Parsing a json datetime in revel

Question

I'm attempting to parse a Datetime in revel from a json request. The request looks something like this:

{
  "startedAt": "2017-06-01 10:39",
  ...
}

The struct it's being decoded into looks like this:

type MyStruct struct {
  StartedAt time.Time `json:"startedAt" bson:"startedAt"`
  ...
}

The decode line looks like this:

json.NewDecoder(c.Request.Body).Decode(&MyStruct)

Revel returns this error:

interface conversion: error is *time.ParseError, not *errors.Error

According to revel's documentation here, https://revel.github.io/manual/parameters.html

The SQL standard date time formats of 2006-01-02, 2006-01-02 15:04 are built in.

In the same document, they also say you can append formats like this:

func init() {
    revel.TimeFormats = append(revel.TimeFormats, "01/02/2006")
}

To verify the format was in the array, I tried this:

func init() {
    revel.TimeFormats = append(revel.TimeFormats, "2016-06-01 12:12")
}

In a final act of desperation I tried submitting it in the same format that revel will return json times in:

{
  "startedAt": "2017-06-22T12:22:16.265618819-05:00",
  ...
}

At this point I'm not sure where to go with this. Has anyone been able to get revel to parse a Datetime?

Update: I tried RickyA's solution below, but now there is a parsing error.

parsing time ""Mon, 02 Jan 2006 15:04:05 -0700"" as "Mon, 02 Jan 2006 15:04:05 -0700": cannot parse ""Mon, 02 Jan 2006 15:04:05 -0700"" as "Mon"

What's even stranger is that I implemented a bit of a hack to get this working in the interrum. I changed the request time field to a string, and gave it a ToX function which converted it. That function works, but when it's moved into the UnmarshalJSON function it fails.

Also, I can't tell if this is a bug or not:

func (t *AnyTime) UnmarshalJSON(b []byte) error {
  fmt.Println(time.RFC1123Z)
  fmt.Println(string(b))
  fmt.Println(reflect.TypeOf(time.RFC1123Z))
  fmt.Println(reflect.TypeOf(string(b)))
  ...

This outputs this:

Mon, 02 Jan 2006 15:04:05 -0700
"Mon, 02 Jan 2006 15:04:05 -0700"
string
string

Notice that only 1 of the string has double quotes. This is leading me to believe that some how the byte array passed to UnmarshalJSON has double quotes within its string.

Final Update: So I'm pretty sure the double quotes are intentional, and in a way it makes sense. The UnmarshalJSON is passing everything from the ':' through the ',' which includes the double quotes. I'm guessing this is done so that it can also support integers and booleans. I don't like the solution, but this is how I fixed it:

func (t *AnyTime) UnmarshalJSON(b []byte) error {
  var err error
  sTime := string(b)
  sTime = strings.TrimSuffix(sTime, "\"")
  sTime = strings.TrimPrefix(sTime, "\"")
  t.Time, err = time.Parse(time.RFC1123Z, sTime)
  ...

try revel.TimeFormats = append(revel.TimeFormats, "2006-02-01 15:04") instead: stackoverflow.com/questions/25845172/… — RickyA
– RickyA, Commented Jun 22, 2017 at 17:38
I realized after the fact, that I'm not using revel to parse the json. This is probably why adding the time format doesn't work. I've updated the post accordingly. — Camway
– Camway, Commented Jun 22, 2017 at 17:55

RickyA · Accepted Answer · 2017-06-22 19:35:24Z

3

I had the same problem and ended up creating a custom type for time.Time

package genericfields

import (
    "encoding/json"
    "time"
    "strings"

    "gopkg.in/mgo.v2/bson"
)

// ANYTIME //

// AnyTime accepts any time format for its unmarshaling //
type AnyTime struct{ time.Time }

func (t AnyTime) MarshalJSON() ([]byte, error) {
    return json.Marshal(t.Time)
}

func (t *AnyTime) UnmarshalJSON(b []byte) error {
    err := json.Unmarshal(b, &t.Time)
    if err != nil { //assume non tz time input
        bstr := strings.Trim(string(b), `"`)
        t.Time, err = time.Parse("2006-01-02T15:04:05", bstr)
        if err != nil {
            return err //TODO add more formats to try
        }
    }
    return nil
}

func (t AnyTime) GetBSON() (interface{}, error) {
    return t.Time, nil
}

func (t *AnyTime) SetBSON(raw bson.Raw) error {
    var tm time.Time
    err := raw.Unmarshal(&tm)
    if err != nil {
        return err
    }
    t.Time = tm.UTC()
    return nil
}

func (t AnyTime) ToTime() time.Time {
    return t.Time
}

Usage:

type MyStruct struct {
  StartedAt genericfields.AnyTime `json:"startedAt" bson:"startedAt"`
  ...
}

You might need to tweak the input for time.Parse somewhat.

edited Jun 22, 2017 at 19:35

answered Jun 22, 2017 at 18:33

RickyA

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3 Comments

Camway Over a year ago

I tried implementing your fix, but I'm still getting an error. I've edited the post with the new information.

RickyA Over a year ago

Ah, I was wondering why quote trimming line was in my code so I deleted it when posting. Now we know why :( Updated the answer.

Camway Over a year ago

I'm still marking you answer as correct, because it lead me to the solution. I updated my post 1 more time to include the final fix. Thanks again for the response.

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