Common

Basic principles and mechanisms of database modules in Kora.

We adhere to the concept that the best way to write queries for SQL databases is to use the SQL language. Other tools often have limitations on using specific functions of a particular database, or a complex program language for building queries that requires a separate understanding.

Entity

An entity is a representation of data from a database in the form of a class with fields.

Entities used as a return value must contain a single public constructor. This can be either a default constructor or a constructor with parameters. If Kora finds a constructor with parameters, the entity object will be created based on it. In the case of an empty constructor, the fields will be filled via setters.

Java Kotlin

public record Entity(String id, String name) {}

data class Entity(val id: String, val name: String)

Table

You can specify which table the entity belongs to, this will be needed if you use macros when building queries.

If no table is specified, macros will use the class name in snake_lower_case.

Java Kotlin

@Table("entities")
public record Entity(String id, String name) {}

@Table("entities")
data class Entity(val id: String, val name: String)

Identifier

Since all data manipulations are performed by converting the entity into a driver query, there is no need to allocate a special primary key within an entity to work with the entity.

Identifying what exactly is a primary key can be useful when using macros, the @Id annotation can be used for this purpose.

Java Kotlin

public record Entity(@Id String id, String name) {}

data class Entity(@field:Id val id: String, val name: String)

Sequential

Let's look at creating an identity as a sequence of numbers using Postgres as an example, Kora suggests using the database mechanism identity column.

An example table for such an entity would look like this:

CREATE TABLE IF NOT EXISTS entities
(
    id BIGINT GENERATED ALWAYS AS IDENTITY,
    name VARCHAR NOT NULL,
    PRIMARY KEY (id)
);

The identifier will be created at the stage of insertion into the database, and it is supposed to be received in the application code with the help of RETURNING construction at insertion:

Java Kotlin

public record Entity(Long id, String name) {}

@Repository
public interface EntityRepository extends JdbcRepository {

    @Query("SELECT * FROM entities WHERE id = :id")
    @Nullable
    Entity findById(long id);

    @Query("INSERT INTO entities(name) VALUES (:entity.name) RETURNING id")
    long insert(Entity entity);
}

data class Entity(val id: Long, val name: String)

@Repository
interface EntityRepository : JdbcRepository {

    @Query("SELECT * FROM entities WHERE id = :id")
    fun findById(id: Long): Entity?

    @Query("INSERT INTO entities(name) VALUES (:entity.name) RETURNING id")
    fun insert(entity: Entity): Long
}

Random

It is suggested to use the standard UUID from Java to create a random identifier:

An example table for such an entity would look like this:

CREATE TABLE IF NOT EXISTS entities
(
    id UUID NOT NULL,
    name VARCHAR NOT NULL,
    PRIMARY KEY (id)
);

The identifier will be created at the stage of object creation in the custom application code:

Java Kotlin

public record Entity(UUID id, 
                     String name) {}

@Repository
public interface EntityRepository extends JdbcRepository {

    @Query("SELECT * FROM entities WHERE id = :id")
    @Nullable
    Entity findById(UUID id);

    @Query("INSERT INTO entities(id, name) VALUES (:entity.id, :entity.name)")
    void insert(Entity entity);
}

data class Entity(val id: UUID,
                  val name: String)

@Repository
interface EntityRepository : JdbcRepository {

    @Query("SELECT * FROM entities WHERE id = :id")
    fun findById(id: UUID): Entity?

    @Query("INSERT INTO entities(id, name) VALUES (:entity.id, :entity.name)")
    fun insert(entity: Entity)
}

Composite

When a composite key is required, it is intended to use the @Embedded annotation to create embedded fields.

Naming

By default, entity field names are translated to snake_lower_case when retrieving a result.

If you want to customize the mapping of specific fields from the database to an entity, you can use the @Column annotation:

Java Kotlin

public record Entity(@Column("ID") String id, 
                     @Column("NAME") String name) {}

data class Entity(@field:Column("ID") val id: String,
                  @field:Column("NAME") val name: String)

Naming Strategy

If you want to use a naming strategy for the entire entity, it is suggested to create a NameConverter implementation and then use it in the @NamingStrategy annotation. It is required that the NameConverter implementation has a constructor without parameters.

Either use the available strategies from Kora:

• NoopNameConverter - the strategy uses the default field name.
• SnakeCaseNameConverter - strategy uses snake_lower_case.
• SnakeCaseUpperNameConverter - strategy uses SNAKE_UPPER_CASE.
• PascalCaseNameConverter - the strategy uses PascalCase.
• CamelCaseNameConverter - the strategy uses camelCase.

