Dibix.Http.Client 1.2.19

Dibix

Seamlessly create use case oriented REST APIs based on T-SQL stored procedures.

Packages

Package	NuGet
Dibix
Dibix.Dapper
Dibix.Http.Client
Dibix.Http.Server
Dibix.Sdk
Dibix.Testing

Background

The aim of Dibix is to rapidly create use case oriented REST APIs without writing any boilerplate code, unlike the general approach of designing ASP<span>.</span>NET APIs by writing controllers and actions. It strictly focuses on a hand-written T-SQL stored procedure, which is described with a bit of metadata markup. The APIs and contracts involved are specified in a declarative JSON format. Basically, each URL defined in an API endpoint results in invoking the SQL stored procedure, materializing the relational result into a hierarchical result and then return that to the client.

Getting started

Creating a project

Dibix follows a database first approach therefore most of the work is done in a SQL server database project. This is where you create use case oriented stored procedures which will later turn into working REST APIs.<br/> We currently offer to split your artifacts into two separate projects:

• Component.Database (DDL)<br/> Contains DDL (Data definition language).<br/> We consider this the default behavior of a database project, where tables, stored procedures, etc. are defined and its intention is to publish these database artifacts to the target database at some point.
• Component.Database.DML (DML)<br/> Contains DML (Data manipulation language).<br/> This project should contain only stored procedures. These will not be published to the target database and instead their statement body will be extracted and compiled into an assembly.

Since DDL gets published at the target database, this means that basically any simple T-SQL statement will end up inside a stored procedure. So far we don't have an exact idea if this is good or bad. The advantage of DDL over DML is that DDL can be easily devop'd at the customer site using SSMS, whereas the DML is compiled into an assembly and therefore harder to patch, especially during development.

Configuring the project

Dibix provides MSBuild targets to integrate it seamlessly into the database project build pipeline. The idea is to install the Dibix.Sdk NuGet package into your project, which will automatically add the necessary imports.<br/> Unfortunately NuGet is not supported in database projects (yet?). Therefore the import has to happen manually. Please check if there is any existing documentation in the product you are working on or ask me for assistance.

Creating a REST API

In this walkthrough, we try to create the following endpoints, that make up a RESTful API:<br /> | Number | Method | URL | Description | | - | - | - | - | | GetPersons | GET | api/Person|Get a list of persons | | GetPerson | GET | api/Person/{personId} | Get details of a person | | CreatePerson | POST | api/Person | Create a person | | UpdatePerson | PUT | api/Person/{personId} | Update a person | | UpdatePersonName | PATCH | api/Person/{personId}/Name | Update the name of a person (partial update) | | DeletePersons | DELETE | api/Person?personIds={personIds} | Delete multiple persons |

Contracts

• Ensure, that there is a folder named "Contracts" at the root of the project
• Create a new .json file named "Person.json" with the following content:

{
  "AccessRights": [
    { "Read": 1 },
    { "Write": 2 },
    { "Execute": 4 }
  ],
  "Gender": [
    "Unsure",
    "Male",
    "Female"
  ],
  "BankAccount": {
    "Id": "uuid",
    "Name": "string"
  },
  "PersonInfo": {
    "Id": {
      "type": "int32",
      "isPartOfKey": "true"
    },
    "Name": "string"
  },
  "PersonDetail": {
    "Id": {
      "type": "int32",
      "isPartOfKey": "true"
    },
    "Name": "string",
    "Gender": "#Gender",
    "AccessRights": "#AccessRights",
    "BankAccounts": "#BankAccounts*",
    "PetId": "int64?"
  },
  "CreatePersonRequest": {
    "Name": "string",
    "Gender": "#Gender",
    "AccessRights": "#AccessRights",
    "PetId": "int64?"
  },
  "Pet":{
    "Name": "string",
    "Kind": "byte"
  },
  "UpdatePersonRequest": {
    "Name": "string",
    "Gender": "#Gender",
    "AccessRights": "#AccessRights",
    "Pets": "#Pet*"
  }
}

The previous example demonstrates the following things:

• Flagged enums (AccessRights)
• Unflagged enums (Gender)
• Primitive types (uuid, string, int32, int64)
• Contract references (#Gender, #AccessRights #BankAccounts; always prefixed with '#')
• Array properties (#BankAccounts*; always suffixed with '*')
• Primary keys ('isPartOfKey')

User-defined types

To pass in multiple ids for the 'DeletePerson' endpoint, we need to create a user-defined table type. Create a new .sql file name 'udt_intset.sql' with the following content:

-- @Name IdSet
CREATE TYPE [dbo].[udt_intset] AS TABLE
(
  [id] INT NOT NULL PRIMARY KEY
)

To pass in multiple items of Pet to the UpdatePerson endpoint, we need another user-defined table type. Create a new .sql file name 'udt_petset.sql' with the following content:

