be used as a navigational tool. Layout
Grid Panel Organizes the components within a layout of rows and columns. Layout
Group Panel Groups a set of components in flow layout mode. Layout
Layout Panel Use to group a set of components in flow layout mode or grid layout mode. Layout
Property Sheet, Property Sheet Section, and Property Lays out a single column of labeled components quickly, and divides the components into sections. Layout
Breadcrumbs Lays out a series of link components separated by right angle brackets (>). Composite
Page Fragment Box Groups components that you want to consistently display on two or more pages. Layout
 

Table 4: Action Components

Component Description Palette Section
Button Button that submits the associated form. Basic
Hyperlink Text field that submits a URL or submits a form. Basic
Image Hyperlink Image that submits a URL or submits a form. Basic
Tree Node Subcomponent of a Tree or Tree Node. A leaf tree node can optionally submit a URL or submit a form. Basic
Tab Subcomponent of a Tab Set or a Tab. A tab can optionally submit a URL or submit a form. Composite
 

You use the component's property sheet in the Properties window to change the appearance and behavior of the component, to bind the component to data, and to associate the component with event handlers.

The following figure shows the properties for a Listbox component.

Figure 10: Listbox Property Sheet in the Properties Window
Figure 10: Listbox Properties in the Properties Window
 

Try It

Open Page2 that you created by following the Try It suggestions in the Creating Web Pages section, or create it if necessary.

Drag various components from the Basic section and the Layout section of the Palette window and play around with their properties. For example, try the following steps:

  1. Drag a Button Component onto the page, type Click Me! and press Enter. In the Properties window, notice how the text property has the value Click Me!. In the Properties window, select the primary property's checkbox and notice how the button's appearance changes.
  2. Drag a Text Field component onto the page. Next, drag a Label component onto the page, type Name: and press Enter. Ctrl-Shift-Click inside the Label component and drag to the Text Field component. Notice how the for property for the Label component is now set to the id for the Text Field Component. Set the labelLevel to Strong (1).
  3. Drag a Message component to the right of the Text Field. Control-Shift-Drag from the Message Component to the Text Field component. As with the Label component, notice how the for property for the Message component is now set to the id for the Text Field Component.
  4. Drag a Drop Down List component onto the page and set its label property to Color. Right-click the Drop Down List component and choose Configure Default Options to raise the Options Customizer.
  5. Press Tab to enter edit mode for Item 1 in the Display column, and type Blue. Press tab twice and change Item 2 to White. Press tab twice more and change Item 3 to Green. Click OK and notice how your changes affect the component in the Visual Designer.

  6. Use steps similar to those for the Drop Down List to create a Radio Button Group component with the choices Blue, White, and Red.

    In addition, select the Select Items checkbox in the Options Customizer, and select one of the radio buttons in the Selected column to set the default selection to that item. Click OK to apply the changes and to dismiss the Options Customizer. In the Properties window, set the columns property to 3 to align the radio buttons horizontally instead of vertically.
  7. Right-click on a blank spot in the page and choose Preview in Browser to see how your browser renders the components.

For More Information

Getting Help

The IDE provides a Help Viewer, which contains help topics about the IDE. Also, when you press F1 on a window, dialog box, or Palette component, the Help viewer appears and displays information about that item. To access the Visual Web Pack help topics, including help about the components, choose Help > Help Contents from the main menu and scroll to Visual Web Pack.

The IDE also provides a Dynamic Help window, which shows links to help topics that are related to the current window or object. When you double-click a link in the Dynamic Help window, the IDE displays the information in the appropriate viewer, such as a browser, the Help viewer, or the Javadoc viewer.


Try It
  1. Add a Label component to a page in the Visual Designer. Notice the topics in the Dynamic Help window.
  2. Add a Drop Down List component to the page. Notice the new topics in the Dynamic Help window.
  3. In the Dynamic Help window, double-click the Drop Down List Component node to view the topic in the Help viewer. Close the Help viewer.
  4. Click in the Properties window for the Drop Down List. Press F1 to view the topic about the Drop Down List component properties.
  5. Select the node for the Text Field component in the Basic section of the Palette. Press F1 to view the help topic about the Text Field component.

