How to Solve UnrecognizedPropertyException: Unrecognized field, not marked as ignorable - JSON Parsing Error using Jackson

While parsing JSON string received from one of our RESTful web services, I was getting this error "Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "person" (class Hello$Person), not marked as ignorable". After some research, I found that this is one of the common error while parsing JSON document using Jackson open source library in Java application. The error messages say that it is not able to find a suitable property name called "person" in our case, let's first take a look at the JSON we are trying to parse, the class we are using to represent the JSON document and the error message itself.

Error Message:
Exception in thread "main" com.fasterxml.jackson.databind.exc.UnrecognizedPropertyException: Unrecognized field "person" (class Hello$Person), not marked as ignorable (4 known properties: , "id", "city", "name", "phone"])

Spring Framework Certification FAQ - Frequently asked Questions Answers for Java Developers

If you are a Java developer, working in Spring framework and thinking to become a certified Spring professional but couldn't to do it in the past due to expensive mandatory training provided by Pivotal and its partners then there is a good news for you. From 10th May 2017, Pivotal made the Spring Core training optional for appearing to Spring certification exam, which means, now, it's not mandatory to take Spring training for Spring certifications (see here). Similar to Oracle's Java certifications, you can become a Pivotal certified Spring Professional by just buying the exam vouchers and scheduling your exam online using examlocal.com from anywhere in the world.

How to find a Process Listening on a Specific Port in Linux? netstat and lsof command examples

In Linux, many times, you want to find out the PID of a process which is listening on a port e.g. if multiple tomcat servers are running on a host and you have to kill that process, but in order to kill that process you need the process id, how do you find the PID of the tomcat listening on port 8080? There are many Linux commands to find the process using a specific port, but I'll share what I use. I always use the netstat command with -p option, which displays process id of the process listening on a port. Btw, netstat is not the only command to find all processes using a particular port, you can also use the lsof command for the same purpose.

Top 5 Free Data Structure and Algorithm Courses for Java and C Programmers

Data Structure and Algorithm is one of the essential topics for programmers, both to get a job and do well on Job. A good knowledge of data structure and algorithm is the foundation of writing good code. If you are familiar with essential data structures e.g. array, string, linked list, tree, map and advanced data structure e.g. tries, AVL trees etc and know when to use which data structure and compute the CPU and memory cost of your code in terms  Even though you don't need to write your own array, linked list or hashtable, given every major programming SKD provides them e.g. JDK or C++ STL library, you will need to understand them so that you can use them in right place. Using a right data structure can drastically improve the performance of an algorithm.

Top 5 Database design and Modelling Books for Programmers and DBAs of All level

The database design and modeling are one of those topics which rarely gets the attention they deserve, especially at the start of the project, but once things have gone out of hand then everybody talks about that. Comments like - this database are designed poorly, it is not performing well, you cannot add a new column easily etc becomes very common. The most problem with database design is that it is mainly done by application developers e.g. Java or C++ developer who knows SQL but they are not the expert of how to design tables and schema. The Database admins or DBAs know database and SQL better than application programmers but they focus on the admin part of the database rather on application part e.g. designing tables and relations between them, which is left to the application developer.

The best Course to Learn Spring Security 5 for Experienced Java Developers

If you are a Java Spring developer and working with Spring Security then you may be familiar with the "Learn Spring Security" course by Eugen Paraschiv of Baeldung.com. It is one of the most advanced and comprehensive courses on Spring Security and the best part of this course is that Eugen always keeps it up-to-date with new Spring Security release. Now that version Spring Security 5 is out - he has updated his course to use new features of Spring Security 5. Btw, there is some really cool new functionality coming in Spring Security 5 for the reactive programming model, and many other improvements and new features. But, the most important one is the release of OAuth2.

JUnit Testing Tips - Constructor is Called Before Executing Test Methods

Even though almost all Java programmers either use JUnit or TestNG for there unit testing need along with some mock object generation libraries e.g. Mockito, but not everyone spends time and effort to learn subtle details of these testing libraries, at least not in proportion of any popular framework like Spring or Hibernate. In this blog post, I am sharing one of such detail, which has puzzled me a couple of years ago. At that time, though I had been using JUnit for a significant time, I wasn't aware that code written inside the constructor of Test class is executed before each test method.  This behavior of JUnit has caused, some of my test to failed and putting hours of investigation in my code, without realizing that this is happening because of JUnit is initializing the object by calling constructor before executing test method annotated with @Test annotation.

