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Configure STA_IF interface of ESP8266 (MycroPython firmware) to connect with WIFI network automatically on boot

ESP8266 can act as both Station / WIFI client (STA_IF interface) and Access Point (AP_IF interface). AP_IF interface is active by default in MycroPython firmware on ESP826 . In the earlier post, we connected to the access point (AP mode) of ESP8266 and used WebREPL to remotely control switch on/off and brightness of an LED. Now, we'll configure the ESP8266 (as WIFI client) so that it connects to the WIFI router automatically after booting.

Example: Remotely switch on/off and control brightness of an LED using MicroPython WebREPL

So far, we have flashed MicroPython firmware onto an ESP8266 and setup WebREPL to run programs over WIFI on the chip. Now it's time for a hands-on excercise. We'll remotely switch on/off and control brightness of an LED using MicroPython WebREPL.

How to setup WebREPL to connect to Python prompt (REPL) of ESP8266 over WIFI network?

WebREPL daemon auto-start is disabled by default in MycroPython on ESP8266 for security reason. Here, we'll enable the same, connect to the REPL over WIFI using locally installed WebREPL client and run a "Hello World" program remotely on the chip.

How to flash MicroPython firmware onto an ESP8266 ESP-12E chip using esptool?

By default, ESP8226 module comes with AT Firmware. In this post, we'll see how to flash MicroPython firmware onto an ESP8266 ESP-12E chip using esptool.

How to uninstall OpenCV (Open Source Computer Vision) from Raspberry Pi - Raspbian Jessie?

To uninstall OpenCV (Open Source Computer Vision) from Raspberry Pi (Raspbian Jessie), follow the steps mentioned below in this article.

Troubleshooting for Hue-Solr Integration

Troubleshooting: Cloudera Hue not able to access Solr collections through Search tab assuming both are set up with CDH4

4 Effective Tips to Reduce Your WordPress Database Size

Are you serious about speeding up your WordPress-hosted website? If so, chances are high that you have shelled out money for clutter-free codes or designs that will reduce your site's loading time. If you are like most Webmasters, you have eagerly devoured webinars, eBooks, and worksheets that teach you how to increase your site's speed. However, as it turns out, you might not need to pony up some dough!

Hadoop Hands on - A POC Covering HDFS API, MapReduce, JSON and AVRO SerDe, HBase API With FuzzyRowFilter usage

My learning phase with Hadoop is still continuing. During this phase what I found is a great lack of a comprehensive POC which covers at least a few prominent Hadoop technologies. My POC can fill up that void. After having set up CDH4.7 in my laptop, I completed implementation of this POC touching HDFS API, MapReduce, JSON and AVRO SerDe, HBase.

Cloudera Hadoop (CDH 5.x) Installation Guide

It is affectionately said that what Oracle is to Relational Database, Cloudera is to Hadoop. Most of the Hadoop aspirants, at the beginning of their Hadoop development learning curve, fiddle with the setting up of CDH, some able to do it smoothly (Cloudera has put up an incredibly exhaustive installation guide), some requires to really sweat it out (few finer details and prerequisites are either missing or not enough emphasized upon) and very few actually gives it up losing their way in the verbose and cover-all-cases installation guide(multiple way of set up and different set of instructions for different linux OS; sometimes too much of variations for impatient starters). So there is a target audience for one more set up document which is leaner, meaner and streamlined with only one (the most preferred) variation. Try it at home!!

Install and Configure Oracle Java ME Embedded on Raspberry Pi

Raspberry Pi is a low cost, credit-card sized and fastest selling personal computer. In this article, we'll install and configure Oracle Java ME Embedded on a Raspberry Pi.

NRT (Near Real Time) Indexing using Cloudera Search And Lily HBase Indexer

You are not so strong with SQL or you are not good at programming? And you need to create distributed scalable search on a very large dataset stored in HBase? And you need to achieve NRT (Near Real Time) indexing? Cloudera search along with Lily Hbase Indexer is there to rescue you!

