|By Michael Muller||
|April 26, 2013 10:00 AM EDT||
Hibernate is one of the most used ORM Java frameworks out there. It is really simple to use, just add few annotations and you're ready to go. However, it is also really easy to experience strange behaviors and bugs if you don't respect Hibernate's best practices. That's why at Tocea we developed rules to detect coding mistakes and to make sure that your experience with Hibernate will be painless.
Our Hibernate repository currently contains 30 rules. Some of them are related to the detection of possible bugs, other treat of maintainability or performance. In this article, we're going to present four rules that deal with a famous Hibernate's usage problem : the implementation of equals() and hashCode() methods.
What's the problem?
Equals and hashCode are used to compare objects. The default implementation of equals compares the object's address in memory. This is good as long as your objects are in memory, but Hibernate's goal is precisely to move them out of memory. Within a Hibernate session, Hibernate takes care of managing objects equality between a persistent identity and a Java identity.
However, when dealing with objects that come from different sessions, Hibernate can't do it. That's why it is necessary to override equals and hashCode.
This is our rule n°1 : HbEntitiesMustImplementEqualsHashCode detects any Hibernate entity that does not implement both methods. We also have HbEmbeddableEntitiesMustImplementEqualsHashCodethat does the same for embeddable entities.
First step to solve it : implement equals()
So, I have a User and I want to implement the equals() method. I can just use its Id...
Ooops, or can't I? Indeed, if your Id is generated (as it is likely to be), it will be assigned once the object is persisted. Before that, all non-persisted entities have the same null id. So you could experience strange equality results... The good solution is to rely on the objects business fields to compare them, like the first name and the last name of my user.
This is our rule n°3 : HbEntitiesEqualsMustAvoidIDField detects usage of id field in equals().
Second step to solve it : implement hashCode()
I'm now ready to implement hashCode(). The Java language requires that if a.equals(b), then a.hashCode() is the same as b.hashCode(). As a consequence, I must use the same fields in hashCode() as I used in equals(). This may seem trivial for simple entities, but through evolution of an entity, this can be easy to forget to add a new field to one of the method.
This is our rule n°4 : HbEntityEqualsAndHashCodeUseDifferentFields detects equals and hashCode methods that use different fields.
To sum up, with this four rules you should be able to prevent a good deal of bugs related to incorrect usage of equals and hashCode in Hibernate entities. Have you already encountered such problems? Do you think there should be more rules regarding the implementation of these two methods? Please let us know in the comments!
Oh, and we have presented four of our thirty Hibernate rules, so that leaves plenty of interesting stuff to talk about : stay tuned!
Is the ongoing quest for agility in the data center forcing you to evaluate how to be a part of infrastructure automation efforts? As organizations evolve toward bimodal IT operations, they are embracing new service delivery models and leveraging virtualization to increase infrastructure agility. Therefore, the network must evolve in parallel to become equally agile. Read this essential piece of Gartner research for recommendations on achieving greater agility.
Aug. 25, 2016 05:15 PM EDT Reads: 604
SYS-CON Events announced today that Hitrons Solutions will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Hitrons Solutions Inc. is distributor in the North American market for unique products and services of small and medium-size businesses, including cloud services and solutions, SEO marketing platforms, and mobile applications.
Aug. 25, 2016 04:15 PM EDT Reads: 375
Smart Cities are here to stay, but for their promise to be delivered, the data they produce must not be put in new siloes. In his session at @ThingsExpo, Mathias Herberts, Co-founder and CTO of Cityzen Data, will deep dive into best practices that will ensure a successful smart city journey.
Aug. 25, 2016 03:30 PM EDT Reads: 1,483
DevOps at Cloud Expo, taking place Nov 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The widespread success of cloud computing is driving the DevOps revolution in enterprise IT. Now as never before, development teams must communicate and collaborate in a dynamic, 24/7/365 environment. There is no time to wait for long dev...
Aug. 25, 2016 03:15 PM EDT Reads: 2,199
Internet of @ThingsExpo, taking place November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, is co-located with 19th Cloud Expo and will feature technical sessions from a rock star conference faculty and the leading industry players in the world. The Internet of Things (IoT) is the most profound change in personal and enterprise IT since the creation of the Worldwide Web more than 20 years ago. All major researchers estimate there will be tens of billions devices - comp...