Building and Testing a Web Application

When you are ready to test a project, press F6 or choose Run > Run Main Project from the main menu. The IDE takes the following actions:

If you have made massive changes, deleted several items, or you are seeing some unexpected behavior, you can choose Build > Clean and Build Main Project from the main menu. The IDE cleans out the project's build directory and dist directory, undeploys the web application, and then builds and deploys the application.


Try It
  1. If your project has less than two pages, create a new one by right-clicking the Web Pages node in the Projects window and choosing New > Page.
  2. Open the start page (the page with the green arrow badge) in the Visual designer.
  3. Drag a Hyperlink component onto the page, type Next Page, and press Enter.
  4. In the Properties window for the Hyperlink component, click the ellipsis button (...) for the url property, select a different page in the project, and click OK. Notice how the IDE sets the url property to /faces/page-name.jsp.
  5. Press F6 to build and run the web application.
  6. Watch the messages that appear in the Output window during the build process. Also notice that output from the server's log appears in the server's tab.
  7. Note the URL that the IDE sends to the browser.
  8. When the start page appears in the browser, click the Next Page link.

  9. In the Runtime window, expand Servers, expand the server's node, expand Applications, expand Web Applications, and note that there is a node for your project, as shown in the following figure.

    Figure 12: Deployed Web Applications
    Figure 12: Deployed Web Applications

For More Information

Connecting Web Pages and Handling User Actions

When a user types a URL, clicks a link, or clicks a button, the browser sends a request to the server. The server maps the request to a JSP page and uses that JSP page and its associated page bean to render a response.

You can specify page navigation in one of two ways:

To access the Page Navigation editor, right-click on a blank spot in the page in the Visual Designer and choose Page Navigation. The Page Navigation editor shows page icons for all the pages in the project. When you click a page icon in the Page Navigation editor, the page expands and shows all its action components. (An action component is a component that has an action property, such as a Button, a Hyperlink, or a Tab.) Next to each component is a connector port. You drag from the connector port to a page icon to create the mapping between that action's request and the page to be rendered as a response. When you release the mouse, the IDE adds a visual representation of that connection , as shown in the connection labeled nextPage in the following figure.

Figure 13: Page Navigation Editor
Figure 13: Page Navigation Editor
 

Note: When a page is submitted, the web application performs conversions and validations before it executes action methods. If a conversion or validation fails, the action methods do not get called. You should put Message Group components on a page during development, so that you can catch any unexpected conversion or validation error that might prevent an action method from being invoked.


Try It
  1. Create two pages named LinkPage1 and LinkPage2. Make LinkPage1 the start page.
  2. Drag a Hyperlink component onto LinkPage1, type Next Page, and press Enter.
  3. Drag a Button component onto LinkPage2, type Go, and press Enter.

  4. Double-click the Button component to access the button's action method.

    Notice that the action method returns null. When an action method returns null, the application redisplays the page.
  5. Click Design in the editing area to switch to the Visual Designer.
  6. In the Visual Designer, right-click on a blank spot in LinkPage2 and choose Page Navigation.
  7. In the Page Navigation editor, click the icon for LinkPage1.jsp to expand the page's icon, and then drag a link from the hyperlink1 component's connector port to the icon for LinkPage2.jsp.
  8. Double-click the Case 1 connector label to change to edit mode, double-click Case 1 to select the text, type nextPage and press Enter.
  9. Use similar steps to create a connector from the button on LinkPage2.jsp back to LinkPage1.jsp and name the connector go.
  10. Click XML in the editing toolbar to view the actual mapping XML that is deployed to the server, then close the Page Navigation editor and click Save when asked whether to save the changes.

