Mendix rest services
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A quick dive into RESTful web services on mendix
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Mendix rest services
- 1. By Acellam Guy @mistaguy 1. Consume JSON REST based services 2. Publish data or microflows through REST API's 3. (Real time) Synchronization of data between Mendix applications
- 2. By Acellam Guy @mistaguy REST ? • REST stands for Representational StateTransfer • BuildWeb services that are lightweight, maintainable, and scalable • A service based on REST is called a RESTful service • REST is not dependent on any protocol
- 3. By Acellam Guy @mistaguy Features of a RESTful webservice • Representations • Messages • URIs • Uniform interface • Stateless • Links between resources • Caching
- 4. By Acellam Guy @mistaguy Representations • Resources and how to provide access to these resources • Format of representation JSON,XML ,etc • Both client and server should be able to comprehend format of representation • A representation should be able to completely represent a resource • The representation should be capable of linking resources to each other
- 5. By Acellam Guy @mistaguy Messages • Contains the actual data and metadata about the message • Based on HTTP 1.1
- 6. By Acellam Guy @mistaguy URI • The job of a URI is to identify a resource or a collection of resources • The actual operation is determined by an HTTP verb Eg. http://localhost:8080/Persons/1 This URL has following format: Protocol://ServiceName/ResourceType/ResourceID
- 7. By Acellam Guy @mistaguy Uniform Interface • Systems should have a uniform interface. HTTP 1.1 provides a set of methods, called verbs, for this purpose Method Operation performed on server Quality GET Read a resource. Safe PUT Insert a new resource or update if the resource already exists. Idempotent POST Insert a new resource. Also can be used to update an existing resource. N/A DELETE Delete a resource . Idempotent OPTIONS List the allowed operations on a resource. Safe HEAD Return only the response headers and no response body. Safe
- 8. By Acellam Guy @mistaguy Statelessness • Does not maintain the application state for any client • A request cannot be dependent on a past request and a service treats each request independently A stateless design looks like so: Request1: GET http://MyService/Persons/1 HTTP/1.1 Request2: GET http://MyService/Persons/2 HTTP/1.1 Each of these requests can be treated separately. A stateful design, on the other hand, looks like so: Request1: GET http://MyService/Persons/1 HTTP/1.1 Request2: GET http://MyService/NextPerson HTTP/1.1
- 9. By Acellam Guy @mistaguy Links Between Resources • A resource representation can contain links to other resources like an HTML page contains links to other pages • The user does not need a map before coming to a website • A service can be (and should be) designed in the same way
- 10. By Acellam Guy @mistaguy Caching • Caching is the concept of storing the generated results and using the stored results instead of generating them repeatedly if the same request arrives in the near future
- 11. By Acellam Guy @mistaguy Mendix REST Module • Mendix 4.4.4+ or Mendix 5.3.1+ • If you want to publish REST services or use the data synchronization features, addIVK_OpenServiceOverview to your main navigation. add StartPublishServices to the startup sequence of your application • map your administrative project role to the Administratorrole in the RestServices for admin features • The 'rest/' request handler needs to be opened if running in the Mendix Standard Cloud (or on premise). • strongly recommended to not use the default HSQLDB engine if you want to publish RestServices while running locally
- 12. By Acellam Guy @mistaguy Consuming REST services • The operations in the 'Consume' folder of the module provide the necessary tools to invoke data • The core of all these operations is the java action request
- 13. By Acellam Guy @mistaguy The REQUEST java action • Request performs an HTTP request and provides the means to both send data and receive data over HTTP • Parameters • Method : HTTP 1.1 verbs • URL : location of the service • optRequestData : provides parameters • optResponseData : provides response • ResquestResult : HTTP response • sendWithFormEncoding
- 14. By Acellam Guy @mistaguy RequestResult Object • contains the meta information of a response • Response code • Etag • ResponseBody :the full and raw response body of the request.
