Introduction to Node.js

Introduction to Node.js 

Node.js is a JavaScript runtime built on Chrome's V8 JavaScript engine. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient. Node.js' package ecosystem, npm, is the largest ecosystem of open source libraries in the world.

Node.js is an open source, cross-platform runtime environment for developing server-side and networking applications. Node.js applications are written in JavaScript, and can be run within the Node.js runtime on OS X, Microsoft Windows, and Linux.

Features of Node.js

Following are some of the important features of Node.js 

• Asynchronous and Event Driven − All APIs of Node.js library are asynchronous, that is, non-blocking. It means a Node.js based server never waits for an API to return data. The server moves to the next API after calling it and a notification mechanism of Events of Node.js helps the server to get a response from the previous API call.
• Fast − Being built on Google Chrome's V8 JavaScript Engine, Node.js library is very fast in code execution.
• Single Threaded and Highly Scalable − Node.js uses a single threaded model with event looping. Event mechanism helps the server to respond in a non-blocking way and makes the server highly scalable. Node.js uses a single threaded program and the same program can provide service to a much larger number of requests than traditional servers like Apache HTTP Server.
• No Buffering − Node.js applications never buffer any data. These applications simply output the data in chunks.
• License − Node.js open source and is released under the MIT license

Where to Use Node.js

Node.js can be used in the following 

• I/O bound Applications
• Data Streaming Applications
• Data Intensive Real-time Applications (DIRT)
• JSON APIs based Applications
• Single Page Applications

3 COMPTIA CERTIFICATION IN DEMAND

3 COMPTIA CERTIFICATION IN DEMAND

In 2016, more than 5.2 million IT jobs contributed to the U.S. economy with an additional 2 million new job postings throughout the year. Peruse those posts, and you’ll find three CompTIA certifications specifically cited as job requirements in thousands of listings: CompTIA Security+, CompTIA A+ and CompTIA Network+.

CompTIA Security+

 CompTIA Security+ is the certification globally trusted to validate foundational, vendor-neutral IT security knowledge and skills. As a benchmark for best practices in IT security, this certification covers the essential principles for network security and risk management – making it an important stepping stone of an IT security career.

In response to CompTIA’s IT Career Insights Survey, 93 percent of IT professionals said they regularly work with security and cyber security technology. Even more importantly, according to CompTIA’s Common IT Employability Skills study, 62 percent of hiring managers in the United States indicated that candidates “must have” these skills to be considered for the job. Hands-on and strategic involvement with security technology makes CompTIA Security+ certification, as well as the forthcoming CompTIA Cybersecurity Analyst (CSA+) certification, a vital part of an IT career, whether you want to enhance your skills for an existing job or apply for a new one.

CompTIA A+

It’s a known fact that IT training helps employees advance in their careers. The CompTIA A+ certification is perfect for individuals new to the field and IT professionals in transition. Because it tests a candidate’s knowledge on all fields of information technology and not on one particular domain, the CompTIA A+ certification is typically given more weight than other vendor certifications.

More than 23,500 job postings in 2016 required applicants to have CompTIA A+ certification. Validating the IT skills required by the most common hardware, software and operating systems while remaining vendor neutral, CompTIA A+ has long been a  foundational certification for IT professionals.

CompTIA Network+

Finally, more than 18,000 jobs posted in 2016 required CompTIA Network+ certification, a vendor-neutral, worldwide networking accreditation that validates an IT professional’s ability to design, configure, manage and troubleshoot both wired and wireless networks. Considering 92 percent of IT professionals in the United States worked with this technology in 2016, CompTIA Network+ is a valuable certification for almost any job applicant.

Although most online job postings do not specifically list IT certification requirements, employers know IT pros with CompTIA certifications are more capable of succeeding in their careers.

When accreditations are preferred, CompTIA Security+ is the fourth-most-requested certification in job postings, behind Certified Information Systems Security Professional, Project Management Professional, and Cisco IT certifications. CompTIA A+ and Network+ ranked 8th and 11th, respectively, according to the Burning Glass Technologies Labor Insights study.

Clearly, CompTIA professional certifications set job candidates apart in a competitive and constantly growing job market—one the U.S. Bureau of Labor Statistics expects to grow 12 percent in the network and computer systems industry over the next seven years.

