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extractjson.go
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extractjson.go
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// Copyright 2015-2017 trivago GmbH
//
// 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 format
import (
"encoding/json"
"fmt"
"github.com/trivago/gollum/core"
"github.com/trivago/tgo/tcontainer"
)
// ExtractJSON formatter
//
// This formatter extracts a specific value from a JSON payload and writes it
// back as a new payload or as a metadata field.
//
// Parameters
//
// - Field: Defines the JSON key to extract. If the field does not exist an
// empty string is returned. Field paths can be defined in a format accepted by
// tgo.MarshalMap.Path.
// By default this parameter is set to "".
//
// - TrimValues: Enables trimming of whitespaces at the beginning and end of the
// extracted value.
// By default this parameter is set to true.
//
// - Precision: Defines the number of decimal places to use when converting
// Numbers into strings. If this parameter is set to 0 no restrictions will
// apply.
// By default this parameter is set to 0.
//
// Examples
//
// ExampleConsumer:
// Type: consumer.Console
// Streams: console
// Modulators:
// - formatter.ExtractJSON
// Field: host
// ApplyTo: host
type ExtractJSON struct {
core.SimpleFormatter `gollumdoc:"embed_type"`
field string `config:"Field"`
trimValues bool `config:"TrimValues" default:"true"`
numberFormat string
}
func init() {
core.TypeRegistry.Register(ExtractJSON{})
}
// Configure initializes this formatter with values from a plugin config.
func (format *ExtractJSON) Configure(conf core.PluginConfigReader) {
precision := conf.GetInt("Precision", 0)
format.numberFormat = fmt.Sprintf("%%.%df", precision)
}
// ApplyFormatter update message payload
func (format *ExtractJSON) ApplyFormatter(msg *core.Message) error {
content := format.GetAppliedContent(msg)
value, err := format.extractJSON(content)
if err != nil {
return err
}
format.SetAppliedContent(msg, value)
return nil
}
func (format *ExtractJSON) extractJSON(content []byte) ([]byte, error) {
values := tcontainer.NewMarshalMap()
err := json.Unmarshal(content, &values)
if err != nil {
format.Logger.Warning("ExtractJSON failed to unmarshal a message: ", err)
return nil, err
}
if value, exists := values[format.field]; exists {
switch value.(type) {
case int64:
val, _ := value.(int64)
return []byte(fmt.Sprintf("%d", val)), nil
case string:
val, _ := value.(string)
return []byte(val), nil
case float64:
val, _ := value.(float64)
return []byte(fmt.Sprintf(format.numberFormat, val)), nil
default:
return []byte(fmt.Sprintf("%v", value)), nil
}
}
format.Logger.Warning("ExtractJSON field not exists: ", format.field)
return nil, nil
}