- 15. By Acellam Guy @mistaguy Sending Request Headers • addHeaderToNextRequest : will add a header to the next (and only the next) request that will be made by the current microflow
- 16. By Acellam Guy @mistaguy Authentication • Only supports Basic authentication out of the box • Other authentication mechanism such as Oauth can be integrated
- 17. By Acellam Guy @mistaguy Consume Methods • get :Tries to retrieve an object from the provided resourceURL • get2: Similar to get, but also accepts a requestData parameter • ?q=Rest%20Services‘ • getCollection : gets a list of objects. JSON array • getCollectionAsync • post • delete • put • getRequestConsumerError
- 18. By Acellam Guy @mistaguy Template URLS • This makes it possible to substitute values directly in an URL
- 19. By Acellam Guy @mistaguy Publishing webservices • Publishing operations, based on a single microflow. • Publishing a part of your data model, and providing a typical rest based API to retrieve, update, delete, create and even real-time sync data. • PLEASE NOTETHATTO BE ABLETO PUBLISH ANY SERVICE,THE MICROFLOW STARTPUBLISHSERVICES SHOULD BE CALLED DURING STARTUP OFTHE APP! • Accessible via http://apphost/rest/yourservice
- 20. By Acellam Guy @mistaguy Publishing a microflow • similar to publishing a webservice • instead of SOAP it uses JSON based messages • Has a single transient object as argument. • Each field in this transient object is considered a parameter (from HTTP perspective) • The return type of the microflow should be a transient object or a String or a filedocument • Publish by calling CreateMicroflowService with the microflow that provides the implementation
- 21. By Acellam Guy @mistaguy Microflow with template path • Allows for constructing more complex URLs, from which values are parsed Eg. groups/{groupId}/users/{userId} http://myapp.com/rest/groups/123/users/John
- 22. By Acellam Guy @mistaguy Publishing a data service • JSON based API to list, retrieve, create, update, delete and track objects in your database • Documentation is generated automatically
- 23. By Acellam Guy @mistaguy End points on the service
- 24. By Acellam Guy @mistaguy How the data service works • persistent entity in your database acting as data source • transient object that acts as view object of your data • Publish Microflow has the responsibility of converting source objects into view objects • Update Microflow is responsible for transforming a view as provided by some consumer into real data in your database • Each source object should be uniquely identifiable by a single key attribute
- 25. By Acellam Guy @mistaguy Example • GET <your-app>/rest/<service name>/<identifier>
- 26. By Acellam Guy @mistaguy Creating a new webservice • Add IVK_OpenServiceOverview to your navigation and create a new Published Service after starting your app • best practice is to use the GetOrCreateDataService microflow in the startup microflow to create your service configuration
- 27. By Acellam Guy @mistaguy Configuring the service • Its done on the form or the create service microflow • Core configuration are: • Name • Description • Source Entity • Source Key Attribute • Source Constraint : xpath • Authentication Role • On Publish Microflow • On Update Microflow • On Delete Microflow
- 28. By Acellam Guy @mistaguy Features • Enable GET : HTTP GET • Enable Listing : HTTP GET • Enable Update : HTTP POST or PUT • Enable Create : HTTP POST • Enable Delete : HTTP DELETE • Enable Change Log: caching • Enable StrictVersion:
- 29. By Acellam Guy @mistaguy Securing Published webservice • * • Rolename • Module.Microflowname : Authentication details found in the header eg key
- 30. By Acellam Guy @mistaguy JSON Serialization • Converts transient object to JSON • Nearest json type • For each owned reference that points to a transient object, another key/value pair is added to the object • For each owned referenceset that points to a transient object, the same approach is taken, except that the value is an array ([]) • Manual serialization process by use of serializeObjectToJson java action.
- 32. By Acellam Guy @mistaguy JSON Desrialization • an be triggered manually by calling deserializeJsonToObject • Converts the json from the consumer into a mendix transient object • key/value pair for primitive attribute in transient object • If the primitive is of type string, but the member with the same name in the transient object is a reference, the process assumes that the string value represents an url. • If the member in the target object is a reference, and the value is a JSON object, a new object of the child type of the reference is instantiated • If target is reference set and JSON is array then reference set is created
- 34. By Acellam Guy @mistaguy Assignment • Consume the twitter rest API and show the recent tweets for your profile
- 35. By Acellam Guy @mistaguy References • http://www.drdobbs.com/web-development/restful-web-services-a- tutorial/240169069 • https://github.com/mendix/RestServices
Editor's Notes
- REST has become the default for most Web and mobile apps, it's imperative to have the basics at your fingertips. Every major development language now includes frameworks for building RESTful Web services Almost every RESTful service uses HTTP as its underlying protocol. In this article
- Use plural nouns for naming your resources. Avoid using spaces as they create confusion. Use an _ (underscore) or – (hyphen) instead. A URI is case insensitive. I use camel case in my URIs for better clarity. You can use all lower-case URIs. You can have your own conventions, but stay consistent throughout the service. Make sure your clients are aware of this convention. It becomes easier for your clients to construct the URIs programmatically if they are aware of the resource hierarchy and the URI convention you follow. A cool URI never changes; so give some thought before deciding on the URIs for your service. If you need to change the location of a resource, do not discard the old URI. If a request comes for the old URI, use status code 300 and redirect the client to the new location. Avoid verbs for your resource names until your resource is actually an operation or a process. Verbs are more suitable for the names of operations. For example, a RESTful service should not have the URIs http://MyService/FetcthPerson/1 orhttp://MyService/DeletePerson?id=1.
- so that your internal data structure is not directly published to the outside. This allows for better maintainability and it guarantees that you can pre- or post-process your data when required.
- It will search for the first source object in your database which key value equals the identifier. If found, this object will be converted by thePublish Microflow into a view object. This view object will be serialized to JSON (or HTML or XML) and returned to the consumer.