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Backend API

basic API for Metalcon backend components

Dependency

<dependency>
  <groupId>de.metalcon</groupId>
  <artifactId>api</artifactId>
  <version>0.1.1</version>
</dependency>

Usage

The basic API is used in the API for your backend component.

Metalcon: Big picture

To let the client (middleware) send requests to your backend component there are three pojects involved:

  1. API: basic Metalcon API defining response classes you can extend
  2. <component>API: component API based upon the basic API that (can) has additional requests and responses.
    Until this point, there is no technology for transmission set.
  3. middleware: client with a dispatcher that uses your component API to send requests and interpret responses.
  4. zmqWorker: worker living in your component that parses incoming requests and your responses and sends them to the client via ZeroMQ. The worker uses the basic API.
  5. <component>: your backend component used your API and the worker. It interprets incoming requests and delegates the responses to the worker.

Requests

Basic request class Request that must be extended in order to use the worker.
Requests do not have any contraints yet.

ShutdownRequest

Send the ShutdownRequest to shutdown the transmission layer. (here: ZeroMQ Worker)

Responses

Basic response class Response that must be extended in order to use the worker.
Responses have a status message at least:

  • success: signalizes that the request was correct
  • error: signalizes an error concerning the request in any layer, see ErrorResponse

SuccessResponse

Simple response signalizing success if no additional information is needed.
Extend SuccessResponse and add fields if you need them.

ErrorResponse

Basic error class ErrorResponse that signalizes an error.
There are three types of errors, representing the layer in which the error occurred, defined in ErrorResponse.ErrorType.
The error type and an error message describing the error must be set.
There is an optional solution field.

Error types:

  • PARSING_ERROR: error occurred when parsing request/response objects
  • INTERNAL_SERVER_ERROR: error occurred in server due to internal reasons
  • USAGE_ERROR: error occurred in server due to misuse by client

ParsingErrorResponse

Response signalizing a parsing error. Used by the worker that handles serialization/deserialization of requests and responses.

InternalServerErrorResponse

Response signalizing an internal server error.

UsageErrorResponse

Response signalizing a misuse by the client.