Hibernate is a lightweight, open-source technique in Java, in this Blog, we will understand the process and mechanism about Hibernate with the top “50 Hibernate interview Questions with the answers.
What is Hibernate?
Hibernate is an open-source object-relational mapping, lightweight tool. It provides a framework to map object-oriented domain models to relational databases for web-based applications.
Here are a few questions we should ask about the application requirements before we adapt the Hibernate:
- Which data model we can use for the new project development, application design, or data model?
- What is the level of cache performance?
- How can we define simple or complex writing?
- What is the use of scalability, and in what scenario can we use it?
- In what scenario is automatic database versioning important?
- Do we need Relational Persistence for JAVA?
- What is the use of Support for Query Language, and what scenario can we use it?
- What are the Transparent Persistence process and their impact on the project?
It interprets data creation, data manipulation, and data access. It is a programming approach that maps the object to the data stored in the database.
What is Hibernate Framework?
Hibernate is an object-relational Java-based ORM tool mapping solution. It is an Object-relational mapping that is the programming procedure to map application domain model objects to the relational database tables. It implements a source of implementation of the Java Persistence API that delivers an excellent choice as an ORM tool with the advantages of loose coupling.
Benefits of Hibernate Framework
- Lightweight with Fast Performance: The performance of the Hibernate framework is agile with the help of a cache, which works internally in the Hibernate framework. Cache in the Hibernate framework is first-level cache and second-level cache.
- Database Autonomous Query: HQL (Hibernate Query Language) is the object-oriented variant of SQL. It creates independent database queries without writing database-specific queries.
- Automatic Table Creation: The Hibernate framework gives the capacity to generate the tables of the database automatically. Without manually creating tables in the database.
- Simplifies Complex Join: Retrieving data from aggregated tables is easy in the Hibernate framework.
- Accommodates Query Statistics and Database Status: Hibernate maintains Query cache and gives statistics fast results.
The Hibernate architecture consolidates many objects such as a persistent object, session factory, transaction factory, connection factory, session, transaction.
Hibernate architecture is classified into four layers:
- Java application tier
- Hibernate framework tier
- Backhand API tier
- Database tier
Why should we choose the Hibernate process?
Here are the below techniques and process which we can use choose when we start the adaptation of process:
- Hibernate allows developers to determine version type fields in the application, which can be modified in real-time data; this feature provides to the user they can save the data and can modify it at the same time.
- Hibernate implements assistance to JPA annotations For-Example: @Entity, @Table, @Col, etc.
- In Hibernate, connection pooling is a technique in the database connections when we create and store in the cache by the external tool, these connections we can reuse from the cache itself in the future if we would need to reuse to connect to the same database in our application which we created
- Hibernate extends the best degree of scalability in any environment. It can be practiced for all sizes of projects, from a small-scale app to one that is used by millions.
- In Hibernate, database versioning is an important tool that supports preventing changes being inadvertently rolled back by other users. It allows for the recording of version types within an application. When data is updated or stored, a version type and timestamp, we can also record for tracking.
- Hibernate implements transparent persistence, and the developer does not need to write code explicitly to map database table tuples to application objects during interaction with RDBMS.
- In Hibernate, Transaction management is the method of accomplishing a set of statements or commands. In Hibernate, transaction management is done by the transaction interface.
Five reasons to consider Hibernate over JDBC
- It solves object-relational complex mismatch problems:
It provides a quick solution in an object-oriented programming language with a relational database.
Example: Discrepancies in data types, structural and integrity differences, manipulative and transactional exceptions can all cause object-relational complex mismatches.
2. Automatic Object Mapping:
JDBC and Hibernate lie in the fact that it supports automatic object mapping.” Transparent Persistence “, this method provides Hibernate to draft database tables to the application objects through interaction.
- Hibernate Query Language (HQL)
Hibernate maintains Structured Query Language (SQL). JDBC only supports SQL, Hibernate Query Language (HQL) is related to SQL in that it is an object-oriented query language. To connect the way, HQL interprets queries toward the SQL queries that can then launch operations in the database.
- Database Independence
Hibernate provides for mapping connecting data tables and applications through XML files; it provides better ways to transfer the data to a new database if needed. While the manner of accessing databases, information is requisite, if in the case of the reusable of it. Caching is an essential component for database performance, which reduces the time and supports the applications in real-time.
- Connection pooling in Hibernate:
Hibernate can achieve more reliable performance; it provides “connection pooling”; this is a process to collect the database connections in the cache. These connections can be reusable from the cache itself if the app attempts to connect to the identical database multiple times.
Hibernate Interview Question and Answers
Question:1 How do you configure Hibernate to write the executed SQL statements and use bind parameters to the log file?