Java Kotlin

@NamingStrategy(NoopNameConverter.class)
public record Entity(String id, 
                     String name) {}

@NamingStrategy(NoopNameConverter::class.java)
data class Entity(val id: String,
                  val name: String)

Required fields

Java Kotlin

By default, all fields declared in an entity are considered required (NotNull).

public record Entity(String id,
                     String name) {}

By default, all fields declared in an entity that do not use the Kotlin Nullability syntax are considered required (NotNull).

data class Entity(val id: String,
                  val name: String)

Optional fields

Java Kotlin

In case a field in an entity is optional, that is, it may not exist then, you can use the @Nullable annotation to match the field in Json and DTO.

public record Entity(String id, 
                     @Nullable String name) {} //(1)!

1. Any @Nullable annotation will do, such as javax.annotation.Nullable / jakarta.annotation.Nullable / org.jetbrains.annotations.Nullable / etc.

It is also possible to specify optional constructor parameters in case the canonical constructor of Record is overridden:

public record Entity(String id,
                     String name) {

    public Entity(String id, 
                  @Nullable String name) { //(1)!
        this.id = id;
        this.name = name;
    }
}

1. Any @Nullable annotation will do, such as javax.annotation.Nullable / jakarta.annotation.Nullable / org.jetbrains.annotations.Nullable / etc.

It is expected to use the Kotlin Nullability syntax and mark such a parameter as Nullable:

data class Entity(val id: String,
                  val name: String?)

Embedded fields

In case you want to use nested fields, i.e. convert entity fields into specific classes, you can use the @Embedded annotation.

Suppose there is a SQL table where there is a composite key which we want to express as a separate class:

CREATE TABLE IF NOT EXISTS entities
(
    name    VARCHAR NOT NULL,
    surname VARCHAR NOT NULL,
    info    VARCHAR NOT NULL,
    PRIMARY KEY (name, surname)
)

Then the entity will look like this:

Java Kotlin

public record Entity(@Id @Embedded UserID id,
                     @Column("info") String info) {

    public record UserID(String name, String surname) {}
}

data class Entity(
    @field:Id @field:Embedded val id: UserID,
    @field:Column("name") val info: String
) {

    data class UserID(
        val name: String,
        val surname: String
    )
}

Then the repository for such an entity would look like this:

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Query("""
            SELECT * FROM entities
            WHERE name = :id.name AND surname = :id.surname;
            """)
    @Nullable
    Entity findById(Entity.UserID id);

    @Query("""
        INSERT INTO entities(name, surname, info)
        VALUES (:entity.id.name, :entity.id.surname, :entity.info)
        """)
    void insert(Entity entity);
}

@Repository
interface EntityRepository : JdbcRepository {

    @Query(
        """
        SELECT * FROM entities
        WHERE name = :id.name AND surname = :id.surname;
        """
    )
    fun findById(id: Entity.CompositeID): Entity?

    @Query(
        """
        INSERT INTO entities(name, surname, name)
        VALUES (:entity.id.name, :entity.id.surname, :entity.info)
        """
    )
    fun insert(entity: Entity)
}

In case the fields shared a common prefix, it could be specified in the @Embedded("user_") annotation:

CREATE TABLE IF NOT EXISTS entities
(
    user_name       VARCHAR NOT NULL,
    user_surname    VARCHAR NOT NULL,
    info            VARCHAR NOT NULL,
    PRIMARY KEY (user_name, user_surname)
)

Repository

Main tool for working with databases in Kora is to use repository pattern when designing the database access abstraction. Repository interface must be annotated with @Repository. Queries for repository methods are described using the @Query annotation. Repository implementation is created at compile time, all @Query methods will execute described query and assemble the query arguments and process the result optimally.

SQL queries are supposed to be written by the developer because it increases the developer's understanding of the query plan, gives more insight and context to the developer about what he is doing and how his query will work. You can use macros to improve the user experience to avoid writing all model fields/columns.

Repository must extend of one of the implementations, in the examples below the JDBC implementation will be considered:

Java Kotlin

@Repository //(1)!
public interface EntityRepository extends JdbcRepository {

    public record Entity(String id, String name) { }

    //(2)!
    @Query("SELECT * FROM entities WHERE id = :id")
    @Nullable
    Entity findById(String id);
}

1. Indicates that the interface is a repository.
2. Indicates that it is necessary to create a method implementation that executes the SQL query specified in the annotation.

