Vasif Mustafayev's blog

Failed to transfer file: http://repo1.maven.org/maven2. Return code is: 501 , ReasonPhrase:HTTPS Required

noreply@blogger.com (SigmaTrader) — Wed, 16 Dec 2020 14:14:00 +0000

If you are getting the following error when you are building your Java project using maven or gradle:

Failed to transfer file: http://repo1.maven.org/maven2.

Return code is: 501 , ReasonPhrase:HTTPS Required

And you are thinking what happened, I haven’t changed anything in my project, no new dependencies, or repositories. The answer is that you haven’t changed anything.

Do not panic! Effective January 15, 2020, the Central Repository is not longer supporting communication over HTTP and it requires requests to the repository must be over HTTPS.

Latency for sharing data while using Hazelcast on Virtual Machine

noreply@blogger.com (SigmaTrader) — Mon, 31 Aug 2020 10:21:00 +0000

A few days back we found out one old app which was running on multiple nodes while having in-memory cache usage. So, as a result, there was a case when the request came to the first node and the second node didn't get that data, and the app wasn't functioning properly.

So, as always first thing which we considered to use Redis. However, we don't have ready to use the Redis cluster and we started looking for other solutions in a market. Finally, I saw there is a Hazelcast which allows sharing data between nodes even without having the Hazelcast cluster. Of course, it is working when you are running in the same network. So, nodes should be able to multicast and make a proper cluster.

Java List vs List<?> vs List<Object>

noreply@blogger.com (SigmaTrader) — Wed, 13 Nov 2019 16:49:00 +0000

Before generics were introduced developers used lists as List which means you can store any type of objects including null inside it and when you read it you need to cast it

List list = new ArrayList();
list.add("String test");
list.add(new Date());

String s = (String) list.get(0);

From code above you can expect ClassCastException because if you try to assign 2nd item to String it will not succeed and you will get an exception during runtime. To prevent it you need to check if your type is correct and then cast as below

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What kind of benefits you can expect in Poland

noreply@blogger.com (SigmaTrader) — Fri, 03 May 2019 19:58:00 +0000

Hey,

I relocated to Poland(Krakow) in 2017 and I'm very happy to be here. I just regret that why I didn't do it 5-10 years ago :)

Except nice and kind people, beautiful, old and safe city you can even expect a lot of benefits from the government and companies. Today I want to share all kind of benefits which I know and use here. If you know additional ones please feel free to leave them in the comment, I'll be happy to check it and add to the list :)

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How to hibernate from the lock screen on Ubuntu 18

noreply@blogger.com (SigmaTrader) — Thu, 23 Aug 2018 14:40:00 +0000

By default Ubuntu doesnt support hibernate option. Even when u enable it using "pm-utils" during resume(wake-up) your laptop will not require password.
And this is very risky moment.

In my case, I created a keyboard shortcut which enables hibernate and lock.
Today I will share steps how you also can do it for your laptop/pc.

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How to change Google Play Country on Android

noreply@blogger.com (SigmaTrader) — Sun, 15 Apr 2018 21:03:00 +0000

As you know, Google Play filters some apps on a per country and/or per region basis. And I also when relocated to Poland wasn't able to download and use Poland based apps.

Long history, in short, most of the time developers or companies (bank and government organizations i.e.) put apps on the market which are allowed to download only by the account/user which belongs to that country.

Today, when I need to change my account to use Poland as a country wasn't easy as expected :) That is why I decided to share easy steps how I did it with you.
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Unable to Find Valid Certification Path to Requested Target while using Java on Server

noreply@blogger.com (SigmaTrader) — Sat, 14 Apr 2018 22:41:00 +0000

SSL Certificates are small data files that digitally bind a cryptographic key to an organization’s details.
When installed on a web server, it activates the padlock and the https protocol and allows secure connections from a web server to a browser.

Typically, SSL is used to secure credit card transactions, data transfer, and logins, and more recently is becoming the norm when securing browsing of social media sites.

Even now, most the browsers show sites as "Not Secure" when they don't have SSL certificates

Maybe you also faced an issue like below:
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Openfire Custom database integration steps

noreply@blogger.com (SigmaTrader) — Tue, 07 Jun 2016 12:16:00 +0000

Instant messaging (IM) has enjoyed phenomenal success as a person-to-person communication tool; in some instances, it has supplanted email as the preferred means of online communication. Now, developers are using this technology for application-to-person and application-to-application communication.

There are too many IM servers which work with XMPP protocol. Some of them are paid/Enterprise and some of them are OpenSource.

We are using "Openfire" as a IM server for our projects. It is free, open source and java based. Except this advantages it has too many plugins which you can use for free. Openfire is a XMPP server and it has own client application with name "Spark".
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Youtube/Shazam mp3/mp4 downloader for Android

noreply@blogger.com (SigmaTrader) — Wed, 01 Jun 2016 14:03:00 +0000

Do you know how to download music or video from Youtube? Or do you know how to download music/mp3 from shazam on your android device?
If you don't know how download music from youtube or shazam on android then you should read this post :)

We have developed 2 applications by name YouMp34 and ShazaMusic which allow you to download from youtube and shazam for free.
Both of this applications is free and only for android users. You can view and download it from our official web site www.yoump34.com

We'll be happy to grow together :)

JDBC URL to connect RAC database or How add multiple hosts in jdbc url

noreply@blogger.com (SigmaTrader) — Thu, 26 Mar 2015 14:11:00 +0000

Today I will share new problem which I have solved.

