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json.go
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json.go
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package reader
import (
"bytes"
"encoding/json"
"fmt"
"github.com/elastic/beats/libbeat/common"
"github.com/elastic/beats/libbeat/logp"
)
const (
JsonErrorKey = "json_error"
)
type JSON struct {
reader Reader
cfg *JSONConfig
}
// NewJSONReader creates a new reader that can decode JSON.
func NewJSON(r Reader, cfg *JSONConfig) *JSON {
return &JSON{reader: r, cfg: cfg}
}
// decodeJSON unmarshals the text parameter into a MapStr and
// returns the new text column if one was requested.
func (r *JSON) decodeJSON(text []byte) ([]byte, common.MapStr) {
var jsonFields map[string]interface{}
err := unmarshal(text, &jsonFields)
if err != nil {
logp.Err("Error decoding JSON: %v", err)
if r.cfg.AddErrorKey {
jsonFields = common.MapStr{JsonErrorKey: fmt.Sprintf("Error decoding JSON: %v", err)}
}
return text, jsonFields
}
if len(r.cfg.MessageKey) == 0 {
return []byte(""), jsonFields
}
textValue, ok := jsonFields[r.cfg.MessageKey]
if !ok {
if r.cfg.AddErrorKey {
jsonFields[JsonErrorKey] = fmt.Sprintf("Key '%s' not found", r.cfg.MessageKey)
}
return []byte(""), jsonFields
}
textString, ok := textValue.(string)
if !ok {
if r.cfg.AddErrorKey {
jsonFields[JsonErrorKey] = fmt.Sprintf("Value of key '%s' is not a string", r.cfg.MessageKey)
}
return []byte(""), jsonFields
}
return []byte(textString), jsonFields
}
// unmarshal is equivalent with json.Unmarshal but it converts numbers
// to int64 where possible, instead of using always float64.
func unmarshal(text []byte, fields *map[string]interface{}) error {
dec := json.NewDecoder(bytes.NewReader(text))
dec.UseNumber()
err := dec.Decode(fields)
if err != nil {
return err
}
transformNumbersDict(*fields)
return nil
}
// transformNumbersDict walks a json decoded tree an replaces json.Number
// with int64, float64, or string, in this order of preference (i.e. if it
// parses as an int, use int. if it parses as a float, use float. etc).
func transformNumbersDict(dict common.MapStr) {
for k, v := range dict {
switch vv := v.(type) {
case json.Number:
dict[k] = transformNumber(vv)
case map[string]interface{}:
transformNumbersDict(vv)
case []interface{}:
transformNumbersArray(vv)
}
}
}
func transformNumber(value json.Number) interface{} {
i64, err := value.Int64()
if err == nil {
return i64
}
f64, err := value.Float64()
if err == nil {
return f64
}
return value.String()
}
func transformNumbersArray(arr []interface{}) {
for i, v := range arr {
switch vv := v.(type) {
case json.Number:
arr[i] = transformNumber(vv)
case map[string]interface{}:
transformNumbersDict(vv)
case []interface{}:
transformNumbersArray(vv)
}
}
}
// Next decodes JSON and returns the filled Line object.
func (r *JSON) Next() (Message, error) {
reader, err := r.reader.Next()
if err != nil {
return reader, err
}
reader.Content, reader.Fields = r.decodeJSON(reader.Content)
return reader, nil
}