The 2018 DevOps RoadMap - Your Guide to become DevOps Engineer

DevOps is really hot at the moment and most of my friends, colleagues and senior developers I know are working hard to become a DevOps engineer and project themselves as DevOps champion in their organization. While I truly understand the benefit of DevOps, which is directly linked to improved software development and deployment, from my limited experience I can say that it's not an easy job. It's very difficult to choose the right path in mind of so many tools and practices. Many of my readers also ask me this question is how to become a DevOps engineer, which tools should I learn? which practices should I follow? does learning Maven and Jenkins must for a DevOps guy? how about Docker and Kubernetes? Does infrastructure automation part of DevOps? should I learn Chef, Puppet, or Ansible are just some of those questions which keep coming to me.

Top 10 Angular Tutorials and Courses for Web Developers - Best of Lot

Hello guys, if you are interested in learning the Angular framework, one of the best and most popular JavaScript frameworks for developing component-based Web GUI and looking for some awesome courses then you have come to the right place. In this article, I am going to share some of the best resources e.g. books, tutorials, and courses to learn the Angular framework, formerly known as Angular JS and now famous as Angular 2. It's backed by Google, hence you should not worry about it being out-dated and lose relevance in a couple of years. Any investment you made in learning Angular will pay you rich dividends in coming years.

When to use intern() method of String in Java?

The String.intern() method can be used to deal with String duplication problem in Java. By carefully using the intern() method you can save a lot of heap memory consumed by duplicate String objects. A String object is said to be duplicate if it contains the same content as another string but occupied different memory location e.g. str1 != str2 but str1.equals(str2) is true. Since String object consumes a large amount of heap memory in average Java application, it makes sense to use the intern() method to reduce duplication and take advantage of String pool feature provided by Java. You can use intern() method to intern a String object and store them into String pool for further reuse.

Top 10 Highest Paying Technical Jobs for Software Engineers, Programmers

If you are a computer science graduate or someone who is thinking to make a career in software development world or an experienced programmer who is thinking about his next career move but not so sure which field you should go then you have a come to the right place. In this article, I will tell you the top 10 highest paying technical jobs you can aim for. All you need is some programming experience and a passion for learning. Particularly the Machine learning and Data science field looking very promising for both beginners and experienced programmers. On average a machine learning specialist and Data Scientist make around anywhere from $110,000 USD to $120,000 and there is a huge demand for them and if you are interested in solving real-world problems they present an exciting opportunity.

Top 5 Jenkins Courses for Java and DevOps Engineers to Learn Online

In today's world of Agile and DevOps, Jenkins has become an indispensable tool for both Java programmers and DevOps engineers. Jenkins allows you to set up continuous integration (CI) and continuous deployment (CD) pipeline, which reduces risk on Software development. This means hassle-free development and deployment. It also means quicker feedback because as soon as a commit has been made into source control, Jenkins can start building artifacts and running unit tests. If the build failed due to an issue or if a unit test doesn't pass, you will receive an email instantly. This quick feedback loop ensures that your codebase remains error free. It is also one of the most compelling technologies of the last decade in terms of its disruption to software development and operational practices.

Kotlin vs Java - Which language Android Developers should Learn?

Ever since Google announced Kotlin as the official language for Android development in Google IO 2017, programmers, who want to become an Android Developer are in dilemma. Now the big questions in front of them are whether they should learn Kotlin or Java? The answer to this questions depends upon your profile. If you are a complete beginner who wants to learn Android development then my answer is Java, but if you are Java developer who wants to jump into the lucrative market of Android App development then my answer is Kotlin. I'll discuss why beginner Android programmer should start with Java and why Java developer should learn Kotlin in this article.