Domain Model in Hibernate

Domain Model in Hibernate

The application domain model is the central character in an ORM. Domain Model are the classes we would be mapping in our application. These domain model classes needs to follow the Plain Old Java Object (POJO) / JavaBean programming model in order to make Hibernate works best.

Applications using Hibernate uses its proprietary XML mapping file format for this purpose. With JPA, most of this information is now defined in a way that is portable across ORM/JPA providers using annotations and/or standardized XML format.

Mapping types

Hibernate understands both the Java and JDBC representations of application data. The ability to read/write this data from/to the database is the function of a Hibernate type. A type, is an implementation of the org.hibernate.type.Type interface.

To help understand the type categorizations, we take an example of a simple table and domain model that we wish to map.

create table ContactInfo (     id integer not null,     firstName varchar(255),     lastName varchar(255),     middleName varchar(255),     notes varchar(255),     starred boolean not null,     website varchar(255),     primary key (id) )

@Entity(name = "ContactInfo") public static class ContactInfo {     @Id     private Integer id;     private Name name;     private String notes;     private URL website;     private boolean starred;     //Getters and setters }

@Embeddable public class Name {     private String firstName;     private String middleName;     private String lastName;     // getters and setters }

In the broadest sense, Hibernate categorizes types into two groups:

• Value types
• Entity types

Value types

A value type is a piece of data that does not define its own lifecycle. It is, owned by an entity, which defines its lifecycle. All the state of an entity is made up entirely of value types. These state fields or JavaBean properties are termed persistent attributes. The persistent attributes of the ContactInfo class are value types.

Value types are further classified into three sub-categories:

Basic types

In mapping the ContactInfo table, all attributes except for name would be basic types.

Embeddable types

The name attribute is an example of an embeddable type.

Collection types

Collection types are also a distinct category among value types.

Entity types

Entities, exist independently of other objects whereas values do not. Entities are domain model classes which correlate to rows in a database table, using a unique identifier. Entities exist independently and define their own lifecycle. The ContactInfo class is an example of an entity. 

Hibernate Architecture Overview

Hibernate Architecture Overview

Hibernate, is an ORM solution, which sits between the Java application data access layer and the Relational Database. The Java application makes use of the Hibernate APIs to load, store, query, etc its domain data. Hibernate implements the Java Persistence API (JPA) specifications. 

SessionFactory (org.hibernate.SessionFactory)

SessionFactory  is a thread-safe representation of the mapping of the application domain model to a database. SessionFactory acts as a factory for org.hibernate.Session instances. The EntityManagerFactory is the JPA equivalent of a SessionFactory.

A SessionFactory is very expensive to create, so, for any given database, the application should have only one associated SessionFactory. The SessionFactory maintains services that Hibernate uses across all Sessions such as second level caches, connection pools, transaction system integrations, etc.

Session (org.hibernate.Session)

A single-threaded, short-lived object conceptually modeling a "Unit of Work". In JPA nomenclature, the Session is represented by an EntityManager.

The Hibernate Session wraps a JDBC java.sql.Connection and acts as a factory for org.hibernate.Transaction instances. 

Transaction (org.hibernate.Transaction)

A single-threaded, short-lived object used by the application to demarcate individual physical transaction boundaries. 

Spring AOP – Advice

Spring AOP – Advice

Spring AOP Advice is the action taken by an aspect at a particular join point. Different types of advice include 

• Around advice
• Before advice
• After advice

Many AOP frameworks, including Spring, model an advice as an interceptor, maintaining a chain of interceptors around the join point.

Types of advice:

• Before advice: Advice that executes before a join point, but which does not have the ability to prevent execution flow proceeding to the join point.
  
  
• After returning advice: Advice to be executed after a join point completes normally.
  
  
• After throwing advice: Advice to be executed if a method exits by throwing an exception.
  
  
• After (finally) advice: Advice to be executed regardless of the means by which a join point exits, normal or exceptional return.
  
  
• Around advice: Advice that surrounds a join point such as a method invocation. This is the most powerful kind of advice. Around advice can perform custom behavior before and after the method invocation. It is also responsible for choosing whether to proceed to the join point or to shortcut the advised method execution by returning its own return value or throwing an exception.