Design - a start-up approach to adopt developers' language

I have to observe lots of developers as part of my job description. I sit back and stare at what they do all the time, how they communicate to each other, how they express their ideas and how easily they get into a fight in a design discussion.

Cucumber Quick Start Guide

I have been told that, medically, Cucumber can cause indigestion. Let's see...

Build, Install and Configure Eclipse Plugin for Apache Hadoop 2.2.0

Apache Hadoop Development Tools (HDT) is still in development phase. So, no official distribution of Hadoop 2.2.0 Eclipse Plugin is available now. But we can build the same using winghc/hadoop2x-eclipse-plugin. In this post, we'll build, install and configure the plugin with the Eclipse or any Eclipse based IDE (say, Spring Tool Suite) to ease the development activities using Hadoop framework.

Shell$ExitCodeException - Caused by: java.lang.NoClassDefFoundError: org/apache/hadoop/service/CompositeService

If you are getting "Exception from container-launch:org.apache.hadoop.util.Shell$ExitCodeException" in FAILED application's Diagnostics (or Command prompt) and "java.lang.NoClassDefFoundError: org/apache/hadoop/service/CompositeService" in 'stderr' containerlogs while running any Hadoop example on Windows, then add all the required Hadoop jars to the property 'yarn.application.classpath' in yarn-site.xml configuration file.

Run Hadoop wordcount MapReduce Example on Windows

In this post, we'll use HDFS command 'bin\hdfs dfs' with different options like mkdir, copyFromLocal, cat, ls and finally run the wordcount MapReduce job provided in %HADOOP_HOME%\share\hadoop\mapreduce\hadoop-mapreduce-examples-2.2.0.jar. On successful execution of the job in the Single Node (pseudo-distributed mode) cluster, an output (contains counts of the occurrences of each word) will be generated.

AttachNotSupportedException: Unable to enqueue operation: the target VM does not support attach mechanism

Following exception occurs in Windows for IBM JDK 6 while executing a JUnit testcase which uses JMockit framework, in-spite of enabling the Attach API "-Dcom.ibm.tools.attach.enable=yes" - java.lang.RuntimeException: com.sun.tools.attach.AttachNotSupportedException: Unable to enqueue operation: the target VM does not support attach mechanism

Maven Build Failure - Hadoop 2.2.0 - [ERROR] class file for org.mortbay.component.AbstractLifeCycle not found

In the previous post on Build, Install, Configure and Run Apache Hadoop 2.2.0 in Microsoft Windows OS, many people have encountered Maven build failure issue ("[ERROR] class file for org.mortbay.component.AbstractLifeCycle not found") for Apache Hadoop Auth project. So thought of sharing the fix as a separate post.

URL Expander

Online URL expansion service to retrieve the actual destination of a shortened URL (bit.ly, TinyURL, Google URL Shortener etc.) before clicking on it for safe browsing.

Escape or Unescape String

Free online tool to escape and unescape string for CSV, HTML, Java, Java Script/EcmaScript and XML.

What is my IP?

Find out your network's public IP address. Click More Details link to get your IP's Geo-Location details as well.

IP Geo Location Finder

Free tool to find Geo-Location details of an IP.

URL Redirection Checker

URL redirection is a technique to forward the original http request from one location to another several times for different purposes like domain forwarding, URL shortening, privacy protection, maintaining similar domain names referring single website, etc. Use this tool to find all redirection locations of a URL.

Link Extractor

Online free tool to extract internal and external links of image, css, javascript and anchor from a particular web page.

HTML Encoder Decoder

Tool to encode or decode string for HTML.

Meta Tags Extractor

It is a free online tool to extract and view meta tags from a web page.

HTML to Plain Text Converter

Free online tool to convert HTML to plain text by stripping all html tags, unwanted scripts and css styles.

Encode or Decode URL string or Form parameter

Free online tool to Encode or decode URL / Link or Form Parameter.