How to enable HTTP Basic Authentication in Spring Security using Java and XML Config

In the last article, I have shown you how to enable Spring security in Java application and today we'll talk about how to enable Basic HTTP authentication in your Java web application using Spring Security. I'll show you how to do that using both the Java configuration and XML configuration if you are using Spring Security 3.1 or lower version, but before that let's understand what is Http basic authentication and why do you need that? One of the most common ways to authenticate a user in a web application is by using form login i.e. you provide a login page and user will enter his username and password for authentication. This works great for human users but sometimes there are situations where you can't use a login form for authentication.

10 Gift Ideas for Programmers, Software Engineers, and IT Professionals

My friend circle has a lot of programmers and non-programmers and when it comes to buying gifts for birthdays, anniversary or holidays, I receive a lot of queries from my non-programmer family and friends about what to buy for a programmer? Well, buying a gift is easy but choosing or finding a right gift for someone is really really tough. I have had this experience when it comes to buying gifts for kids. I know they like toys but my wife told me to buy something more valuable, which not only keep them engaged but also provide value, help them in learning and they appreciate every time they use. That's a lot to cater in one gift, but that's the perfect gift, isn't it?

3 Ways to convert String to Boolean in Java? Examples

You can convert a String object to Boolean object or boolean primitive by using the Boolean.valueOf() and Boolean.parseBoolean() method. The steps are similar rot converting to String to other data types e.g. String to Integer and String to Long. You can use valueOf() method to convert String to Boolean object and parseBoolean() method to convert given String to boolean primitive value. Internally, valueOf() also uses parseBoolean() for parsing String but on top of that it also provides caching e.g. it can return Boolean.TRUE and Boolean.FALSE cached value for "true" and "false" string.  In fact, the Boolean.TRUE is returned only when String is equal to true ignoring case e.g. "True", "true", "TRUE" will evaluate into boolean true, hence Boolean.TRUE will be returned. For string like "Yes", Boolean.FALSE will be returned. We'll discuss the rules of String to boolean conversion in next section.

Top 5 Courses to learn Angular Framework in 2018 - Best of Lot

If you are a JavaScript developer or someone who wants to learn Angular for web development and looking for some awesome resources e.g. books, online courses, and tutorials then you have come to the right place. In the past, I have shared some of the best Angular tutorials and today, In this article, I am going to share some of the best Angular courses to learn modern day web development. If you don't know what is Angular and how it helps you to develop modern day web development, let me give you a brief overview. It's a Javascript framework which allows you to build a modern-day big e-commerce web application as well as a single page web application which runs on a browser.

Top 5 IntelliJ IDEA and Android Studio Courses for Java and Android Development - Best of Lot

There is no doubt that IntelliJ IDEA is THE best IDE for Java development, even though Eclipse may still be probably used by more people because it's FREE, IntelliJ IDEA is the most feature rich and complete IDE. The Android Studio, which is the official IDE for Android development in Java is also based upon IntelliJ IDEA, which further cement its place as the IDE Java developer should learn. The only thing which stops me and many other Java developers to moving from IntelliJ IDEA in the past was the lack of resources. Since Eclipse was free from the start, there are tons of resources e.g. books, courses, and tutorials are available. There are also a lot of resources to learn productivity tips e.g. keyboard shortcuts and debugging techniques, but there were not many for Intelli IDEA.

Top 10 Programming and Coding Interview Courses for Programmers

To be honest with you, getting your first job is never easy. It is, in fact, the hardest task and you need to put your best effort to find a job in your dream company. Most of the computer science graduates dream of working for Google, Facebook, Amazon, Microsoft, and Apple but they often not able to clear their rigors coding interviews. The single most important reason for failing those coding job interviews is lack of knowledge and practice, hence it becomes increasingly important that you prepare hard in advance. Unfortunately, I learned this little too late, after spoiling my chances at Microsoft and Amazon but you can learn from my experience and prepare better for your programming job interviews.

Top 5 Java EE Courses to Learn Online - Best of Lot

The Java Platform Enterprise Edition 8 or Java EE 8 was released last year along with Java 9 in September 2017. If you are a Java developer or someone who wants to learn Java EE for web development and looking for some good courses to kickstart your learning then you have come to the right place. In this article, I am going to share five awesome Java EE courses which cover both Java EE 7 and Java EE 8 and very useful for learning Java EE in 2018. If you are wondering what is Java EE and what does Java EE 8 brings into the table, let me give you a brief overview of Java EE first.