-- @Name PetSet
CREATE TYPE [dbo].[udt_petset] AS TABLE
(
  [position] TINYINT      NOT NULL PRIMARY KEY
, [type]     TINYINT      NOT NULL
, [name]     NVARCHAR(50) NOT NULL
)

HTTP endpoints

• Ensure, that there is a folder named "Endpoints" at the root of the project
• Create a new .json file named "Person.json" with the following content:

{
  "Person": [
    {
      "method": "GET",
      "target": "GetPersons"
    },
    {
      "method": "GET",
      "target": "GetPerson",
      "childRoute": "{personId}"
    },
    {
      "method": "POST",
      "target": "CreatePerson",
      "childRoute": "{personId}",
      "body": "CreatePersonRequest",
      "params": {
        "accessrights": "BODY.Rights"
      }
    },
    {
      "method": "PUT",
      "target": "CreatePerson",
      "childRoute": "{personId}",
      "body": "UpdatePersonRequest",
      "params": {
        "pets": {
          "source": "BODY.Pets",
          "items": {
            "position": "ITEM.$INDEX",
            "type": "ITEM.Kind"
          }
        }
      }
    },
    {
      "method": "PATCH",
      "target": "UpdatePersonName",
      "childRoute": "{personId}/Name/{name}"
    },
    {
      "method": "DELETE",
      "target": "DeletePersons"
    }
  ]
}

Stored procedures

In the following sections, each endpoint is implemented using a stored procedure. Each procedure is decorated with a few metadata properties inside T-SQL comments in the header.

GetPersons

Stored Procedures\getpersons.sql

-- @Name GetPersons
-- @Return PersonInfo
CREATE PROCEDURE [dbo].[getpersons]
AS
    SELECT [id]   = [p].[personid]
         , [name] = [p].[name]
    FROM (VALUES (1, N'Luke')
               , (2, N'Maria')) AS [p]([personid], [name])

Remarks

The previous example describes two metadata properties:

• @Name controls the name of the target
• @Return describes an output.<br />For each SELECT a @Return hint has to be defined. The @Return property has several sub properties. In the previous statement we rely on the default which is equivalent to 'ClrTypes:PersonInfo Mode:Multiple'. This means, that multiple rows are returned and each should be mapped to the 'PersonInfo' contract.

HTTP request

GET /api/Person

HTTP response body

[
  {
    "id": 1,
    "name": "Luke"
  },
  {
    "id": 2,
    "name": "Maria"
  }
]

GetPerson

Stored Procedures\getperson.sql

-- @Name GetPerson
-- @Return ClrTypes:PersonDetail;BankAccount SplitOn:id Mode:Single
CREATE PROCEDURE [dbo].[getperson] @personid INT
AS
    SELECT [id]           = [p].[personid]
         , [name]         = [p].[name]
         , [gender]       = [p].[gender]
         , [accessrights] = [p].[accessrights]
         , [petid]        = [p].[petid]
         , [id]           = [b].[bankaccountid]
         , [name]         = [b].[name]
    FROM (VALUES (1, N'Luke',  1 /* Male */,   7 /* All */,  10)
               , (2, N'Maria', 2 /* Female */, 1 /* Read */, NULL)) AS [p]([personid], [name], [gender], [accessrights], [petid])
    LEFT JOIN (VALUES (100, N'Personal', 1)
                    , (101, N'Savings', 1)) AS [b]([bankaccountid], [name], [personid]) ON [p].[personid] = [b].[personid]
    WHERE [p].[personid] = @personid

Remarks

The previous sample is a bit trickier. Here we expect a single result of the 'PersonDetail' contract. The related entity 'BankAccount' is loaded within the same query. This requires that two entity contracts are specified for the 'ClrTypes' property combined with the ';' separator. The 'SplitOn' is also required to mark where the next related entity starts. In this case 'id' is the bank account id column. If you have more related entities, the split on columns are combined with a ',' separator.<br /> Important: If you are working with multi map, make sure to define a key on each parent entity using the isPartOfKey property as defined in the contracts above. Otherwise you might end up with duplicated results.

