Im developeing a RESTful Service in which Processes can be executed and proivde a resulting calculation. For this i have modeled the process itself as a Resource (Example: /processes/translate). I want to execute the process by sending a GET request with appended Input Parameter as Query Parameter (Example: /processes/translate?input1=xxxx&input2=xxxxx).
Each process has different Input Parameter which are defined during the process creation in the backend. My Question is how should i document or describe which inputs are needed to execute a process in machine readable form. For Example in XML.
Until now ive integrated atom:link elements in the Representation. i thought that maybe including XFORM could be a soluttion?
Best Regards
Andre
I would not model this with a GET. While it's the easier solution, it's also (IMO) the least RESTful. I would have clients POST a document describing what they want you to translate and your service sends them back a URI where their answer can be found (some translations might take a while).
Example (ommiting a lot of HTTP headers/context)
POST /processes/translate
Content-Type: application/xml
...
<translation-request>
<input1 type="type1">....</input1>
<input2 type="type5">....</input2>
</translation-request>
Response:
200 OK
Content-Location: /processes/translate/jobs/1234
....
That's always an interesting question. We have a project called RESTx (http://restx.org), with which you can create RESTful web services very easily. You can write custom component code in either Java or Python and then create RESTful resources by sending parameter sets to the server, which are then stored. Each parameter set gets its own URI, though, so you can always just run the code with those parameters by accessing the new parameter set's URI.
Importantly, the entire RESTful API, is automatically created. RESTx examines the component code and then assembles the API description. We decided to describe parameters in a way that is human as well as machine readable. You can see examples of what that looks like in a browser or in plain JSON.
I'm the lead developer on that, so please feel free to contact me about any questions you might have.
Related
I am using wiremock json stubs, and have been reading the doc at http://wiremock.org/docs/stubbing/ But I can't seem to locate a complete list of all the options one can put in the response part of json stub file.
I can see how to give a response, and even how to cycle through scenarios and the like. But can't seem to find a way to do something else when I hit a particular end point. Is there a way to specify one's own script to be run when a particular end point is hit? Preferably with the endpoint as an argument supplied to the script?
In my case, and I anticipate in others there is a good reason to have side effects when end points are hit.
Out of the box there isn't a way to call an external script. WireMock intended use is to provide a response to a request. There is a decent API and if your confident in java then it's not difficult to create custom Body transformer with the required logic.
I have a design question on REST. I need to expose a validate method as a rest resource. Let us say it looks like this
public ValidatedResult validate(ObjectToBeValidated object)
ObjectToBeValidated is a class that contains the actual Object and also some parameters concerning the validation.
When I design this as a Restful resource, which action do I use? From my understanding GET is the action that best suits this case. If that is so, how I can pass my ObjectTobeValidated as an object but not as URL parameters? I shy away from URL parameters because ObjectToBeValidated may contain a lot of properties, ending up with an URL like below which is feel is too long
http://localhost/rest/validate?prop1=somevalu&prop2=somevalue&prop3=something&prop11=somevalu&prop22=somevalue&prop33=something
Any help would be appreciated
Thanks
Kay
The HTTP standard allows you to use the POST method. It does not necessary need to have a side effect.
The action performed by the POST method might not result in a resource
that can be identified by a URI. In this case, either 200 (OK) or 204
(No Content) is the appropriate response status, depending on whether
or not the response includes an entity that describes the result.
HTTP 1.1 / method definitions / POST
In your case you can do something like this if you want to follow the noun-verb approach Tim suggested:
POST /api/my/object/validator
Be aware that by REST the messages must be self-descriptive, so either you need a vendor MIME type or you need to add meta-data e.g. RDF to describe what this link does and what params are allowed. Otherwise we are not talking about REST, just a regular webapp.
I'm looking for a convention on how to serialize my data when I have a (long) list of items that I want to POST to the server.
For example, if I have a resource /users and I wanted to POST a new one to it, I'd http-encode the fields for the new user and put it in the request body like this: name=foo&age=20
But if I have a list of users, like this [{ name: 'foo', age: 20 }, { name: 'bar', age: 10 }], is there a conventional way of POSTing this?
I'm thinking name[0]=foo&age[0]=20&name[1]=bar&age[1]=10 but I can't find anything to back it up. What do web servers usually accept/expect?
Quick question which may change my answer: Are you POSTing directly from an HTML form or are you expecting something more sophisticated (e.g. javascript processsing, or not even a web-based client)
If you have a sophisticated enough client, you could just construct a JSON string and POST with a content type of application/json. Then whatever resource is processing the POST could use any number of json libraries to read the posted string and process as is.