@Repository //(1)!
interface EntityRepository : JdbcRepository {

    data class Entity(val id: String, val name: String)

    //(2)!
    @Query("SELECT * FROM entities WHERE id = :id")
    fun findById(id: String): Entity?
}

1. Indicates that the interface is a repository.
2. Indicates that it is necessary to create a method implementation that executes the SQL query specified in the annotation.

Batch query

Kora supports batch queries with the @Batch annotation.

Unlike executing SQL queries sequentially, batch processing allows you to send an entire set of queries in a single call, reducing the number of network connections required and allowing some queries to be executed in parallel on the database side, which can increase the speed of execution.

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Query("INSERT INTO entities(id, name) VALUES (:entity.id, :entity.name)")
    void insert(@Batch List<Entity> entity);
}

@Repository
interface EntityRepository : JdbcRepository {

    @Query("INSERT INTO entities(id, name) VALUES (:entity.id, :entity.name)")
    fun insert(@Batch entity: List<Entity>)
}

Affected rows

Kora does not process the contents of the query, the result of the method is always derived from the rows returned by the database. If you want to get the number of updated rows as a result, you should use a special type UpdateCount.

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Query("INSERT INTO entities(id, name) VALUES (:entity.id, :entity.name)")
    UpdateCount insert(Entity entity);
}

@Repository
interface EntityRepository : JdbcRepository {

    @Query("INSERT INTO entities(id, name) VALUES (:entity.id, :entity.name)")
    fun insert(entity: Entity): UpdateCount
}

Manual query

In case there is not enough functionality for some reason with queries in @Query annotation or manual control of the connection is required, you can use the built-in connection factory method to create a method with fully manual control.

You can also use other repository methods within the method and they will also be executed within a single transaction if required. For more details about transactions, see the documentation for the specific repository implementation.

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    public record Entity(Long id, String name) {}

    default int insert(Entity entity) {
        return getJdbcConnectionFactory().inTx(connection -> {
            String sql = "INSERT INTO entities(name) VALUES (?) RETURNING id";
            try(PreparedStatement preparedStatement = connection.prepareStatement(sql)) {
                preparedStatement.setString(1, entity.name());
                try(ResultSet resultSet = preparedStatement.executeQuery()) {
                    return resultSet.getInt(1);
                }
            }
        });
    }
}

@Repository
interface EntityRepository : JdbcRepository {

    data class Entity(val id: Long, val name: String)

    fun insert(entity: Entity): Int {
        return jdbcConnectionFactory.inTx<Int> { connection ->
            val sql = "INSERT INTO entities(name) VALUES (?) RETURNING id"
            connection.prepareStatement(sql).use { preparedStatement ->
                preparedStatement.setString(1, entity.name)
                preparedStatement.executeQuery().use { resultSet -> resultSet.getInt(1) }
            }
        }
    }
}

Macros

The most frustrating part of writing SQL queries can be listing and keeping the columns and fields of an entity up to date.

In order to solve this problem you can use special macros constructions within the SQL query within the @Query annotation. These constructions allow you to operate target entity and expand it into specific SQL constructions and easily augment into SQL queries. Macros is an assistant when writing SQL queries, expands into constructions that the user could write with his own hands.

The syntax of the macros looks as follows: %{return#selects}.

1. The macros is limited by the syntactic construction %{ and }
2. The target of the macros is specified first, it can be either the name of any method argument or the return value using the return keyword
3. Then the # character is used to separate the macros target and the macros command
4. The macros command is then specified, which tells which SQL construction to expand the entity into

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Table("entities")
    public record Entity(@Id Long id, 
                         @Column("entity_name") String name, 
                         String code) {}

    @Query("SELECT %{return#selects} FROM %{return#table}") //(1)!
    List<Entity> findAll();
}

1. Expands into a query:

   SELECT id, entity_name, code FROM entities
   

@Repository
interface EntityRepository : JdbcRepository {

    @Table("entities")
    data class Entity(@field:Id val id: Long, 
                      @field:Column("entity_name") val name: String, 
                      val code: String)

    @Query("SELECT %{return#selects} FROM %{return#table}") //(1)!
    fun findAll(): List<Entity>
}

1. Expands into a query:

   SELECT id, entity_name, code FROM entities
   

Commands

Available macros commands:

• table - construction exposes the entity value in annotation @Table or if none is available, translates the entity name to snake_lower_case
• selects - creates an entity column enumeration construction for a SELECT query
• inserts - creates a table, column enumeration construction and corresponding entity fields for an INSERT query
• updates - creates a column enumeration construction and corresponding entity fields for UPDATE query
• where - creates a column enumeration construction with a value from the entity for the WHERE part of the query

Field enumeration

The macros supports additional syntax for enumerating certain fields in a command, if you suddenly need to do a partial update or data retrieval. For this purpose, a special construction is used after the command: %{return#updates=name}.