10 Reasons to Learn Python in 2018

If you are a regular reader of this blog then you may be wondering that why am I writing a blog post to tell people to learn Python in a Java blog? Didn't I ask you to prefer Java over Python a couple of years ago? Well, things have changed a lot since then. In 2016, Python replaced Java as the most popular language in colleges and University and since then it has never looked back. Python is growing and growing big time. If you read programming and technology news or blog post then you might have noticed the rise of Python as many popular developer communities including StackOverflow and CodeAcademy has mentioned the rise of Python as a major programming language.

The @SpringBootApplication Annotation Example in Java + Spring Boot

Hello guys, today, we'll learn about the @SpringBootApplication annotation, one of the most important annotations from popular Spring Boot framework, which has changed the way Java developers use Spring framework for writing Java applications. In this article, I'll explain you the meaning of @SpringBootApplication and it's used in a simple Spring Boot application. We use @SpringBootApplication annotation on our Application or Main class to enable a host of features e.g. Java-based Spring configuration, component scanning, and in particular for enabling Spring Boot's auto-configuration feature.

Top 5 Java SE 8 Certification Books - Best of Lot Must Read

If you are preparing for Oracle Certified Associate, Java SE 8 Programmer, also known as Java SE 8 Programmer I or OCAJP8 exam and looking for some good resources e.g. books, study notes, and mock exams then you have come to right place. I have been sharing some of the most useful resources for Java 8 certification aspirants ever since the exam was launched. You can find a lot of this exam and essential resources in this blog. To continue that tradition, I am going to share some of the best books to crack the Java SE certification i.e. OCAJP 8 (1Z0-808)  and OCPJP 8 (1Z0-89). Yes, you need to pass two exams to become Java 8 certified professional. The OCAJP is also a prerequisite for OCPJP exam, which is a professional level exam. Alternatively, if you already hold a Java certification e.g. Java SE 6 or before then you can take one of the upgrade exams e.g. 1Z0-810 to become Java SE 8 certified professional.

Top 5 Java 8 Certifications Courses to Prepare OCAJP (1Z0-808) Exam Online

If you are preparing for Oracle Certified Java SE 8 Associate exam, also known as OCAJP 8 and OCPJP 8 with exam codes 1Z0-808 and looking for a decent online course to kick start with your preparation then you have come to the right place. In this article, I will share some of the best online courses to prepare for Java SE 8 certifications. Btw, first of all, configurations to make the right decision. If you are a Java developer then certifying for your skill will not only distinguish you from millions of other non-certified Java programmers but also improve your knowledge and understanding of Java SE 8. If you are looking for a job then this can help you to get a better job and if you are looking for a career growth e.g. to become senior Java developer, these certifications can help you to get a promotion.

10 DevOps Courses for Experienced Programmers to Learn Online - Best of Lot

DevOps is really hot at this moment and there are many job opportunities lying for distinguished engineers and DevOps professionals. If you are an experienced Java programmer and want to become a DevOps engineer then you have come to the right place. In this article, I am going to share some of the best online training courses you can take to become a DevOps professional. The most important advantage of DevOps is that it helps you to deliver better software and provide more control over your environment and software development process with the help of modern tools and automation. That's the reason the demand for DevOps professionals is growing exponentially. It's also one of the high paying jobs along with Data Science and Machine learning specialists.

Clean Code by Uncle Bob - Book Review - Must read for Software Engineers

Even though, the Clean Code book has been released many years ago and there are lots of good reviews already available, I couldn't resist to write my own experience about this great book. I came across this book many years ago but since then I have read it multiple times and I have recommended it to my readers, students, and fellow developers. It is one of those books which make you feel that why didn't you come across it earlier, I felt the same when I first learned about this book. The Clean Code is all about writing good quality code and how do you judge the quality of code? Well, you won't appreciate good until you have seen bad code and that's what this book do.

Top 5 Soft Skill and Career Development books and Courses for Programmers

Most of the software developers, programmers, and coders spend a considerable amount of their time and energy on learning technologies which get obsolete in few years e.g. a new framework or a new programming language but they neglect something more important e.g. soft skills. Unlike technical stuff, soft skills will not only serve you good in your job and career but also in your life and it won't get obsolete as quickly as the new web application development framework you have just learned. Similarly, most of us put a lot of effort to get a job but after that, we don't put much effort to grow on that job, the result is many programmers and software developer stuck in their career.