Further Rambling:
What framework/languages are you using to construct your REST service? Do they have built-in functionality/conventions to help you?
For example if you're using JAX-RS to build your service, there is a built in annotation #FormParam which can be used to process posted forms... for example: if you posted the following with a content type of application/x-www-form-urlencoded: name=foo&age=20&name=bar&age=10
You could retrieve parallel lists on the service side via:
#POST
#Consumes("application/x-www-form-urlencoded")
public void createUsers(#FormParam("name") List<String> name, #FormParam("age") List<String> age) {
// Store your users
}
But you would then have to deal with the question of what if one list is shorter/longer than the other, how do you resolve that? What happens if a new field is required or optional to create a list of users? (But as I mentioned initially, a JSON array of JSON objects would solve that issue... there are a number of libraries out there that support automagic JSON deserialization in JAX-RS or there is also the option of creating your own MessageBodyReader.
(Disclaimer on the next section: I don't know rails, my experience is more in the Java services world... I'm basing this on this guide). It looks like Rails has a convention of name[]=foo&name[]=bar to process posted data into arrays automagically, and a similar convention to populate structure like user[name]=foo&user[age]=20... Perhaps if you are on rails there is some way to use/abuse both of these features to get the desired result?
Other REST frameworks and languages may have their own conventions and functionality :)
Rails serializes forms on a format not unlike what you suggest. If you have a nested model it encodes it like this:
name=theo&company[name]=acme
(the equivalent JSON would be {"name": "theo", "company": {"name": "acme"}})
I can't say that I've seen a Rails application sending arrays, but there's no reason why it wouldn't work (worst case you would end up with a hash with string keys).
PHP has another convention, if you want to send an array you do
names[]=alice&names[]=bob&names[]=steve
But I don't know how you do nested objects that way.
The HTTP spec, or if it's the URI spec, not sure which atm, actually specifies that if you pass the same argument multiple times you get array of values (instead of the last-wins behaviour of most application frameworks). You can see this in the API docs for Jetty, for example: http://api.dpml.net/org/mortbay/jetty/6.1.5/org/mortbay/jetty/Request.html#getParameterValues(java.lang.String)
However, most of this applies to GET requests, not necessarily POST (but perhaps application/x-url-encoded should adhere to the same standards as GET).
In short, I don't think there is a standard for doing this, POST bodies are a bit of a wild west territory. I think, however, that either you should go with JSON, because it's made to describe structures, and application/x-url-encoded is not, or you should try to represent the structure of your data better, something like:
users[0][name]=foo&users[0][age]=20&users[1][name]=bar&users[1][age]=10
That has some kind of chance of actually being interpretable by a Rails app out of the box, for example.
I am creating a new REST service.
What is the standard for passing parameters to REST services. From different REST implementations in Java, you can configure parameters as part of the path or as request parameters. For example,
Path parameters
http://www.rest.services.com/item/b
Request parameters
http://www.rest.services.com/get?item=b
Does anyone know what the advantages/disadvantages for each method of passing parameters. It seems that passing the parameters as part of the path seems to coincide better with the notion of the REST protocol. That is, a single location signifies a unique response, correct?
Paths tend to be cached, parameters tend to not be, as a general rule.
So...
GET /customers/bob
vs
GET /customers?name=bob
The first is more likely to be cached (assuming proper headers, etc.) whereas the latter is likely not to be cached.
tl;dr: You might want both.
Item #42 exists:
GET /items/42
Accept: application/vnd.foo.item+json
--> 200 OK
{
"id": 42,
"bar": "baz"
}
GET /items?id=42
Accept: application/vnd.foo.item-list+json
--> 200 OK
[
{
"id": 42,
"bar": "baz"
}
]
Item #99 doesn't exist:
GET /items/99
Accept: application/vnd.foo.item+json
--> 404 Not Found
GET /items?id=99
Accept: application/vnd.foo.item-list+json
--> 200 OK
[
]
Explanations & comments
/items/{id} returns an item while /items?id={id} returns an item-list.
Even if there is only a single element in a filtered item-list, a list of a single element is still returned for consistency (as opposed to the element itself).
It just so happens that id is a unique property. If we were to filter on other properties, this would still work in exactly the same way.
Elements of a collection resource can only be named using unique properties (e.g. keys as a subresource of the collection) for obvious reasons (they're normal resources and URIs uniquely identify resources).
If the element is not found when using a filter, the response is still OK and still contains a list (albeit empty). Just because we're requesting a filtered list containing an item that doesn't exist doesn't mean the list itself doesn't exist.
