Attributes

Attributes are how you describe endpoints in MARS. They live mainly in MARS.Core.Attributes.pas (with more in MARS.Metadata.Attributes.pas, MARS.Core.JSON.pas and the data units). This page groups them by purpose; see Reference ▸ Attributes for a compact cheat-sheet.

All MARS attributes descend from MARSAttribute.

Routing

[Path]

Sets the route segment. On a class it is the resource root; on a method it is appended as a sub-path. Supports template tokens {name} and a trailing wildcard {*}.

[Path('orders')]            // resource
TOrdersResource = class
  [GET, Path('{id}/items')] // method -> orders/{id}/items
  function Items([PathParam] id: Integer): TArray<TItem>;
end;

HTTP method attributes

[GET], [POST], [PUT], [DELETE], [PATCH], [HEAD], [OPTIONS], [QUERY]. Exactly one per endpoint method. Internally each derives from HttpMethodAttribute and matches the request's HTTP method.

Content negotiation

[Produces('media/type')]

Declares the media type(s) a method can return. Multiple [Produces] are allowed; MARS picks the best match against the request's Accept header.

[GET, Produces(TMediaType.APPLICATION_JSON), Produces(TMediaType.APPLICATION_YAML)]
function GetData: TData;

[Consumes('media/type')]

Declares the media type(s) a method accepts for its request body — used to pick the MessageBodyReader for [BodyParam].

[POST, Consumes(TMediaType.APPLICATION_JSON)]
function Save([BodyParam] AData: TData): TData;

Use the constants in TMediaType (e.g. TMediaType.APPLICATION_JSON) rather than literal strings.

Parameter binding

These decorate method parameters and bind request data to them. The value is converted to the parameter's Delphi type (using a MessageBodyReader when one matches, otherwise a string-to-type fallback).

Attribute	Source	Example
[PathParam]	a {token} in the route	[PathParam] id: Integer
[QueryParam]	the query string ?q=…	[QueryParam] q: string
[FormParam]	a form field (urlencoded / multipart)	[FormParam] file: TBytes
[HeaderParam]	a request header	[HeaderParam('X-Trace')] trace: string
[CookieParam]	a cookie	[CookieParam('sid')] sid: string
[BodyParam]	the entire request body	[BodyParam] order: TOrder

By default the parameter name is used to find the value; pass an explicit name to override: [QueryParam('page')] aPage: Integer.

Collection binders

To receive all values of a kind at once, use the plural attributes:

[GET, Path('{name}/{surname}')]
function Info(
  [PathParams]  AParams: TMARSPathParams;
  [QueryParams] AQuery:  TMARSQueryParams;
  [Headers]     AHeaders: TMARSHeaders;
  [Cookies]     ACookies: TMARSCookies
): string;

([FormParams] works similarly for form data.) See the NewAttributesDemo.

[Required]

Marks a bound parameter as mandatory; a missing value raises an HTTP error. [PathParam] is always required by nature.

[GET] function Find([QueryParam, Required] q: string): TArray<TItem>;

Dependency injection

[Context]

Injects a framework- or user-provided value into a field, property or parameter before the method runs. Built-in context values include IMARSRequest, IMARSResponse, TMARSURL, IMARSActivation, TMARSToken, TFDConnection/TMARSFireDAC (data units) and the generated TOpenAPI.

[Context] Token: TMARSToken;
[Context] Request: IMARSRequest;

Configuration parameter injection

Inject values from the engine/application Parameters:

• [EngineParam('Name'[, Default])] — from engine parameters.
• [ApplicationParam('Name'[, Default])] — from application parameters.

[ApplicationParam('JWT.Secret')] JWTSecret: string;
[EngineParam('Port', 8080)]      Port: Integer;

There are also function-valued variants ([EngineParamFunc], [ApplicationParamFunc]) that inject a TConfigParamFunc for dynamic lookups.

See Parameters & Injection for registering custom injection services.

Security

Applied to a resource (affecting all its methods) or an individual method (overriding the resource-level rule):

Attribute	Effect
[PermitAll]	Allow any caller, authenticated or not.
[DenyAll]	Deny everyone (highest priority).
[RolesAllowed('a','b')]	Allow callers whose token has any listed role.

[Path('admin'), RolesAllowed('admin')]
TAdminResource = class
  [GET, PermitAll]            function Ping: string;        // public
  [DELETE, Path('{id}')]      procedure Remove([PathParam] id: Integer); // admin only
end;

See Authorization.

Response shaping

Attribute	Effect
[ContentType('media/type')]	Force the response Content-Type.
[CustomHeader('Name','Value')]	Add a fixed response header.
[Encoding('UTF8')]	Set the text encoding used when serializing (see below).
[IsReference]	The returned object is a reference MARS must not free.
[JSONP(True)]	Wrap a JSON response as JSONP using a callback query parameter.

Lifecycle hooks (method-level)

Mark methods on a resource to run at specific points of the activation:

Attribute	When it runs
[BeforeInvoke]	Before the selected endpoint method is invoked.
[AfterInvoke]	After the endpoint method returns.
[InvokeError]	When the endpoint method raises.
[AfterContextCleanup]	After injected context objects are freed (teardown).

These complement the global TMARSActivation.RegisterBeforeInvoke/AfterInvoke/InvokeError hooks.

Metadata & OpenAPI

From MARS.Metadata.Attributes.pas and the OpenAPI units — they enrich the generated OpenAPI 3 spec:

Attribute	Effect
[MetaSummary('...')]	Short summary for a resource/method.
[MetaDescription('...')]	Longer description for a resource/method/parameter.
[MetaVisible(False)]	Hide the resource/method from metadata and OpenAPI.
[OAPISummary], [OAPIDescription]	OpenAPI-only text for a resource, method, type, field or parameter.
[OAPIRequired], [OAPIDefault], [OAPIPattern], [OAPIMinimum], [OAPIMaximum], [OAPIMinLength], [OAPIMaxLength]	JSON-schema hints on record/class fields and method parameters.

JSON serialization control

From MARS.Core.JSON.pas — applied to record/class fields:

Attribute	Effect
[JSONName('customName')]	Map the field to a different JSON key.
[JSONSkip]	Exclude the field from (de)serialization.
[JSONSkipEmptyValues] / [JSONIncludeEmptyValues]	Override the empty/null inclusion policy.

See JSON Serialization.

FireDAC

From the data units — see FireDAC & Datasets:

Attribute	Effect
[Connection('DEFNAME')]	Select the FireDAC connection definition to inject.
[SQLStatement('Name','SELECT …')]	Declare a named SQL statement on a dataset resource.