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Version: 1.9.1

Configuration

Storm can be configured through StormConfig, system properties, or Spring Boot's application.yml. These properties control runtime behavior for features like dirty checking and entity caching. All properties have sensible defaults, so configuration is optional. Storm works out of the box without any configuration.

Properties​

PropertyDefaultDescription
storm.update.default_modeENTITYDefault update mode for entities without @DynamicUpdate
storm.update.dirty_checkINSTANCEDefault dirty check strategy (INSTANCE or VALUE)
storm.update.max_shapes5Maximum UPDATE shapes before fallback to full-row
storm.entity_cache.retentiondefaultCache retention mode: default or light
storm.template_cache.size2048Maximum number of compiled templates to cache
storm.validation.record_modefailRecord validation mode: fail, warn, or none
storm.validation.schema_modenoneSchema validation mode: none, warn, or fail (Spring Boot only)
storm.validation.strictfalseTreat schema validation warnings as errors

Setting Properties​

Via JVM arguments:

java -Dstorm.update.default_mode=FIELD \
     -Dstorm.update.dirty_check=VALUE \
     -Dstorm.update.max_shapes=10 \
     -Dstorm.entity_cache.retention=light \
     -Dstorm.template_cache.size=4096 \
     -jar myapp.jar

Programmatically via StormConfig:

StormConfig holds an immutable set of String key-value properties. Pass a StormConfig to ORMTemplate.of() to apply the configuration. Any property not explicitly set falls back to the system property, then to the built-in default.

val config = StormConfig.of(mapOf(
    "storm.update.default_mode" to "FIELD",
    "storm.entity_cache.retention" to "light",
    "storm.template_cache.size" to "4096"
))

val orm = ORMTemplate.of(dataSource, config)

// Or using the extension function
val orm = dataSource.orm(config)

When StormConfig is omitted, ORMTemplate.of(dataSource) reads system properties and built-in defaults automatically.

In Spring Boot's application.yml (requires storm-spring-boot-starter or storm-kotlin-spring-boot-starter):

storm:
  ansi-escaping: false
  update:
    default-mode: ENTITY
    dirty-check: INSTANCE
    max-shapes: 5
  entity-cache:
    retention: default
  template-cache:
    size: 2048
  validation:
    record-mode: fail
    schema-mode: none
    strict: false

The Spring Boot Starter binds these properties and builds a StormConfig that is passed to the ORMTemplate factory. Values not set in YAML fall back to system properties and then to built-in defaults. See Spring Integration for details.

ORMTemplate Factory Overloads​

The ORMTemplate.of() factory method is the main entry point for creating an ORM template outside of Spring. It accepts optional parameters for configuration and template decoration, so you can combine StormConfig (for runtime properties) with a TemplateDecorator (for name resolution customization) at creation time.

The simplest form takes only a DataSource and uses all defaults. From there, you can add a StormConfig for property overrides, a decorator for custom naming conventions, or both. The decorator parameter is a UnaryOperator<TemplateDecorator> that receives the default decorator and returns a modified version.

// Minimal: defaults only
val orm = dataSource.orm

// With configuration
val orm = dataSource.orm(config)

// With decorator (custom name resolution)
val orm = dataSource.orm { decorator ->
    decorator.withTableNameResolver(TableNameResolver.toUpperCase(TableNameResolver.DEFAULT))
}

// With both configuration and decorator
val orm = dataSource.orm(config) { decorator ->
    decorator.withColumnNameResolver(ColumnNameResolver.toUpperCase(ColumnNameResolver.DEFAULT))
}

When using Spring Boot, the starter creates the ORMTemplate for you and applies configuration from application.yml. You can still customize name resolution by defining a TemplateDecorator bean. See Spring Integration: Template Decorator for details.

Naming Conventions​

Storm uses pluggable name resolvers to convert Kotlin/Java names to database identifiers. By default, camelCase names are converted to snake_case. You can replace or wrap these resolvers to match any naming convention your database requires, whether that means uppercase identifiers, table prefixes, or entirely custom logic.

