Registering a SQL function with JPA and Hibernate

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I would like to know what's the best way to register a custom SQL function with JPA/Hibernate.

Do I have to go through extending the MysqlInnodb dialect or is there a better way?

Can anyone please provide code samples and pointers to relevant documentation?

Yes extending the dialect is a good way of registering custom SQL function.

Add something like this in your Dialect classes constructor.

registerFunction("current_timestamp", new NoArgSQLFunction(Hibernate.TIMESTAMP) );
registerFunction("date", new StandardSQLFunction(Hibernate.DATE) );

Look at the source code of one of the existing dialect classes. http://www.koders.com/java/fid0E7F787E2EC52F1DA8DFD264EDFBD2DE904A0927.aspx

How to call custom database functions with JPA and Hibernate, I register it as a StandardSQLFunction which dynamically defines the return type based on the type of the first parameter. package org.thoughts.on.java.db;. However, if the SQL function is used in the SELECT clause, and Hibernate has not registered the SQL function (be it a database-specific or user-defined function), you will have to register the function prior to using it in an entity query.

As I explained in this article, since Hibernate ORM 5.2.18 and 5.3.1, the best way to register a SQL function is to supply a MetadataBuilderContributor like this:

public class SqlFunctionsMetadataBuilderContributor 
        implements MetadataBuilderContributor {

    @Override
    public void contribute(MetadataBuilder metadataBuilder) {
        metadataBuilder.applySqlFunction(
            "group_concat",
            new StandardSQLFunction(
                "group_concat", 
                StandardBasicTypes.STRING
            )
        );
    }
}

Which you can pass to Hibernate via the hibernate.metadata_builder_contributor configuration property:

<property>
    name="hibernate.metadata_builder_contributor" 
    value="com.vladmihalcea.book.hpjp.hibernate.query.function.SqlFunctionsMetadataBuilderContributor"
</property>

Or, if you bootstrap Hibernate natively, you can just apply the SQL function to the MetadataBuilder during bootstrap.

You might read articles telling you to register the SQL function by extending the Hibernate Dialect, but that's a naive solution. For more details, read this article.

The best way to use SQL functions in JPQL or Criteria API queries , Learn how to register and call any SQL function in JPQL, HQL or JPA Criteria API queries with JPA and Hibernate. JPA supports calling user-defined functions like this: select i from Item i where function( 'substring', i.name, 1, 3 ) = 'abc'" ) First of all, your function is not complete, you only pasted the body, but not the function name. Second, you are concatenation strings so you are risking SQL Injection attacks. Third, the HQL is malformed: from e.id

Register SQL Method every version

        //Add Hibernate Properties
        properties.put("hibernate.dialect",
                        "com.sparkslink.web.config.sql.RegisterSqlFunction");

        //Create A Class 
        public class RegisterSqlFunction extends MySQLDialect {

            public RegisterSqlFunction() {
                super();
                registerFunction("group_concat", new StandardSQLFunction("group_concat", StandardBasicTypes.STRING));
            }
        }

        //Dao Method

        public List<Client> getTest() {
                Query query = getSession()
                        .createQuery("SELECT sl.name as name ,group_concat(sl.domain) as domain FROM SlClient sl GROUP BY sl.name");
                query.setResultTransformer(Transformers.aliasToBean(Client.class));
                return query.list();
            }
//DTO Class
    public class Client {
        private String name;
        private String domain;
    //Getter 
    //Setter
    }

JPA + Hibernate, The complete list of H2 built-in database functions is here. public class ExampleMain { private hibernate-core 5.2.13.Final: The core O/RM functionality as provided by Hibernate. Date; import java.sql.Time; import java.sql. Using the hibernate.metadata_builder_contributor configuration property is the best way to register a SQL function with Hibernate, and you can parameterize the function so that you can pass it entity properties and even standard query parameters, as it’s the case of the UTC parameter we used when calling the DATE_TRUNCT function.

Hibernate ORM 5.2.18.Final User Guide, Configuring the SessionFactory Metadata via the JPA bootstrap Serializable, and registered under the specific java.io. be generated by calls to the standard ANSI SQL function current_timestamp (rather than triggers or DEFAULT values):. In this tutorial, we will learn how to define a one-to-many unidirectional mapping between two entities using JPA and Hibernate.

Uses of Interface org.hibernate.dialect.function.SQLFunction , Methods in org.hibernate.cfg with parameters of type SQLFunction (as defined by both the ANSI SQL and JPA specs) in cases where the dialect may not support the full trim function itself. Locate a registered sql function by name. If you use Hibernate as your JPA implementation, you have to also register the function in the dialect to use it in the SELECT part of the query. You therefore should extend an existing dialect for your specific database and register the additional functions in the constructor.

Stored Procedures with Hibernate, Stored Procedures are sets of compiled SQL statements residing in the If you are using JPA 2.1 and the Hibernate implementation of the  Thanks to the ListResultTransformer utility, that’s also offered by the amazing Hibernate Types project, we can use a Java Lambda function to define the Hibernate ResultTransformer logic. For more details about DTO projections with JPA and Hibernate, check out this article.

Comments
  • Do I have to create a new class and extends an existing dialect or is there another simpler way?
  • Yes create a new class that extends an existing dialect class. Use your class as the dialect class in the hibernate configuration.
  • Thanks! Also: Interesting and relevant link