Integrate ZK with JSR 303: Bean Validation

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DocumentationSmall Talks2011MayIntegrate ZK with JSR 303: Bean Validation
Integrate ZK with JSR 303: Bean Validation
Author
Simon Pai, Engineer, Potix Corporation
Date
May 20, 2011
Version
ZK 5.0.7

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What is JSR 303: Bean Validation

JSR 303 is a standard designed for working on property validation in Java beans. In brief, the constraints of a bean property are specified by Java annotations, and validation against the bean can be invoked by API.

A known implementation of JSR 303 is Hibernate Validator. In the following section we will use Hibernate Validator to demonstrate how to utilize this tool in a ZK application.


 

How to use Bean Validation

The usage of this tool is quite straightforward: You just need to specify property constraints and invoke validation.

Bean

public class User {
	
	@NotEmpty(message = "Last name can not be null.")
	private String _lastName;
	
	@Past(message = "Birth date must be in the past.")
	private Date _birthDate;
	
}

Invoke Validation

// prepare for Validator
ValidatorFactory vf = Validation.buildDefaultValidatorFactory();
Validator validator = vf.getValidator();

// suppose we have a bean of User like this:
User user = new User();
user.setLastName(""); // wrong, should not be empty

// invoke validation, which will return a set of violations to the constraints
Set<ConstraintViolation<User>> violations = validator.validate(user);
for(ConstraintViolation<User> v : violations)
	System.out.println(v.getMessage()); // will print out: "Last name can not be null."


 

How to use Bean Validation in your ZK application

The following is a step-by-step guide to show a simple integration of JSR 303 with data binding.

Required Jars

The following is a sample dependency list for setting up Hibernate Validator to work with data binding: 

	<!-- required for data binding -->
	<dependency>
		<groupId>org.zkoss.zk</groupId>
		<artifactId>zkplus</artifactId>
		<version>5.0.7</version>
	</dependency>
	
	<dependency>
		<groupId>org.hibernate</groupId>
		<artifactId>hibernate-validator</artifactId>
		<version>4.0.2.GA</version>
	</dependency>
	<dependency>
		<groupId>org.slf4j</groupId>
		<artifactId>slf4j-api</artifactId>
		<version>1.6.1</version>
	</dependency>
	<dependency>
		<groupId>org.slf4j</groupId>
		<artifactId>slf4j-log4j12</artifactId>
		<version>1.6.1</version>
	</dependency>

Hibernate Validator assumes the use of log4j to log information. You can use any log4j implementation you prefer.

 

Setup

Under project classpath, you need to prepare

  1. log4j.properties
  2. META-INF/validation.xml

Here are examples of minimal settings in these files:

log4j.properties 

log4j.rootLogger=info, stdout
log4j.appender.stdout=org.apache.log4j.ConsoleAppender
log4j.appender.stdout.layout=org.apache.log4j.PatternLayout
log4j.appender.stdout.layout.ConversionPattern=%5p [%t] (%F:%L) - %m%n

META-INF/validation.xml 

<?xml version="1.0" encoding="UTF-8"?>
<validation-config
	xmlns="http://jboss.org/xml/ns/javax/validation/configuration"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://jboss.org/xml/ns/javax/validation/configuration">
	<default-provider>org.hibernate.validator.HibernateValidator</default-provider>
	<message-interpolator>org.hibernate.validator.engine.ResourceBundleMessageInterpolator</message-interpolator>
	<traversable-resolver>org.hibernate.validator.engine.resolver.DefaultTraversableResolver</traversable-resolver>
	<constraint-validator-factory>org.hibernate.validator.engine.ConstraintValidatorFactoryImpl</constraint-validator-factory>
</validation-config>

You can customize the setting depending on your requirement.

 

Working with data binding

Upon the validation phase of data binding, you can use the JSR 303 Validator to verify the value against the constraints.

For example:

index.zul 

<?page title="Bean Validation" ?>
<?init class="org.zkoss.zkplus.databind.AnnotateDataBinderInit" ?>
<zk>
	<style>
		.errmsg {
			color: red;
			font-weight: bold;
		}
	</style>
	<window id="win" apply="org.zkoss.demo.DemoController">
		<grid width="500px">
			<columns>
				<column width="100px" />
				<column width="150px" />
				<column width="250px" />
			</columns>
			<rows>
				<row>
					First Name
					<textbox id="firstNameBox" value="@{win$composer.user.firstName, save-when='submit.onClick'}" />
					<label id="firstNameErr" sclass="errmsg" />
				</row>
				<row>
					Last Name
					<textbox id="lastNameBox" value="@{win$composer.user.lastName, save-when='submit.onClick'}" />
					<label id="lastNameErr" sclass="errmsg" />
				</row>
				<row>
					Birth Date
					<datebox id="birthDateBox" value="@{win$composer.user.birthDate, save-when='submit.onClick'}" />
					<label id="birthDateErr" sclass="errmsg" />
				</row>
			</rows>
		</grid>
		<button id="submit" label="Submit" />
	</window>
</zk>

DemoController.java 

public class DemoController extends GenericForwardComposer {
	
	private final Logger _logger = LoggerFactory.getLogger(this.getClass());
	private final Validator _validator = Validation.buildDefaultValidatorFactory().getValidator();
	private User _user = UserSamples.getUser();
	
	private Textbox firstNameBox, lastNameBox;
	private Datebox birthDateBox;
	private Label firstNameErr, lastNameErr, birthDateErr;
	
	// getter //
	public User getUser() {
		return _user;
	}
	
	// event handler //
	public void onBindingValidate$submit(Event event) {
		
		// collect violations
		List<ConstraintViolation<User>> violations = new ArrayList<ConstraintViolation<User>>();
		violations.addAll(validate(User.class, "_firstName", firstNameBox.getValue(), firstNameErr));
		violations.addAll(validate(User.class, "_lastName", lastNameBox.getValue(), lastNameErr));
		violations.addAll(validate(User.class, "_birthDate", birthDateBox.getValue(), birthDateErr));
		
		if(!violations.isEmpty()) {
			String errmsg = null;
			for(ConstraintViolation<User> v : violations) {
				String s = v.getMessage() + " (Invalid Value: " + v.getInvalidValue() + ")";
				// grab the first violation message and show it on Messagebox
				if(errmsg == null)
					errmsg = s;
				// log here
				_logger.info(s);
			}
			// this will interrupt binding value to bean, so bean is not modified
			throw new WrongValueException(errmsg); 
		}
		_logger.info("Data saved to user: " + _user.getFullDesc());
	}
	
	// helper //
	private <T> Set<ConstraintViolation<T>> validate(Class<T> clazz, String fieldName, Object value, Label errLabel){
		// use Validator to check the value
		Set<ConstraintViolation<T>> violations = _validator.validateValue(clazz, fieldName, value);
		// show error message (only for the first violation) on UI, if any
		errLabel.setValue(violations.isEmpty() ? "" : violations.iterator().next().getMessage());
		return violations;
	}
	
}

Demo


 

References


 

Comments



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