How to map Hibernate entity fields using camelCase to snake_case (underscore) database identifiers

Question

I have database fields in underscore. I have entity fields in camelcase. I can't change either of those.

Is there something, maybe a class level annotation I can use to default entity column name annotations to the camelcase equivalent?

for example, I have an entity like this:

@Entity
public class AuthorisationEntity {

    @Column(name = "non_recoverable")
    private BigDecimal nonRecoverable;

    @Column(name = "supplier_recoverable")
    private BigDecimal supplierRecoverable;

    @Column(name = "refund_amount")
    private BigDecimal refundAmount;

}

I dream of this:

@Entity
@DatabaseIsUnderscoreAndThisAnnotationConvertsThemToCamelCaseByDefault
public class AuthorisationEntity {

    private BigDecimal nonRecoverable;

    private BigDecimal supplierRecoverable;

    private BigDecimal refundAmount;

}

I can't find the class `@DatabaseIsUnderscoreAndThisAnnotationConvertsThemToCamelCaseByDefault` ... Just kidding, but I really wanted to paste this to my friend. :) — Kenny Cason, Nov 07 '16 at 23:37

Vlad Mihalcea · Answer 1 · 2021-01-09T13:25:25.003

You can achieve this using a custom Hibernate naming strategy.

All you need to do is to use the hibernate-types open-source project.

Hibernate 5.2 or later

You need to add the following Maven dependency:

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-52</artifactId>
    <version>${hibernate-types.version}</version>
</dependency>

And set the following Hibernate configuration property:

<property name="hibernate.physical_naming_strategy"
          value="com.vladmihalcea.hibernate.type.util.CamelCaseToSnakeCaseNamingStrategy"
/>

Hibernate 5.0 and 5.1

You need to add the following Maven dependency:

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-5</artifactId>
    <version>${hibernate-types.version}</version>
</dependency>

And set the following Hibernate configuration property:

<property name="hibernate.physical_naming_strategy"
          value="com.vladmihalcea.hibernate.type.util.CamelCaseToSnakeCaseNamingStrategy"
/>

Hibernate 4.3

You need to add the following Maven dependency:

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-43</artifactId>
    <version>${hibernate-types.version}</version>
</dependency>

And set the following Hibernate configuration property:

<property name="hibernate.ejb.naming_strategy"
          value="com.vladmihalcea.hibernate.type.util.CamelCaseToSnakeCaseNamingStrategy"
/>

Hibernate 4.2 and 4.1

You need to add the following Maven dependency:

<dependency>
    <groupId>com.vladmihalcea</groupId>
    <artifactId>hibernate-types-4</artifactId>
    <version>${hibernate-types.version}</version>
</dependency>

And set the following Hibernate configuration property:

<property name="hibernate.ejb.naming_strategy"
          value="com.vladmihalcea.hibernate.type.util.CamelCaseToSnakeCaseNamingStrategy"
/>

Testing time

Assuming you have the following entities:

@Entity(name = "BookAuthor")
public class BookAuthor {
 
    @Id
    private Long id;
 
    private String firstName;
 
    private String lastName;
 
    //Getters and setters omitted for brevity
}
 
@Entity(name = "PaperBackBook")
public class PaperBackBook {
 
    @Id
    @GeneratedValue(
        strategy = GenerationType.SEQUENCE
    )
    private Long id;
 
    @NaturalId
    private String ISBN;
 
    private String title;
 
    private LocalDate publishedOn;
 
    @ManyToOne(fetch = FetchType.LAZY)
    private BookAuthor publishedBy;
 
    //Getters and setters omitted for brevity
}

When using the CamelCaseToSnakeCaseNamingStrategy custom naming strategy, Hibernate is going to generate the following database schema using the hbm2ddl tool:

CREATE SEQUENCE hibernate_sequence
START WITH 1 INCREMENT BY 1
 
CREATE TABLE book_author (
    id          BIGINT NOT NULL,
    first_name  VARCHAR(255),
    last_name   VARCHAR(255),
    PRIMARY KEY (id)
)
 
CREATE TABLE paper_back_book (
    id              BIGINT NOT NULL,
    isbn            VARCHAR(255),
    published_on    DATE, 
    title           VARCHAR(255),
    published_by_id BIGINT, 
    PRIMARY KEY (id)
)

Cool, right?

Two shots of whiskey to this gentleman! This finally fixes snake case naming strategy for hibernate 5! — AbstractVoid, Mar 12 '19 at 18:29
This is not working. Do you have any idea what it could be? `javax.persistence.PersistenceException: org.hibernate.exception.SQLGrammarException: could not extract ResultSet`. I am using the `implementation("com.vladmihalcea", "hibernate-types-52","2.10.0")` and I put the property in the `hibernate.cfg` — Braian Coronel, Oct 14 '20 at 01:04
You can find plenty of test cases on GitHub that prove it works. Compare my tests to yours to see where they differ — Vlad Mihalcea, Oct 14 '20 at 04:59
hibernate-types is awesome! I'm using it for Postgres extensions support. — mokaymakci, Mar 31 '21 at 13:18

przemek hertel · Accepted Answer · 2014-09-05T08:51:04.427

15

You can use hibernate's naming strategy. Such naming strategy class describes how to generate database names for given java names.

See:

naming strategy example

second example

very good oracle naming strategy - it converts camel to underscore convention, and much more

edited Sep 05 '14 at 08:51

answered Sep 05 '14 at 08:39

przemek hertel

3,604
1
17
24

This looks like it will do what I need, nice one – Paul Stanley Sep 05 '14 at 08:59

score 3 · Answer 3 · answered Jun 27 '19 at 12:11

I was experiencing the same problem in a Spring boot application, I tried adding the above Hibernate config to the spring properties file with no success, added it as a java bean, again with no success.

I am using Hibernate Properties object, adding the hibernate configuration within this solved my issue:

        protected Properties buildHibernateProperties() {
        Properties hibernateProperties = new Properties();
        hibernateProperties.setProperty("hibernate.implicit_naming_strategy", SpringImplicitNamingStrategy.class.getName());
        hibernateProperties.setProperty("hibernate.physical_naming_strategy", SpringPhysicalNamingStrategy.class.getName());

        return hibernateProperties;
    }

score 1 · Answer 4 · edited Nov 15 '18 at 20:40

import org.hibernate.cfg.DefaultNamingStrategy;
import org.hibernate.cfg.ImprovedNamingStrategy;

public class NamingStratagyTest {
    public static void main(String[] args) {
        String colName = DefaultNamingStrategy.INSTANCE.columnName("UserName");
        System.out.println(colName); // UserName
        colName = ImprovedNamingStrategy.INSTANCE.columnName("UserName");
        System.out.println(colName);// user_name
    }
}

There you go, choose the naming strategy that suits your need.

How to map Hibernate entity fields using camelCase to snake_case (underscore) database identifiers

4 Answers4

Hibernate 5.2 or later

Hibernate 5.0 and 5.1

Hibernate 4.3

Hibernate 4.2 and 4.1

Testing time

Linked