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Questions tagged [hibernate]

Hibernate is an object-relational mapping (ORM) library for the Java language enabling developers to utilize POJO-style domain models in their applications in ways extending well beyond Object/Relational Mapping.

Hibernate is the umbrella for a collection of , most notably Hibernate ORM which provides Object/Relational Mapping for domain objects.
In addition to its own "native" API, Hibernate ORM is also an implementation of the Java Persistence API () specification.

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Beginner's resources

Frequently asked questions

People often ask the following questions:

94278 questions
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What are the possible values of the Hibernate hbm2ddl.auto configuration and what do they do

I really want to know more about the update, export and the values that could be given to hibernate.hbm2ddl.auto I need to know when to use the update and when not? And what is the alternative? These are changes that could happen over DB: new…
Suzan
878
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33 answers

How to fix the Hibernate "object references an unsaved transient instance - save the transient instance before flushing" error

I receive following error when I save the object using Hibernate object references an unsaved transient instance - save the transient instance before flushing
Tushar Ahirrao
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Difference between FetchType LAZY and EAGER in Java Persistence API?

What is the difference between FetchType.LAZY and FetchType.EAGER in Java Persistence API?
leon
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22 answers

What's the difference between JPA and Hibernate?

I understand that JPA 2 is a specification and Hibernate is a tool for ORM. Also, I understand that Hibernate has more features than JPA 2. But from a practical point of view, what really is the difference? I have experience using iBatis and now…
Anthony
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628
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9 answers

JPA JoinColumn vs mappedBy

What is the difference between: @Entity public class Company { @OneToMany(cascade = CascadeType.ALL , fetch = FetchType.LAZY) @JoinColumn(name = "companyIdRef", referencedColumnName = "companyId") private List branches; …
Mike
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18 answers

Hibernate throws MultipleBagFetchException - cannot simultaneously fetch multiple bags

Hibernate throws this exception during SessionFactory creation: org.hibernate.loader.MultipleBagFetchException: cannot simultaneously fetch multiple bags This is my test case: Parent.java @Entity public Parent { @Id …
blow
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14 answers

What is the difference between DAO and Repository patterns?

What is the difference between Data Access Objects (DAO) and Repository patterns? I am developing an application using Enterprise Java Beans (EJB3), Hibernate ORM as infrastructure, and Domain-Driven Design (DDD) and Test-Driven Development (TDD) as…
Thurein
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24 answers

How can I log SQL statements in Spring Boot?

I want to log SQL statements to a file. I have the following properties in…
Oleg Pavliv
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513
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33 answers

How to print a query string with parameter values when using Hibernate

Is it possible in Hibernate to print generated SQL queries with real values instead of question marks? How would you suggest to print queries with real values if it is not possible with Hibernate API?
craftsman
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32 answers

How to solve the “failed to lazily initialize a collection of role” Hibernate exception

I have this problem: org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: mvc3.model.Topic.comments, no session or session was closed Here is the model: @Entity @Table(name = "T_TOPIC") public class Topic…
Eugene
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447
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4 answers

Create the perfect JPA entity

I've been working with JPA (implementation Hibernate) for some time now and each time I need to create entities I find myself struggling with issues as AccessType, immutable properties, equals/hashCode, ... . So I decided to try and find out the…
Stijn Geukens
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435
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5 answers

Hibernate show real SQL

if I set true in my hibernate.cfg.xml configuration file in the console I can see the SQL. But it's not real SQL... Can I see the SQL code that will be passed directly to database? Example: I see select…
Tommaso Taruffi
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390
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20 answers

The JPA hashCode() / equals() dilemma

There have been some discussions here about JPA entities and which hashCode()/equals() implementation should be used for JPA entity classes. Most (if not all) of them depend on Hibernate, but I'd like to discuss them JPA-implementation-neutrally (I…
MRalwasser
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15 answers

Hibernate: hbm2ddl.auto=update in production?

Is it okay to run Hibernate applications configured with hbm2ddl.auto=update to update the database schema in a production environment?
cretzel
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379
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10 answers

What is the easiest way to ignore a JPA field during persistence?

I'm essentially looking for a "@Ignore" type annotation with which I can stop a particular field from being persisted. How can this be achieved?
m2o
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