Home » Author Archives: Vlad Mihalcea (page 4)

Author Archives: Vlad Mihalcea

Vlad Mihalcea is a software architect passionate about software integration, high scalability and concurrency challenges.

Hibernate collections optimistic locking

jboss-hibernate-logo

Introduction Hibernate provides an optimistic locking mechanism to prevent lost updates even for long-conversations. In conjunction with an entity storage, spanning over multiple user requests (extended persistence context or detached entities) Hibernate can guarantee application-level repeatable-reads. The dirty checking mechanism detects entity state changes and increments the entity version. While basic property changes are always taken into consideration, Hibernate collections ...

Read More »

Hibernate application-level repeatable reads

jboss-hibernate-logo

Introduction In my previous post I described how application-level transactions offer a suitable concurrency control mechanism for long conversations. All entities are loaded within the context of a Hibernate Session, acting as a transactional write-behind cache. A Hibernate persistence context can hold one and only one reference of a given entity. The first level cache guarantees session-level repeatable reads. If ...

Read More »

MongoDB Incremental Migration Scripts

mongodb-logo

Introduction An incremental software development process requires an incremental database migration strategy. I remember working on an enterprise application where the hibernate.hbm2ddl.auto was the default data migration tool. Updating the production environment required intensive preparation and the migration scripts were only created on-the-spot. An unforeseen error could have led production data corruption. Incremental updates to the rescue The incremental database ...

Read More »

Integration testing done right with Embedded MongoDB

mongodb-logo

Introduction Unit testing requires isolating individual components from their dependencies. Dependencies are replaced with mocks, which simulate certain use cases. This way, we can validate the in-test component behavior across various external context scenarios. Web components can be unit tested using mock business logic services. Services can be tested against mock data access repositories. But the data access layer is ...

Read More »

Logical vs physical clock optimistic locking

software-development-2-logo

Introduction In my previous post I demonstrated why optimistic locking is the only viable solution for application-level transactions. Optimistic locking requires a version column that can be represented as: a physical clock (a timestamp value taken from the system clock) a logical clock (an incrementing numeric value) This article will demonstrate why logical clocks are better suited for optimistic locking ...

Read More »

The fastest way of drawing UML class diagrams

software-development-2-logo

A picture is worth a thousand words Understanding a software design proposal is so much easier once you can actually visualize it. While writing diagrams might take you an extra effort, the small time investment will pay off when others will require less time understanding your proposal. Software is a means, not a goal We are writing software to supports ...

Read More »

Preventing lost updates in long conversations

software-development-2-logo

Introduction All database statements are executed within the context of a physical transaction, even when we don’t explicitly declare transaction boundaries (BEGIN/COMMIT/ROLLBACK). Data integrity is enforced by the ACID properties of database transactions. Logical vs Physical transactions An logical transaction is an application-level unit of work that may span over multiple physical (database) transactions. Holding the database connection open throughout ...

Read More »

A beginner’s guide to database locking and the lost update phenomena

software-development-2-logo

Introduction A database is highly concurrent system. There’s always a chance of update conflicts, like when two concurring transactions try to update the same record. If there would be only one database transaction at any time then all operations would be executed sequentially. The challenge comes when multiple transactions try to update the same database rows as we still have ...

Read More »

Hibernate bytecode enhancement

jboss-hibernate-logo

Introduction Now that you know the basics of Hibernate dirty checking, we can dig into enhanced dirty checking mechanisms. While the default graph-traversal algorithm might be sufficient for most use-cases, there might be times when you need an optimized dirty checking algorithm and instrumentation is much more convinient than building your own custom strategy.         Using Ant ...

Read More »

How to customize Hibernate dirty checking mechanism

java-interview-questions-answers

Introduction In my previous article I described the Hibernate automatic dirty checking mechanism. While you should always prefer it, there might be times when you want to add your own custom dirtiness detection strategy. Custom dirty checking strategies Hibernate offers the following customization mechanisms:   Hibernate Interceptor#findDirty() CustomEntityDirtinessStrategy A manual dirty checking exercise As an exercise, I’ll build a manual ...

Read More »
Want to take your Java Skills to the next level?
Grab our programming books for FREE!
  • Save time by leveraging our field-tested solutions to common problems.
  • The books cover a wide range of topics, from JPA and JUnit, to JMeter and Android.
  • Each book comes as a standalone guide (with source code provided), so that you use it as reference.
Last Step ...

Where should we send the free eBooks?

Good Work!
To download the books, please verify your email address by following the instructions found on the email we just sent you.