  11. In LinkPage2, double-click the Button component to access the button's action method.

    Notice that the action method now returns the string "go". The mapping that you created in the Page Navigation editor instructs the server to display LinkPage1.jsp whenever LinkPage2.jsp returns "go."
  12. Press F6 to run the application and try out the new page navigation.

For More Information

Editing Java Code

The IDE's Java Editor is packed full of features to facilitate the programming process, many more than can be discussed in this introductory tutorial. The following list of examples of editing features is just the tip of the iceberg.


Try It

Note: The following exercises have you type code in the destroy method. The code that you type is meant to illustrate the editing features. You would not normally put code like this in this method. After you complete the steps, you should remove the code.

  1. Create a page or open an existing page. Drop a Hyperlink component onto the page. Click Java in the editing toolbar to display the Java source code.
  2. Right-click in the left margin and choose Show Line Numbers. Press Ctrl-G in the Java source, type 50 in the Go To Line dialog box, and press Enter. Right-click in the source and choose Go To from the pop-up menu. Note the actions available from the submenu.
  3. In the Navigator window, double-click destroy() to position the source code on that method. In the destroy() method, type getSessionBean1(). and pause. The Code Completion box appears. Type d to see the box narrow the list down to destroy(). Press Enter to use that selection. Type ; and press Enter. Now type this.getH, and pause for the Code Completion box to appear. If it does not appear, press Ctrl-Space to raise the Code Completion box. Move the cursor down to getHyperlink1() and press Enter. Type the period, pause for the Code Completion box, and type set. After the Code Completion box narrows the list to all methods that start with set, type te to narrow the list to setText(Object text) and press Enter. The IDE inserts setText() after the period and positions the cursor inside the parentheses. Type "hello", press End, and type ;.
  4. Start a new line, type serr and press the Spacebar to expand the abbreviation to System.err.println(""). Remove the semi-colon from the end of the line. Press F9 to compile the file. The Output window displays several links to errors. Click the first link that appears in the window. The IDE displays the statement that caused the error. Replace the semi-colon that you just removed.
  5. Start a new line, type getSes and press Ctrl-K. The IDE replaces the string with the first matching word from the source code above the current line.
  6. To clean up the code, place the cursor on the first line in the destroy method body and press Ctrl-E to remove that line. Use Ctrl-E to remove the remaining lines in the method body.
  7. Hover over the icons in the editing toolbar and try each one out.
  8. Right-click in the Java source and choose Code Folds from the pop-up menu. Try the various actions in the submenu.
  9. Try dragging code clips from the Palette to see what they offer.

For More Information

Handling User Input

The IDE provides validator and converter objects to facilitate input checking and formatting. These objects can be found in their respective sections in the Palette.

You bind a validator to an input component, such as a Text Field component, by dropping the validator onto the input component. For example, after you add a Text Field component to a page in the Visual Designer, you can drag a Length Validator from the Validators section in the Palette and drop it on the Text Field.

Alternatively, you can drop the validator onto the page and set the input component's validator property to that validator object. For example, you can drop a Long Range Validator on a blank spot on the page, which adds longRangeValidator1 to the Outline window. You can then select an input component in the visual designer, such as the Text Field component, and choose longRangeValidator1 from its validatorExpression property's drop-down list. You can use the same validator for more than one component.

The mechanisms are similar for converters. You can also associate converters with output components, such as the Static Text component. Note that when you bind a component to a data provider field, the conversions are done automatically. You learn about binding to data providers in the Connecting to Databases section.

You use the validator's Properties window to set the validation rules, such as the minimum and maximum value or the minimum and maximum length. Similarly, you use the converter's Properties window to set the conversion rules, such as the pattern that the value should match or the method to call to do the validation. The Number converter has a special wizard that appears when you first drop the Number Converter onto the page or onto a visual component.

The Basic section of the Palette provides the Message component and the Message Group component for automatically displaying conversion errors, validation errors, and required-field messages. The Message Group component displays global error messages, runtime errors and, optionally, all the component error messages. A Message component displays only the messages for the component to which it is bound. You bind a Message component to another component by setting the Message component's for property or by pressing Ctrl-Shift on the Message component and dragging the mouse to the component to which you want to bind the Message component.

