REST headers and status codes

Include an HTTP header in a REST request to indicate the format of the request and allowed response, or to enable optimistic updating with ETag.

Response headers provide information about the status of the request, and return ETag information. The response also includes a status code.

HTTP defines a set of standard request and response headers. Use the headers to provide information about the entity or other resource that you are requesting. The Decision Server Insights REST API supports the following HTTP headers.

Request headers

Table 1. Request headers
Header name	Description	Examples
Accept	Specifies the content types that are valid in the response message. If the server cannot respond with the requested content type, the `406 Not Acceptable` HTTP status message is returned.	`application/xml` `application/json`
Content-Type	Indicates the content type that is used in the body of the request. The supported content type is XML.	`application/xml`
If-Match	Including If-Match in the header enables optimistic updating with ETag. The server checks to make sure that the entity version numbers match, then writes the entity and increments the version.	`a8f34`, or any string of characters that represents a specific version of the entity
If-None-Match	Including If-None-Match in the header enables optimistic reading of entities by using ETag. The server determines whether the ETag information matches when a GET request is processed. If the information matches, then the entity did not change since the last request. The server returns the HTTP status message `304 Not Modified` and does not retrieve the entity. If there is not a match, the GET request is processed.	`a8f34`, or any string of characters that represents a specific version of the entity

Response headers

Table 2. REST response headers
Header name	Description	Example
Allow	Lists the allowed request types for the solution or entity. If an invalid request is received, the HTTP status message `405 Method not allowed` is returned.	GET
Content-Type	The MIME type of the response content.	`application/xml`
ETag	An alphanumeric string that represents the entity version.	`a8f34`, or any string that represents a specific version of the entity
Status	The Status line in the HTTP response indicates whether the server responded to the request successfully, or if there was an error.	`200 - OK` indicates a successful response `405 - Method not allowed` indicates an error

Response status codes

The REST response includes a status code that indicates whether the request was successful, and if not, the type of error that occurred.

Table 3. REST response status codes
Code	Description
200	OK: the request was successful.
201	Created: the request was successful, and one or more entities was created.
304	Not Modified: the entity was not updated, possibly because the ETag condition, such as If-Match or If-None-Match, stopped the request from completing.
400	Bad Request: the request was not properly formed and therefore was not successful.
404	Not Found: the URI path is incorrect, or communication with the server was unsuccessful.
405	Method Not Allowed: the syntax of the request does not match the request type. The Allow header provides more information about the supported types.
406	Not Acceptable: the Accept header response type is not supported. The supported types are XML and JSON.
409	Conflict: the entity or entities cannot be overwritten or deleted.
412	Precondition Failed: when the If-Match header is included in the request, this status indicates that the ETag information did not match and therefore the entity was not updated.
413	Request Too Large: the number of entities that is returned is too large.
415	Unsupported Media Type: the request contains a format that the server cannot interpret.
503	Service Not Available: the solution is not ready and could not respond to the request.