JavaScript Extractor

Free online tool to extract embedded JavaScript code from a web page.

HTTP Headers Viewer

Online tool to extract and view HTTP response headers for a web page. Uncheck Follow Redirection checkbox if you do not want to follow redirections of a URL.

Configure SSL/HTTPS support on Apache Tomcat 7

By default, HTTPS / SSL is not configured and enabled in Tomcat Web server. SSL setup is required to make your web application accessible over HTTPS protocol. This post will guide you to configure SSL in Tomcat 7 Web server.

Get Redirections of a URL using Apache HttpComponents HttpClient

Many websites use URL redirection technique to forward the original request from one location to another several times for different reasons (Domain forwarding, URL shortening, Privacy protection, Maintaining similar domain names referring single website, etc.). In this post, I'll try to demonstrate how to get all the redirections of a URL using Apache HttpComponents HttpClient. A live demo will be a bonus here.

Determine Click Position (Row and Column Number) on click of a table cell

This example shows how to determine click position (row and column number) on click of a table cell using jQuery.

ERROR util.Shell: Failed to locate the winutils binary in the hadoop binary path

If we directly take the binary distribution of Apache Hadoop 2.2.0 release and try to run it on Microsoft Windows, then we'll encounter ERROR util.Shell: Failed to locate the winutils binary in the hadoop binary path.In the previous post - Build, Install, Configure and Run Apache Hadoop 2.2.0 in Microsoft Windows OS, I have already described how to build Windows distribution of Apache Hadoop 2.2.0. But if you are feeling little bit lazy to perform all the lengthy steps described there and want to get started with Hadoop quickly by-passing those steps, then this is the post worth looking into.

Build, Install, Configure and Run Apache Hadoop 2.2.0 in Microsoft Windows OS

Good news for Hadoop developers who want to use Microsoft Windows OS for their development activities. Finally Apache Hadoop 2.2.0 release officially supports for running Hadoop on Microsoft Windows as well. But the bin distribution of Apache Hadoop 2.2.0 release does not contain some windows native components (like winutils.exe, hadoop.dll etc). As a result, if we try to run Hadoop in windows, we'll encounter ERROR util.Shell: Failed to locate the winutils binary in the hadoop binary path.In this article, I'll describe how to build bin native distribution from source codes, install, configure and run Hadoop in Windows Platform.

Expand Shortened Link using Java

Nowadays we use different URL shortening services (like bit.ly, TinyURL, Google URL Shortener etc.) to shorten long URL to fit in micro-blogging sites (like Twitter), to beautify a link, view analytics on link clicks, make a link manageable for sharing (in SMS or printed hard copy, book, magazine etc.) or obscure the underlying address. But large portion of shortened links are used just to disguise spam or bad-sites containing malware, spyware, XSS attacks etc. So for safe browsing, sometimes revealing the destination of shortened link is necessary too.Here, we'll discuss one programmatic approach (using java.net.HttpURLConnection) to expand shortened links.

Free online URL Deobfuscator tool

URL deobfuscator tool to simplify complex looking encoded URL and extract information stored in it.

Spring Security HTTP Basic Authentication Example

HTTP basic authentication (BA) is a simple authentication mechanism. When a web client requests any secured web resources, server sends an HTTP response with status code 401 (Unauthorized) and WWW-Authenticate HTTP header like WWW-Authenticate: Basic realm="realm here". And browser pops up a login dialog prompting for User name and Password for that realm. This example shows how to configure HTTP basic authentication using Spring Security framework.

Spring Security Custom Login Form Example

In previous posts <a href="http://www.srccodes.com/p/article/31/spring-security-3-hello-world-example">Spring Security 3 Hello World Example</a> and <a href="http://www.srccodes.com/p/article/32/spring-security-logout-example">Spring Security Logout Example</a>, we have used default login form generated by Spring Security framework. Now we'll set up a custom login form for authentication with username and password.

