Memory profiling – simple examples
Posted on Feb 4, 2016
| 5 minutes
Recently I have been trying to learn different memory profiling tools to monitor Java applications. I have looked into the command line tools that are shipped as part of JDK like jstat, jps, jvisualvm etc. Licensed tools like Yourkit provide wholesome information about a running JVM including memory usage, CPU time, thread count etc. Running a java application with -verbose:gc option prints memory usage of each generation after every garbage collection event.
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JPA Entity Relationships
Posted on Jan 15, 2016
| 7 minutes
In a relational database, the relationships between two tables are defined by foreign keys. Typically, one table has a column that contains the primary key of another table’s row. In JPA, we deal with entity objects that are Java representations of database tables. So we need a different way for establishing relationship between two entities. JPA entity relationships define how these entities refer to each other.
For the purpose of this article, I will work with JPA 2.
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Introduction to jdb
Posted on Jan 11, 2016
| 4 minutes
jdb (Java Debugger) is a simple command-line debugger for Java classes that is provided as part of the JDK tools and utilities.
jdb is based on a server-client model. While debugging, you have one JVM where the code is executed and another JVM where debugger runs. Either VMs can act as the server. There are two ways to start the debugger. You can directly fire up the debugger by giving the main class name with the jdb command.
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It’s a grammatically error-prone life
Posted on Jan 1, 2016
| 1 minutes
Plurals of regular nouns don’t need an apostrophe, people!
Step by step guide to set up a service discovery environment
Posted on Dec 17, 2015
| 4 minutes
In a microservices environment we can run multiple instances of a service for resilience and scalability. In a cloud environment these instances can go up and down arbitrarily. So we need some kind of service discovery mechanism to keep track of running instances. When a service A needs to call a service B, it asks for the address of any running instance of service B from the service discovery. The service discovery can also load balance the incoming requests.
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How to set up a local spring cloud config server
Posted on Dec 15, 2015
| 4 minutes
From the official documentation,
Spring Cloud Config provides server and client-side support for externalized configuration in a distributed system. With the Config Server you have a central place to manage external properties for applications across all environments.
Steps to configure config server a. Create a new Gradle project for the config server. In https://start.spring.io/, select the starters for config server.
b. In your project, navigate to src/main/resources. Rename the automatically generated application.
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Building with Gradle
Posted on Oct 24, 2015
| 6 minutes
Gradle is a popular build tool to manage Java projects. Gradle’s build scripts are written in Groovy. The design of Gradle is aimed to be used as a language, not as a rigid framework. In this article, I want to give some basic idea about what a Gradle build script is composed of and some of the features provided by Gradle.
Gradle is based upon two basic concepts: projects and tasks.
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Tail Recursion
Posted on Aug 26, 2015
| 4 minutes
Tail recursion is one of those functional programming concepts that are likely to be unknown to someone coming from a Java background, like me. I encountered this term while skimming through the first few pages of SICP. After some quick R&D (i.e. googling), the following is a summary of what I have learnt.
Before understanding tail recursion, we need to be familiar with the term tail call. Simply put, if in a function definition, the last instruction before returning is a function call, then that function call is called a tail call.
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How unit testing leads to improved code
Posted on Aug 9, 2015
| 6 minutes
In Test Driven Development, the purpose of unit testing is to help us design our classes and not just to validate the correctness of our code. In this article I want to demonstrate how unit testing forces us to write better code, with help of an example. I will use Mockito for mocking.
First, let me define the problem domain I’ll be using in the example. Suppose we have an online booking portal where customers make reservations for travel or accommodation.
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Scheming with the Little Schemer
Posted on Aug 5, 2015
| 2 minutes
From a very long time, I have been an admirer of Lisp, an often praised but seldom used programming language. Common consensus about Lisp is that it is the kind of language you don’t need to know to get your daily tasks done, but any programmer worth his salt should be familiar with its concepts.
For a beginner, perhaps the easiest way to get a taste of Lisp is to go through The Little Schemer.
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