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templatejson.go
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templatejson.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 (
"bytes"
"encoding/json"
"github.com/trivago/gollum/core"
"github.com/trivago/tgo/tcontainer"
"text/template"
)
// TemplateJSON formatter
//
// This formatter unmarshals the given data as JSON and applies the results to
// the given go template. The JSON data will be replaced with the rendered
// template result. The template language is described in the go documentation:
// https://golang.org/pkg/text/template/#hdr-Actions
//
// Parameters
//
// - Template: Defines the go template to execute with the received JSON data.
// If the template cannot be parsed or the JSON payload cannot be unmarshaled,
// the incoming JSON data is preserved.
// By default this parameter is set to "".
//
// Examples
//
// This example extracts the fields "Name" and "Surname" from a JSON encoded
// payload and writes them both back as a plain text result.
//
// exampleConsumer:
// Type: consumer.Console
// Streams: "*"
// Modulators:
// - format.TemplateJSON:
// Template: "{{.Name}} {{.Surname}}"
type TemplateJSON struct {
core.SimpleFormatter `gollumdoc:"embed_type"`
template *template.Template
}
func init() {
core.TypeRegistry.Register(TemplateJSON{})
}
// Configure initializes this formatter with values from a plugin config.
func (format *TemplateJSON) Configure(conf core.PluginConfigReader) {
var err error
tpl := conf.GetString("Template", "")
format.template, err = template.New("Template").Parse(tpl)
conf.Errors.Push(err)
}
// ApplyFormatter update message payload
func (format *TemplateJSON) ApplyFormatter(msg *core.Message) error {
values := tcontainer.NewMarshalMap()
err := json.Unmarshal(format.GetAppliedContent(msg), &values)
if err != nil {
format.Logger.Warning("TemplateJSON failed to unmarshal a message: ", err)
return err
}
var templateData bytes.Buffer
err = format.template.Execute(&templateData, values)
if err != nil {
format.Logger.Warning("TemplateJSON failed to template a message: ", err)
return err
}
format.SetAppliedContent(msg, templateData.Bytes())
return nil
}