Answer: Here are the below steps:
Create two different log sections and log levels to log the executed SQL statements and bind parameters:
- Category org.hibernate.SQL.
- org.hibernate.type.descriptor.sql category with log level TRACE.
Question:2 Describe your favourite features of the Hibernate framework.
Answer: ORM Tool, Hibernate provides a powerful query language (HQL)
Question:3 How can you differentiate Entity Beans and Hibernate.
Answer: Entity beans are containers, classes, descriptors. Hibernate is a tool that instantly persists the object tree to a class.
Question:4 Explain the process of Session object and how we can use it in a first-level cache and a second-level cache?
Answer: First level caching: It starts with each session basis, with a “session” object.
Second level caching: It can be shareable beyond multiple sessions.
Question:5 How does inheritance work in Hibernate? What are the various strategies available to implement it?
Answer: Three types of Inheritance:
- Table Per Hierarchy
- Table Per Concrete class
- Table Per Subclass
Question:6 How does Locking work in Hibernate? What are the various locking mechanisms available?
Answer: Locking mechanisms are optimistic and pessimistic.
Question:7 How does transaction management work in Hibernate?
Answer: It works with the help of (JTA, JDBC).
Question:8 What is lazy loading in Hibernate?
Answer: This mechanism on entities and their associations by implementing a proxy of classes.
Question:9 What are the various fetching strategies available in Hibernate?
Answer: Join fetching and Select fetching
Question:10 What are the various fetching strategies available in Hibernate?
Answer: Join-Fetching and Select Fetchings are the fetchings available in Hibernate.
Question:11 What is the difference between getting () and load() methods in Hibernate?
Answer: getting() and load() which are used for fetching data for the assigned identifier. Get() method return null,load() method throws error of object not found type of exception.
Question:12 Why should you not make the entity class final?
Answer: It is used for entity binding.
Question:13 Explain the advantages and disadvantages of detached objects.
Answer: It connected with the Hibernate session in the past; it has a description in the database
Question:14 What is Hibernate Query Language (HQL)?
Answer: It’s based on OOPS concepts.
Question:15 State the role of SessionFactory interface plays in Hibernate.
Answer: It is a process of a thread-safe object and can be used in the application thread process
Question:16 What is the benefit of Hibernate over JDBC?
Answer: It provides the fastest performance and scalability.
Question:17 Describe some databases maintained by Hibernate.
Answer: Relational database using JDBC.
Question:18 How can you differentiate session.save() and session.persist() method?
Answer: Session.save() it’s used for saving the object in the database and session.persist() for transient, persistent objects.
Question:19 Explain about the update and merge method?
Answer: It can be used to transform the object, which is in a detached state.
Question:20 Is it possible to perform collection mapping with One-to-One and Many-to-One?
Answer: It can be used in a Table which is mapped to many rows in another table.
Question:21 How to perform a transaction in Hibernate?
Answer: With the help of the @transctional class declaration, we can perform a transaction.
Question:22 Where is object/relational mappings represented in Hibernate?
Answer: Hibernate ORM is an object/relational mappings.
Question:23 What is your thought of Light Object?
Answer: Session, Query, Criteria, Transaction are the concept of Light Object.
Question:24 What is @Transient in Hibernate? What is the advantage of this?
Answer: @Transient It applied in javax, its persistence package.
Question:25 How to combine Struts Spring Hibernate?
Answer: With the help of ContextLoaderPlugIn, we can combine.
Question: 26 Explain about the Hibernate Log4j Logging.
Answer: It consists of By log4j.xml file and log4j.properties file.
Question: 27 How can we restrict concurrent updates in Hibernate?
Answer: With the help of the Pessimistic locking Process, we can restrict concurrent updates.
Question: 28 What are the best methods for determining your Hibernate persistent classes?
Answer: There are many best methods and best practices that we can use with Mapping persistent class and its mechanisms.
Question: 29 What is the concept of Modifying persistent objects?
Answer: persistent objects are pursued by hibernating and are stored into the database when a commit request happens.
Question: 30 What is One to Many Bi-directional Relation in Hibernate?
Answer: It is the Reference of the handle of the association attribute of the many views as the benefit of the mappedBy attribute, Hibernate has all the erudition it needs. With these processes, we need to define a bidirectional many-to-one association.
Question: 31 What is Value replacement in Message Resource Bundle work?
Answer: Hibernate Validator’s ResourceBundleMessageInterpolator generates two instances of ResourceBundleLocator one for UserDefined validation Standard validation messages – defaultResourceBundleLocator.
Question: 32 Explain the process of the SQL statements execution order.
Answer: It s second-level cache in a particular order because of foreign-key constraints cannot be broken: Inserts, Updates, Deletion of array elements, Insertion of array elements, Deletes, in the direction they were presented
Question: 33 How can you set 2nd level cache in Hibernate with EHCache?
