Java EE – Learn With Somayeh

ASP .Net, C#, Core Java, Design Pattern, Framework, Inversion of Control, Java EE, Library

Library vs Framework

Posted on January 23, 2020 by learnwithsomayeh

The key difference between Library and Framework is in IoC (Inversion of Control)

by using a feature from a Library you are in control.
The Framework include some abstract design with built-in behaviors. Control is inverted and the framework calls you; framework code will call the code at those various points that behavior has inserted. The Hollywood principle: Don’t call Us, we’ll call You.

Library	Framework
A certain set of reusable functions of an application (mostly organized into classes)	As a skeleton of an application
A collection of class definitions	A collection of patterns
You call the library APIs in your code	A framework calls your code
The control is always with you	The control in with the framework if you’re using it
Libraries meant to do some specific tasks only	Framework is a predefined design
You need to scaffold your project manually	Super easy to scaffold

Groovy, Java EE, JSON

Groovy String comparison in WorkFusion

Posted on July 12, 2019July 12, 2019 by learnwithsomayeh

For instance I have this variable of json expression:

<var-def name=”successFlag”>
<json expression =”$….Response…..SuccessFlag”>
<var name=”HTTP_RESPONSE” />
</json>
</var-def>

to compare it with for an if else condition case, I need to create a boolean variable then put it in the condition; this was really tricky to use, I tried equals, == and some converting ones but this one works like a piece of cake:

then:

<case>
<if condition=”${eduSuccess.equals(‘true’)}”>
.

</if>

<else>

</else>

</case>

Core Java, Groovy, Java EE

Groovy vs Java

Posted on April 1, 2019 by learnwithsomayeh

	Java	Groovy
Access modifier (by default)	package	public
getters and setters	Need to provide for fields	Are automatically generated for class members
Utility methods	System.out.println	println
Support substitution		Can print dynamic content without string concatation Println(“Hello $name !”)
Specifying type definition		Instead use keyword def Mandatory for methods, optional for method arguments
Using semicolons	Every statements end with semicolon	optional
main method	To make a class executable	Don’t need
Initializing String arrays, static arrays	Curly braces { “abc”, “dfg”}	Square brackets [“abc”, “dfg”]
autoboxing/unboxing/conversion of primitives	yes	No, everything is Object and uses only Objects
Inner static classes	yes	no
Anonymous classes	yes	no

Core Java, Interface, Java EE, Object Oriented Programming

Functional Interface vs Marker Interface

Posted on January 8, 2019January 15, 2019 by learnwithsomayeh

a Marker interface doesn’t have any methods or fields declaration (an empty interface) such as “Serializable” or “Cloneable”.

a Functional Interface is an interface with just one abstract method declared in it such as Runnable interface that only has run() method.

Core Java, Interface, Java EE, Object Oriented Programming

Iterator

Posted on November 14, 2018January 15, 2019 by learnwithsomayeh

An “interface” to iterate through and each and every element of a list (it’s not a class).

Java EE, JDBC

Statement vs. PreparedStatement in JDBC

Posted on July 14, 2016July 14, 2016 by learnwithsomayeh

Statement	PreparedStatement
for executing static SQL statements	execute dynamic queries with parameter inputs
use String Concatenation to create the query and it can’t accept input parameters	Use setter methods to set the input parameters for the query
Suitable for DDL	Suitable for DML
Slower	Faster
	Prevent SQL Injection attacks

AOP, Java EE, Spring

AOP Concepts

Posted on June 21, 2016June 21, 2016 by learnwithsomayeh

Joinpoint	A specific point in the code, every method in every class is a Joinpoint.
Pointcut	A collection of one or more Joinpoints, for example all the methods of a class.
Advice	The implementation of crosscutting concern, it means what do I want to do with crosscutting concern (Before, Around, After).
Aspect	What crosscutting concern do I execute (=Advice) at which location (=Pointcut); in other words what do I want to do, where do I want to do it in the code. –> advice + pointcut
Weave	The advice code together + Target code at corresponding Pointcuts such that we get the correct execution; it means different methods together with right sequence.

And this would be an example how we can write a Pointcut:

poincut

App-server, Java EE, Tomcat, Uncategorized, Web-Server

Application Server vs. Web Server

Posted on June 10, 2016June 10, 2016 by learnwithsomayeh

This chart* perfectly captures different features of App Servers versus Web Servers:

	Application Server	Web Server
What is it?	A server that exposes business logic to client applications through various protocols including HTTP.	A server that handles HTTP protocol.
Job	Application server is used to serve web based applications and enterprise based applications(i.e servlets, jsps and ejbs…). Application servers may contain a web server internally.	Web server is used to serve web based applications.(i.e servlets and jsps)
Functions	To deliver various applications to another device, it allows everyone in the network to run software off of the same machine.	Keeping HTML, PHP, ASP, etc files available for the web browsers to view when a user accesses the site on the web, handles HTTP requests from clients.
Supports	distributed transaction and EJB’s	Servlets and JSP
Resource utilization	High	Low

Question: Apache Tomcat is a Web Server or an Application Server?

Answer: Tomcat is a web server (can handle HTTP requests/responses) and web container (implements Java Servlet API, also called servletcontainer) in one. Some may call it an application server, but it is definitely not an fullfledged Java EE application server (it does not implement the whole Java EE API).**

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* source: http://www.diffen.com/difference/Application_Server_vs_Web_Server

**http://stackoverflow.com/questions/2469949/tomcat-is-web-server-or-application-server