I've written a RESTful web service that supports the standard CRUD operations, and that can return a set of objects matching certain criteria (a SEARCH verb), but I'd like to add a higher-order COUNT verb, so clients can count the resources matching search criteria without having to fetch all of them.
A few options that occur to me:
Ignoring the HTTP specification and returning the object count in the response body of a HEAD request.
Duplicating the SEARCH verb's logic, but making a HEAD request instead of a GET request. The server then would encode the object count in a response header.
Defining a new HTTP method, COUNT, that returns the object count in the response body.
I'd prefer the API of the first approach, but I have to strike that option because it's non-compliant. The second approach seems most semantically correct, but the API isn't very convenient: clients will have to deal with response headers, when most of the time they want to be able to do something easy like response.count. So I'm leaning toward the third approach, but I'm concerned about the potential problems involved with defining a new HTTP method.
What would you do?
The main purpose of rest is to define a set of resources that you interact with using well defined verbs. You must thus avoid to define your own verbs. The number of resources should be considered as a different resource, with its own uri that you can simply GET.
For example:
GET resources?crit1=val1&crit2=val2
returns the list of resources and
GET resources/count?crit1=val1&crit2=val2
Another option is to use the conneg: e.g. Accept: text/uri-list returns the resources list and Accept: text/plain returns only the count
You can use HEAD without breaking the HTTP specification and you can indicate the count by using an HTTP Range header in the response:
HEAD /resource/?search=lorem
Response from the service, assuming that you return the first 20 results by default:
...
Content-Range: resources 0-20/12345
...
This way you transfer the amount of resources to the client within the header of the response message without the need to return a message body.
Update:
The solution suggested Yannick Loiseau will work fine. Just wanted to provide one other alternative approach which can be used to achieve what you need without the need to define a new resource of verb.
You can use GET and add the count into the body of the message. Then, if you API allows clients to request a range of results, you can use that in order to limit the size of message body to a minimum (since you only want the count). One way to do that would be to request an empty range (from 0 to 0), for example:
GET /resource/?search=lorem&range=0,0
The service could then respond as follows, indicating that there are 1234 matching resources in the result set:
<?xml version="1.0" encoding="UTF-8" ?>
<resources range="0-0/1234" />
Ignoring the HTTP specification and returning the object count in the response body of a HEAD request.
IMHO, this is a very bad idea. It may not work simply because you might have intermediaries that don't ignore the HTTP spec.
Defining a new HTTP method, COUNT, that returns the object count in the response body.
There is no problem with this approach. HTTP is extendable and you can define your own verbs. Some firewalls prohibit this, but they are usually also prohibit POST and DELETE and X-HTTP-Method-Override header is widely supported.
Another option, to add a query param to your url, something like: ?countOnly=true
Related
I want to design my rest endpoint with the appropriate method for the following scenario.
There is a group. Each group has a status. The group can be activated or inactivated by the admin.
Should I design my end point as
PUT /groups/api/v1/groups/{group id}/status/activate
OR
PATCH /groups/api/v1/groups/{group id}
with request body like
{action:activate|deactivate}
The PATCH method is the correct choice here as you're updating an existing resource - the group ID. PUT should only be used if you're replacing a resource in its entirety.
Further information on partial resource modification is available in RFC 5789. Specifically, the PUT method is described as follows:
Several applications extending the Hypertext Transfer Protocol
(HTTP) require a feature to do partial resource modification. The
existing HTTP PUT method only allows a complete replacement of a
document. This proposal adds a new HTTP method, PATCH, to modify an
existing HTTP resource.
The R in REST stands for resource
(Which isn't true, because it stands for Representational, but it's a good trick to remember the importance of Resources in REST).
About PUT /groups/api/v1/groups/{group id}/status/activate: you are not updating an "activate". An "activate" is not a thing, it's a verb. Verbs are never good resources. A rule of thumb: if the action, a verb, is in the URL, it probably is not RESTful.
What are you doing instead? Either you are "adding", "removing" or "updating" an activation on a Group, or if you prefer: manipulating a "status"-resource on a Group. Personally, I'd use "activations" because they are less ambiguous than the concept "status": creating a status is ambiguous, creating an activation is not.
POST /groups/{group id}/activation Creates (or requests the creation of) an activation.
PATCH /groups/{group id}/activation Updates some details of an existing activation. Since a group has only one activation, we know what activation-resource we are referring to.
