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Author Archives: Biju Kunjummen

Spring retry – ways to integrate with your project

spring-interview-questions-answers

If you have a need to implement robust retry logic in your code, a proven way would be to use the spring retry library. My objective here is not to show how to use the spring retry project itself, but in demonstrating different ways that it can be integrated into your codebase. Consider a service to invoke an external system: ...

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Solving “Water buckets” problem using Scala

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I recently came across a puzzle called the “Water Buckets” problem in this book, which totally stumped me. You have a 12-gallon bucket, an 8-gallon bucket and a 5-gallon bucket. The 12-gallon bucket is full of water and the other two are empty. Without using any additional water how can you divide the twelve gallons of water equally so that ...

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Spring RestTemplate with a linked resource

spring-interview-questions-answers

Spring Data REST is an awesome project that provides mechanisms to expose the resources underlying a Spring Data based repository as REST resources. Exposing a service with a linked resource Consider two simple JPA based entities, Course and Teacher:           @Entity @Table(name = "teachers") public class Teacher { @Id @GeneratedValue(strategy = GenerationType.AUTO) @Column(name = "id") private ...

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Externalizing session state for a Spring-boot application using spring-session

spring-interview-questions-answers

Spring-session is a very cool new project that aims to provide a simpler way of managing sessions in Java based web applications. One of the features that I explored with spring-session recently was the way it supports externalizing session state without needing to fiddle with the internals of specific web containers like Tomcat or Jetty. To test spring-session I have ...

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Spring boot war packaging

spring-interview-questions-answers

Spring boot recommends creating an executable jar with an embedded container (tomcat or jetty) during build time and using this executable jar as a standalone process at runtime. It is common however to deploy applications to an external container instead and Spring boot provides packaging the applications as a war specifically for this kind of a need. My focus here ...

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Spring Caching abstraction and Google Guava Cache

spring-interview-questions-answers

Spring provides a great out of the box support for caching expensive method calls. The caching abstraction is covered in a great detail here. My objective here is to cover one of the newer cache implementations that Spring now provides with 4.0+ version of the framework – using Google Guava Cache In brief, consider a service which has a few ...

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Docker RabbitMQ cluster

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I have been trying to create a Docker based RabbitMQ cluster on and off for sometime and got it working today – fairly basic and flaky but could be a good starting point for others to improve on. This is how the sample cluster looks on my machine, this is a typical cluster described in the RabbitMQ clustering guide available ...

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Spring @Configuration – RabbitMQ connectivity

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I have been playing around with converting an application that I have to use Spring @Configuration mechanism to configure connectivity to RabbitMQ – originally I had the configuration described using an xml bean definition file. So this was my original configuration:             <beans ...;> <context:property-placeholder/> <rabbit:connection-factory id="rabbitConnectionFactory" username="${rabbit.user}" host="localhost" password="${rabbit.pass}" port="5672"/> <rabbit:template id="amqpTemplate" connection-factory="rabbitConnectionFactory" exchange="rmq.rube.exchange" ...

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