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# Annotations

In many places, applications can use Java 5 annotations as an alternative to XML and Java properties configuration. This page serves as a reference for all annotations across the framework.

## Action Annotations

Since Struts 2.1, these annotations are provided by the Convention Plugin. Codebehind and Zero Config plugins are deprecated from Struts 2.1 on.

Action annotations are available when the framework scans the classpath for Action classes, rather than specifying individual mappings through XML configuration. See the Convention Plugin page for information on how to set up classpath scanning to allow the use of Action annotations.

Annotation | Description
--- | ---
Actions Annotation | Group of `@Action` annotations, maps multiple URLs to the same action
Action Annotation | Defines the URL of an action
InterceptorRefs Annotation | Group of `@InterceptorRef` annotations
InterceptorRef Annotation | Interceptor, or interceptor stack to be applied to at action
Results Annotation | Group of `@Result` annotations
Result Annotation | Defines a result for an action
Namespace Annotation | Set the path of the action URL (used to overwrite the default)
ResultPath Annotation | Set where the results are located (used to overwrite the default)
ParentPackage Annotation | Set the parent package of the actions (used to overwrite the default)
ExceptionMappings | Group of `@ExceptionMapping` annotations
ExceptionMapping | Defines an exception mapping

## Workflow Annotations

Annotation | Description
--- | ---
InputConfig Annotation | Defines what method to execute, or result to be returned if there are validation errors

## Interceptor Annotations

To use these annotations, you have to specify the AnnotationWorkflowInterceptor to your interceptor stack.

Annotation | Description
--- | ---
After Annotation | Marks a action method that needs to be executed after the result.
Before Annotation | Marks a action method that needs to be executed before the main action method.
BeforeResult Annotation | Marks a action method that needs to be executed before the result.

## Validation Annotations

To use annotation-based validation, annotate the class or interface with Validation Annotation.

Annotation | Description
--- | ---
ConversionErrorFieldValidator Annotation | Checks if there are any conversion errors for a field.
DateRangeFieldValidator Annotation | Checks that a date field has a value within a specified range.
DoubleRangeFieldValidator Annotation | Checks that a double field has a value within a specified range.
EmailValidator Annotation | Checks that a field is a valid e-mail address.
ExpressionValidator Annotation | Validates an expression.
FieldExpressionValidator Annotation | Uses an OGNL expression to perform its validator.
IntRangeFieldValidator Annotation | Checks that a numeric field has a value within a specified range.
RegexFieldValidator Annotation | Validates a regular expression for a field.
RequiredFieldValidator Annotation | Checks that a field is non-null.
RequiredStringValidator Annotation | Checks that a String field is not empty.
StringLengthFieldValidator Annotation | Checks that a String field is of the right length.
UrlValidator Annotation | Checks that a field is a valid URL.
Validation Annotation | Marker annotation for validation at Type level.
Validations Annotation | Used to group validation annotations.
VisitorFieldValidator Annotation | Invokes the validation for a property’s object type.
CustomValidator Annotation | Use this annotation for your custom validator types.

### Resources

- Validation using Annotations (arsenalist)

## Type Conversion Annotations

By default, type conversion for Maps and Collections using generics is directly supported.

In short, instead of specifying the types found in collections and maps as documented in Type Conversion, the collection’s generic type is used. By using annotations, an application should be able to avoid using any `ClassName-conversion.properties` files.

To use annotation-based type conversion, annotate the class or interface with the Conversion Annotation.

Annotation | Description
--- | ---
Conversion Annotation | Marker annotation for type conversions at Type level.
CreateIfNull Annotation | For Collection and Map types: Create the types within the Collection or Map, if null.
Element Annotation | For Generic types: Specify the element type for Collection types and Map values.
Key Annotation | For Generic types: Specify the key type for Map keys.
KeyProperty Annotation | For Generic types: Specify the key property name value.
TypeConversion Annotation | Used for class and application wide conversion rules.

## Tiles Annotations

The Tiles Plugin provides it’s own set of Annotations. They can be used to keep `tiles.xml` short. Instead tiles definitions can be created by annotating actions.

Annotation | Description
--- | ---
TilesDefinition | Represents a `<definition>` element in tiles.xml
TilesDefinitions | A list of `TilesDefinition` Annotations
TilesPutAttribute | Represents a `<put-attribute>` element in tiles.xml
TilesPutListAttribute | Represents a `<put-list-attribute>` element in tiles.xml
TilesAddAttribute | Represents a `<add-attribute>` element in tiles.xml
TilesAddListAttribute | Represents a `<add-list-attribute>` element in tiles.xml

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