What is Hibernate in Java?
Hibernate is one of the most extensively used ORM (Object/Relational mapping) tool for Java apps. It’s quite widely used a lot in enterprise applications for the purpose of database operations. It is a very popular framework of Java that permits an effectual Object-Relational mapping using structured files in an XML format. After the process of Java objects mapping to various database tables, the database is then used and is handled using Java objects without having to write complex database queries.
Other than aiding in freeing Java developers
from developing JDBC and database communication codes, Hibernate also aids in coming up with the novel and innovative solutions on caching, proxy as well as lazy loading which considerably mends the performance graph of your Java Web application. Given its significant importance in Java Web application development, turf, Hibernate has developed into one of the most sought-after skills and the best part it also works smoothly with the Spring Framework
Hibernate Interview Questions
These questions are exceptionally valuable for both telephonic as well as the eye to eye round of meetings and is helpful for both the beginners and experienced Java engineers up to 2 to 5 years can profit by these set of questions. On the off chance that you are currently getting ready for Java interviews
then you can likewise look at ‘Java Programming Interview Exposed’ which is an amazing website, it not just contains questions from Spring
and Hibernate yet additionally other vital Java themes e.g. center Java, information structure and calculations, Servlet, JSP, JSF and configuration designs.
List of Hibernate Interview Questions
- What is Hibernate?
- What are the benefits of Hibernate over JDBC?
- What is HQL?
- Why should you use Hibernate?
- What are the Key segments of Hibernate?
- Difference between get() vs load() method in Hibernate?
- What is the difference between save() and persist() method in Hibernate?
- What is the difference between the first and second level cache in Hibernate?
- What is a Session in hibernate?
- Has Hibernate Session interface been thread-safe in Java?
- Shed some light on other ORM frameworks? Is there any substitute for Hibernate?
- What is Transaction in hibernate?
- What is a Query in hibernate?
- What is ORM?
- For what reason is ORM favored over JDBC?
- What are the different levels of ORM quality?
- What do you mean by a pure relational ORM?
- What is a SessionFactory in hibernate?
- How do you log SQL queries issued by the Hibernate framework in Java application?
- Highlight the Core interfaces of Hibernate framework?
- What is called lazy fetching from Hibernate?
- Elucidate the difference between merge and update method?
- How various components are used in Hibernate?
- What are Criteria in hibernate?
- Explain the Transaction object in Hibernate?
- What is a One-to-One association in Hibernate?
- What is One-to-Many association in Hibernate?
- What is first level cache in Hibernate?
- What is the second level cache in Hibernate?
- What is Query level cache in Hibernate?
Hibernate Interview Questions and Answers
Hibernate interview questions are to a certain extent prevalent in almost all the Java interviews
. We are providing you with a few commonly asked Hibernate interview questions to brush up your knowledge and confidence before the interview.
Hibernate Interview Questions for Fresher
Q1). What is Hibernate?
Hibernate is one of the most extensively used ORM (Object/Relational mapping) tool for Java apps. It’s quite widely used a lot in enterprise applications for the purpose of database operations.
Q2). What are the benefits of Hibernate over JDBC?
Other than a good persistence i.e. saving as well as loading the data from a given Database, Hibernate also offer the following aids
- Lazy Loading
- The developer is absolutely free from scripting code to either load or store data into the database.
- A good relationship management and offers code for mapping an object right to the data.
Q3). What is HQL?
HQL is the acronym of Hibernate Query Language. It considers the java questions comparably as that of the SQL. It is an Object-Oriented Query Language and is independent of the database.
Q4). Why should you use Hibernate?
A portion of the upsides of Hibernate are:
- It gives Simple Querying of information.
- An application server isn't required to work.
- The complex relationship of objects in the database can be controlled.
- The database gets to is limited with savvy getting procedures.
- It deals with the mapping of Java classes to database tables without composing any code.
- Properties of the XML document is changed if there should arise an occurrence of any required change in the database.
Q5). What are the Key segments of Hibernate?
The Key segments of Hibernate are:
- Session: It is utilized to get a physical system with a database.
- Transaction: It speaks to the unit of work with a database.
- Query: It utilizes SQL and HQL string to recover the information from the database and make objects.
- Criteria: It is utilized to make and execute protest situated questions and recover the items.
- Configuration: It speaks to the properties of records required by Hibernate
- Session Factory: It designs sleep for the application utilizing the gave arrangement document and instantiates the session protest.
Q6). Difference between get() vs load() method in Hibernate?
The key contrast amongst getting () and load() technique is that load() will throw an exception if id passed to them aren’t found, however, get() will return null. Another imperative distinction is that load can return intermediary without hitting the database unless required (when you get to any characteristic other than id) yet get() dependably go to the database, so once in a while utilizing load() can be quicker than the get() technique. It bodes well to utilize the load() technique on the off chance that you know the question exists yet to get() strategy if you don’t know about object’s presence.
Q7). What is the difference between save() and persist() method in Hibernate?
The foremost difference between save() and persist() system is that save returns the result of a Serializable object while the return type of persisting () system is void, so it doesn’t yield anything as such.
Q8). What is the difference between the first and second level cache in Hibernate?
This is a likely follow-up question of the previous Hibernate interview question. The first level cache is preserved at the Session level through the second level cache is maintained at a SessionFactory level and is shared by all the sessions. You can consider reading further on caching in Hibernate.
Q9). What is a Session in hibernate?
