my journey to use a validation framework

My Journey to Validate

Muhammad Saqib [email protected]

1.To share my experience(thought process) of choosing a Validator framework.

2.To deliver basic knowledge of my chosen tool.

Basic Goals

Muhammad Saqib Sarwar [email protected]

• New Change Arrived in current project

•DB Fields From 11 to 137•Account [54 Fields] Customer [74 Fields] Customer_account[9 Fields]•So Big Change on Message Validations• For: Create an Account Message

•Total: 46 Fields•14 Mandatory Fields

•13 have length checks•5 have pattern checks

•others if exist should be validated too ….

How I felt the need ?

Simply Means a huge collection

of if-else statements


•1st I written required if-else statements.

•BUT Soon

I Found

Myself

In huge

Mess ..

How I felt the need ?


•Asked the BOSS•Google “how to avoid too many if-else”•Placed Question on JavaRanch•Consulted with Colleagues

Surprised !•Business layer validation frameworks

exist in java world•I only know them as presentation

layer validator.

What I did next …


•There are many available like•Spring’s own validation•Commons Validator•JaValid•Hibernate Validator (My Chosed One)•And many more …

•Now the Question is

Which one to use ?•So I Sorted Few Priorities

•It should Solves the problem•It should have Short learning curve

Which one to use ..?


•First I looked at Validation in Spring 2.0.8 (as we already using it)•Two Parts in the Validation Package

•Validator Interface Implementation•DataBinder

•Primarily used in Spring-MVC framework•Have to implement complete validation logic in validate() method•Separate Validator for each entity•Not fallow any standard (like few emerging in the market)

Validation in Spring 2.0.8


•Validation of JavaBeans based on an xml file•Provides two distinct sets of functionality

1. A configurable (typically XML) validation engine

2. Reusable "primitive" validation methods

Steps– Create XML file– Instantiate Validator class

(org.apache.commons.validator.Validator)

– Add Resources (JavaBean,Locale)– Call Validator’s validate method– Evaluate Results

Commons Validator


•Heavily depends on XML•Manual evaluation of errors []•No default error messages•Lengthy validation code•Fallow No Standard

Commons Validator


•I want something easier than XML so searched for Annotation based bean validation frameworks and found JaValid.org•It is an Annotations based bean validation framework•Could be used standalone•Provides full integration with Spring, JSF, Facelets and DB•Customizable and Extensible•Built in annotations for basic validations•Well elaborated documentation•Well documented source code


1. Annotate Bean’s Properties/(getter Methods)

2. Instantiate Validator implementation

3. Pass bean instance to Validator

4. Validator returns List<ValidationMessage>

Steps to use JaValid


• only few built in annotation constraints• building new constraints are little lengthier• use XML configuration file to know about annotation classes and their related validator classes.• error messages are hard coded• ValidationMessage object is not customizable• does not fallow any standard for validation

Few disadvantages of JaValid !

Good Solution but not as simple and easy as hibernate validator


•Annotations based bean validation framework•Aims to provide implementation of the emerging standard (JSR - 303 Bean Validation)•Purely intended for multi-layered data validation•Constraints are expressed in a single place (model)•Not limited to use with hibernate

•Can be used any where in application•Can be used with any java persistence provider

Hibernate Validator


•Decent Collection of Built in Constraints

•@Length (min=,max=)•@Max(value=)•@Min(value=)•@NotNull•@NotEmpty•@Past•@Future•@Size(min=, max=)

Hibernate Validator

•@Pattern(regex="regexp”, flag=)

•@Range(min=, max=)•@AssertFalse•@AssertTrue•@Valid•@Email•@CreditCardNumber•@Digits•@EAN•Few more …


•Error Messages• Validator returns array of InvalidValue • InvalidValue contains constraint violation information (bean, name, path, value etc)• It also contains Error Description Message• we can override Error Messages

• By Creating Own ValidatorMessages.properties• we can embed constraint parameters in messages

Hibernate Validator


Sample Code [Annotated Account Bean]

/*--------- Simple Bean ---------------*/

public class Account

{

@NotEmpty

@Length(min=10,max=100)

private String accountTitle;

@NotEmpty

private String processingCode;

// regular getters and setters methods

}

Hibernate Validator


Validation Code:

Account account = new Account();

account.setAccountTitle("Mobex Ltd");

ClassValidator<Account> accountValidator = new ClassValidator<Account>(Account.class);

InvalidValue[] validationMessages = accountValidator.getInvalidValues(account);

for(InvalidValue msg:validationMessages)

System.out.println(msg.getPropertyPath()+"-"+msg.getMessage());

OUTPUT

accountTitle-length must be between 10 and 100

processingCode-may not be null or empty

Hibernate Validator



{

@NotEmpty



@NotEmpty



}

Hibernate Validator



{

@NotEmpty



@NotEmpty

@ProcessingCode(code=IProcessingCode. CHECK_BALANCE)



}

Hibernate Validator


Steps For Writing Our Own Constraints1. Constraint Descriptor (annotation)

2. Constraint Validator (implementation class)

Hibernate Validator


1. Constraint Descriptor (annotation)

@Documented

@ValidatorClass(ProcessingCodeValidator.class)

@Target({METHOD, FIELD})

@Retention(RUNTIME)

public @interface ProcessingCode {

String code();

String message() default "Invalid Processing Code";

}

Hibernate Validator

org.hibernate.validator.ValidatorClass


2. Constraint Validator Implementation Class

public class ProcessingCodeValidator implements Serializable, Validator<ProcessingCode> {

private static final long serialVersionUID = 1146464976464879846L;

private String code;

public void initialize(ProcessingCode parameter) {

code = parameter.code();

}

public boolean isValid(Object value) {

if ( value == null )return false;

if (!( value instanceof String)) return false;

String str = (String) value;

if(str.equals(code)) return true;

return false;

}

}


Account account = new Account();

account.setAccountTitle("Mobex Ltd");

account.setProcessingCode(IProcessingCode.CREDIT_ACCOUNT);

ClassValidator<Account> accountValidator = new ClassValidator<Account>(Account.class);

InvalidValue[] validationMessages = accountValidator.getInvalidValues(account);

for(InvalidValue msg:validationMessages)

System.out.println(msg.getPropertyPath()+"-"+msg.getMessage());

OUTPUT

accountTitle-length must be between 10 and 100

processingCode-Invalid Processing Code

Hibernate Validator


Using the Validator1. Database Schema-Level Validation

2. ORM Integration1. Hibernate event-based validation

– PreInsertEvent– PreUpdateEvent

2. Java Persistence event-based validation

3. Application-level validation

4. Presentation layer validation

Hibernate Validator


Benifits• simplicity

•Avoid XML based configuration•Could be learned in short time•Could be implemented in minutes

•Constraints annotation could be applied to•Property•Getter method•Bean Class

•Aims to Fallows a developing standard (JSR-303 Bean Validation)•Fallows DRY Principle [multi-layered validation]• etc [many more to explore]


•We Use Validation Framework•To avoid series of messy if-else statements•To Increase code readability•To make code easily maintainable•To avoid writing validation on multiple layers•To increase productivity

Summary


my journey to use a validation framework

Technology