Why JPA Entity or Hibernate Persistence Class Should Not be Final? Answer

One of the interesting hibernate interview questions is, why you should not make a Hibernate persistent class final? I'll try to answer this question in this short blog post. The use of proxies is the core feature of Hibernate (one of the most popular ORM frameworks for Java Projects) for implementing key performance features e.g. lazy loading and lazy associations fetching. In order to use a proxy in place of a real class, your hibernate persistence class must be either non-final or the implementation of an interface that declares all of the public methods. 

10 Difference between Hibernate and JDBC in Java

JDBC is the core technology to access database from Java application but it require lot of boiler plate coding. Hibernate on the other hand an ORM (Object Relational Mapping) framework, which automatically map Java object to tables and records in database. You don't need to execute query to populate objects, Hibernate will do that for you. It also provides several benefit as compared to JDBC e.g. performance improvement via Proxy, lazy loading of associations and Caching, that's why both enterprise Java application and web application uses Hibernate to implement the DAO layer of application.

Top 50 Hibernate and JPA Interview Questions Answers for 3 to 5 Years Experienced Java developers

Hello guys, if you are preparing for Java developer interview then apart  from preparing core Java questions like Collections, Multithreading, Serialization, and Data Structures you should also prepare Spring Boot and Hibernate interview questions. Both Spring and Hibernate are two of the essential frameworks in Java world and its expected from an experienced Java developer to know them. I have given more than 50 interview in my career and in most of them I have seen questions from both Spring and Hibernate, especially on the jobs where Hibernate and Spring Framework is mentioned as required skills. 

What is lazy loading in Hibernate? Lazy vs Eager loading Example

Lazy loading in Hibernate is a feature which allows Hibernate to load the dependent objects lazily to improve performance of Java application. By default Hibernate does eager or aggressive loading for single valued associations (many to one and one-to-one ) and lazy loading for collection-valued associations (one to many or many-to-many). If you set the loading to lazy=false or FetchType.EAGER then object will be eagerly loader, means when an object is loaded from database all its relationship and associated objects are also loaded from Database e.g. when an Author entity object is initialized then all the books written by this author will also be loaded into memory.

What is N+1 SELECT Problem in Hibernate? Strategies to avoid this?

In some cases while using Hibernate for object-relational mapping, you will encounter the N+ 1 select problem. That is, Hibernate will execute (n+1) queries to populate a list of records of size n, I mean 5 SELECT queries will be required to populate 4 records. This happens when each object contains reference of another object which needs to be populated. For example, suppose you have list of authors and you want to print out title of books written by each other. A naive ORM will first do a SELECT query to load all authors and then execute another N SELECT query to load book for each author. That's your N + 1 SELECT problem because it involves N+1 database roundtrips'. There are some mechanisms suggested by Hibernate that can be used to mitigate this risk e.g. EAGER fetching mode.

Top 10 Hibernate Interview Questions and Answers for 3 to 5 Years Experienced Java Developers

Hibernate Interview Questions are asked on Java J2EE Interviews, mostly for web-based enterprise application development roles. The success and acceptability of Hibernate framework on the Java world have made it one of the most popular Objects Relational Mapping (ORM) solutions in the Java technology stack. Hibernate frees you from database-specific coding and allows you to focus more on utilizing powerful object-oriented design principles to implement core business logic. By using Hibernate you can switch between databases rather easily and also take advantage of out-of-box caching facilities provided by Hibernate, in terms of second-level cache and query cache.

Difference between JPA, Hibernate, and MyBatis in Java

Hello guys are you tired of using plain old SQL to access your database? Are you looking for a better way to manage your database interactions in Java? Well, you're in luck because JPA, Hibernate, and MyBatis are here to save the day! If you're a Java developer, you've likely come across the terms JPA, Hibernate, and MyBatis when working with databases. While they all deal with object-relational mapping (ORM), they have their own distinct approaches and features. Understanding the differences between them can help you make informed decisions when choosing which one to use for your projects.

Difference between First and Second Level Cache in Hibernate [Answer]

If you have used Hibernate in past then you know that one of the strongest points of the Hibernate framework is caching, which can drastically improve the performance of the Java application's persistence layer if configured and used correctly. Hibernate provides caching at many levels e.g. first level cache at Session level, second-level cache at the SessionFactory level, and query cache to cache frequently executed SQL queries. The first level cache minimizes database access for the same object. For example, if you call the get() method to access Employee object with id = 1 from one session, it will go to the database and load the object into memory, but it will also cache the object in the first-level cache.

Difference between get and load in Hibernate

get vs load in Hibernate

Difference between get and load method in Hibernate is one of the most popular questions asked in Hibernate and spring interviews. Hibernate Session class provides two methods to access object e.g. session.get() and session.load() both looked quite similar to each other but there are subtle differences between load and get method which can affect the performance of the application. The main difference between get() vs load method is that get() involves database hit if an object doesn't exist in Session Cache and returns a fully initialized object which may involve several database calls while load method can return proxy in place and only initialize the object or hit the database if any method other than getId() is called on persistent or entity object.

Difference between save vs persist and saveOrUpdate in Hibernate

Save vs. saveOrUpdate vs. persist in Hibernate

What is the difference between save and saveOrUpdate or Difference between saving and persist are common interview question in any Hibernate interview, much like the difference between get and load method in Hibernate. Hibernate Session class provides a couple of ways to save an object into the database by methods like save, saveOrUpdate, and persist.  You can use either save(),  saveOrUpdate() or persist() based upon your requirement for persisting objects into the database. The key thing is that all these objects are used to store data into the database but they also make a transient object persistent in Hibernate.

Difference between Transient, Persistent, and Detached Objects in Hibernate

In the Hibernate framework, an entity can be in three states, transient, persistent, and detached. When an object is in a transient state, it is commonly referred to as a transient object, similarly, if it is in persistence and detached state, it is known as a persistent and detached object. When an entity is first created using the new operator like new User() and not associated with Hibernate session like you haven't called session.save(user) method then it is known as a transient object. At this stage, Hibernate doesn't know anything about this object and the object doesn't have any representation in the database like a corresponding row in the User table.