Top 5 Java Programming Courses for Beginners to Learn Online - Best of Lot

If you are a computer science graduate or someone who wants to learn Java and looking for some awesome resources e.g. books, tutorials, and online courses then you have come to the right place. In the past, I have shared some great books and tutorials to learn Java and in this article, I am going to share some of the best Java courses beginners can join to learn Java. One of the main problems with learning Java is to keep pace with increasing number of releases. For example, Java 8 was released in 2014 which completely changed how Java is written and now within last 6 month, we have two major Java releases in form of Java 9 and Java 10. But the good thing is that core of Java is still same and all its releases are backward compatible.

Top 5 Online Courses to Learn Web Development in 2018

Udemy is running their flash sale this weekend, where they are offering all the courses in just $10.99 and I have been spending a lot of time going through their website to buy some of the top quality courses in this sale. If you look at the price, its nothing, if you escape snakes for 1 day you can buy a course in Udemy to learn and the best part of this is that you get the lifetime access of course. So you can use it whenever you get time, maybe this week, this month, or sometime later. I love learning and for the most part of my life, I learned by reading books but ever since I come across online courses on Udemy and Pluarlsight, I have spent most of my time learning through online courses. They are the best way to start with the new technology and get yourself up and running in no time.

5 Courses to Learn Kotlin Programming language for Java and Android Developers

If you don't know Kotlin, it's a relatively new programming language that makes programming for Android or Javascript easy. Ever since Google announced Kotlin as the official language for Android Development, I received a lot of queries from my readers should Java developer learn Kotlin now? or which one is better to start with Android development, Kotlin or Java? I have answered that question in my last article but I am still receiving a lot of queries about learning Kotlin and whether Java developer should Learn Kotlin or not? Well, to be honest with you, being a Polyglot programmer i.e. a programmer who knows more than one programming language is important and distinguish skill. It not only widen your thoughts but also make you a better developer and that's why I recommend every Java developer to at least learn one more JVM language and Kotlin is a good one to start with.

Top 5 Node.js and Express JS online courses for Web Developers

There is no doubt that JavaScript is the #1 Programming language in the world and Node.js is one of the biggest reason for that. Initially, JavaScript was considered just a client-side scripting language but Node.js has changed all that by allowing developers to create dynamic web pages on the server side using JavaScript. It is also rated as the most popular framework of 2017 on StackOverflow Developers survey. The most important benefit of Node.js is that it allows you to build a full stack application based on just one language, JavaScript. This is especially useful for start-ups which put a lot of emphasis on being able to iterate early and often.

3 Best Spring Security Online Training Courses for Java Developers

The Spring Security is one of the leading open source, security framework which allows you to implement security in Java based web applications. It provides several security features e.g. authentication, authorization, remember me out-of-the-box, which means you can directly use them without adding code or changing your class. Yes, Spring Security implements security at application level i.e. you can even secure your non-secure resource without modifying them. It is also the leading framework to secure RESTful Web Services. Because of all these, the demand for Java developers with good knowledge of Spring Security is very high. They are also some of the highly paid Java developers. Many Java and Spring developer, particularly those who are involved in enterprise and Java web development are learning Spring Security.

3 Ways to Learn Spring Core, Spring MVC, Spring Security, and Spring Boot Framework

If you are a Java developer and wants to learn Spring framework then you have come to the right place. In this article, I will share three ways to learn Spring framework, but before that let's understand what is a spring framework and why Java developers should learn Spring framework? Well, Spring is a framework which assists you to develop Java application by following some best practices, particularly the principle of dependency injection and inversion of control. As per this principle, instead of class asking for its dependency, the framework provides them at runtime.  Following these principles improves your code quality because it reduces coupling between different part of your applications e.g. between modules and classes, which makes them easier to test and develop.