Spaces can be placed only between fields in the enumeration or special enumeration symbol.

Special enumeration symbols are available:

1. = - only the entity fields name specified after the symbol will participate in the command expansion
2. -= - all entity fields except those specified after the symbol will participate in command expansion

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Table("entities")
    public record Entity(@Id Long id, 
                         @Column("entity_name") String name, 
                         String code) {}

    @Query("INSERT INTO %{entity#inserts=name,code}") //(1)!
    UpdateCount insert(Entity entity);
}

1. Expands into a query:

   INSERT INTO entities(entity_name, code) 
   VALUES(:entity.name, :entity.code)
   

@Repository
interface EntityRepository : JdbcRepository {

    @Table("entities")
    data class Entity(@field:Id val id: Long, 
                      @field:Column("entity_name") val name: String, 
                      val code: String)

    @Query("INSERT INTO %{entity#inserts=name,code}") //(1)!
    fun insert(entity: Entity): UpdateCount
}

1. Expands into a query:

   INSERT INTO entities(entity_name, code) 
   VALUES(:entity.name, :entity.code)
   

Identifier

When listing fields in a macro, it is possible to use the special keyword @id to refer immediately to the entity identifier annotated with annotation @Id.

This can be especially useful when the identifier is a compound key, to list all columns at once.

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Table("entities")
    public record Entity(@Id Long id, 
                         @Column("entity_name") String name, 
                         String code) {}

    @Query("INSERT INTO %{entity#inserts-=@id}") //(1)!
    UpdateCount insert(Entity entity);
}

1. Expands into a query:

   INSERT INTO entities(entity_name, code) 
   VALUES(:entity.name, :entity.code)
   

@Repository
interface EntityRepository : JdbcRepository {

    @Table("entities")
    data class Entity(@field:Id val id: Long, 
                      @field:Column("entity_name") val name: String, 
                      val code: String)

    @Query("INSERT INTO %{entity#inserts-=@id}") //(1)!
    fun insert(entity: Entity): UpdateCount
}

1. Expands into a query:

   INSERT INTO entities(entity_name, code) 
   VALUES(:entity.name, :entity.code)
   

Repository example

Example of a complete repository with all the basic methods for operating an entity for Postgres SQL:

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Table("entities")
    record Entity(@Id String id,
                  @Column("value1") int field1,
                  String value2,
                  @Nullable String value3) {}

    @Query("SELECT %{return#selects} FROM %{return#table} WHERE id = :id") //(1)!
    @Nullable
    Entity findById(String id);

    @Query("SELECT %{return#selects} FROM %{return#table}") //(2)!
    List<Entity> findAll();

    @Query("INSERT INTO %{entity#inserts}")  //(3)!
    UpdateCount insert(@Batch List<Entity> entity);

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}")  //(4)!
    UpdateCount update(@Batch List<Entity> entity);

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (id) DO UPDATE SET %{entity#updates}")  //(5)!
    UpdateCount upsert(@Batch List<Entity> entity);

    @Query("DELETE FROM entities WHERE id = :id")
    UpdateCount deleteById(String id);

    @Query("DELETE FROM entities")
    UpdateCount deleteAll();
}

1. Expands into a query:

   SELECT id, value1, value2, value3 
   FROM entities 
   WHERE id = :id
   

2. Expands into a query:

   SELECT id, value1, value2, value3 
   FROM entities
   

3. Expands into a query:

   INSERT INTO entities(id, value1, value2, value3) 
   VALUES(:entity.id, :entity.field1, :entity.value2, :entity.value3)
   

4. Expands into a query:

   UPDATE entities
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   WHERE id = :entity.id
   

5. Expands into a query:

   INSERT INTO entities(id, value1, value2, value3) 
   VALUES(:entity.id, :entity.value1, :entity.value2, :entity.value3)
   ON CONFLICT (id) DO UPDATE 
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   

@Repository
interface EntityRepository : JdbcRepository {

    @Table("entities")
    data class Entity(
        @field:Id val id: String,
        @field:Column("value1") val field1: Int,
        val value2: String,
        @field:Nullable val value3: String
    )

    @Query("SELECT %{return#selects} FROM %{return#table} WHERE id = :id") //(1)!
    fun findById(id: String?): Entity?