Problem: failed to create task or type eclipse.refreshLocal

Eclipse platform provides different useful Ant tasks to interact with the workspace. If you have added any such Ant task (say eclipse.refreshLocal) in your ant build script and started getting "Problem: failed to create task or type eclipse.refreshLocal. Cause: The name is undefined.", then this is the post worth looking into.

Integrate Free Anti-Bot Service reCAPTCHA with Spring MVC application

reCAPTCHA is a free CAPTCHA service to protect a site against spam and other types of automated abuse by bots or computer programs. reCAPTCHA provides widget which can easily be integrated to your blog, forum, comment, registration form, contact form, etc and you can be rest assured that only human is posting in your site. This post will guide you on how to integrate free anti-bot service reCAPTCHA with a Spring MVC application.

Spring Security Logout Example

Spring Security provides Logout Handling Service for logging out by navigating to a particular URL (by default /j_spring_security_logout). LogoutFilter starts processing when a request comes for /j_spring_security_logout url and delegates to LogoutHandler(s) to perform the actual logout functionality like clearing security context, invalidating session, etc. Based on logout configuration, a redirect will be performed to the URL logout-success-url after logout.In this example, we'll integrate Spring Logout handling mechanism in Spring Security 3 Hello World Example to demonstrate logout functionality.

Spring Security 3 Hello World Example

Security is of great concern in any web application. If you are looking for a proven and industry standard solution to secure your Java/J2ee based application, then widely used and highly customizable authentication and access control framework - Spring Security is well worth considering. This post will show all the steps to setup, configure and integrate Spring Security 3 to protect your web application from being breached using a simple hello world example.

Build Hadoop Eclipse Plug-in Jar From Source Code And Install That Plug-in In Eclipse IDE

Hadoop Eclipse plug-in (installed in Eclipse IDE or Spring Tool Suite) eases the experience of Map/Reduce on Hadoop. Hadoop distribution does not include Hadoop Eclipse plug-in jar, but includes source code of that plug-in. In this post, we'll see all the steps to build Hadoop eclipse plug-in from source code and install that plug-in in Eclipse / Spring Tool Suite to access Hadoop Environment in "Map/Reduce" perspective of the IDE.

Spring Asm Dependency Issue: java.lang.IncompatibleClassChangeError - Fixed

If you have migrated / upgraded your project to Spring Framework 3.2 and project builds successfully but when application starts, you are getting IncompatibleClassChangeError, then this post will help you to resolve the same.

Get started with Open Source Code Quality Management Platform - Sonar in few minutes

Sonar is an open source platform for code quality management. It covers different aspects of code quality management like code duplication, complexity, coverage by unit tests, architecture and design, rule based defect identification etc. This post will help you to get started with Sonar in few minutes.

Make HTML table sortable using jQuery Tablesorter plugin

This post describes how to make an HTML table (having THEAD and TBODY) sortable in few minutes using tablesorter jQuery plugin. This plugin can parse and sort many types of data like number, text, currency, URI, IP address, date, time including linked data in a table cell.

Setup, Run and Experience Chrome OS in Oracle VM VirtualBox before you buy Google's Chromebook

Are you planning to buy a Google's Chromebook? Want to experience how it looks like before you decide? Then this is the post worth looking into. Here we'll see how to setup, run and explore Chrome OS in Oracle VM VirtualBox.

Spring Mobile Hello World Example that includes DeviceResolver, SitePreference, urlPath SiteSwitcher and LiteDeviceDelegatingViewResolver

Spring Mobile is an extension to Spring MVC for development of mobile web applications. The Spring Mobile Device module provides a feature (DeviceResolver / LiteDeviceResolver) to detect devices like mobile and tablet in the server side. Device aware view management is very useful specially when it is required to serve different optimized versions of same website based on request generating device type or specific devices. Another feature called site preference management allows user to set his / her preference (SitePreference) to view a particular site in either "normal", "mobile" or "tablet" mode from a particular device. Spring mobile also provides different types of site switchers (like mDot, dotMobi and urlPath SiteSwitcher) which automatically redirect users to the device specific site based on the device generating the request and site preference set by the user.