In my last project I was connected to Oracle database (RAC) database using multiple hosts and I want to share oracle connection string which uses multiple hosts.

So while you are connecting from oracle clients (as PL/SQL developer) it is easy to define multiple hosts in tnsnames.ora

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Oracle JDBC problem - Locale not recognized on Glassfish

noreply@blogger.com (SigmaTrader) — Thu, 25 Sep 2014 05:11:00 +0000

When you create JDBC connection pool for oracle you may seen error like below:

Ping Connection Pool failed for DBNAME. Connection could not be allocated because: Locale not recognized Please check the server.log for more details.

Solution of this problem is so simple. How we can solve this problem???

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Shuffle an Array in Java with Easy or Fast way

noreply@blogger.com (SigmaTrader) — Tue, 17 Sep 2013 11:52:00 +0000

Objects are a powerful software engineering construct, and Java uses them extensively. While developing Android applications you need fast way of doing something. For example:
Often u need randomized Array which u will save state of stage or something.
In that case how you change order of Array randomly???

There are 2 famous way for this:
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SOLVED: Unknown type '246 in column 2 of 3 in binary-encoded result set

noreply@blogger.com (SigmaTrader) — Thu, 18 Jul 2013 09:40:00 +0000

Today at our firm was problem like as "Unknown type '246 in column 2 of 3 in binary-encoded result set" when selected table has column as decimal(10, 2) type. This errors cause because we use old version of mysql jdbc driver. Solution for this problem is:

Download new version of driver

Convert double column to char on selection.

SELECT CAST(your_column AS char(15)) your_column FROM your_table;

So in this case on java side u can get it as Double again.

Create your web services with Spring

noreply@blogger.com (SigmaTrader) — Sat, 16 Mar 2013 18:50:00 +0000

In this post I will show "Spring way" to build RESTful web services. It also explained how to produce multiple representations (JSON, XML and etc.), which is an important feature for RESTful web services.
This article explains another way to produce multiple representations using HttpMessageConverter, and examples in the article show how to use RestTemplate with HttpMessageConverter to communicate with services. HTTP requests and responses are text based, meaning a browser and server communicate by exchanging raw texts. With Spring, however, methods in the controller class return pure 'String' type and domain models (or other Java built-in objects). How can Spring serialize/de-serialize the objects to raw texts? This is handled by HttpMessageConverter. Spring has bundled implementations that can meet your common needs. Table 1 shows some examples.
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Read data from SSL X.509 Certificates

noreply@blogger.com (SigmaTrader) — Tue, 25 Dec 2012 08:36:00 +0000

According to X.509, you can create certificates with either RSA or DSA key pairs. But only RSA key pairs are capable of exchanging keys when starting a new SSL connection with a SSL server. You can only use RSA key pairs as your server certificates. On the other hand, CAs do not have to exchange keys. They only issue other certificates. You can use either RSA or DSA key pair as your CAs. But, some SSL programs do not support the DSA algorithm yet.

Sometimes u need check certificate valid date on server. U can do this in java simple: Read more »

Captcha for Java

noreply@blogger.com (SigmaTrader) — Mon, 19 Nov 2012 12:53:00 +0000

       A CAPTCHA is a program that protects websites against bots by generating and grading tests that humans can pass but current computer programs cannot. For example, humans can read distorted text as the one shown on image, but current computer programs can't.
       The term CAPTCHA (for Completely Automated Public Turing Test To Tell Computers and Humans Apart) was coined in 2000 by Luis von Ahn, Manuel Blum, Nicholas Hopper and John Langford of Carnegie Mellon University.
       When u create web project sometimes u need captcha with colors of your site. That cases u can create captcha yourself as following:
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Parse XML and Properties config files

noreply@blogger.com (SigmaTrader) — Sun, 04 Nov 2012 15:58:00 +0000

       .xml(Extensible Markup Language) and .properties is a file extension for files mainly used in Java related technologies to store the configurable parameters of an application.(.properties files can also be used for storing strings for Internationalization and localization - these are known as Property Resource Bundles.)

       Let's first start with XML config files. There are many XML parser technologies, but I will show how u can use Apache Commons Configuration library to parse and use XML config files.

       The Commons Configuration software library provides a generic configuration interface which enables a Java application to read configuration data from a variety of sources:
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Power of Spring's @ModelAttribute and @SessionAttributes

noreply@blogger.com (SigmaTrader) — Thu, 18 Oct 2012 11:24:00 +0000

The Spring Framework is an open source application framework that aims to make J2EE development easier. Unlike single-tier frameworks, such as Struts or Hibernate, Spring aims to help structure whole applications in a consistent, productive manner, pulling together best-of-breed single-tier frameworks to create a coherent architecture.