Because they're so different and independently useful, you might want both. The client will want to differentiate between all cases (e.g. whether the list is empty or the list itself doesn't exist, in which case you should return a 404 for /items?...).
Disclaimer: This approach is by no means "standard". It makes so much sense to me though that I felt like sharing.
PS: Naming the item collection "get" is a code smell; prefer "items" or similar.
Your second example of "request parameters" is not correct because "get" is included as part of the path. GET is the request type, it should not be part of the path.
There are 4 main types of requests:
GET
PUT
POST
DELETE
GET requests should always be able to be completed without any information in the request body. Additionally, GET requests should be "safe", meaning that no significant data is modified by the request.
Besides the caching concern mentioned above, parameters in the URL path would tend to be required and/or expected because they are also part of your routing, whereas parameters passed in the query string are more variable and don't affect which part of your application the request is routed to. Although could potentially also pass a variable length set of parameters through the url:
GET somedomain.com/states/Virginia,California,Mississippi/
A good book to read as a primer on this topic is "Restful Web Services". Though I will warn you to be prepared to skim over some redundant information.
I think it depends. One URL for one resource. If you want to receive that resource in a slightly different way, give it a query string. But for a value that would deliver a different resource, put it in the path.
So in your example, the variable's value is directly related to the resource being returned. So it makes more sense in the path.
The first variation is a little cleaner, and allows you to reserve the request parameters for things like sort order and page, as in
http://www.rest.services.com/items/b?sort=ascending;page=6
This is a great fundamental question. I've recently come to the conclusion to stay away from using path parameters. They lead to ambiguous resource resolution. The URL is a basically the 'method name' of a piece of code running somewhere on a server. I prefer not to mix variable names with method names. The name of your method is apparently 'customer' (which IMHO is a rotten name for a method but REST folks love this pattern). The parameter you're passing to this method is the name of the customer. A query parameter works well for that, and this resource and query-parameter value can even be cached if desired.
There is no physical IT customer resource. There is likely no file on disk under a customer folder that's named after the customer. This is a web-service that performs some kind of database transaction. The 'resource' is your service, not the customer.
This obsession over REST and web-verbs reminds me of the early days of Object Oriented programming where we attempted to cram our code into virtual representations of physical objects. Then we realized that objects are usually virtual concepts in a system. OO is still useful when done the right way. REST is also useful if you realize that RESTful resources are services, not objects.
What is the best way to version REST URIs? Currently we have a version # in the URI itself, ie.
http://example.com/users/v4/1234/
for version 4 of this representation.
Does the version belong in the queryString? ie.
http://example.com/users/1234?version=4
Or is versioning best accomplished another way?
Do not version URLs, because ...
you break permalinks
The url changes will spread like a disease through your interface. What do you do with representations that have not changed but point to the representation that has? If you change the url, you break old clients. If you leave the url, your new clients may not work.
Versioning media types is a much more flexible solution.
Assuming that your resource is returning some variant of application/vnd.yourcompany.user+xml all you need to do is create support for a new application/vnd.yourcompany.userV2+xml media type and through the magic of content negotiation your v1 and v2 clients can co-exist peacefully.
In a RESTful interface, the closest thing you have to a contract is the definition of the media-types that are exchanged between the client and the server.
The URLs that the client uses to interact with the server should be provided by the server embedded in previously retrieved representations. The only URL that needs to be known by the client is the root URL of the interface. Adding version numbers to urls only has value if you construct urls on the client, which you are not suppose to do with a RESTful interface.
If you need to make a change to your media-types that will break your existing clients then create a new one and leave your urls alone!
And for those readers currently saying that this makes no sense if I am using application/xml and application/json as media-types. How are we supposed to version those? You're not. Those media-types are pretty much useless to a RESTful interface unless you parse them using code-download, at which point versioning is a moot point.
I would say making it part of the URI itself (option 1) is best because v4 identifies a different resource than v3. Query parameters like in your second option can be best used to pass-in additional (query) info related to the request, rather than the resource.
Ah, I'm putting my old grumpy hat on again.
From a ReST perspective, it doesn't matter at all. Not a sausage.
The client receives a URI it wants to follow, and treats it as an opaque string. Put whatever you want in it, the client has no knowledge of such a thing as a version identifier on it.
What the client knows is that it can process the media type, and I'll advise to follow Darrel's advice. Also I personally feel that needing to change the format used in a restful architecture 4 times should bring huge massive warning signs that you're doing something seriously wrong, and completely bypassing the need to design your media type for change resiliance.
But either way, the client can only process a document with a format it can understand, and follow links in it. It should know about the link relationships (the transitions). So what's in the URI is completely irrelevant.
