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https://github.com/felixdes/hibernate6customfunctions
This project provides several examples of how to implement custom SQM functions in Hibernate 6.2
https://github.com/felixdes/hibernate6customfunctions
hibernate java postgresql spring-boot sql testcontainers
Last synced: 10 days ago
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This project provides several examples of how to implement custom SQM functions in Hibernate 6.2
- Host: GitHub
- URL: https://github.com/felixdes/hibernate6customfunctions
- Owner: FelixDes
- Created: 2023-03-29T21:19:59.000Z (almost 2 years ago)
- Default Branch: master
- Last Pushed: 2023-05-09T13:26:51.000Z (over 1 year ago)
- Last Synced: 2024-11-08T14:49:40.303Z (2 months ago)
- Topics: hibernate, java, postgresql, spring-boot, sql, testcontainers
- Language: Java
- Homepage:
- Size: 108 KB
- Stars: 4
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: Readme.md
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README
# Hibernate 6 custom SQM functions
## Description
This project provides several examples of how to implement custom SQM functions in Hibernate 6.2.
## Start Up
1. Run tests:
*[Hibernate6CustomFunctionsApplicationTests.java](/src/test/java/com/test/hibernate6customfunctions/Hibernate6CustomFunctionsApplicationTests.java)*
*Note*: database runs in docker container provided by Testcontainers
2. Explore
## Guide for implementing custom functions
1. Firstly, create your own SQL Dialect:
```java
public class BetterPGDialect extends PostgreSQLDialect {
// Default constructors...
}
```
2. Pass this dialect to Spring Boot config (or to Hibernate config):
```yaml
spring.jpa.properties:
hibernate.dialect: com.test.hibernate6customfunctions.dialect.BetterPGDialect
```
3. Create your SQM function
1. Firstly, define your function in database
```sql
create or replace function second_max_salary()
returns numeric as
$$
select max(salary)
from Employee
where salary <> (select max(salary) from Employee)
$$ language SQL;
```
2. Create new class: SecondMaxSqmFunction
```java
public class SecondMaxSqmFunction extends AbstractSqmSelfRenderingFunctionDescriptor {
public SecondMaxSqmFunction(String name, TypeConfiguration typeConfiguration) {
super(
name,
// Function type
FunctionKind.NORMAL,
// Setting argument validation. In this case we have no input args
new ArgumentTypesValidator(StandardArgumentsValidators.NO_ARGS),
// Setting return type: numeric (mapped for Double)
StandardFunctionReturnTypeResolvers.invariant(typeConfiguration.getBasicTypeRegistry()
.resolve(StandardBasicTypes.DOUBLE)),
// No arguments, so argument type resolver is null
null
);
}
}
```
3. Override the render method
```java
public class SecondMaxSqmFunction extends AbstractSqmSelfRenderingFunctionDescriptor {
// Constructor...
@Override
public void render(SqlAppender sqlAppender,
List extends SqlAstNode> sqlAstArguments, SqlAstTranslator> walker) {
render(sqlAppender, sqlAstArguments, null, walker);
}
@Override
public void render(
SqlAppender sqlAppender,
List extends SqlAstNode> sqlAstArguments,
Predicate filter,
SqlAstTranslator> translator) {
// Appending function name and its parenthesis to result SQL query
sqlAppender.appendSql(getName());
sqlAppender.appendSql("()");
// You can pass whole SQL query to sqlAppender
}
}
```
*Note*: for implementing aggregate functions you can
visit
*[CountItemsGreaterValSqmFunction.java](src/main/java/com/test/hibernate6customfunctions/fuctions/CountItemsGreaterValSqmFunction.java)*
4. Register your function to sqm function registry
```java
public class BetterPGDialect extends PostgreSQLDialect {
// Default constructors...
@Override
public void initializeFunctionRegistry(FunctionContributions functionContributions) {
super.initializeFunctionRegistry(functionContributions);
functionContributions.getSqmFunctionRegistry().register(
"secondMaxSalary", // Name that can be used in queries
new SecondMaxSqmFunction(
"second_max_salary", // Name of the function in the database
functionContributions.getTypeConfiguration())
);
}
}
```
*Note*: for Hibernate 6.1 it is:
```java
public class BetterPGDialect extends PostgreSQLDialect {
// Default constructors...
@Override
public void initializeFunctionRegistry(QueryEngine queryEngine) {
super.initializeFunctionRegistry(queryEngine);
queryEngine.getSqmFunctionRegistry().register(/*...*/);
}
}
```
5. Finally, use your custom function:
* *Example*: JPQL query in JpaRepository
```java
@Repository
public interface EmployeeRepo extends JpaRepository {
@Query("select secondMaxSalary()")
BigDecimal getSecondMaxSalaryCustom();
}
```
* *Example*: Criteria API
```java
@Repository
public class CriteriaRepo {
EntityManager entityManager;
// You can access HibernateCriteriaBuilder by calling
// entityManagerFactory.unwrap(SessionFactory.class);
HibernateCriteriaBuilder criteriaBuilder;
@Autowired
CriteriaRepo(EntityManagerFactory entityManagerFactory,
EntityManager entityManager) {
this.entityManager = entityManager;
SessionFactory sessionFactory = entityManagerFactory.unwrap(SessionFactory.class);
this.criteriaBuilder = sessionFactory.getCriteriaBuilder();
}
public Double getSecondMaxSalary() {
CriteriaQuery query = criteriaBuilder.createQuery(Double.class);
query.select(criteriaBuilder.function("secondMaxSalary", Double.class, null));
TypedQuery typedQuery = entityManager.createQuery(query);
return typedQuery.getSingleResult();
}
}
```
## License
> This project is distributed under the **MIT** license.