PUT /groups/{group id}/activation Inserts-or-replaces the old activation. Since a group has only one activation, we know what activation-resource we are referring to.
DELETE /groups/{group id}/activation Will cancel, or remove the activation.
This pattern is useful when the "activation" of a Group has side-effects, such as payments being made, mails being sent and so on. Only POST and PATCH may have such side-effects. When e.g. a deletion of an activation needs to, say, notify users over mail, DELETE is not the right choice; in that case you probably want to create a deactivation resource: POST /groups/{group_id}/deactivation.
It is a good idea to follow these guidelines, because this standard contract makes it very clear for your clients, and all the proxies and layers between the client and you, know when it is safe to retry, and when not. Let's say the client is somewhere with flaky wifi, and its user clicks on "deactivate", which triggers a DELETE: If that fails, the client can simply retry, until it gets a 404, 200 or anything else it can handle. But if it triggers a POST to deactivation it knows not to retry: the POST implies this.
Any client now has a contract, which, when followed, will protect against sending out 42 emails "your group has been deactivated", simply because its HTTP-library kept retrying the call to the backend.
Updating a single attribute: use PATCH
PATCH /groups/{group id}
In case you wish to update an attribute. E.g. the "status" could be an attribute on Groups that can be set. An attribute such as "status" is often a good candidate to limit to a whitelist of values. Examples use some undefined JSON-scheme:
PATCH /groups/{group id} { "attributes": { "status": "active" } }
response: 200 OK
PATCH /groups/{group id} { "attributes": { "status": "deleted" } }
response: 406 Not Acceptable
Replacing the resource, without side-effects use PUT.
PUT /groups/{group id}
In case you wish to replace an entire Group. This does not necessarily mean that the server actually creates a new group and throws the old one out, e.g. the ids might remain the same. But for the clients, this is what PUT can mean: the client should assume he gets an entirely new item, based on the server's response.
The client should, in case of a PUT request, always send the entire resource, having all the data that is needed to create a new item: usually the same data as a POST-create would require.
PUT /groups/{group id} { "attributes": { "status": "active" } }
response: 406 Not Acceptable
PUT /groups/{group id} { "attributes": { "name": .... etc. "status": "active" } }
response: 201 Created or 200 OK, depending on whether we made a new one.
A very important requirement is that PUT is idempotent: if you require side-effects when updating a Group (or changing an activation), you should use PATCH. So, when the update results in e.g. sending out a mail, don't use PUT.
I would recommend using PATCH, because your resource 'group' has many properties but in this case, you are updating only the activation field(partial modification)
according to the RFC5789 (https://www.rfc-editor.org/rfc/rfc5789)
The existing HTTP PUT method only allows a complete replacement of
a document. This proposal adds a new HTTP method, PATCH, to modify
an existing HTTP resource.
Also, in more details,
The difference between the PUT and PATCH requests is reflected in the
way the server processes the enclosed entity to modify the resource
identified by the Request-URI. In a PUT request, the enclosed entity
is considered to be a modified version of the resource stored on the
origin server, and the client is requesting that the stored version
be replaced. With PATCH, however, the enclosed entity contains a set
of instructions describing how a resource currently residing on the
origin server should be modified to produce a new version. The PATCH
method affects the resource identified by the Request-URI, and it
also MAY have side effects on other resources; i.e., new resources
may be created, or existing ones modified, by the application of a
PATCH.
PATCH is neither safe nor idempotent as defined by [RFC2616],
Section
9.1.
Clients need to choose when to use PATCH rather than PUT. For
example, if the patch document size is larger than the size of the
new resource data that would be used in a PUT, then it might make
sense to use PUT instead of PATCH. A comparison to POST is even more
difficult, because POST is used in widely varying ways and can
encompass PUT and PATCH-like operations if the server chooses. If
the operation does not modify the resource identified by the Request-
URI in a predictable way, POST should be considered instead of PATCH
or PUT.
The response code for PATCH is
The 204 response code is used because the response does not carry a
message body (which a response with the 200 code would have). Note
that other success codes could be used as well.
also refer thttp://restcookbook.com/HTTP%20Methods/patch/
Caveat: An API implementing PATCH must patch atomically. It MUST not
be possible that resources are half-patched when requested by a GET.
Since you want to design an API using the REST architectural style you need to think about your use cases to decide which concepts are important enough to expose as resources. Should you decide to expose the status of a group as a sub-resource you could give it the following URI and implement support for both GET and PUT methods:
/groups/api/groups/{group id}/status
The downside of this approach over PATCH for modification is that you will not be able to make changes to more than one property of a group atomically and transactionally. If transactional changes are important then use PATCH.