You can programmatically send custom error messages to the Message Group component using the error, warn, fatal, and info methods in any Page Bean. To learn more about these methods, choose Tools > Javadoc Index Search, type FacesBean in the text field for the drop-down list, and click Find.


Try It
  1. Create a page and drag a button onto the page. Set the button's text to Go.
  2. Drag a Text Field component onto the page. In the Properties window for the Text Field component, select the required property's checkbox.
  3. Drop a Label component above the Text Field component, type Price: and press Enter.
  4. In the Properties window for the Label component, select textField1 from the drop-down list for the for property. Note how the label in the Visual Designer shows an asterisk to indicate that input is required for its associated Text Field component.

  5. In the Palette, expand the Validators section. Drag a Double Range Validator and drop it on the Text Field component. In the Outline window, select the newly created doubleRangeValidator1 node. In the Properties window for the validator, set the maximum to 10.0 and set the minimum to 1.0, as shown in the following figure.

    Figure 16: Double Range Validator Properties
    Figure 16: Double Range Validator Properties

  6. In the Palette, expand the Converters section. Drag a Number Converter and drop it on the Text Field component. A Number Format dialog box appears, as shown in the following figure. Select currency from the Type drop-down list, select English (United States) from the Locale drop-down list, and click OK.

    Figure 17: Number Format
    Figure 17: Number Format

  7. Add a Message component to the page. Press Ctrl-Shift on the component and drag to the Text Field component.

    Notice that the IDE sets the Message component's for property to the Text Field component's id.
  8. Add a Message Group component to the page.

  9. Make the page the start page and run the application. Try clicking the button with no price entered, with 1.5 entered, with a non-numeric value, and with a price greater than $10.00. Finally, type $1.50 in the text field and click the button.

    Notice how the application rejects all values that do not conform to the number format and that do not fall within the specified range. Notice the different messages that appear in the Message and Message Group components.
  10. Experiment with setting the showGlobalOnly checkbox for the Message Group component.

Storing and Passing Data

You use the Application Bean, the Session Bean, and the Request Bean to store information for use by other pages.

To add a property to the Session Bean, right-click the SessionBean1 node in the Outline window and choose Add > Property. The IDE adds a declaration, a getter method, and a setter method for the property. The property appears as a subnode under SessionBean1 in the Outline window, but usually not right away. Use similar steps to add a property to the Request Bean or the Application Bean.

Note that you can also add properties to a page bean (the backing bean that the IDE creates for each page). To add a property to a page bean, right-click on a blank spot in the page in the Visual Designer and choose Add > Property from the pop-up menu. However, page bean property values last only as long as the page bean is instantiated. For example, when the user clicks a Button component that rerenders the page (that is, the action method returns null), a new instance of that page bean is created, and the page bean's property values are reinitialized. If you want to pass a value to the postback, you can use Hidden Field components.

To associate a component with a bean's property, right-click the component and choose Bind to Data. In the Bind to Data dialog box, select the Bind to Object tab and choose the bean's property, as shown in the following figure.

Figure 18: Bind to Data Dialog Box
Figure 18: Bind to Data Dialog Box
 

Note: For most components, the pop-up menu provides two binding actions - Property Bindings and Bind to Data. The Property Bindings dialog box enables you to bind any of the component's properties to a managed bean property or a data provider field. The Bind to Data dialog box is a shortcut for binding the component's value-holding property to a managed bean property or a data provider field. Use the Bind to Data Provider tab to bind to any data provider that you have added to the page or a managed bean. Use the Bind to an Object tab to bind to a page property or a managed bean property.


Try It

  1. Right-click the RequestBean1 node in the Outline window and choose Add > Property. Name the property parm, make it a String, and click OK.