This section covers global name resolution configuration. For per-entity annotation overrides (@DbTable, @DbColumn), see Entities: Custom Table and Column Names.

Name Resolvers​

Storm splits name resolution into three independent concerns. Each resolver is a functional interface with a single method, so you can configure them with lambdas or with full class implementations.

ResolverMethod SignaturePurpose
TableNameResolverresolveTableName(RecordType)Maps an entity or projection class to a table name
ColumnNameResolverresolveColumnName(RecordField)Maps a record field to a column name
ForeignKeyResolverresolveColumnName(RecordField, RecordType)Maps a foreign key field to its column name, given the target entity type

The separation means you can, for example, use uppercase table names while keeping lowercase column names, or apply a custom foreign key naming pattern without affecting regular columns.

Default Conversion: CamelCase to Snake_Case​

Out of the box, Storm converts camelCase identifiers to snake_case by inserting underscores before uppercase letters and lowercasing the result. This matches the most common convention in relational databases.

Field/ClassResolved Name
idid
emailemail
birthDatebirth_date
postalCodepostal_code
firstNamefirst_name
UserRoleuser_role

For foreign keys, _id is appended after the conversion. This convention makes it clear which columns are foreign keys when reading the schema directly.

FK FieldResolved Column
citycity_id
petTypepet_type_id
homeAddresshome_address_id

Configuring Name Resolvers​

To replace the default resolvers, pass a TemplateDecorator when creating the ORM template. The decorator exposes withTableNameResolver(), withColumnNameResolver(), and withForeignKeyResolver() methods. You only need to set the resolvers you want to change; any resolver you leave unset keeps its default behavior.

val orm = dataSource.orm { decorator ->
    decorator
        .withTableNameResolver(TableNameResolver.camelCaseToSnakeCase())
        .withColumnNameResolver(ColumnNameResolver.camelCaseToSnakeCase())
        .withForeignKeyResolver(ForeignKeyResolver.camelCaseToSnakeCase())
}

The example above is equivalent to the defaults and is shown for illustration. In practice, you would only call these methods when you want to override the default behavior.

Uppercase Conversion​

Some databases (notably Oracle) use uppercase identifiers by default. Rather than writing a new resolver from scratch, Storm provides toUpperCase() wrappers that decorate any existing resolver and uppercase its output.

val orm = dataSource.orm { decorator ->
    decorator
        .withTableNameResolver(TableNameResolver.toUpperCase(TableNameResolver.camelCaseToSnakeCase()))
        .withColumnNameResolver(ColumnNameResolver.toUpperCase(ColumnNameResolver.camelCaseToSnakeCase()))
        .withForeignKeyResolver(ForeignKeyResolver.toUpperCase(ForeignKeyResolver.camelCaseToSnakeCase()))
}

This produces:

Field/ClassResolved Name
birthDateBIRTH_DATE
UserUSER
city (FK)CITY_ID

Composing Resolvers​

The toUpperCase() wrapper demonstrates a general pattern: because each resolver is a functional interface, you can compose wrappers that add behavior to any existing resolver. This is more flexible than subclassing because wrappers are independent of each other and can be combined in any order.

For example, a wrapper that adds a table name prefix. This is useful when multiple applications share a database and each uses a common prefix to avoid table name collisions.

fun withPrefix(prefix: String, resolver: TableNameResolver) = TableNameResolver { type ->
    "$prefix${resolver.resolveTableName(type)}"
}

val orm = dataSource.orm { decorator ->
    decorator.withTableNameResolver(withPrefix("app_", TableNameResolver.camelCaseToSnakeCase()))
}
// User -> app_user, OrderItem -> app_order_item

Note that each resolver should return a plain identifier (the table name, column name, or foreign key column name). Do not include schema qualifiers or other SQL syntax in the resolved name.

