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;  } 

Answer 1

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?