How does @ModelAttribute work?
@ModelAttribute is a Spring-MVC specific annotation used for preparing the model data. It is also used to define the command object that would be bound with the HTTP request data. The annotation works only if the class is a Controller class (i.e. annotated with @Controller).

ModelAttribute can be applied on both methods as well as method-parameters. It accepts an optional "value", which indicates the name of the attribute. If no value is supplied to the annotation, then the value would be defaulted to the return type name in case of methods and parameter type name in case of method-parameters.
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Spring 3 MVC Internationalization & Localization (i18n & l10N) and Reloader

noreply@blogger.com (SigmaTrader) — Tue, 18 Sep 2012 15:05:00 +0000

In this post I will discuss about Internationalization (I18N) and Localization (L10N) in Spring 3.0 MVC.

What is i18n and L10n?

In computing, internationalization and localization are means of adapting computer software to different languages and regional differences. Internationalization is the process of designing a software application so that it can be adapted to various languages and regions without engineering changes. Localization is the process of adapting internationalized software for a specific region or language by adding locale-specific components and translating text.

The terms are frequently abbreviated to the numeronyms i18n (where 18 stands for the number of letters between the first i and last n in internationalization) and L10n respectively, due to the length of the words. The capital L in L10n helps to distinguish it from the lowercase i in i18n. Let's begin:

Intercepting requests (annotation based request mapping)

noreply@blogger.com (SigmaTrader) — Thu, 13 Sep 2012 09:39:00 +0000

Spring Interceptors has the ability to pre-handle and post-handle the web requests. Each interceptor class should extend the HandlerInterceptorAdapter class. Here we will create a Login Interceptor by extending the HandlerInterceptorAdapter class. You can override any of the three callback methods preHandle(), postHandle() and afterCompletion(). As the names indicate the preHandle() method will be called before handling the request, the postHandle() method will be called after handling the request and the afterCompletion() method will be called after rendering the view.

Difference between Oracle DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, TIMESTAMP WITH LOCAL TIME ZONE

noreply@blogger.com (SigmaTrader) — Tue, 05 Jun 2012 13:43:00 +0000

In Oracle there are four date&time datatype:

DATE
TIMESTAMP
TIMESTAMP WITH TIME ZONE
TIMESTAMP WITH LOCAL TIME ZONE

What is difference between this datatypes???

TIMESTAMP datatype differs from DATE only with that it includes fractional seconds. But TIMESTAMP WITH TIME ZONE and TIMESTAMP WITH LOCAL TIME ZONE is more interesting :-)

Avoiding the "javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed" error

noreply@blogger.com (SigmaTrader) — Fri, 25 May 2012 11:37:00 +0000

Hey folks,

today I'm gonna share one solution for a problem related to https hand-shake.

The SSLHandshakeException is thrown by java when the host you are trying to contact doesn't have a valid SSL certificate for that hostname.
For example, when I wanted to connect to the site which certificate details look like "This CA Root certificate is not trusted because it is not in the Trusted Root Certification Authorities store."

So when we are making a request to that site using java URLConnection it gives us an exception look like "javax.net.ssl.SSLHandshakeException: sun.security.validator.ValidatorException: PKIX path building failed" . Then I did research for this problem and found a solution as follows:

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Broken pipe and Transactional update cache is full

noreply@blogger.com (SigmaTrader) — Fri, 06 Apr 2012 05:37:00 +0000

In your web applications u can see errors like following:

2012-04-06 10:01:05,031 WARN [webscripts.connector.RemoteClient] [http-80-1] Exception during close() of HTTP API connection ClientAbortException: java.net.SocketException: Broken pipe

Solution: In most situations this occurs when your client ajax connection is closed but response is ready. And server can't write response for client. In my case, I used YUI AJAX Get connection and set timeout "5000". When I see this warning message I increase timeout time to "300000" and log tail is happy now :)

End old tasks in Alfresco from Admin

noreply@blogger.com (SigmaTrader) — Fri, 02 Mar 2012 13:31:00 +0000

I have been working with Alfresco for a while now. It is a very comprehensive tool, but today I need delete old tasks in archive task node.

The purpose of the Workflow JavaScript API is to allow access to Alfresco advanced workflows from within JavaScript. The API supports EMCA Script 1.6 compatible JavaScript. Through this API workflow definitions, instances, paths, tasks and transitions can be accessed and managed.

Connect to Remote database through SSH using Port Forwarding with Java

noreply@blogger.com (SigmaTrader) — Wed, 29 Feb 2012 12:54:00 +0000

Yesterday I need connect connect our remote MySQL database that was setup on SSH enabled server and query database. Since it was on SSH enabled server, we can’t connect it directly using JDBC connection API.To achieve this, we first need to create SSH session and then using Port Forwarding we can forward the request to server and connect to database. I used JSch. JSch is a pure Java implementation of SSH2.

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