Spring 3 MVC Framework Based Hello World Web Application Example Using Maven, Eclipse IDE And Tomcat Server

In this post, we'll see how to get started with a Spring Web model-view-controller (MVC) framework based Hello World web application in few steps. Here, we have used m2e-wtp (Maven Integration for Eclipse WTP) to generate a web project, Eclipse IDE to develop the code and Tomcat Server 7 to deploy and run the web application which will print 'Hello World!' in the browser.

Build Android application package file (APK) using Eclipse IDE and Android Development Tools (ADT) Plugin

Android application package file (APK) is program binary used to distribute and install Android application onto the Android operating system. Here we'll see step by step procedure of creating .apk file ready to be installed in Android device.

Android Hello World Example using Eclipse IDE and Android Development Tools (ADT) Plugin

This tutorial will help you to write your first Android 'Hello World!' program. Here, we'll use Eclipse IDE with Android Development Tools (ADT) plugin to build the application and Android Emulator - Android Virtual Device (AVD) to run the application which will draw 'Hello World!' text on the screen.

Logback using SLF4J Hello World Example

Logback is an increasingly popular logging framework intended as a successor to the popular log4j project. It is designed by the founder of log4j. Logback offers many advantages over log4j like faster, smaller memory footprint, automatic reloading of configuration files, automatic compression of archived log files, conditional processing of configuration files and many more.This tutorial describes how to configure SLF4J and Logback as logging solution of an application.

Java File and Directory operations made easy in JDK 7

Here we'll see two examples - Copy operation and Traversing a file tree. If you have already worked using JDk 6 or earlier versions then you can see how easy it is to use JDK 7's nio package. And you need to write less code to implement the same.

org.springframework.aop.framework.AopConfigException: Cannot proxy target class because CGLIB2 is not available

Spring AOP uses either JDK dynamic proxies or CGLIB to create the proxy for a given target object. If the target object to be proxied, does not implement any interfaces then a CGLIB proxy will be created. In this situation if CGLIB is not present in the classpath following exception will be shown - "org.springframework.aop.framework.AopConfigException: Cannot proxy target class because CGLIB2 is not available. Add CGLIB to the class path or specify proxy interfaces."

Send logs by Email Notification using Apache log4j SMTPAppender

It is always better to get notified as soon as any major issues / exceptions occurred in the Application, instead of manually going thorugh huge logs to find probable exception messages. Apache log4j provides out of the box log Appender (called SMTPAppender) to send email alerts for the log level configured in log4j configuration file.

Deploy to AppFog PaaS using Cloud Foundry Integration plugin of Eclipse / STS

AppFog Cloud Platform is built by using the Cloud Foundry OSS bits alongside its own set of custom extensions and enhancements. AppFog provides good command line tool to deploy application but we can configure Cloud Foundry Integration plugin of Eclipse / Spring Tool Suite (STS) to deploy web application directly from IDE to the AppFog.

Configure Simple Logging Facade for Java (SLF4J) with log4j as underlying logging framework

Simple Logging Facade for Java (SLF4J) is an abstraction of different logging frameworks (eg. log4j, java.util.logging, commons logging etc.). This tutorial describes how to configure SLF4J with log4j as underlying logging framework.

Example to Generate Random Alpha Numeric Text - srccodes.com

This example shows how to generate random alpha numeric text which is not easy to guess.

Dynamically create image from text using Java Servlet - srccodes.com

This example shows how we can dynamically create an image from a text ('Hello World!') by writing a simple Java Servlet. In the next post, we'll see how this dynamic creation of image can be used to implement custom CAPTCHA validation.