Aug. 25, 2016 02:00 PM EDT Reads: 3,543
Kubernetes, Docker and containers are changing the world, and how companies are deploying their software and running their infrastructure. With the shift in how applications are built and deployed, new challenges must be solved. In his session at @DevOpsSummit at19th Cloud Expo, Sebastian Scheele, co-founder of Loodse, will discuss the implications of containerized applications/infrastructures and their impact on the enterprise. In a real world example based on Kubernetes, he will show how to ...
Aug. 25, 2016 01:45 PM EDT Reads: 1,358
SYS-CON Events announced today that Venafi, the Immune System for the Internet™ and the leading provider of Next Generation Trust Protection, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. Venafi is the Immune System for the Internet™ that protects the foundation of all cybersecurity – cryptographic keys and digital certificates – so they can’t be misused by bad guys in attacks...
Aug. 25, 2016 01:00 PM EDT Reads: 2,592
The 19th International Cloud Expo has announced that its Call for Papers is open. Cloud Expo, to be held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA, brings together Cloud Computing, Big Data, Internet of Things, DevOps, Digital Transformation, Microservices and WebRTC to one location. With cloud computing driving a higher percentage of enterprise IT budgets every year, it becomes increasingly important to plant your flag in this fast-expanding business opportuni...
Aug. 25, 2016 01:00 PM EDT Reads: 3,885
As the world moves toward more DevOps and Microservices, application deployment to the cloud ought to become a lot simpler. The Microservices architecture, which is the basis of many new age distributed systems such as OpenStack, NetFlix and so on, is at the heart of Cloud Foundry - a complete developer-oriented Platform as a Service (PaaS) that is IaaS agnostic and supports vCloud, OpenStack and AWS. Serverless computing is revolutionizing computing. In his session at 19th Cloud Expo, Raghav...
Aug. 25, 2016 12:45 PM EDT Reads: 576
DevOps at Cloud Expo – being held November 1-3, 2016, at the Santa Clara Convention Center in Santa Clara, CA – announces that its Call for Papers is open. Born out of proven success in agile development, cloud computing, and process automation, DevOps is a macro trend you cannot afford to miss. From showcase success stories from early adopters and web-scale businesses, DevOps is expanding to organizations of all sizes, including the world's largest enterprises – and delivering real results. Am...
Aug. 25, 2016 12:15 PM EDT Reads: 3,383
Fact: storage performance problems have only gotten more complicated, as applications not only have become largely virtualized, but also have moved to cloud-based infrastructures. Storage performance in virtualized environments isn’t just about IOPS anymore. Instead, you need to guarantee performance for individual VMs, helping applications maintain performance as the number of VMs continues to go up in real time. In his session at Cloud Expo, Dhiraj Sehgal, Product and Marketing at Tintri, wil...
Aug. 25, 2016 11:00 AM EDT Reads: 541
Ixia (Nasdaq: XXIA) has announced that NoviFlow Inc.has deployed IxNetwork® to validate the company’s designs and accelerate the delivery of its proven, reliable products. Based in Montréal, NoviFlow Inc. supports network carriers, hyperscale data center operators, and enterprises seeking greater network control and flexibility, network scalability, and the capacity to handle extremely large numbers of flows, while maintaining maximum network performance. To meet these requirements, NoviFlow in...
Aug. 25, 2016 11:00 AM EDT Reads: 1,827
StarNet Communications Corp has announced the addition of three Secure Remote Desktop modules to its flagship X-Win32 PC X server. The new modules enable X-Win32 to safely tunnel the remote desktops from Linux and Unix servers to the user’s PC over encrypted SSH. Traditionally, users of PC X servers deploy the XDMCP protocol to display remote desktop environments such as the Gnome and KDE desktops on Linux servers and the CDE environment on Solaris Unix machines. XDMCP is used primarily on comp...
Aug. 25, 2016 10:30 AM EDT Reads: 489
SYS-CON Events announced today that StarNet Communications will exhibit at the 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. StarNet Communications’ FastX is the industry first cloud-based remote X Windows emulator. Using standard Web browsers (FireFox, Chrome, Safari, etc.) users from around the world gain highly secure access to applications and data hosted on Linux-based servers in a central data center. ...
Aug. 25, 2016 09:15 AM EDT Reads: 603
SYS-CON Events announced today that eCube Systems, a leading provider of middleware modernization, integration, and management solutions, will exhibit at @DevOpsSummit at 19th International Cloud Expo, which will take place on November 1–3, 2016, at the Santa Clara Convention Center in Santa Clara, CA. eCube Systems offers a family of middleware evolution products and services that maximize return on technology investment by leveraging existing technical equity to meet evolving business needs. ...
Aug. 25, 2016 09:00 AM EDT Reads: 497