If you do decide to expose the status as a sub-resource of a group it should be a link in the representation of the group. For example if the agent gets group 123 and accepts XML the response body could contain:
<group id="123">
<status>Active</status>
<link rel="/linkrels/groups/status" uri="/groups/api/groups/123/status"/>
...
</group>
A hyperlink is needed to fulfill the hypermedia as the engine of application state condition of the REST architectural style.
One possible option to implement such behavior is
PUT /groups/api/v1/groups/{group id}/status
{
"Status":"Activated"
}
And obviously, if someone need to deactivate it, PUT will have Deactivated status in JSON.
In case of necessity of mass activation/deactivation, PATCH can step into the game (not for exact group, but for groups resource:
PATCH /groups/api/v1/groups
{
{ “op”: “replace”, “path”: “/group1/status”, “value”: “Activated” },
{ “op”: “replace”, “path”: “/group7/status”, “value”: “Activated” },
{ “op”: “replace”, “path”: “/group9/status”, “value”: “Deactivated” }
}
In general this is idea as #Andrew Dobrowolski suggesting, but with slight changes in exact realization.
I would generally prefer something a bit simpler, like activate/deactivate sub-resource (linked by a Link header with rel=service).
POST /groups/api/v1/groups/{group id}/activate
or
POST /groups/api/v1/groups/{group id}/deactivate
For the consumer, this interface is dead-simple, and it follows REST principles without bogging you down in conceptualizing "activations" as individual resources.
My application has a resource at /foo. Normally, it is represented by an HTTP response payload like this:
{"a": "some text", "b": "some text", "c": "some text", "d": "some text"}
The client doesn't always need all four members of this object. What is the RESTfully semantic way for the client to tell the server what it needs in the representation? e.g. if it wants:
{"a": "some text", "b": "some text", "d": "some text"}
How should it GET it? Some possibilities (I'm looking for correction if I misunderstand REST):
GET /foo?sections=a,b,d.
The query string (called a query string after all) seems to mean "find resources matching this condition and tell me about them", not "represent this resource to me according to this customization".
GET /foo/a+b+d My favorite if REST semantics doesn't cover this issue, because of its simplicity.
Breaks URI opacity, violating HATEOAS.
Seems to break the distinction between resource (the sole meaning of a URI is to identify one resource) and representation. But that's debatable because it's consistent with /widgets representing a presentable list of /widget/<id> resources, which I've never had a problem with.
Loosen my constraints, respond to GET /foo/a, etc, and have the client make a request per component of /foo it wants.
Multiplies overhead, which can become a nightmare if /foo has hundreds of components and the client needs 100 of those.
If I want to support an HTML representation of /foo, I have to use Ajax, which is problematic if I just want a single HTML page that can be crawled, rendered by minimalist browsers, etc.
To maintain HATEOAS, it also requires links to those "sub-resources" to exist within other representations, probably in /foo: {"a": {"url": "/foo/a", "content": "some text"}, ...}
GET /foo, Content-Type: application/json and {"sections": ["a","b","d"]} in the request body.
Unbookmarkable and uncacheable.
HTTP does not define body semantics for GET. It's legal HTTP but how can I guarantee some user's proxy doesn't strip the body from a GET request?
My REST client won't let me put a body on a GET request so I can't use that for testing.
A custom HTTP header: Sections-Needed: a,b,d
I'd rather avoid custom headers if possible.
Unbookmarkable and uncacheable.
POST /foo/requests, Content-Type: application/json and {"sections": ["a","b","d"]} in the request body. Receive a 201 with Location: /foo/requests/1. Then GET /foo/requests/1 to receive the desired representation of /foo
Clunky; requires back-and-forth and some weird-looking code.
Unbookmarkable and uncacheable since /foo/requests/1 is just an alias that would only be used once and only kept until it is requested.
I would suggest the querystring solution (your first). Your arguments against the other alternatives are good arguments (and ones that I've run into in practise when trying to solve the same problem). In particular, the "loosen the constraints/respond to foo/a" solution can work in limited cases, but introduces a lot of complexity into an API from both implementation and consumption and hasn't, in my experience, been worth the effort.