RecordType and RecordField Reference​

Custom resolvers receive RecordType and RecordField objects that provide metadata about the entity or field being resolved. These objects give you access to the class, its annotations, and individual field details, so your resolvers can make decisions based on package names, annotation presence, field types, or any other metadata.

RecordType is passed to TableNameResolver and ForeignKeyResolver. It represents the entity or projection class being mapped.

MethodReturn TypeDescription
type()Class<?>The record class
annotations()List<Annotation>All annotations on the record class
fields()List<RecordField>Metadata for all record fields, in declaration order
isAnnotationPresent(Class)booleanWhether an annotation type is present
getAnnotation(Class)AnnotationRetrieve a single annotation by type

RecordField is passed to ColumnNameResolver and ForeignKeyResolver. It represents a single field (record component) being mapped to a column.

MethodReturn TypeDescription
name()StringThe field name (e.g., "birthDate")
type()Class<?>The raw field type
declaringType()Class<?>The class that declares this field
annotations()List<Annotation>All annotations on the field
isAnnotationPresent(Class)booleanWhether an annotation type is present
nullable()booleanWhether the field can be null

Custom Resolvers​

When the built-in resolvers and wrappers are not enough, you can implement fully custom naming strategies. There are two approaches: lambda expressions for simple, inline logic, and interface implementations for strategies that are complex or shared across projects.

Lambda-Based Configuration​

Lambdas are convenient for quick, self-contained overrides. Since each resolver is a functional interface, a single lambda replaces the entire resolution strategy for that concern.

// Identity resolver: use the field name as-is, without any conversion
val orm = dataSource.orm { decorator ->
    decorator.withColumnNameResolver { field -> field.name() }
}

// Custom prefix for foreign key columns
val orm = dataSource.orm { decorator ->
    decorator.withForeignKeyResolver { field, type ->
        "fk_${ForeignKeyResolver.camelCaseToSnakeCase().resolveColumnName(field, type)}"
    }
}

Interface-Based Implementation​

For more complex or reusable naming strategies, implement the resolver interfaces as standalone classes. This approach is preferable when the resolver contains non-trivial logic, needs to be tested independently, or is shared across multiple ORM template instances.

The examples below show three resolvers working together: a table name resolver that adds a prefix based on the entity's package, a column name resolver that marks encrypted columns, and a foreign key resolver that uses the target table name instead of the field name.

class PrefixedTableNameResolver : TableNameResolver {
    override fun resolveTableName(type: RecordType): String {
        val pkg = type.type().packageName
        val prefix = if (pkg.contains(".admin")) "admin_" else ""
        val tableName = TableNameResolver.camelCaseToSnakeCase().resolveTableName(type)
        return "$prefix$tableName"
    }
}

class EncryptedColumnNameResolver : ColumnNameResolver {
    override fun resolveColumnName(field: RecordField): String {
        val columnName = ColumnNameResolver.camelCaseToSnakeCase().resolveColumnName(field)
        return if (field.isAnnotationPresent(Encrypted::class.java)) "enc_$columnName" else columnName
    }
}

class TargetTableForeignKeyResolver : ForeignKeyResolver {
    override fun resolveColumnName(field: RecordField, type: RecordType): String {
        val targetTable = TableNameResolver.camelCaseToSnakeCase().resolveTableName(type)
        return "${targetTable}_fk"
    }
}

Register custom implementations:

val orm = dataSource.orm { decorator ->
    decorator
        .withTableNameResolver(PrefixedTableNameResolver())
        .withColumnNameResolver(EncryptedColumnNameResolver())
        .withForeignKeyResolver(TargetTableForeignKeyResolver())
}

Per-Entity and Per-Field Overrides​

Annotations on individual entities and fields always take precedence over configured resolvers. This means you can set a global naming convention through resolvers and still override specific tables or columns where the convention does not apply (for example, a legacy table with a non-standard name).

Use @DbTable to override a table name, @DbColumn to override a column name, and the string parameter on @PK or @FK to override their respective column names. See Entities: Custom Table and Column Names for details and examples.

