Tutorial Step 5 Processing the Form in Java

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52 Tutorial Step 5 Processing the Form
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In this step of the tutorial we deal with the issues related to the entire form and not just to individual fieldsThe first thing to do is convert the standard HTML form into a Dojo Form widget
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521 Creating a Dojo Form Widget
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We ve already defined a form on the HTML page Now we need to convert it to a Dojo Form widget It is easy enough for us to do now that we re familiar with the general technique for creating Dojo widgetsWe simply add the dojoType attribute to the form element as the following code illustrates (with our required changes in bold)
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52 Tutorial Step 5 Processing the Form
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<form action="/submitjsp" method="get" name="custForm" dojoType="dijitformForm" />
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Of course, we also need to make sure that the Dojo code for the widget is available to the parserWe ll add another require statement to our list
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dojorequire("dijitformForm");
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That s all there is to itWe ve now converted the standard HTML form into a Dojo Form widget
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522 Intercept Form Submission
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The form is now a Dojo widget and possesses some new super powers It gives us the ability to intercept the request when a user clicks the Send button so that we can perform our own processing By specifying a special attribute, we can cause the browser to pass control to a function instead of submitting the request to the serverWe ll set the value of the execute attribute to the name of a function that we will use to handle the form submission
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<form action="/submitjsp" method="get" name="custForm" dojoType="dijitformForm" execute="processForm" />
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We need to create a new function called processForm, and we need a place to put it So we ll create a new file called processFormjs, and we ll include it in our page by using the <script> tag Add the new <script> tag to the current set of <script> tags at the top of the page as shown as follows
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<script type="text/javascript" src="validateUserNamejs"></script> <script type="text/javascript" src="populateCityjs"></script> <script type="text/javascript" src="processFormjs"></script>
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For now, let s just create the stub for the form handler function Create a file called processFormjs and place it in the same directory as our form Following is the code for the stub function
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// Process form function processForm { // Re-validate form fields // Place focus on first invalid field // If all fields are valid then submit form }
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We re now ready to implement the function
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Processing Forms with Dojo
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523 Check That All Form Elements Are Valid
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What should we do in our form handler We need to validate the fields in the form and notify the user by performing the following actions 1 Re-validate each of the fields in the form 2 If an invalid field is found, then display an error message and place the cursor in the field First we need to identify a technique for iterating through the form fields On each field, we ll check to see if the field is validThis can be easily accomplished by calling the isValid() method on the form elementThis method will return a true if the field is valid or a false otherwise Iteration should stop on the first field that is not valid, and we should display an error message and place focus on that field Displaying an error message turns out to be something that happens automatically Simply by calling the isValid() method on the element, the message text specified in the invalidMessage message attribute in the elements tag will appear Placing the field in focus is accomplished by executing the focus() method on the element We ve now walked through the necessary code for implementing the form validation Let s see what it looks like altogether in the following code snippet Our changes to the function are shown in bold
// Process form function processForm { // Re-validate form fields var custForm = dijitbyId( custForm ); var firstInvalidWidget = null; dojoevery(custFormgetDescendants(), function(widget){ firstInvalidWidget = widget; return !widgetisValid || widgetisValid(); }); if (firstInvalidWidget != null) { // set focus to first field with an error firstInvalidWidgetfocus(); } }