I'll weakly counter your "seems to mean" argument with a common example: consider the resource that is a large list of objects (GET /Customers). It's perfectly reasonable to page these objects, and it's commonplace to use the querystring to do that: GET /Customers?offset=100&take=50 as an example. In this case, the querystring isn't filtering on any property of the listed object, it's providing parameters for a sub-view of the object.
More concretely, I'd say that you can maintain consistency and HATEOAS through these criteria for use of the querystring:
the object returned should be the same entity as that returned from the Url without the querystring.
the Uri without the querystring should return the complete object - a superset of any view available with a querystring at the same Uri. So, if you cache the result of the undecorated Uri, you know you have the full entity.
the result returned for a given querystring should be deterministic, so that Uris with querystrings are easily cacheable
However, what to return for these Uris can sometimes pose more complex questions:
returning a different entity type for Uris differing only by querystring could be undesirable (/foo is an entity but foo/a is a string); the alternative is to return a partially-populated entity
if you do use different entity types for sub-queries then, if your /foo doesn't have an a, a 404 status is misleading (/foo does exist!), but an empty response may be equally confusing
returning a partially-populated entity may be undesirable, but returning part of an entity may not be possible, or may be more confusing
returning a partially populated entity may not be possible if you have a strong schema (if a is mandatory but the client requests only b, you are forced to return either a junk value for a, or an invalid object)
In the past, I have tried to resolve this by defining specific named "views" of required entities, and allowing a querystring like ?view=summary or ?view=totalsOnly - limiting the number of permutations. This also allows for definition of a subset of the entity that "makes sense" to the consumer of the service, and can be documented.
Ultimately, I think that this comes down to an issue of consistency more than anything: you can meet HATEOAS guidance using the querystring relatively easily, but the choices you make need to be consistent across your API and, I'd say, well documented.
I've decided on the following:
Supporting few member combinations: I'll come up with a name for each combination. e.g. if an article has members for author, date, and body, /article/some-slug will return all of it and /article/some-slug/meta will just return the author and date.
Supporting many combinations: I'll separate member names by hyphens: /foo/a-b-c.
Either way, I'll return a 404 if the combination is unsupported.
Architectural constraint
REST
Identifying resources
From the definition of REST:
a resource R is a temporally varying membership function MR(t), which for time t maps to a set of entities, or values, which are equivalent. The values in the set may be resource representations and/or resource identifiers.
A representation being an HTTP body and an identifier being a URL.
This is crucial. An identifier is just a value associated with other identifiers and representations. That's distinct from the identifier→representation mapping. The server can map whatever identifier it wants to any representation, as long as both are associated by the same resource.
It's up to the developer to come up with resource definitions that reasonably describe the business by thinking of categories of things like "users" and "posts".
HATEOAS
If I really care about perfect HATEOAS, I could put a hyperlink somewhere in the /foo representation to /foo/members, and that representation would just contain a hyperlink to every supported combination of members.
HTTP
From the definition of a URL:
The query component contains non-hierarchical data that, along with data in the path component, serves to identify a resource within the scope of the URI's scheme and naming authority (if any).
So /foo?sections=a,b,d and /foo?sections=b are distinct identifiers. But they can be associated within the same resource while being mapped to different representations.
HTTP's 404 code means that the server couldn't find anything to map the URL to, not that the URL is not associated with any resource.
Functionality
No browser or cache will ever have trouble with slashes or hyphens.
Actually it depends on the functionality of the resource.
If for example the resource represents an entity:
/customers/5
Here the '5' represents an id of the customer
Response:
{
"id": 5,
"name": "John",
"surename": "Doe",
"marital_status": "single",
"sex": "male",
...
}
So if we will examine it closely, each json property actually represents a field of the record on customer resource instance.
Let's assume consumer would like to get partial response, meaning, part of the fields. We can look at it as the consumer wants to have the ability to select the various fields via the request, which are interesting to him, but not more (in order to save traffic or performance, if part of the fields are hard to compute).
I think in this situation, the most readable and correct API would be (for example, get only name and surename)
/customers/5?fields=name,surename
Response:
{
"name": "John",
"surename": "Doe"
}
HTTP/1.1
if illegal field name is requested - 404 (Not Found) is returned
if different field names are requested - different responses will be generated, which also aligns with the caching.
Cons: if the same fields are requested, but the order is different between the fields (say: fields=id,name or fields=name,id), although the response is the same, those responses will be cached separately.
