Alejandro Gervasio

Alejandro Gervasio is a senior System Analyst from Argentina who has been involved in software development since the mid-80's. He has more than 12 years of experience in PHP development, 10 years in Java Programming, Object-Oriented Design, and most of the client-side technologies available out there.

Alejandro's articles

Using Java Bean Validation for Method Parameters and Return Values

Java

By Alejandro Gervasio, June 01, 2017

Validate arguments and return values of methods and constructors with Bean Validation's ExecutableValidator and automate it with Java EE interceptors.

Three Design Patterns That Use Inversion of Control

Java

By Alejandro Gervasio, April 24, 2017

Inversion of control is not just dependency injection - the observer and template method patterns use it as well. Study all three to become an IoC expert!

Validate Object Graphs with Java Bean Validation’s @Valid Annotation

Java

By Alejandro Gervasio, April 19, 2017

Use Java Bean Validation's @Valid Annotation for validating entire object graphs with one method call.

Java Bean Validation’s validateProperty() and validateValue() in Three Minutes

Java

By Alejandro Gervasio, April 12, 2017

Use the Java Bean Validation methods validateValue() and validateProperty() to independently check fields of a target class or even their potential values.

Using CDI/Weld to Inject JPA/Hibernate Entity Managers

Java

By Alejandro Gervasio, January 30, 2017

A tutorial on how to use Contexts and Dependency Injection (CDI) / Weld and Hibernate in the development of a full-blown JPA application.

Introduction to Contexts and Dependency Injection (CDI)

Java

By Alejandro Gervasio, December 19, 2016

A tutorial on how to use Contexts and Dependency Injection (CDI) and Weld in Java SE, covering core features like annotations, qualifiers, and producers.

Effective Domain Model Validation with Hibernate Validator

Java

By Alejandro Gervasio, October 27, 2016

A hands-on guide to domain model validation with the Java Beans Validation standard (JSR 303) and Hibernate Validator (Apache BVal is very similar.)

Building a Web App with Java Servlets

Java

By Alejandro Gervasio, October 10, 2016

This tutorial builds a simple Java web application with Java's Servlet API. It shows how to set the project up, create views / controllers, and deploy.

A Hibernate Introduction – Persisting Java Objects the Easy Way

Java

By Alejandro Gervasio, September 22, 2016

JPA/Hibernate is a common approach to persistence in Java. This tutorial creates a simple CRUD app using Hibernate's EntityManager and the DAO pattern.

Alejandro's articles

Using Java Bean Validation for Method Parameters and Return Values

Three Design Patterns That Use Inversion of Control

Validate Object Graphs with Java Bean Validation’s @Valid Annotation

Java Bean Validation’s validateProperty() and validateValue() in Three Minutes

Using CDI/Weld to Inject JPA/Hibernate Entity Managers

Introduction to Contexts and Dependency Injection (CDI)

Effective Domain Model Validation with Hibernate Validator

Building a Web App with Java Servlets

A Hibernate Introduction – Persisting Java Objects the Easy Way

Inversion of Control – The Hollywood Principle

The Single Responsibility Principle

The Open/Closed Principle

Introduction to the Law of Demeter

The Null Object Pattern – Polymorphism in Domain Models

Constructors and Breaking the Liskov Substitution Principle

The Template Method Pattern – Override Strategy Logic

Subtype Polymorphism – Swapping Implementation at Runtime

Patterns for Flexible View Handling, Part 2 – Using Decorators

Patterns for Flexible View Handling, Part 1 – Working with Composites

An Introduction to the Front Controller Pattern, Part 2

An Introduction to the Front Controller Pattern, Part 1

Reusing Implementation – a Walk-through of Inheritance, Composition, and Delegation

The Layer Supertype Pattern: Encapsulating Common Implementation in Multi-Tiered Systems

Managing Class Dependencies: An Introduction to Dependency Injection, Service Locators, and Factories, Part 2

Managing Class Dependencies: An Introduction to Dependency Injection, Service Locators, and Factories, Part 1

Decoupling Interfaces from Implementation – Using Separated Interfaces

Implementing a Unit of Work – Handling Domain Objects through a Transactional Model

Handling Collections of Aggregate Roots – the Repository Pattern

The Dependency Inversion Principle

An Intro to Virtual Proxies, Part 2