Identifier Escaping​

When a table or column name conflicts with a SQL reserved word, the database will reject the query unless the identifier is escaped. Storm automatically detects and escapes common reserved words. For cases that are not caught automatically, you can force escaping with the escape parameter on @DbTable or @DbColumn. Storm uses the escaping syntax appropriate for the active database dialect (double quotes for most databases, square brackets for SQL Server).

@DbTable("order", escape = true)  // "order" is a reserved word
data class Order(
    @PK val id: Int = 0,
    @DbColumn("select", escape = true) val select: String  // "select" is reserved
) : Entity<Int>

Dirty Checking Properties​

These properties control how Storm detects changes to entities during update operations. Dirty checking determines whether an UPDATE statement is sent to the database and, if so, which columns it includes. Choosing the right mode depends on your entity size, update frequency, and whether you use immutable records or mutable objects. See Dirty Checking for a detailed explanation of each strategy.

storm.update.default_mode​

Controls the default update mode for entities that don't have an explicit @DynamicUpdate annotation. This setting applies globally and can be overridden per entity with the @DynamicUpdate annotation.

ValueBehavior
OFFNo dirty checking. Always update all columns.
ENTITYSkip UPDATE if entity unchanged; full-row update if any field changed.
FIELDUpdate only the columns that actually changed.

storm.update.dirty_check​

Controls how Storm compares field values to detect changes. The choice between INSTANCE and VALUE depends on whether your entities are truly immutable. Immutable records (the recommended pattern) work correctly with INSTANCE because unchanged fields share the same object reference. If your entities contain mutable objects that could change without creating a new reference, use VALUE to compare by equals() instead.

ValueBehavior
INSTANCECompare by reference identity. Fast, works well with immutable records.
VALUECompare using equals(). More accurate for mutable objects.

storm.update.max_shapes​

In FIELD mode, each unique combination of changed columns produces a distinct UPDATE statement shape (e.g., updating only email is a different shape than updating email and name). Each shape occupies a slot in the database's prepared statement cache. This property caps the number of shapes per entity type. Once the limit is reached, Storm falls back to full-row updates to prevent statement cache bloat.

Lower values (3-5) are better for applications with many entity types, where the total number of cached statements across all entities matters. Higher values (10-20) allow more granular updates but increase statement cache pressure.

Entity Cache Properties​

Storm maintains a transaction-scoped entity cache that ensures the same database row maps to the same object instance within a single transaction. This property controls the cache's memory behavior. See Entity Cache for details on how the cache interacts with identity guarantees and garbage collection.

storm.entity_cache.retention​

Controls how long entities are retained in the cache during a transaction. The choice is a trade-off between memory consumption and dirty-checking reliability. With default, entities are retained for the duration of the transaction, which provides reliable dirty checking while still allowing the JVM to reclaim entries under memory pressure. With light, the JVM can reclaim cached entities as soon as your code no longer holds a reference, which reduces memory usage but may cause dirty-check cache misses.

ValueBehavior
defaultEntities retained for the transaction duration. Reliable dirty checking. The JVM may still reclaim entries under memory pressure.
lightEntities can be garbage collected when no longer referenced by your code. Memory-efficient but may cause full-row updates due to cache misses.

Template Cache Properties​

Storm compiles SQL templates into reusable prepared statement shapes. This compilation step resolves aliases, derives joins, and expands column lists. Caching the compiled result avoids repeating this work for the same query pattern with different parameter values. See SQL Templates for details on how compilation and caching work.

storm.template_cache.size​

Sets the maximum number of compiled templates to keep in the cache. When the cache is full, the least recently used templates are evicted.

The default of 2048 is sufficient for most applications. A typical application uses a few hundred distinct query patterns. Increase this value if you have many distinct query patterns (for example, from dynamically constructed queries) and observe cache eviction in your metrics. Each cached entry is small (the compiled SQL structure and metadata), so increasing the limit has minimal memory impact.