HATEOAS
In my opinion pure HATEOAS is not suitable for solving this particular problem. Because in order to achieve that, you need a separate resource for every permutation of field combinations, which is overkill, as it is bloating the API extensively (say you have 8 fields in a resource, you will need permutations!).
if you model resources only for the fields but not all the permutations, it has performance implications, e.g. you want to bring the number of round trips to minimum.
If a,b,c are property of a resource like admin for role property the right way is to use is the first way that you've suggested GET /foo?sections=a,b,d because in this case you would apply a filter to the foo collection. Otherwise if a,b and c are a singole resource of foo collection the the way that would follow is to do a series of GET requests /foo/a /foo/b /foo/c. This approach, as you said, has a high payload for request but it is the correct way to follow the approach Restfull. I would not use the second proposal made by you because plus char in a url has a special meaning.
Another proposal is to abandon use GET and POST and create an action for the foo collection like so: /foo/filter or /foo/selection or any verb that represent an action on the collection. In this way, having a post request body, you can pass a json list of the resource you would.
you could use a second vendor media-type in the request header application/vnd.com.mycompany.resource.rep2, you can't bookmark this however, query-parameters are not cacheable (/foo?sections=a,b,c) you could take a look at matrix-parameters however regarding this question they should be cacheable URL matrix parameters vs. request parameters
I'm writting a RESTful api, and at I'm thinking about the process of a user creating a key. I have the following possibilities:
GET request to /new/<keyname> - although it's very easy I think I won't use this, because I heard GET is for retrieving and/or listing information;
POST request to /<keyname> - This seemed to me easy and simple enough, but does not pass any data in the request body. Can I do it this way ? Is this weird ?
POST request to /keys passing in the request body "keyname=SomeKey" - Is this the correct way ?
I looked at this API from joyent and in all their PUT and POST requests they pass some data in the request body. Is this expected ? Is it really wrong not to require a request body in a PUT and POST request ?
I asked this question on the Http-WG. This was the most precise answer I got http://lists.w3.org/Archives/Public/ietf-http-wg/2010JulSep/0276.html
In summary, POST does not require a body. I would expect the same justification can be applied to PUT.
RFC2616 is the base RFC for HTTP 1.1
In the most general form, an HTTP message is this (note the optional body):
generic-message = start-line
*(message-header CRLF)
CRLF
[ message-body ]
start-line = Request-Line | Status-Line
Reading further gives this:
9.5 POST
The POST method is used to request that the origin server accept the
entity enclosed in the request as a new subordinate of the resource
identified by the Request-URI in the Request-Line. ...
and
9.6 PUT
The PUT method requests that the enclosed entity be stored under the
supplied Request-URI. ...
The fundamental difference between the POST and PUT requests is
reflected in the different meaning of the Request-URI. The URI in a
POST request identifies the resource that will handle the enclosed
entity. That resource might be a data-accepting process, a gateway to
some other protocol, or a separate entity that accepts annotations.
In contrast, the URI in a PUT request identifies the entity enclosed
with the request -- the user agent knows what URI is intended and the
server MUST NOT attempt to apply the request to some other resource.
Both POST and PUT include the phrase entity enclosed in the request.
Based on my reading, I believe that a body is desired (a non-normative description, I know) for both POST and PUT.
In the context of REST, POST is create and PUT is update. I can imagine creating an empty object (perhaps a placeholder for future information), but I don't imagine much use of an empty update.
It is not required. You can send a POST/PUT request without a body and instead use query string parameters. But be careful if your parameters contain characters that are not HTTP valid you will have to encode them.
For example if you need to POST 'hello world' to and end point you would have to make it look like this: http://api.com?param=hello%20world
Probably the best way is your third option: POST to /keys with keyname=SomeKey.
Here's why: You may wish to add another function to your API, for example create_new_user. It would then be difficult to tell the difference between a user trying to POST a key called create_new_user and a user trying to use the create_new_user function.
You are correct in saying that you should not be using GET to do this operation as the GET operation "SHOULD NOT have the significance of taking an action
other than retrieval." (RFC 2616).
To answer your question in one line. Yes it is expected to have Body/Content in body, but it is not required(Mandatory).
According to okHttp3 (an HTTP library for android): the following methods need a body: POST, PUT, PATCH, PROPPATCH (WebDAV) and REPORT (source). It even crashes if you try to do a request with the given methods without a body.
I need to invoke a process which doesn't require any input from the user, just a trigger. I plan to use POST /uri without a body to trigger the process. I want to know if this is considered bad from both HTTP and REST perspectives?