How to retain DOCTYPE declaration while saving DOM Document to an XML file

If we save a DOM Document to an XML file using javax.xml.transform.Transformer, DOCTYPE declaration gets emitted by default. This example shows how we can retain PUBLIC and SYSTEM id of the DOCTYPE declaration for external DTD.

Configure GZIP Filter on Jetty 8 for dynamic compression of contents

Jetty provides Gzip Filter to enable dynamic compression of contents like html, javascript, css etc. A servlet filter 'org.eclipse.jetty.servlets.GzipFilter' needs to be configured in web.xml for this purpose.

Spring 3 Hello World Example / Tutorial using Maven Tool and Eclipse IDE

This tutorial will help you to write your first Hello World Spring program. We will use Maven tool to generate the project and Eclipse IDE to implement a method which will print 'Hello World!' in the console.

Java/J2EE development tutorials, articles, examples and source codes

Technology Blog - Java, J2EE, Servlet, JSP, JSF, ANT Script, Hibernate, Spring, Struts, Maven, jQuery, JSON, log4j, EJB, Webservices, xml, xsl, jstl, javascript, html development tutorials, articles, examples and source codes, tips and tricks

Programmatically Start or Stop an Application, deployed in IBM WebSphere Application Server (WAS) using Java Code and ANT script

This tutorial describes how an application, deployed in IBM WebSphere Application Server (WAS) can be started or stopped programmatically using Java code. The sample java code invokes and executes an ANT script which uses 'wsadmin' scripting tool and the AdminControl object to start / stop the application.

Invoke and Execute Hello World Ant Script Programmatically using Java Code

Apache Ant is an XML-based build tool to automate different tasks like compile, assemble, test source code, building deployment packages and run Java applications. This Hello World example shows how to invoke and run a simple Ant script programmatically using java code.

Full Text Hibernate Lucene Search Hello World Example Using Maven and SQLite

Hibernate Search is a full text search engine built using Apache Lucene framework. Hibernate Search indexes your domain model, keep the index upto date and also performs full text search functionality to fetch matching domain objects. This Hello World example shows how you can setup hibernate search and get your domain objects based on free text search query. In this tutorial we will use Maven tool to build the project, Eclipse IDE to code and SQLite database to save our domain objects.

Hibernate Hello World example using Maven build tool and SQLite database

This tutorial will help you to write an annotation based hibernate java program which will save some records into a database and fetch them all using Hibernate API. We will use Maven tool to build the project, Eclipse IDE to code and SQLite database to save / retrieve records. SQLite is a self-contained, serverless, zero-configuration, transactional SQL database engine. To learn hibernate, following this tutorial you do not have to install any database or SQLite database separately. However to browse the database you can use 'SQLite Manager - Firefox addon' which provides a very nice GUI for SQLite database.

How to traverse a folder or directory recursively using Java File API

This example shows how we can traverse a folder or directory structure using recursive algorithm by writing a small java program using Java File API.

Hello World Example of Simple Logging Facade for Java or SLF4J

Simple Logging Facade for Java (SLF4J) is an abstraction of different logging frameworks (eg. log4j, java.util.logging, commons logging etc.). This gives the developer an opportunity to plug-in desired logging framework at deployment time without changing the code.

How to perform binary search on a java.util.ArrayList

This example shows how an element of a java.util.ArrayList can be searched using 'binarySearch' method of java.util.Collections class. This method internally applies binary search algorithm to search a particular element.

Tomcat Hello World Servlet using Eclipse IDE

This simple tutorial explains you, how you can run your first Servlet class that will print "Hello World!" string in the browser. We will use Eclipse IDE to develop the code and Tomcat webserver to run the servlet code.

JSP Hello World Example using Eclipse IDE and Tomcat web server

This simple tutorial describes how you can print "Hello World!" string in your browser by writing a simple JSP (Java server pages) program developed using eclipse IDE.

Java Hello World Example using Eclipse IDE

This article describes how to create a "Hello World" java program using Eclipse IDE. This program will print "Hello World" in the console.