Top 5 Web Development Frameworks Java Programmers Should Learn in 2018 - Best of Lot

Hello guys, if you are a Java developer and wondering which Java frameworks you should learn in 2018 then you have come to the right place. In this article, I am going to share top 5 Java frameworks developers can learn to keep pace with modern day development. This is the second part of my article on what should Java programmer learn this year. In the first part, 10 Things Java developer should learn where I have focused on essential upgrades like Java 8, Java 9, Spring 5 etc, but in this article, I'll talk about some of the best Java frameworks you should learn to give your career a boost. Technology changes really fast, in just a couple of years what was the hottest technology or framework of 2014 is no longer used anymore and as a programmer and application developer, our biggest challenge is to keep pace with the technology.

5 Must Read Books to become Software Architect or Solution Architect

I receive a lot of queries from senior Java developers, who aspire to become software architect or solution architect e.g. what can they do to become a software architect? Which books, resources, or certifications can help? and general queries like how much experience you need to become software architect etc. In the past, I have been suggesting them individually about some books to read to expand their knowledge base and look at the software from architecture and design perspective and this article is a compilation of many of such suggestions. Since a lot of books can confuse, I have only select 5 best and must-read books from software architect perspective.

Top 5 Android Online Training Courses for Java Developers - Best of Lot

Java has been very lucky that Android uses it as a programming language. This opened a big door of opportunities for Java developers in Android app development. Many people ask me why Java Developer should learn Android? My simple answer is that good knowledge of Android OS improves your chances of getting a job and making a difference in people's lives because Android Apps is the direct way to connect billions of people. Android is without a doubt THE biggest mobile platform in the world, with over 80% market share and over billions of devices running Android. By creating apps for such a big platform, you have great opportunity to make a difference. You can also develop for Android on a Windows, Mac or Linux, which means your existing Java development experience will not go wasted.

Top 5 Apache Kafka Courses to learn Online - Best of Lot

Hello guys, you might have heard about Apache Kafka, the next generation, Big Data messaging system which is handling billions of messages per day on companies like LinkedIn, Uber, Airbnb, Twitter etc. In past, I have shared some awesome courses on Big Data, Spark, and Hadoop and many of my readers requested me to share similar suggestions for Apache Kafka. If you are interested in Apache Kafka and looking for some awesome courses to learn online then you have come to the right place. In this article, I am going to share some of the best Apache Kafka courses to learn online. If you know about Big Data then there is a good chance that you have also heard about Apache Kafka, the software which handles data feed for any organization. It's a distributed streaming platform developed by Apache foundation for building real-time data pipelines.

Top 5 Big Data and Apache Spark Courses for Java Developers to Learn Online in 2018

Slowing economy and the recent trend of job cuts in India and elsewhere have made many programmers anxious about their job security. I receive a lot of emails and Facebook chats about suggestions to improve IT skills to remain competitive and marketable. So, if you are in the same boat, you can learn Big Data and IT Automation to remain marketable. These two skills are in great demand and will generate a lot of jobs in future. I have suggested many Java developers around the world to learn Big Data Technologies e.g. Apache Spark to give their CV a new boost. Since it's not easy to learn a new technology and at a certain age, you feel a lot of restriction and resistance from both your body and mind. In order to overcome that I found a combination of books and online courses works great.

Top 5 Spring Cloud Courses for Java Developers to Learn Online - Best Of Lot

Hello guys, if you are learning Spring Cloud for developing cloud-based Java application and looking for some good resources to start with e.g. online courses and books then you have come to the right place. In this article, I am going to share some of the best courses to learn Spring Cloud and develop a cloud-based application in Java. One of the common question when it comes to learning a new technology is how to start? I was a big fan of books earlier but nowadays I personally like to start with an online course to learn things.  It works better because you gain a lot from instructor's experience and you also have a chance to ask questions to the instructor.

Top 5 Java 9 Courses to Learn Online - Best of Lot

The year of 2017 was the year of releases for Java developer. With releases of JDK 9, Spring 5, Spring Boot 2.0 and Spring Security 5.0 there was so much to learn for Java developers and all at once, but like many others, I didn't make a good process and I am looking to turn it around in 2018. One of my top priority goal for New Year to learn new features of Java 9 as quickly as possible to write more about it. It's also important for you to learn Java 9 quickly to improve your career prospects.