    Note that the newly added property might not appear in the Outline window. To make the property appear, right-click in the Visual Designer and choose Refresh from the pop-up menu. You can also open and save the RequestBean1 source file to make the property appear, as you do in the following steps.
  2. In the Outline window, right-click the Request Bean and choose Edit Java Source from the pop-up menu.
  3. Scroll to the bottom of the source file to see the getParm and setParm methods that the IDE added for the property.
  4. Close and save the file.
  5. Create a page named First with a Button component and a Text Field component.
  6. Right-click the Text Field component and choose Bind to Data from the pop-up menu. Click the Bind to an Object tab, select RequestBean1 > parm, and click OK.
  7. Create a page named Next. Add a Button component and add a Static Text component.
  8. Bind the Static Text component on the Next page to RequestBean1 > parm using the same steps that you used for the Text Field component on the First page.
  9. Right-click in the source and choose Page Navigation from the pop-up menu.
  10. In the Page Navigation editor, create a connector from the Button component on the First page to the Next page. Leave the Button component on the Next page alone, because you want this button to cause the Next page to simply rerender itself.
  11. Set First.jsp as the start page and run the application. Enter a value and click the button. Note that the Next page displays the value that you entered on the First page. Behind the scenes, an instance of RequestBean1 was instantiated to store the Text Field component's value in the parm property. The value of that parm property was subsequently retrieved for the response (the HTML for the Next page). Once the response was rendered, the RequestBean1 instance was destroyed.
  12. Click the button that is on the Next page to cause the Next page to rerender itself. Notice how the Static Text component no longer shows a value. This is because the RequestBean1 instance that held the value only lived as long as the request that began when the First page was submitted and that ended when the HTML for the Next page was sent back to the client.

Connecting to Databases

The Runtime window includes a Databases node, which shows all the databases that are registered with the IDE, as shown in the following figure. The Visual Web Pack provides a sample TRAVEL database which you use in the remainder of this tutorial.

Figure 19: Data Sources
Figure 19: Data Sources
 

Before you can access a database from a project, you must first connect the IDE to the database. You must do this every time you start the IDE and open a project that is connected to the database.

If a database's badge is broken and you cannot expand the database's node, the IDE is not connected to the database. To connect to the TRAVEL database, right-click the databases node in the Runtime window and choose Connect from the pop-up menu. If the Connect dialog box appears, enter travel for the Password and select Remember Password During This Session. If you do not see a jdbc node for the TRAVEL database, see the Visual Web Pack Sample Database section in the NetBeans Visual Web Pack Installation Instructions for information about making the database available to the IDE.

Note: If your web application uses a different server than the Sun Java System Application Server, you must put a copy of the derbyclient.jar file in your server's library directory. For example, if you want to use the TRAVEL database with Tomcat, copy the derbyclient.jar file into netbeans-install-directory \enterprise3\apache-tomcat-5.5.17\common\lib. You can find a copy of the derbyclient.jar in javadb\lib\derbyclient.jar under the the installation directory for the Sun Java System Application Server.

When you open an existing project, the Visual Designer might show an error screen. Typically, this is because the Visual Designer needs to get information from the database, but the IDE is not connected to the database. Try connecting to the database server and clicking the Continue button in the error screen to resolve the problem.

You can connect a page to a database table by dragging the table from the data sources section and either dropping it on a component or dropping it on the page. When you do this, the IDE adds a data provider to the page and a rowset to the SessionBean1 class, as shown in the following figure.

Figure 20: Data Provider and Row Set
Figure 20: Data Provider and Row Set
 

The rowset object makes the connection to the database, executes the queries, and manages the result set. The data provider object provides a common interface for accessing many types of composite data, from database tables, to ArrayList objects, to Enterprise JavaBeans objects. Typically, the only time that you work with the rowset object is when you need to set query parameters. In most cases, you use the data provider object to access and manipulate the data.

Once you have added a data provider to a project, you can bind a component to the data provider by right-clicking the component and choosing Bind to Data. In the Bind to Data dialog box, click the Bind to Data Provider tab to bring it to the front. The Choose a Data Provider drop-down list shows all the project's data providers from which you can select the data provider to bind to the component. After you select the data provider, choose the appropriate data column to be bound to the component. For some components, such as the Drop Down List component, you must choose both a Value field and a Display field.

