Blog Archives
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02: HTTP basics on headers, MIME types, & cookies for Java developers

Q1. What happens when you open up a browser and type a URL to request a Web page or RESTFul web service data? A1. HTTP is a stateless protocol on top of TCP (Transmission Control Protocol). 1) When the IP address is obtained, … Read more ›...

03: Identifying and fixing NonUniqueObjectException in Hibernate

NonUniqueObjectException is thrown when there is an object already associated with the session with the same id (primary key) (i.e. a duplicate). It is important to understand the concept of a “detached” object in Hibernate. This is one of the most common errors, understanding why and when this error is thrown will save you time in identifying and fixing this issue.

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04: Identifying and fixing LazyInitializationException in Hibernate

LazyInitializationException is thrown when an object becomes detached, and if you try to access associated (i.e. proxied) object(s) of a detached object.

Q. What is a detached object in Hibernate?

When you close an individual Hibernate Session, the persistent objects you are working with are detached.

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05: Debugging Hibernate & handling 4 common issues

#1. Enable Logging in your log4j.xml,, or myapp-logback.xml

In the file, you can enable Hibernate SQL logging as shown below

or in your log4j.xml or myapp-logback.xml as

You can then check your logs for the SQLs executed and the parameters passed. The example below shows 3 parameters passed to an update query


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06: Debugging NoSuchBeanDefinitionException in Spring

#1. Adding the @Named annotation to the interface instead of the implementation Adding the @Named, @Component, @Repository, etc annotation on the interface as opposed to the implementation class. The code below can throw “NoSuchBeanDefinitionException” FIX: The @Named annotation is now in the implementation class. … Read more ›...

07: Debugging Spring Transaction Management

Never just trust that adding @Transactional annotation is going to create a transactional boundary for your service layer. EventRestController –> EventMergeProcesorImpl –> EventControlDAOImpl The @Transactional annotations added to “public” methods of the EventMergeProcesorImpl. Spring creates a proxy around the “EventMergeProcesorImpl”. … Read more ›...

15+ Apache Spark best practices, memory mgmt & performance tuning interview FAQs – Part-1

There are so many different ways to solve the big data problems at hand in Spark, but some approaches can impact on performance, and lead to performance and memory issues. Here are some best practices to keep in mind when writing Spark jobs. General Best Practices #1 Favor DataFrames over...

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