    @Query("SELECT %{return#selects} FROM %{return#table}") //(2)!
    fun findAll(): List<Entity>

    @Query("INSERT INTO %{entity#inserts}") //(3)!
    fun insert(@Batch entity: List<Entity>): UpdateCount

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}") //(4)!
    fun update(@Batch entity: List<Entity>): UpdateCount

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (id) DO UPDATE SET %{entity#updates}") //(5)!
    fun upsert(@Batch entity: List<Entity>): UpdateCount

    @Query("DELETE FROM entities WHERE id = :id")
    fun deleteById(id: String): UpdateCount

    @Query("DELETE FROM entities")
    fun deleteAll(): UpdateCount
}

1. Expands into a query:

   SELECT id, value1, value2, value3 
   FROM entities 
   WHERE id = :id
   

2. Expands into a query:

   SELECT id, value1, value2, value3 
   FROM entities
   

3. Expands into a query:

   INSERT INTO entities(id, value1, value2, value3) 
   VALUES(:entity.id, :entity.value1, :entity.value2, :entity.value3)
   

4. Expands into a query:

   UPDATE entities
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   WHERE id = :entity.id
   

5. Expands into a query:

   INSERT INTO entities(id, value1, value2, value3) 
   VALUES(:entity.id, :entity.value1, :entity.value2, :entity.value3)
   ON CONFLICT (id) DO UPDATE 
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   

Composite example

Example repository with composite identifier and basic methods to operate on an entity, it is almost identical to the previous one except for the WHERE conditions for search and delete for Postgres SQL:

Java Kotlin

@Repository
public interface EntityRepository extends JdbcRepository {

    @Table("entities")
    record Entity(@Id @Embedded  EntityId id,
                  @Column("value1") int field1,
                  String value2,
                  @Nullable String value3) {

        public record EntityId(String code, String type) { }
    }

    @Query("SELECT %{return#selects} FROM %{return#table} WHERE %{id#where}") //(1)!
    @Nullable
    Entity findById(EntityId id);

    @Query("SELECT %{return#selects} FROM %{return#table}") //(2)!
    List<Entity> findAll();

    @Query("INSERT INTO %{entity#inserts}")  //(3)!
    UpdateCount insert(@Batch List<Entity> entity);

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}")  //(4)!
    UpdateCount update(@Batch List<Entity> entity);

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (code, type) DO UPDATE SET %{entity#updates}")  //(5)!
    UpdateCount upsert(@Batch List<Entity> entity);

    @Query("DELETE FROM entities WHERE %{id#where}")
    UpdateCount deleteById(EntityId id);

    @Query("DELETE FROM entities")
    UpdateCount deleteAll();
}

1. Раскрывается в запрос:

   SELECT code, type, value1, value2, value3 
   FROM entities 
   WHERE code = :code AND type = :type
   

2. Раскрывается в запрос:

   SELECT code, type, value1, value2, value3 
   FROM entities
   

3. Раскрывается в запрос:

   INSERT INTO entities(code, type, value1, value2, value3) 
   VALUES(:entity.code, :entity.type, :entity.value1, :entity.value2, :entity.value3)
   

4. Раскрывается в запрос:

   UPDATE entities
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   WHERE code = :entity.id.code AND type = :entity.id.type
   

5. Раскрывается в запрос:

   INSERT INTO entities(code, type, value1, value2, value3) 
   VALUES(:entity.code, :entity.type, :entity.value1, :entity.value2, :entity.value3)
   ON CONFLICT (code, type) DO UPDATE 
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   

@Repository
interface EntityRepository : JdbcRepository {

    @Table("entities")
    data class Entity(
        @field:Id @field:Embedded val id: EntityId,
        @field:Column("value1") val field1: Int,
        val value2: String,
        val value3: String?
    ) {

        data class EntityId(val code: String, val type: String)
    }

    @Query("SELECT %{return#selects} FROM %{return#table} WHERE %{id#where}") //(1)!
    fun findById(id: EntityId): Entity?

