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handler.go
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handler.go
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/*******************************************************************************
* Copyright 2019 Dell Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except
* in compliance with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software distributed under the License
* is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
* or implied. See the License for the specific language governing permissions and limitations under
* the License.
*******************************************************************************/
package errorconcept
import (
"net/http"
"github.com/edgexfoundry/go-mod-core-contracts/clients/logger"
)
type ErrorConceptType interface {
httpErrorCode() int
isA(err error) bool
message(err error) string
}
type Handler struct {
logger logger.LoggingClient
}
type ErrorHandler interface {
Handle(w http.ResponseWriter, err error, ec ErrorConceptType)
HandleManyVariants(w http.ResponseWriter, err error, allowableErrors []ErrorConceptType, defaultError ErrorConceptType)
HandleOneVariant(w http.ResponseWriter, err error, allowableError ErrorConceptType, defaultError ErrorConceptType)
}
func NewErrorHandler(l logger.LoggingClient) ErrorHandler {
h := Handler{l}
return &h
}
// Handle applies the specified error and error concept tot he HTTP response writer
func (e *Handler) Handle(w http.ResponseWriter, err error, ec ErrorConceptType) {
message := ec.message(err)
e.logger.Error(message)
http.Error(w, message, ec.httpErrorCode())
}
// HandleOneVariant applies general error-handling with a single allowable error and a default error to be used as a
// fallback when none of the allowable errors are matched
func (e *Handler) HandleOneVariant(w http.ResponseWriter, err error, allowableError ErrorConceptType, defaultError ErrorConceptType) {
if allowableError != nil && allowableError.isA(err) {
e.Handle(w, err, allowableError)
return
}
e.Handle(w, err, defaultError)
}
// HandleManyVariants applies general error-handling for the specified set of allowable errors and a default error to be used
// as a fallback when none of the allowable errors are matched
func (e *Handler) HandleManyVariants(w http.ResponseWriter, err error, allowableErrors []ErrorConceptType, defaultError ErrorConceptType) {
for key := range allowableErrors {
if allowableErrors[key].isA(err) {
e.Handle(w, err, allowableErrors[key])
return
}
}
e.Handle(w, err, defaultError)
}