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.

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The HelloWorld example of JSF 2.2 with Myfaces

I just did by myself create a very simple app "HelloWorld" of JSF 2.2 with a concrete implementation Myfaces that we can use it later on for our further JSF trying out. I attached the source code link at the end part. Just follow these steps below: 1. Create a Maven project in Eclipse (Kepler) with a simple Java web application archetype "maven-archetype-webapp". Maven should be the best choice for managing the dependencies , so far. JSF is a web framework that is the reason why I chose the mentioned archetype for my example. 2. Import dependencies for JSF implementation - Myfaces (v2.2.10) into file pom.xml . The following code that is easy to find from http://mvnrepository.com/ with key words "myfaces". <dependency> <groupId>org.apache.myfaces.core</groupId> <artifactId>myfaces-api</artifactId> <version>2.2.10</version> </dependency> <dependency> <groupId>org.apache.myfaces.core<...

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...

Google I/O 2017 Notes

WOW! How meaningful this below video explains about the name of "I/O". Sundar Pichai talked a lot of Machine Learning Machine Learning is a very hot trend these days. Google uses it for their products. Google Assistant: Easily booking an online meal by talking with Google Assistant like a staff of partners, for example. Google Home: Hands-free calling. Google Photos: sharing suggestion, shared library, photo books and google lens. Youtube: 360 degree video, live stream. Kotlin became an official programming language for Android https://kotlinlang.org I'm on the way to Kotlin! ^^ Reference: [1]. https://www.youtube.com/watch?v=Y2VF8tmLFHw

Styling Sort Icons Using Font Awesome for Primefaces' Data Table

So far, Primefaces has used image sprites for displaying the sort icons. This leads to a problem if we want to make a different style for these icons; for example, I would make the icon "arrow up" more blurry at the first time the table loading because I want to highlight the icon "arrow down". I found a way that I can replace these icons with Font Awesome icons. We will use "CSS Pseudo-classes" to achieve it. The hardest thing here is that we should handle displaying icons in different cases. There is a case both "arrow up" and "arrow down" showing and other case is only one of these icons is shown. .ui-sortable-column-icon.ui-icon.ui-icon-carat-2-n-s { background-image: none; margin-left: 5px; font-size: 1.1666em; position: relative; } .ui-sortable-column-icon.ui-icon.ui-icon-carat-2-n-s:not(.ui-icon-triangle-1-s)::before { content: "\f106"; font-family: "FontAwesome"; position: ...

Regex - Check a text without special characters but German, French

Special characters such as square brackets ([ ]) can cause an exception " java.util.regex.PatternSyntaxException " or something like this if we don't handle them correctly. I had met this issue. In my case, my customers want our application should allow some characters in German and French even not allow some special characters. The solution is that we limit the allowed characters by showing the validation message on GUI. For an instance, the message looks like the following: "This field can't contain any special characters; only letters, numbers, underscores (_), spaces and single quotes (') are allowed." I used Regular Expression to check it. For entering Germany and French, I actually don't have this type of keyboard, so I referred these sites: * German characters: http://german.typeit.org/ * French characters: http://french.typeit.org/ Here is my code: package vn.nvanhuong.practice; import java.util.regex.Matcher; import java.util...

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