I personally would vote for http://localhost/3f3405d5-5984-4683-bf26-aca186d21c04
A perfectly valid identifier that will prevent any further client developer or person touching the system to question if one should put v4 at the beginning or at the end of a URI (and I suggest that, from the server perspective, you shouldn't have 4 versions, but 4 media types).
You should NOT put the version in the URL, you should put the version in the Accept Header of the request - see my post on this thread:
Best practices for API versioning?
If you start sticking versions in the URL you end up with silly URLs like this:
http://company.com/api/v3.0/customer/123/v2.0/orders/4321/
And there are a bunch of other problems that creep in as well - see my blog:
http://thereisnorightway.blogspot.com/2011/02/versioning-and-types-in-resthttp-api.html
These (less-specific) SO questions about REST API versioning may be helpful:
Versioning RESTful services?
Best practices for web service REST API versioning
There are 4 different approaches to versioning the API:
Adding version to the URI path:
http://example.com/api/v1/foo
http://example.com/api/v2/foo
When you have breaking change, you must increment the version like: v1, v2, v3...
You can implement a controller in you code like this:
#RestController
public class FooVersioningController {
#GetMapping("v1/foo")
public FooV1 fooV1() {
return new FooV1("firstname lastname");
}
#GetMapping("v2/foo")
public FooV2 fooV2() {
return new FooV2(new Name("firstname", "lastname"));
}
Request parameter versioning:
http://example.com/api/v2/foo/param?version=1
http://example.com/api/v2/foo/param?version=2
The version parameter can be optional or required depending on how you want the API to be used.
The implementation can be similar to this:
#GetMapping(value = "/foo/param", params = "version=1")
public FooV1 paramV1() {
return new FooV1("firstname lastname");
}
#GetMapping(value = "/foo/param", params = "version=2")
public FooV2 paramV2() {
return new FooV2(new Name("firstname", "lastname"));
}
Passing a custom header:
http://localhost:8080/foo/produces
With header:
headers[Accept=application/vnd.company.app-v1+json]
or:
headers[Accept=application/vnd.company.app-v2+json]
Largest advantage of this scheme is mostly semantics: You aren’t cluttering the URI with anything to do with the versioning.
Possible implementation:
#GetMapping(value = "/foo/produces", produces = "application/vnd.company.app-v1+json")
public FooV1 producesV1() {
return new FooV1("firstname lastname");
}
#GetMapping(value = "/foo/produces", produces = "application/vnd.company.app-v2+json")
public FooV2 producesV2() {
return new FooV2(new Name("firstname", "lastname"));
}
Changing Hostnames or using API Gateways:
Essentially, you’re moving the API from one hostname to another. You might even just call this building a new API to the same resources.
Also,you can do this using API Gateways.
I wanted to create versioned APIs and I found this article very useful:
http://blog.steveklabnik.com/posts/2011-07-03-nobody-understands-rest-or-http
There is a small section on "I want my API to be versioned". I found it simple and easy to understand. The crux is to use Accept field in the header to pass version information.
If the REST services require authentication before use, you could easily associate the API key/token with an API version and do the routing internally. To use a new version of the API, a new API key could be required, linked to that version.
Unfortunately, this solution only works for auth-based APIs. However, it does keep versions out of the URIs.
If you use URIs for versioning, then the version number should be in the URI of the API root, so every resource identifier can include it.
Technically a REST API does not break by URL changes (the result of the uniform interface constraint). It breaks only when the related semantics (for example an API specific RDF vocab) changes in a non backward compatible way (rare). Currently a lot of ppl do not use links for navigation (HATEOAS constraint) and vocabs to annotate their REST responses (self-descriptive message constraint) that's why their clients break.
Custom MIME types and MIME type versioning does not help, because putting the related metadata and the structure of the representation into a short string does not work. Ofc. the metadata and the structure will frequently change, and so the version number too...
So to answer your question the best way to annotate your requests and responses with vocabs (Hydra, linked data) and forget versioning or use it only by non backward compatible vocab changes (for example if you want to replace a vocab with another one).
I'd include the version as an optional value at the end of the URI. This could be a suffix like /V4 or a query parameter like you've described. You might even redirect the /V4 to the query parameter so you support both variations.
I vote up for doing this in mime type but not in URL.
But the reason is not the same as other guys.
I think the URL should be unique (excepting those redirects) for locating the unique resource.
So, if you accept /v2.0 in URLs, why it is not /ver2.0 or /v2/ or /v2.0.0? Or even -alpha and -beta? (then it totally becomes the concept of semver)
So, the version in mime type is more acceptable than the URL.