interceptors.md

Interceptors

Kohttp provides a DSL to add interceptors. Custom Interceptors can be defined by implementing the okhttp3.Interceptors. Interceptors are added by forking the defaultHttpClient.

val forkedClient = defaultHttpClient.fork {
    interceptors {
          +interceptor1
          +interceptor2
    }
 }

Logging Interceptor: A Request Logging Interceptor.

Parameters: 1. strategy: LoggingStrategy = HttpLoggingStrategy(): Formatting strategy: CURL / HTTP 2. log: (String) -> Unit = ::println: function as a parameter to consume the log message. It defaults to println. Logs Request body when present.

Usage:

val client = defaultHttpClient.fork {
                interceptors {
                    +LoggingInterceptor()
                }
            }

Sample Output: [2019-01-28T04:17:42.885Z] GET 200 - 1743ms https://postman-echo.com/get

Retry Interceptor: Provides a configurable method to retry on specific errors.

Parameters:

1. failureThreshold: Int: Number of attempts to get response with. Defaults to 3.
2. invocationTimeout: Long: timeout (millisecond) before retry. Defaults to 0
3. ratio: Int: ratio for exponential increase of invocation timeout. Defaults to 1
4. errorStatuses: List<Int>: HTTP status codes to be retried on. Defaults to listOf(503, 504)

Usage:

val client = defaultHttpClient.fork {
                interceptors {
                    +RetryInterceptor()
                }
            }

Signing Interceptor: Enables signing of query parameters. Allowing creation of presigned URLs.

Parameters: 1. parameterName: String: The name of the parameter with signed key 2. signer: HttpUrl.() -> String: Function with okhttp3.HttpUrl as a receiver to sign the request parameter

Usage:

val client = defaultHttpClient.fork {
                interceptors {
                    +SigningInterceptor("key") {
                        val query = (query() ?: "").toByteArray()
                        urlEncoder.encodeToString(md5.digest(query))
                    }
                }
            }