Blog Archives

02: Understanding Hibernate proxy objects and avoiding potential pitfalls

Q. How does hibernate support lazy loading? A. Hibernate uses a proxy object to support lazy loading. Basically as soon as you reference a child or lookup object via the...



03: Identifying and fixing NonUniqueObjectException in Hibernate

NonUniqueObjectException is thrown when there is an object already associated with the session with the same id (primary key) (i.e. a duplicate). It is important to understand the concept of a “detached”

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04: Identifying and fixing LazyInitializationException in Hibernate

LazyInitializationException is thrown when an object becomes detached, and if you try to access associated (i.e. proxied) object(s) of a detached object.

Q. What is a detached object in Hibernate?

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05: Debugging Hibernate & handling 4 common issues

#1. Enable Logging in your log4j.xml, log4j.properties, or myapp-logback.xml

In the log4j.properties file, you can enable Hibernate SQL logging as shown below

or in your log4j.xml or myapp-logback.xml as

You can then check your logs for the SQLs executed and the parameters passed.

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07: Hibernate mistakes – accessing objects outside of a transaction

Hibernate does require the same EntityManager to be available in order to lazily load objects. If you have no EntityManager, then you have no knowledge of the datastore. … Read...



08: Hibernate automatic dirty checking of persistent objects and handling detached objects

Q1. What do you understand by automatic dirty checking in Hibernate? A1. Dirty checking is a feature of hibernate that saves time and effort to update the database when states...



09: Hibernate entities with auditable, soft delete & optimistic locking fields

There are certain generic columns that database tables have like Auto generated identity columns. Auditing columns like createdDtTm, createdBy, modifiedDtTm, and modifiedBy. Soft delete or logical delete flags like inactive...



10: Spring, JavaConfig (i.e @Configuration), JPA & Hibernate by example

Example #1 Wiring JDBC Datasource application.yml where the datasource properties are read from. Example #2 Wiring JDBC Datasource with JNDI Example #3 Wiring the JPA persistence unit processors Callback interface...



11: Hibernate dependency jars and plugins

Here is a sample maven pom.xml snippets containing the dependency jars.  The above snippet defines the version numbers. The snippet below defines the dependencies. If you want to auto-generate your...



12: Hibernate custom data type : Blob type example

There are times you want to define a custom data type in Hibernate. Here is an example of using a custom ImageType defined as a Blob databse type to store images,

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8 Hibernate interview Q&As

FAQ Hibernate interview questions & answers are covered below.

Q1. What is an Object-to-Relational Mapping (i.e. ORM) tool?
A1. There are several ways to persist data to a database from your Java applications.

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Hibernate First & second level cache interview Q&As

Q. What is a first-level cache in Hibernate? A. First-level cache always is associated with a “Session” object. Hibernate uses this cache by default. You can’t turn it off. …...



Q08 – Q15 Hibernate interview Q&As

Extends 15+ Hibernate interview questions & answers – Q1 – Q7. Hibernate interview questions & answers with diagrams & code snippets to not only prepare for the job interviews, …...



800+ Java Interview Q&As

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