A Session is something which is used to get a somatic connection with a database. The Session object is lightweight and is planned to be instantiated each time an interaction is needed with the database.
Q10). Has Hibernate Session interface been thread-safe in Java?
The answer is no, Session object is not thread-safe in the Hibernate framework and is proposed to be used within the single thread in the application.
Q11). Shed some light on other ORM frameworks? Is there any substitute for Hibernate?
This is a very common question, occasionally asked to start the conversation on Hibernate and other times to finish the interview. EJB and TopLink frameworks from Oracle are two of the most widely held substitutes of a Hibernate framework.
Q12). What is Transaction in hibernate?
A Transaction signifies a unit of work with the database and maximum of the RDBMS back up the transaction functionalities. Transactions in Hibernate are controlled by a basic operation manager and transaction.
Q13). What is a Query in hibernate?
Query objects use the SQL or Hibernate Query Language (HQL) string to recover data from the database and generate objects. A Query request is used to bind inquiry parameters, bound the number of results given back by the query, and lastly to perform the query.
Hibernate Interview Questions for experienced people
The interview questions for experienced personnel is different in Hibernate. Once you hold some experience it is but obvious that the employer expects you to be well versed with a few concepts that a person with the experience that you have is expected to know.
Q14). What is ORM?
ORM stands for Object/Relational mapping. It is the automatic and transparent persistence of objects present in a Java application into the tables of a relational database by means of the metadata that defines the mapping between the objects and the database.
Q15). For what reason is ORM favored over JDBC?
ORM is favored over JDBC because of the following reasons-
- It permits business access to the articles instead of Database tables.
- It shrouds the subtle elements of SQL questions from OO rationale.
- It depends on JDBC "under the hood".
- Dealing with database execution isn't required.
- Entities depend on business ideas as opposed to database structures.
- It creates the programmed key and Transaction administration.
- Application improvement is quicker.
Q16). What are the different levels of ORM quality?
Four levels defined for ORM quality:
- Pure relational
- Light object mapping
- Medium object mapping
- Full object mapping
Q17). What do you mean by a pure relational ORM?
The whole application, together with the user interface, is planned around the relational model and on SQL-based relational operations.
Q18). What is a SessionFactory in hibernate?
A configuration object is used to make a SessionFactory object which in turn arranges Hibernate for the application by means of the supplied configuration file and then permits for a Session object to be instantiated.
Q19). How do you log SQL queries issued by the Hibernate framework in Java application?
You can procedure the show_sql property to log SQL queries
delivered by the Hibernate framework.
Q20). Highlight the Core interfaces of Hibernate framework?
There are mainly five core interfaces being utilized widely in each Hibernate application. Using these interfaces you can either store or salvage any insistent objects and also regulate transactions.
- Session interface
- Session Factory interface
- Configuration interface
- Transaction interface
- Query and Criteria interfaces
Q21). What is called lazy fetching from Hibernate?
In Hibernate Lazy fetching is concomitant with child objects that are loading for their parent objects. By way of a Hibernate mapping file (.hbm.xml), you can specify the selection of loading the various child objects. By default, Hibernate does not load child objects. Lazy=true command means not to load the child objects.
Q22). Elucidate the difference between merge and update method?
Use update() method only when you are sure that the session does not comprise a previously insistent occurrence with the same identifier, and merge() method in case you want to merge your alterations at any time without deliberation of the state of the session.
Q23). How various components are used in Hibernate?
Components let the object to be stored as a value and not as a reference. It is utilized to be stored directly without the necessity to affirm the properties of the various interfaces or identifiers in the given application. Components in Hibernate describe the empty constructor in which the references that are common are not sustained.
Q24). What are Criteria in hibernate?
Criteria object are utilized to generate and implement object-oriented
criteria queries to recover objects.
Q25). Explain the Transaction object in Hibernate?
It represents a unit of work with the database and the majority of the RDBMS (Relational Database Management System) underpins exchange usefulness.
In Hibernate, exchanges are overseen by a basic exchange administrator and exchange from JDBC or JTA.
It is a discretionary question and the Hibernate Application don't utilize this interface, rather, they handle the exchanges in their code.
Q26). What is a One-to-One association in Hibernate?
It is like the many-to-one association and the distinction lies in the section that will be set as a unique one. The many-to-one component is utilized to characterize balanced affiliation.
To the characterized variable a name property is set in the parent class and the section ascribe is utilized to set segment name in the parent table, or, in other words, that just a single object gets related with another.
Q27). What is One-to-Many association in Hibernate?
In this affiliation, one question can be related to various items.
The One-to-Many mapping is actualized utilizing a Set Java accumulation that does not have any excess component.
A One-to-Many component of the set component shows the connection of one protest numerous objects.
Q28). What is first level cache in Hibernate?
It is session reserve and compulsory cache. It is from the first level store through which every one of the solicitations must pass.
The session question stores an object under its control before submitting it to the database.
Q29). What is the second level cache in Hibernate?
It is a discretionary cache. What's more, dependably the primary level reserve will be counseled before any endeavor is performed to find an object in the second level store. This store can be designed on a pre-accumulation and per-class premise and it is for the most part in charge of reserving objects over the sessions.
Q30). What is Query level cache in Hibernate?.
In sleep, a store question can be actualized that outcomes in sets and incorporates intimately with the second level cache. It is a discretionary component and it requires two extra reserve locales that can hold the stored inquiry results and furthermore the timestamps at whatever point a table is refreshed. This is helpful just for the inquiries that run every now and again holding similar parameters.
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