HTTP request

GET /api/Person/1

HTTP response body

{
  "Id": 1,
  "Name": "Luke",
  "Gender": 1,
  "AccessRights": 7,
  "BankAccounts": [
    {
      "Id": 100,
      "Name": "Personal"
    },
    {
      "Id": 101,
      "Name": "Savings"
    }
  ],
  "PetId": 10
}

CreatePerson

Stored Procedures\createperson.sql

-- @Name CreatePerson
-- @Return ClrTypes:int Mode:Single
CREATE PROCEDURE [dbo].[createperson] @name NVARCHAR(255), @gender TINYINT, @accessrights TINYINT, @petid BIGINT
AS
    DECLARE @personid INT = 1

    DECLARE @persons TABLE
    (
        [personid]     INT           NOT NULL
      , [name]         NVARCHAR(128) NOT NULL
      , [gender]       TINYINT       NOT NULL
      , [accessrights] TINYINT       NOT NULL
      , [petid]        BIGINT        NULL
      , PRIMARY KEY([personid])
    )
    INSERT INTO @persons ([personid], [name], [gender], [accessrights], [petid])
    VALUES (@personid, @name, @gender, @accessrights, @petid)

    SELECT @personid

HTTP request

POST /api/Person

{
  "Name": "Luke",
  "Gender": 1,
  "Rights": 7,
  "PetId": 10
}

Remarks

As you can see here the stored procedure parameter accessrights doesn't match a property on the body. It will however be mapped from Rights, because a custom parameter mapping using the BODY source was defined in the endpoint configuration above. This is useful if the names of the client property and the parameter name in the target stored procedure differ.

HTTP response body

1

UpdatePerson

Stored Procedures\updateperson.sql

-- @Name UpdatePerson
CREATE PROCEDURE [dbo].[updateperson] @personid INT, @name NVARCHAR(255), @gender TINYINT, @accessrights TINYINT, @pets [dbo].[udt_petset] READONLY
AS
    UPDATE @persons SET [name] = @name, [gender] = @gender, [accessrights] = @accessrights
    WHERE [personid] = @personid

    -- Do something with @pets, like MERGE

HTTP request

PUT /api/Person/1

{
  "Name": "Luke",
  "Gender": 1,
  "AccessRights": 7,
  "Pets": [
    {
      "Name": "Pet",
      "Kind": 1
    }
  ]
}

Remarks

The body contains a collection property named Pets. Collections will be mapped to a UDT, which needs to exist in the target database. In this case [dbo].[udt_petset]. The properties of the collection items will be mapped to matching columns of the UDT.<br /> For this endpoint there are some custom parameter mappings defined in the endpoint configuration above:

• The position column of the UDT just serves as a primary key and will be mapped from the index of the item in the collection. This is done using the internal $INDEX property on the ITEM source.
• The type column of the UDT will be mapped from the Kind property of each instance of Pet.
• The name column doesn't require a mapping and will be automatically mapped from the matching Name property of each instance of Pet.

UpdatePersonName

Stored Procedures\updatepersonname.sql

-- @Name UpdatePersonName
CREATE PROCEDURE [dbo].[updatepersonname] @personid INT, @name NVARCHAR(255)
AS
    UPDATE @persons SET [name] = @name
    WHERE [personid] = @personid

HTTP request

PATCH /api/Person/1/Name/Luke

DeletePersons

Stored Procedures\deletepersons.sql

-- @Name DeletePersons
CREATE PROCEDURE [dbo].[deletepersons] @personids [dbo].[udt_intset] READONLY
AS
    DELETE [p]
    FROM @persons AS [p]
    INNER JOIN @personids AS [pi] ON [p].[personid] = [pi].[personid]

HTTP request

DELETE /api/Person?personIds[]=1&personIds[]=2

Compiling the project

Once you have created all the necessary artifacts, you can build the database project. With the Dibix MSBuild targets automatically integrated into the build pipeline, you end up with a .dll next to your .dacpac file in your output directory. The assembly contains everything required to feed a web server with the REST API definitions.<br /> As of right now Dibix itself does not contain a runtime implementation for the web server. So again, please check if there is any existing documentation in the product you are working on or ask me for assistance.

Consuming endpoints

If the project contains any HTTP endpoints, a client assembly and an OpenAPI document are also created during compilation. The client assembly contains a service interface and implementation for each endpoint defined in the project along with their referenced contracts. A host project can consume these client assemblies and register the implementation in the DI container to make the interface available to consumers via IoC. <br /> The implementation is based on the Dibix.Http.Client runtime and the generated services may require a few dependencies: | Type | Required | Implementation(s) | | - | - | - | | IHttpClientFactory | Optional |DefaultHttpClientFactory | | IHttpAuthorizationProvider | Required (if endpoint requires authorization) | - |

The OpenAPI document will be generated in YAML and JSON format and can be used to generate other artifacts, for example clients in other languages like TypeScript.

Syntax reference

Stored procedure

In this section, the markup properties to declare input and output of the stored procedure is explained in more detail. The documentation is still in progress. You can also have a look at these tests for more examples.

Name

PascalCase naming is recommended for referencing actions in API definitions. If all lower case naming is used in T-SQL, this enables you to generate a PascalCase name for the action.

-- @Name GetPersons

{
  "Person": [
    {
      "target": "GetPersons"
    }
  ]
}

Namespace

Allows to group actions into a separate (relative) namespace.

-- @Name GetPersons
-- @Namespace Group

{
  "Person": [
    {
      "target": "Group.GetPersons"
    }
  ]
}

To be continued...