You use the Query Editor for a rowset object to define the SQL query to use to retrieve the data, as shown in the following figure.

Figure 21: Query Editor
Figure 21: Query Editor
 
Try It
  1. Create a page, make it the start page, and drop a Listbox component onto the page.
  2. In the Runtime window, expand Databases, expand the jdbc node for the TRAVEL database, and expand the Tables node.

  3. Drag the TRIPTYPE node and drop it on the page.

    If TRAVEL database's badge is broken and you cannot expand the database's node, the IDE is not connected to the database. To connect to the TRAVEL database, right-click the databases node in the Runtime window and choose Connect from the pop-up menu. If the Connect dialog box appears, enter travel for the Password, select Remember Password During This Session, and click OK.
  4. Right-click the Listbox component and choose Bind to Data from the pop-up menu.
  5. In the Bind to Data dialog, click the Bind to Data Provider tab, and make sure that tripTypeDataProvider is selected in the drop-down list.
  6. Set the Value Field to TRIPTYPE.TRIPTYPEID (the default selection) and set the Display Field to TRIPTYPE.DESCRIPTION. Click OK.
  7. Run the application to see how the listbox is filled with data from the table.
  8. Expand SessionBean1 in the Outline window and double-click the triptypeRowSet node to open its Query Editor. In the DESCRIPTION row of the grid panel, choose Ascending from the drop-down list in the Sort Type column.
  9. Click the X in the Query Editor's tab to close the Query Editor, and run the program again. Note how the items now appear in alphabetical order.

  10. (Optional) Look in the _init method in the page's Java source code to see the code for associating the data provider with the rowset. This method is folded by default. To unfold the code, click the code fold box that appears next to the left margin.

    Double-click the Session Bean node in the Projects window to open the Java source code for the session bean. Look in the session bean's _init method to see how the rowset code implements the query. Right-click on the data provider and rowset methods, and choose Show Javadoc from the pop-up menu to view the documentation about what the methods do.
  11. (Optional) Choose Help > Javadoc References > Data Provider and choose Help > Javadoc References > RowSet to see the related API.

For More Information

Debugging a Web Application

The IDE has a built-in debugger to help you troubleshoot your programs, as shown in the following figure. You can use it to set breaks and watches, to step through code, and to run until it reaches the code statement that the cursor is on.

You set a breakpoint by clicking in the left margin of the Java Editor. You set a watch by right-clicking a variable or expression choosing New Watch. To run the debugger, choose either Run > Debug Main Project or Run > Run to Cursor from the main menu.

Figure 22: Debugger Window
Figure 22: Debugger Window
 

Tip: Here are some other features that you can use to diagnose and resolve problems:


Try It
  1. Create, or reuse, a start page. Add a Static Text component, set its text property to Hello, and set its id property to helloText.

  2. Add a Button component. Double-click the Button component to access its action method (button1_action) and replace the method's body with the following code:

    Code Sample 1: button1_action Method 
    String oldString = (String) this.helloText.getText();
this.helloText.setText("Good Bye");
String newString = (String) this.helloText.getText();
return null;
  3. Right-click oldString, choose New Watch, and click OK. Do the same for newString. Click in the left margin to set a breakpoint for the first statement in the method's body.
  4. Choose Run > Debug Main Project from the main menu.
  5. When the page displays in the Web Browser, click the button. When the debugger breaks in the button1_action method, click the Watches tab in the Debugger window to see the current value of newString and oldString.
  6. Choose Run > Step Over from the main menu or click the Step Over button in the toolbar. Look in the Watches tab. Step over the code two more times and observe the Value column in the Watches tab.
  7. Explore the Local Variables and Call Stack tabs.
  8. Choose Run > Finish Debugger Session to close the debugger session.

For More Information

Summary



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This page was last modified:  February 26, 2007

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