Answer: Terracotta Ehcache is a modern cache that worked as a Hibernate second-level cache. It can be practiced as a standalone second-level cache.
Question: 34 What is the main variance between Entity Beans and Hibernate?
Answer: Entity beans continue to be performed by descriptors, containers, classes. Hibernate is just a mechanism that immediately endures the object tree to a class hierarchy in a database.
Question: 35 Explain the steps to join handled using Hibernate?
Answer: With the help of SQL Join, we can handle it.
Question: 36 Explain the process of Hibernate proxy?
Answer: Hibernate proxy is “a functioning mechanism which allows you to serve as the deputy or substitute for another.” This refers to Hibernate when we call Session. load().
Question: 37 What is the main advantage of using the Hibernate than using the SQL?
Answer: With the practice of ORM and with the use of Hibernate, then using the SQL is that Hibernate avoids writing large scale queries.
Question: 38 Explain the design patterns which we can use in Hibernate?
Answer: Proxy pattern, Domain model, and object model are the design patterns.
Also Read: Career in Full Stack Development
Question: 39 Explain Hibernate’s Architecture.
Answer: Hibernate has a layered architecture which accommodates the user to manage without having to understand the underlying APIs
Question: 40 List out the Data types supported in Hibernate?
Question: 41 What is (JDO, CMP)?
Answer: Its Java persistence technologies.
Question: 42 What is the main variance between spring and Hibernate?
Answer: Spring and hibernate are two separate frameworks. Spring contracts with amplifying flow of the application. Hibernate is about the interaction between the application and the database.
Question: 43 When can we find the ORM solutions in Hibernate?
Answer: Hibernate is the concept of Object/Relational Mapping (ORM) solution for Java; the term Object/Relational Mapping regards the procedure of mapping data among an object model description to a relational data model description.
Question:44 Mention the step by step process to complete a transaction in Hibernate.
Answer: with the help of ACID-> properties (Atomicity, Consistency, Isolation, and Durability).
Question:45 Where are the mappings in Hibernate?
Answer: Hibernate mappings are the features of Hibernate; they organize the connection among two database tables while attributes in your model. That lets you quickly drive the associations in your model and Standards queries.
Question:46 Can you touch upon the varying types of relationships possible in Hibernate mapping?
Answer: One-to-one, Many-to-one, One-to-Many, Many-to-Many.
Question:47 Where can we define the object mappings in Hibernate?
Answer: Conversion of Java objects into SQL queries for storing the data.
Question:48 Can you list out the numerous collection types in Hibernate?
Answer: HashMap, HashSet, TreeSet, and Arraylist are the collection types in Hibernate.
Question:49 What’s the process of fetching the data from the database in Hibernate?
Answer: With the help of Hibernate criteria using beginTransaction() API function with the session, we can fetch the data.
Question:50 Explain about the Hibernate mapping files through the use of JPA annotations @NamedQuery and @NamedNativeQuery.
Answer: @NamedQuery and @NamedNativeQuery are the types of HQL query, which handles the complexities of transforming the HQL into the numerous SQL dialects.
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What are the limitations of using Hibernate?
The most prominent and common disadvantage of Hibernate is its complexity. There are plenty of APIs that one has to understand prior to gaining command on Hibernate and learning them requires a lot of effort. Furthermore, there are more complexities in terms of Joins and Mappings. Secondly, due to Hibernate’s poor performance for Batch processing, it is highly recommended to opt for JDBC completely for Batch processing. Third is Hibernate’s struggle with performance and debugging which is difficult especially if you are carrying out large projects. Finally, for small projects, it’s not advisable to use Hibernate Framework as there are lesser tables.
In what aspects is JDBC better than Hibernate?
In terms of Slowness, JDBC is a better option than Hibernate. Hibernate generates tons of SQL statements and queries during runtime whereas that’s not the case for JDBC. The other common advantage of using JDBC over Hibernate is its support for specific queries; for instance, you can’t insert multiple objects using a single query in a table through Hibernate whereas that can be done by JDBC. Writing queries in JDBC requires minimal effort as you can directly write them. Finally, JDBC’s compatibility with Batch processing is comparatively easier than Hibernate. Hibernate’s performance during Batch processing can cause issues when handling huge projects.
What are the few things that I should know before learning Hibernate?
Hibernate Framework primarily focuses on operations related to databases. Being an Object Relational Mapping Tool, Hibernate uses the mapping technique to map your Java class with Database tables. Therefore, the basic concepts that you can learn before diving deep into Hibernate are JDBC, SQL, Java Programming Language, and Relational Database Management System. Once you have a basic understanding of the above concepts, understanding Hibernate becomes easier.