Contract

In this section the schema for defining contracts is described. The documentation is still in progress. For now you can use the JSON schema as a reference or have a look at these tests as samples.

Endpoint

In this section the schema for defining endpoints is described. The documentation is still in progress. For the sake of completeness, you can use the JSON schema as a reference.

An endpoint JSON starts with a root object. Each property inside the root object maps to an endpoint. An endpoint is similar to a controller in ASP.NET. The property name defines the name of the endpoint. Along with the area name (based on the component name), it controls the URL of the API: api/{areaName}/{endpointName}.

{
  "EndpointName": [
    {
      "method": "GET",
      "target": "GetEntity",
      "childRoute": "{id}"
    }
  ]
}

Each endpoint object consists of an array, in which the respective actions are defined. To ensure a RESTful API, each action is distinguished by its HTTP verb, which follows CRUD operations, and a unique path. To extend the path to the API, the childRoute property can be used, which is appended to the path base, extending the route template as such: api/{areaName}/{endpointName}/{childRoute}.

Target

The target property should contain the name of the stored procedure that is invoked by this API action.

To be continued...

HTTP status code

By default Dibix endpoints return 200 OK for operations that have a result and 204 NoContent for those that do not return a result.<br /> However sometimes you need to return a different HTTP status code, for example to indicate that the request is invalid. Ideally you could return a different response body along with a specific HTTP status code, however this is not an easy task and gets very complex with the current way how response types are declared and also validated with the according T-SQL output statements.<br /> Therefore currently it's only possible to return a specific HTTP status code (supported are currently some client and some server errors) along with an additional error code and a message, both which are returned as custom HTTP response headers.

To return an error response, use the T-SQL THROW statement

4xx client error

Supported: Code|Name|Sample use cases | - | - | - | | 400 | BadRequest | Client syntax error (malformed request) | | 401 | Unauthorized | Either the request is missing credentials or the credentials were not accepted | | 403 | Forbidden | The authorized user is not allowed to access the current resource | | 404 | NotFound | Resource with given ID not found, Feature not available/configured | | 409 | Conflict | The resource is currently locked by another request (might resolve by retry) | | 422 | UnprocessableEntity | The client content was not accepted because of a semantic error (i.E. schema validation) |

SQL

THROW 404017, N'Service not available', 1

The error code of the THROW statement is used to indicate the HTTP status code (first three digits) and a custom error code (last three digits) for the application/feature, which can be used for custom handling or resolve a translation for the error message on the client.<br />

HTTP response

HTTP/1.1 404 Not Found
X-Error-Code: 17
X-Error-Description: Service not available

5xx server error (Supported: 504)

For server errors, custom error codes are not supported, since they quite possibly cannot be fixed/handled by the client and could also disclose sensitive information.<br />

Supported: Code|Name|Sample use cases | - | - | - | | 504 | GatewayTimeout | External service did not respond in time |

SQL

THROW 504000, N'Request with id '' + @id + '' timed out', 1

HTTP response

HTTP/1.1 504 Gateway Timeout

Builtin parameter source providers

This section describes known parameter sources that are already registered and can help to dynamically map a stored procedure parameter from. They are used in the endpoint definition json and are accessible within the parameter configuration.

QUERY

This source provides access to the query string arguments.

PATH

This source provides access to the path segment arguments. For example use PATH.userId to access the userId parameter in the URL User/{userId}.

BODY

This source provides access to the properties on a JSON object supplied in the body. It requires the body property to be set on the action definition to specify the expected contract of the body.

Sample:

{
  "Person": [
    {
      "method": "POST",
      "target": "CreatePerson",
      "body": "CreatePersonRequest",
      "params": {
        "accessrights": "BODY.Rights"
      }
    }
  ]
}

HEADER

This source provides access to the request headers. For example HEADER.Authorization.

REQUEST

This source provides access to the HTTP request. It supports the following properties: PropertyName|Type|Value | - | - | - | | Language | string | The value provided in the Accept-Language header |

ENV

This source provides access to the server environment. It supports the following properties: PropertyName|Type|Value | - | - | - | | MachineName | string | The value of System.Environment.MachineName | | CurrentProcessId | int | The value of System.Diagnostics.Process.GetCurrentProcess().Id

Roadmap

• Continue writing this documentation 🤓
• Dibix.Server<br /> This is the overall goal, which drives the whole project, since the idea at the end is to have an independent lightweight server application, that consumes only declarative API registrations rather than DLLs.
• Make it work with NuGet (see above)
• Complete OpenAPI generator<br /> Right now a JSON and YAML file is generated for each project. It's not published to an output folder yet and can be found in the intermediate folder of the project (obj\Debug). The document itself is not yet completed and can currently only be consumed for contract generation (components.schemas).