Call REST endpoints

The gc-http-caller kamelet is the canonical way to make any REST/JSON call out of the connector. Use it for every HTTP method by passing ?method=GET|POST|PUT|DELETE|PATCH. It handles retries, timeouts, headers, query params, and path variables, and produces structured Grand Central errors through JOLT.

How the kamelet reads inputs

The kamelet reads the URL, query parameters, path variables, and headers from the exchange. Set them before the .to(...) call.

Where to put it	Key	Type	Purpose
Exchange property	`gc-http-caller-url`	`String`	The full URL to call; interpolate the vendor base URL with the path
Exchange property	`gc-http-caller-queryParams`	`Map<String, Object>`	Query parameters appended to the URL
Exchange property	`gc-http-caller-pathVariables`	`Map<String, Object>`	Path variables to substitute into `{name}` placeholders in the URL
Header	`gc-http-caller-headers`	`Map<String, Object>`	Additional headers to send with the call

The kamelet writes all of these onto the outgoing HTTP request and clears them after the call returns.

Kamelet parameters you can tune

The following parameters have defaults, but you can override them in configuration properties in the Grand Central DevHub Application Live repository of your installation:

https://github.com/bb-ecos-${installation}/gc-devhub-${installation}-applications-live/tree/main/runtimes/{runtime}/values/{namespace}/{deployment-name}-values.yaml

Parameter	Default	Purpose
`method`	`GET`	HTTP verb: one of `GET`, `POST`, `PUT`, `DELETE`, or `PATCH`
`contentType`	`application/json`	`Content-Type` header for the request
`accept`	`application/json`	`Accept` header for the response
`gc-http-caller-retry`	`false`	Enable retry on transient failures
`retryStatuses`	`429,500,502,503,504`	HTTP status codes that trigger a retry
`connectTimeout`	`5000` ms	TCP connect timeout
`soTimeout`	`5000` ms	Socket read timeout
`responseTimeout`	`5000` ms	Wait-for-response timeout
`connectionsPerRoute`	`20`	Pooled connections per route
`maxTotalConnections`	`200`	Pool size cap across routes
`gc-http-caller-handleExceptionsInConnector`	`false`	If `true`, the kamelet doesn’t auto-wrap errors and the connector must handle them
`errorTemplate`	`transform-error-details.json`	JOLT spec used to map vendor errors to Grand Central error JSON

Typical call forms

// Simplest GET
.setProperty("gc-http-caller-url", simple("{{vendor.base.url}}/api/path"))
.to("kamelet:gc-http-caller?method=GET");

// GET by ID using a header
.setProperty("gc-http-caller-url",
    simple("{{vendor.base.url}}/api/path/${header.entityId}"))
.to("kamelet:gc-http-caller?method=GET");

// GET with query params from a Map
.setProperty("gc-http-caller-queryParams", paramsMap)
.setProperty("gc-http-caller-url", simple("{{vendor.base.url}}/api/path"))
.to("kamelet:gc-http-caller?method=GET");

// POST with retry enabled
.to("kamelet:gc-http-caller?method=POST&gc-http-caller-retry={{retryFlag}}");

Exception-handler kamelets

You typically register these once in configure() through onException(...). Each turns a thrown exception into a structured Grand Central error response. Kamelet files are available in the grandcentral-platform-kamelets artifact.

Kamelet	Use it for
`http-exception-handler`	`HttpOperationFailedException` from the vendor; wraps in Grand Central error JSON through JOLT
`json-validation-exception-handler`	`JsonValidationException` from the schema validator; returns HTTP 400 with GC024 and detailed errors
`service-exception-handler`	Service-level failures
`grand-central-service-exception-handler`	`GrandCentralServiceException` thrown explicitly from the connector
`generic-exception-handler`	Catch-all fallback for unknown exceptions
`validation-exception-handler`	General validation errors, for example from `PredicatesValidatingProcessor`
`custom-http-error-handler`	Custom HTTP error mapping when the standard handler isn’t enough

Example registration:

onException(JsonValidationException.class)
    .handled(true)
    .to("kamelet:json-validation-exception-handler"
        + "?schemaErrorTemplate=transform-schema-validation-error-details.json");

onException(HttpOperationFailedException.class)
    .handled(true)
    .to("kamelet:http-exception-handler?errorTemplate=transform-error-details.json");

onException(Exception.class)
    .handled(true)
    .to("kamelet:generic-exception-handler");

Next step

For the Camel building blocks that connect these calls, see Use Camel EIPs.

Overview

Capabilities

Developer guides

Security and reliability

Platform administration

Reference

How the kamelet reads inputs

Kamelet parameters you can tune

Typical call forms

Exception-handler kamelets

Next step

​How the kamelet reads inputs

​Kamelet parameters you can tune

​Typical call forms

​Exception-handler kamelets

​Next step

How the kamelet reads inputs

Kamelet parameters you can tune

Typical call forms

Exception-handler kamelets

Next step