I asked this question on the IETF HTTP working group a few months ago. The short answer is: NO, it's not a bad practice (but I suggest reading the thread for more details).
Using a POST instead of a GET is perfectly reasonable, since it also instructs the server (and gateways along the way) not to return a cached response.
POST is completely OK. In difference of GET with POST you are changing the state of the system (most likely your trigger is "doing" something and changing data).
I used POST already without payload and it "feels" OK. One thing you should do when using POST without payload: Pass header Content-Length: 0. I remember problems with some proxies when I api-client didn't pass it.
If you use POST /uri without a body it is something like using a function which does not take an argument .e.g int post (void); so it is reasonable to have function to your resource class which can change the state of an object without having an argument. If you consider to implement the Unix touch function for a URI, is not it be good choice?
Yes, it's OK to send a POST request without a body and instead use query string parameters. But be careful if your parameters contain characters that are not HTTP valid you will have to encode them.
For example if you need to POST 'hello world' to and end point you would have to make it look like this: http://api.com?param=hello%20world
Support for the answers that POST is OK in this case is that in Python's case, the OpenAPI framework "FastAPI" generates a Swagger GUI (see image) that doesn't contain a Body section when a method (see example below) doesn't have a parameter to accept a body.
the method "post_disable_db" just accepts a path parameter "db_name" and doesn't have a 2nd parameter which would imply a mandatory body.
#router.post('/{db_name}/disable',
status_code=HTTP_200_OK,
response_model=ResponseSuccess,
summary='',
description=''
)
async def post_disable_db(db_name: str):
try:
response: ResponseSuccess = Handlers.databases_handler.post_change_db_enabled_state(db_name, False)
except HTTPException as e:
raise (e)
except Exception as e:
logger.exception(f'Changing state of DB to enabled=False failed due to: {e.__repr__()}')
raise HTTPException(HTTP_500_INTERNAL_SERVER_ERROR, detail=e.__repr__())
return response
I guessed that the name of each of the request method has a relationship with the operations they performed in some manner. But I can't get it!
Detials:
GET means posted argument are showed in the url and POST means they are sent but not shown in the url. But what is that related to POST/GET? What is gotten/posted or what does the posting/getting job? Do you have any glues?
I understand what GET and POST method is. What I wanna know is why do we GET/POST, why don't we call it TYPE1/TYPE2, or another more make-sense name like ON-URL/OFF-URL
Please discuss if you know that.
This should help you:
Methods GET and POST in HTML forms - what's the difference?
http://www.cs.tut.fi/~jkorpela/forms/methods.html
The Definitive Guide to GET vs POST
http://carsonified.com/blog/dev/the-definitive-guide-to-get-vs-post/
get and post
http://catcode.com/formguide/getpost.html
From RFC 2616:
GET
The GET method means retrieve whatever information (in the form of an entity) is identified by the Request-URI.
POST
The POST method is used to request that the origin server accept the entity enclosed in the request as a new subordinate of the resource identified by the Request-URI in the Request-Line.
So, GET should be used to read a resource, whereas POST should be used to create, update, or delete a resource.
GET and POST are called HTTP Verbs. See the RFC for details.
GET will get a resource identified by a URL. If using GET as the action for a form the entries will be encoded in the URL (look at a google search for an example).
POST will send the data separately, to the specified URL.
The biggest difference is that if you use GET on a form submit, you can copy the URL of the page you landed at and use it directly to get the same results. All information will also be visible in the URL (don't use this method for passwords). If you POST the data the URL of the landing page will not be enough to reproduce the same results; you will have to go through the form again.
Take a look at the RFC definitions here:
http://www.w3.org/Protocols/rfc2616/rfc2616-sec9.html
But essentially, GET is used to retrieve a resource and POST is used to create a new one or make a change to a resource.
Seems to me that #Nam G. VU is asking an English-language question.
"Get" implies that the flow of data is from the server to the client. More specifically, the client is asking the server to send some data.
"Post" implies that the client is pushing data to the server. The word "post" implies that it's a one-way operation.
Of course, neither of these is 100% unidirectional: GETs can send data to the server in the
URL as path and/or query arguments, and POSTS return data to the client.
But, in the simplest sense, the English verbs imply the principal direction of data flow.
From the REST standpoint, GET METHOD signifies that it is used to GET a (list of similar) resource(s). POST is used to create (or POST) a resource.
Apart from this, GET carries all parameters in the URL in the format of ?name=value& pairs, whereas POST carries all of them in the Request Body.