BeansBindingInExamplesPart2

Introduction

Today we will walk through acris-binding showcase where you can learn how to create bound form with validation support. For validation related stuff we will use JSR-303 annotations and gwt-validation project which implements it.

In three (+1 optional) steps you get a form with validation!

Setup

Let's suppose (and we already have them) two POJOs: SimpleBean and Company

To be able to use them for binding we need to get wrappers for them. Because we are smart and don't want to write boilerplate code we use acris-binding for that purpose.

As a first step we create bean wrappers either by using annotation @BeanWrapper (or any other) or by creating bean wrapper interface by hand. The implementation of the bean wrapper interface is left for BeanWrapperGenerator class.

To be able to use acris-binding with validation we need to extend our module configuration to contain not only bean wrapper generator but also a generator that connects validator generator and bean wrapper generator together - for that purpose we have validator delegate generator. You can find it in ValidatorDelegateGenerator class.

Necessary configuration can be found in Showcase.gwt.xml:

	<generate-with
		class="sk.seges.acris.binding.rebind.bean.BeanWrapperGenerator">
		<any>
			<when-type-assignable
				class="sk.seges.acris.binding.client.samples.mocks.SimpleBeanBeanWrapper" />
			<when-type-assignable
				class="sk.seges.acris.binding.client.samples.mocks.CompanyBeanWrapper" />
		</any>
	</generate-with>

	<generate-with
		class="sk.seges.acris.binding.rebind.binding.ValidatorDelegateGenerator">
		<any>
			<when-type-assignable
				class="sk.seges.acris.binding.client.samples.mocks.SimpleBeanBeanWrapper" />
			<when-type-assignable
				class="sk.seges.acris.binding.client.samples.mocks.CompanyBeanWrapper" />
		</any>
	</generate-with>

As you can see when we hit e.g. SimpleBeanBeanWrapper class with GWT.create we will generate implementation of the bean wrapper + validator implementation for SimpleBean bean + validation delegate class that binds these two together in one class as a result.

Extend the form binding

To let acris-binding know we have bound form we use @BindingFieldsBase annotation. By simply adding two other parameters we get the form extended with validation support:

• validationStrategy = ValidationStrategy.ON_SUBMIT
• (optional) validationHighlighter = ExampleHighlighter.class

Feel free to look into showcase example SimpleForm, it looks like this:

@BindingFieldsBase(updateStrategy=UpdateStrategy.READ_WRITE,validationStrategy=ValidationStrategy.ON_SUBMIT, validationHighlighter = ExampleHighlighter.class)
public class SimpleForm extends StandardFormBase implements IBeanBindingHolder<SimpleBean> {

... in application bind them

Finally we can validate the form by clicking Submit button. Our click handler looks like this:

		submit.addClickHandler(new ClickHandler() {
			@Override
			public void onClick(ClickEvent event) {
				if(selectedButton != null) {
					selectedButton.setText(simpleForm.getBean().getName());
				}
				
				IValidator<SimpleBean> validator = GWT.create(SimpleBeanBeanWrapper.class);
				Set<InvalidConstraint<SimpleBean>> constraints = validator.validate(simpleForm.getBean());
				ValidationMediator.highlightConstraints(simpleForm, constraints);
			}
		});

Here we just receive a bean from the form simpleForm.getBean() and execute validation. As a result we get validation constraints which can be highlighted by calling: ValidationMediator.highlightConstraints

Example highlighter

Maybe you noticed optional attribute in the form binding annotation. Yes, its purpose is to choose one lovely component responsible for highlighting invalid constraints - usually by changing a color or showing a dialog.

For the purpose of the showcase we have one example highlighter.