    @Query("SELECT %{return#selects} FROM %{return#table}") //(2)!
    fun findAll(): List<Entity>

    @Query("INSERT INTO %{entity#inserts}") //(3)!
    fun insert(@Batch entity: List<Entity>): UpdateCount

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}") //(4)!
    fun update(@Batch entity: List<Entity>): UpdateCount

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (code, type) DO UPDATE SET %{entity#updates}") //(5)!
    fun upsert(@Batch entity: List<Entity>): UpdateCount

    @Query("DELETE FROM entities WHERE %{id#where}")
    fun deleteById(id: EntityId): UpdateCount

    @Query("DELETE FROM entities")
    fun deleteAll(): UpdateCount
}

1. Раскрывается в запрос:

   SELECT code, type, value1, value2, value3 
   FROM entities 
   WHERE code = :code AND type = :type
   

2. Раскрывается в запрос:

   SELECT code, type, value1, value2, value3 
   FROM entities
   

3. Раскрывается в запрос:

   INSERT INTO entities(code, type, value1, value2, value3) 
   VALUES(:entity.code, :entity.type, :entity.value1, :entity.value2, :entity.value3)
   

4. Раскрывается в запрос:

   UPDATE entities
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   WHERE code = :entity.id.code AND type = :entity.id.type
   

5. Раскрывается в запрос:

   INSERT INTO entities(code, type, value1, value2, value3) 
   VALUES(:entity.code, :entity.type, :entity.value1, :entity.value2, :entity.value3)
   ON CONFLICT (code, type) DO UPDATE 
   SET value1 = :entity.field1, value2 = :entity.value2, value3 = :entity.value3 
   

Inheritance example

You can also create an abstract CRUD repository and then use it in inheritance for Postgres SQL:

Java Kotlin

public interface PostgresJdbcCrudRepository<K, V> extends JdbcRepository {

    @Query("SELECT %{return#selects} FROM %{return#table}")
    List<V> findAll();

    @Query("INSERT INTO %{entity#inserts}")
    UpdateCount insert(V entity);

    @Query("INSERT INTO %{entity#inserts}")
    UpdateCount insert(@Batch List<V> entity);

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}")
    UpdateCount update(V entity);

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}")
    UpdateCount update(@Batch List<V> entity);

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (%{entity#selects = @id}) DO UPDATE SET %{entity#updates}")
    UpdateCount upsert(V entity);

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (%{entity#selects = @id}) DO UPDATE SET %{entity#updates}")
    UpdateCount upsert(@Batch List<V> entity);

    @Query("DELETE FROM %{entity#table} WHERE %{entity#where = @id}")
    UpdateCount delete(V entity);

    @Query("DELETE FROM %{entity#table} WHERE %{entity#where = @id}")
    UpdateCount delete(@Batch List<V> entity);
}

@Repository
public interface EntityRepository extends PostgresJdbcCrudRepository<String, Entity> {

    @Table("entities")
    record Entity(@Id String id,
                  @Column("value1") int field1,
                  String value2,
                  @Nullable String value3) {
    }

    @Query("DELETE FROM entities WHERE id = :id")
    UpdateCount deleteById(String id);

    @Query("DELETE FROM entities")
    UpdateCount deleteAll();
}

interface PostgresJdbcCrudRepository<K, V> : JdbcRepository {

    @Query("SELECT %{return#selects} FROM %{return#table}")
    fun findAll(): List<V>

    @Query("INSERT INTO %{entity#inserts}")
    fun insert(entity: V): UpdateCount

    @Query("INSERT INTO %{entity#inserts}")
    fun insert(@Batch entity: List<V>): UpdateCount

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}")
    fun update(entity: V): UpdateCount

    @Query("UPDATE %{entity#table} SET %{entity#updates} WHERE %{entity#where = @id}")
    fun update(@Batch entity: List<V>): UpdateCount

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (%{entity#selects = @id}) DO UPDATE SET %{entity#updates}")
    fun upsert(entity: V): UpdateCount

    @Query("INSERT INTO %{entity#inserts} ON CONFLICT (%{entity#selects = @id}) DO UPDATE SET %{entity#updates}")
    fun upsert(@Batch entity: List<V>): UpdateCount

    @Query("DELETE FROM %{entity#table} WHERE %{entity#where = @id}")
    fun delete(entity: V): UpdateCount

    @Query("DELETE FROM %{entity#table} WHERE %{entity#where = @id}")
    fun delete(@Batch entity: List<V>): UpdateCount
}

@Repository
interface EntityRepository : PostgresJdbcCrudRepository<String, Entity> {

    @Table("entities")
    data class Entity(
        @field:Id val id: String,
        @field:Column("value1") val field1: Int,
        val value2: String,
        @field:Nullable val value3: String
    )

    @Query("DELETE FROM entities WHERE id = :id")
    fun deleteById(id: String): UpdateCount

    @Query("DELETE FROM entities")
    fun deleteAll(): UpdateCount
}