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Author Archives: Biju Kunjummen

Spring @Bean and PropertyPlaceHolderConfigurer

spring-interview-questions-answers

I was recently stumped by what I thought was going to be a fairly straightforward implementation – Consider the following Spring Java based bean definition file ( @Configuration):                 package root; ... @Configuration @PropertySource("classpath:root/test.props") public class SampleConfig { @Value("${test.prop}") private String attr; @Bean public SampleService sampleService() { return new SampleService(attr); } } Here ...

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Spring MVC Error handling flow

spring-interview-questions-answers

There are broadly three ways of handling an exception flow using Spring MVC, the objective being to intercept any application exception and present a friendly and informative view back to the user. 1. Using error-page tag in web.xml file: This is a servlet specs driven approach, where the exceptions that bubble up from the application are intercepted based on either ...

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Testing Spring “session” scope

spring-interview-questions-answers

In a Spring based Web application, beans can be scoped to the user “session”. This essentially means that state changes to the session scoped bean are only visible in the scope of the user session. The purpose of this entry is to simply highlight a way provided by Spring Test MVC to test components which have session scoped beans as ...

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Spring Integration File Polling and Tests

spring-interview-questions-answers

I recently implemented a small project where we had to poll a folder for new files and then trigger a service flow on the contents of the file. Spring Integration is a great fit for this requirement as it comes with a channel adapter that can scan a folder for new files and then take the file through a messaging ...

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Spring Bean names

spring-interview-questions-answers

Spring bean names are straightforward, except for cases where names are not explicitly specified. To start with, Spring bean names for an xml based bean definition is specified this way:                 <bean name='sampleService1' class='mvcsample.beanname.SampleService'> <constructor-arg> <bean class='mvcsample.beanname.SampleDao'></bean> </constructor-arg> </bean> For a Java @Configuration based bean definition, the method name of the @Bean annotated ...

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Spring Data JPA and pagination

spring-interview-questions-answers

Let us start with the classic JPA way to support pagination. Consider a simple domain class – A ‘Member’ with attributes first name, last name. To support pagination on a list of members, the JPA way is to support a finder which takes in the offset of the first result(firstResult) and the size of the result(maxResults) to retrieve, this way: ...

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Mixin in Java with Aspects – for a Scala traits sample

java-interview-questions-answers

Scala traits allow new behaviors to be mixed into a class. Consider two traits to add auditing and version related fields to JPA entities:                   package mvcsample.domain import javax.persistence.Version import scala.reflect.BeanProperty import java.util.Date trait Versionable { @Version @BeanProperty var version: Int = _ } trait Auditable { @BeanProperty var createdAt: Date = ...

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Spring Property Placeholder Configurer – A few not so obvious options

spring-interview-questions-answers

Spring’s PropertySourcesPlaceholderConfigurer is used for externalizing properties from the Spring bean definitions defined in XML or using Java Config. There are a few options that PlaceholderConfigurer supports that are not obvious from the documentation but are interesting and could be useful. To start with, an example from Spring’s documentation, consider a properties file with information to configure a datasource:   ...

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Spring MVC – Customizing RequestMappingHandlerMapping

spring-interview-questions-answers

When Spring MVC is configured using <mvc:annotation-driven/> in an xml bean definition file, internally a component called RequestMappingHandlerMapping gets registered with Spring MVC. This component or in general a HandlerMapping component is responsible for routing request URI’s to handlers which are the controller methods annotated with @RequestMapping annotation.               There are two specific configurations ...

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JUnit test method ordering

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Junit until version 4.10 uses the order of test methods in a test class as returned by the reflection API as the order of test method execution – Class.getMethods(). To quote the Javadoc of getMethods() api: The elements in the array returned are not sorted and are not in any particular order. thus the order of test method execution in ...

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