Monday vhandit #2

Introduction to OpenLDAP directory service

"A directory is a specialized database specially designed for searching and browsing, in addition to supporting basic lookup and update functions"

A directory service can be local, providing a restricted context; or global, providing service to a much broader context. Curlie is a good example of a directory service.

LDAP (Lightweight Directory Access Protocol) is a protocol for accessing directory services, specifically X.500-based directory services.

OpenLDAP is an open-source implementation of LDAP.

Writing system software: code comments

I have read Clean Code (by Uncle Bob) and I thought that I should void comments since the code it explains its implementation itself. That is right but not always true. In this post, the author categorized the comments into 9 types. Only "trivial comments" and "backup comments" are the ones that should be avoided. I myself agree with "writing good comments is harder than writing good code".

How To Become A Hacker

This is an old post, but worth reading. Previously, I used to think that hackers are kind of bad people since they usually are known as someone trying to steal users' accounts, make a system down, etc. But, no! Hackers build stuff. Hackers are heroes to build the Internet and keep it safe for users. I am building myself to become a hacker as well.

And, Hacker News is my most favorite website for my daily updates.

Comments

Avoiding Time-Wasting Pitfalls in Agile Estimation

If you do Scrum at work, you might be very familiar to the estimation in Planning 1 . My PO has once complained to my team that why it took too long for estimating just a story. Wasting time results in the planning timebox is violated. I give you some advice from my experience: Estimation is estimation, not measure. When you read some requirements, you see some risks but you actually don't know how complicated it will be. Don't try to influence the others by explaining how to do it in too detail. Just keep in mind that you know the business domain pertaining to customer needs and estimate how much effort you will spend for it. The effort should be compared to your baseline one that you use for a simple requirement. The bottom line is we do "relative estimation", not absolute estimation. For example, you are asked to estimate the height of a building. Basically, you just need to answer "how many times higher is the build than your height"; you do...

Multiple Inheritance of State and Implementation

Today, I was just curious about why an enum can not extend anything else. I took a look on the Oracle document here , and I found the answer is below: "All enums implicitly extend java.lang.Enum. Because a class can only extend one parent (see Declaring Classes), the Java language does not support multiple inheritance of state (see Multiple Inheritance of State, Implementation, and Type), and therefore an enum cannot extend anything else." I have been learned of it before. But, wait a sec...! Why Java does not support multiple inheritance of state? Since I have worked with other programming languages like C++, I was able to make a class extend some other classes. The short answer is to avoid the issues of multiple inheritance of state . I wonder if other programming languages have these below terms but Java does. Multiple inheritance of state It is the ability to inherit fields from multiple classes. There is a problem and Java avoids it. "For exa...

Strategy Design Pattern

For example, I have a program with an Animal abstract class and two sub-classes Dog and Bird. I want to add new behavior for the class Animal, this is "fly". Now, I face two approaches to solve this issue: 1. Adding an abstract method "fly" into the class Animal. Then, I force the sub-classes should be implemented this method, something like: public abstract class Animal{ //bla bla public abstract void fly(); } public class Bird extends Animal{ //bla bla public void fly(){ System.out.println("Fly high"); } } public class Dog extends Animal{ //bla bla public void fly(){ System.out.println("Cant fly"); } } 2. Creating an interface with method "fly" inside. The same issue to an abstract class, I force the classes these implement this interface should have a method "fly" inside: public interface Flyable{ public void fly(); } public class Bird implements Flyable{ //bla bla public void fly(){ System.out.pr...

Junit - Test fails on French or German string assertion

In my previous post about building a regex to check a text without special characters but allow German and French . I met a problem that the unit test works fine on my machine using Eclipse, but it was fail when running on Jenkins' build job. Here is my test: @Test public void shouldAllowFrenchAndGermanCharacters(){ String source = "ÄäÖöÜüß áÁàÀâÂéÉèÈêÊîÎçÇ"; assertFalse(SpecialCharactersUtils.isExistSpecialCharater(source)); } Production code: public static boolean isExistNotAllowedCharacters(String source){ Pattern regex = Pattern.compile("^[a-zA-Z_0-9_ÄäÖöÜüß áÁàÀâÂéÉèÈêÊîÎçÇ]*$"); Matcher matcher = regex.matcher(source); return !matcher.matches(); } The result likes the following: Failed tests: SpecialCharactersUtilsTest.shouldAllowFrenchAndGermanCharacters:32 null A guy from stackoverflow.com says: "This is probably due to the default encoding used for your Java source files. The ö in the string literal in the J...

MS SQL Server Views

"Creates a virtual table whose contents (columns and rows) are defined by a query. Use this statement to create a view of the data in one or more tables in the database. For example, a view can be used for the following purposes: - To focus, simplify, and customize the perception each user has of the database. - As a security mechanism by allowing users to access data through the view, without granting the users permissions to directly access the underlying base tables. - To provide a backward compatible interface to emulate a table whose schema has changed." [1] Beside that, our team used view in order to improve the performance of our web apps when a database has a very complicated relationship between its tables by using ORM Frameworks such as Hibernate. Example code: --create CREATE VIEW placeholders AS SELECT EMPKEY AS empkey, CONNUMB AS connumb, EMPNBR AS empNbr, ACEEMPN AS empFirstName, ACEEMPFN AS empLastName, EMPNAM AS empFullName, ...

vhandit

Search This Blog