RestClient

Abstract client that calls remote endpoints using the HTTP/REST protocol.

Implements: IConfigurable, IReferenceable, IOpenable

Description

The RestClient class allows you to create clients that call remote endpoints using the HTTP/REST protocol.

Configuration parameters

  • base_route: base route for a remote URI
  • connection(s):
    • discovery_key: (optional) key to retrieve the connection from IDiscovery
    • protocol: connection protocol (http or https)
    • host: host name or IP address
    • port: port number
    • uri: resource URI or connection string with all parameters in it
  • options:
    • retries: number of retries (default: 3)
    • connect_timeout: connection timeout in milliseconds (default: 10 sec)
    • timeout: invocation timeout in milliseconds (default: 10 sec)
    • context: a context to trace execution through a call chain.

References

  • *:logger:*:*:1.0 - (optional) ILogger components to pass log messages
  • *:counters:*:*:1.0 - (optional) ICounters components to pass collected measurements
  • *:traces:*:*:1.0 - (optional) ITracer components to record traces
  • *:discovery:*:*:1.0 - (optional) IDiscovery services to resolve a connection

Fields

_counters

A list of counters.

protected CompositeCounters _counters = new CompositeCounters()

_client

The HTTP client.

protected Client _client

_uri

The remote service uri which is defined on openning.

protected String _url

_timeout

The invocation timeout in milliseconds.

protected long _timeout = 10000

_connectionResolver

The connection resolver.

protected HttpConnectionResolver _connectionResolver = new HttpConnectionResolver()

_logger

The logger.

protected CompositeLogger _logger = new CompositeLogger()

_counters

The performance counters.

protected CompositeCounters _counters = new CompositeCounters()

_tracer

The tracer.

protected CompositeTracer **_tracerv = new CompositeTracer()

_options

The configuration options.

protected ConfigParams _options = new ConfigParams()

_baseRoute

The base route.

protected String _baseRoute

_retries

The number of retries.

protected int _retries = 1

_headers

The default headers to be added to every request.

protected MultivaluedMap<String, Object> _headers = new MultivaluedHashMap<>()

_connectTimeout

The connection timeout in milliseconds.

protected long _connectTimeout = 10000

Instance methods

addTraceId

Adds a trace id (trace_id) to invocation parameter map.

protected String addTraceId(String route, IContext context)

  • route: String - route.
  • context: IContext - (optional) a context to trace execution through a call chain.
  • returns: String - trace id.

addFilterParams

Adds filter parameters (with the same name as they defined) to the invocation parameter map.

protected String addFilterParams(String route, FilterParams filter)

  • params: route - route.
  • filter: FilterParams - (optional) filter parameters
  • returns: String - invocation parameters with added filter parameters.

addPagingParams

Adds paging parameters (skip, take, total) to invocation parameter map.

protected String addPagingParams(String route, PagingParams paging)

  • route: String - invocation parameters.
  • paging: PagingParams - (optional) paging parameters
  • returns: String - invocation parameters with added paging parameters.

call

Calls a remote method via HTTP/REST protocol.

protected T call(Class type, IContext context, String method, String route, Object requestEntity) throws ApplicationException

  • type: Class - the class type of data.
  • context: IContext - (optional) a context to trace execution through a call chain.
  • method: String - HTTP method: “get”, “head”, “post”, “put”, “delete”
  • route: String - a command route. Base route will be added to this route
  • requestEntity: Object - request body object.
  • returns: T - result object

close

Closes a component and frees used resources.

public void close(IContext context)

  • context: IContext - (optional) a context to trace execution through a call chain.

configure

Configures a component by passing configuration parameters.

public void configure(ConfigParams config)

  • config: ConfigParams - configuration parameters to be set.

instrument

Adds instrumentation to log calls and measures call time. It returns a Timing object that is used to end the time measurement.

protected InstrumentTiming instrument(IContext context, String name)

  • context: IContext - (optional) a context to trace execution through a call chain.
  • name: string - method name.
  • returns: InstrumentTiming - InstrumentTiming object used to end the time measurement.

isOpen

Checks if the component is open.

public boolean isOpen()

  • returns: boolean - True if the component is open and False otherwise.

open

Opens the component.

public void open(IContext context) throws ApplicationException

  • context: IContext - (optional) a context to trace execution through a call chain.

setReferences

Sets references to dependent components.

public void setReferences(IReferences references) throws ReferenceException

  • references: IReferences - references used to locate the component dependencies.

Examples

{@code
  class MyRestClient extends RestClient implements IMyClient {
     ...
 
     public MyData getData(IContext context, String id) {
         Timing timing = this.instrument(context, 'myclient.get_data');
         MyData result = this.execute(MyData.class, context, HttpMethod.POST, "/get_data", new MyData(id));
         timing.endTiming();
         return result;
     }
     ...
  }
 
  MyRestClient client = new MyRestClient();
  client.configure(ConfigParams.fromTuples(
      "connection.protocol", "http",
      "connection.host", "localhost",
      "connection.port", 8080
  ));
 
  MyData data = client.getData("123", "1");
  ...
  }

See also