Validation Properties​

Storm provides two independent validation subsystems, each controlled by a mode property. Record validation checks that your entity and projection definitions are structurally correct (valid primary key types, proper annotation usage, no circular dependencies). Schema validation compares your definitions against the actual database schema to catch mismatches before they surface as runtime errors.

storm.validation.record_mode​

Controls whether record (structural) validation runs when Storm first encounters an entity or projection type.

ValueBehavior
failValidation errors cause startup to fail with a PersistenceException (default).
warnErrors are logged as warnings; startup continues.
noneRecord validation is skipped entirely.

storm.validation.schema_mode​

Controls whether schema validation runs at startup (Spring Boot only; for programmatic use, see Validation).

ValueBehavior
noneSchema validation is skipped (default).
warnMismatches are logged at WARN level; startup continues.
failMismatches cause startup to fail with a PersistenceException.

storm.validation.strict​

When true, schema validation warnings (type narrowing, nullability mismatches, missing unique/foreign key constraints) are promoted to errors. This is useful in CI environments where any schema drift should be caught.

See Validation for a complete list of what each validation level checks.

Monitoring

Storm exposes runtime metrics for template compilation, dirty checking, and entity cache behavior through JMX MBeans. See Metrics for details.

Per-Entity Configuration​

System properties set global defaults, but individual entities often have different update characteristics. An entity with a large text column benefits from field-level updates, while a small entity with three columns does not. Per-entity annotations let you tune update behavior where it matters most, without changing the global default.

@DynamicUpdate​

Override the update mode for a specific entity. This is most valuable for entities with large or variable-size columns where sending unchanged data wastes bandwidth.

@DynamicUpdate(FIELD)
data class Article(
    @PK val id: Int = 0,
    val title: String,
    val content: String  // Large column - benefits from field-level updates
) : Entity<Int>

Dirty Check Strategy Per Entity​

You can also override the dirty check strategy on a per-entity basis. This is useful when a specific entity contains mutable objects that require value-based comparison, while the rest of your application uses the default instance-based comparison.

@DynamicUpdate(value = FIELD, dirtyCheck = VALUE)
data class User(
    @PK val id: Int = 0,
    val email: String
) : Entity<Int>

Configuration Precedence​

Entity-level annotations take the highest precedence, followed by explicit StormConfig values, then system properties, and finally built-in defaults:

1. @DynamicUpdate annotation on entity class
   ↓ (if not present)
2. StormConfig (explicit value passed to factory)
   ↓ (if not set)
3. System property (-Dstorm.*)
   ↓ (if not set)
4. Built-in default

When using the Spring Boot Starter, StormConfig is built from application.yml properties. Properties not set in YAML fall through to system properties and then to built-in defaults.

The following profiles cover common scenarios. Start with the defaults and adjust only when profiling reveals a specific bottleneck.

Default (Most Applications)​

The built-in defaults work well for most applications. No configuration needed:

  • ENTITY mode skips UPDATE when nothing changed, but sends all columns when any field changes
  • INSTANCE comparison is fast and correct with immutable records/data classes
  • default cache retention provides reliable dirty checking

High-Write Applications​

For applications with frequent updates to large entities, field-level updates reduce the amount of data sent to the database on each UPDATE. This matters most when entities have large text or binary columns where sending unchanged data wastes network bandwidth and database I/O.

java -Dstorm.update.default_mode=FIELD \
     -Dstorm.update.max_shapes=10 \
     -jar myapp.jar

This reduces network bandwidth by only sending changed columns.

Memory-Constrained Bulk Operations​

For transactions that load a very large number of entities (bulk migrations, large reports), light cache retention allows the JVM to reclaim cached entities sooner. The trade-off is that dirty checking may encounter cache misses, resulting in full-row updates.

java -Dstorm.entity_cache.retention=light \
     -jar myapp.jar

This reduces memory usage at the cost of less efficient dirty checking.