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I'm creating a web service in Java using a Spring framework. It takes in an HTTP request with parameters 'payer', 'points', and 'timestamp'.

I need to store the data objects in a list and sort the list by timestamp, so I'm trying to convert the timestamp string to a Date object. Here's my current code:

String[] payers; // stores all payers
int totalPayers = 0; // number of payers in 'payers'

@GetMapping("/transaction")
    public void addTrans(@RequestParam(value="payer") String payer, @RequestParam(value="points") int points, @RequestParam(value="timestamp") String time) throws Exception{

        Date timestamp = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssZ").parse(time);
        
        Transaction newTrans = new Transaction(timestamp, payer, points);
        totalTrans++;

        // if the payer is new, add them to the payers list
        boolean newPayer = true;
        for(int i = 0; i < totalPayers; i++){
            if (payer == payers[i]){
                newPayer = false;
                break;
            }
        }
        if(newPayer){
            payers[totalPayers++] = payer;
        }

        transactions.add(newTrans); // add the new transaction to the list
        totalPoints += newTrans.getPoints();

        Collections.sort(transactions); // sort the list by timestamp

        return;
    }

When I run it, I'm getting the error:

java.text.ParseException: Unparseable date: "2020-11-02T14:00:00Z"

Does anyone know of something I may be missing? Is there an easier way to convert the string?

Alex Green
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3 Answers3

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You nee single quotes around the Z too.

Date timestamp = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss'Z'").parse(time);

The Z is not part of the pattern the function is supposed to recognize.

SamuelMR
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  • This is so very wrong. ***Never* put quote marks around the Z.** The Z provides vital crucial information: the offset from UTC. By quoting, you are telling the formatter to ignore the Z altogether, thereby discarding the vital info. Please delete this Answer before this disinformation spreads. – Basil Bourque Jul 02 '22 at 00:01
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Avoid legacy date-time classes

You are using terrible date-time classes that were years ago supplanted by the modern java.time classes defined in JSR 310. Never use Date, SimpleDateFormat, etc.

java.time

Your input format complies with the ISO 8601 standard used by default in the java.time classes. So no need to specify a formatting pattern.

The T separates the date portion from the time-of-day portion. The Z on the end tells you the date and time is a moment as seen with an offset from UTC of zero hours-minutes-seconds. The Z is pronounced “Zulu” per aviation and military conventions.

Parsing text in standard ISO 8601 format:

String input = "2022-01-23T12:34:56Z" ;
Instant instant = Instant.now( input ) ;

Generating text in standard ISO 8601 format:

String output = instant.toString() ;
Basil Bourque
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If you are using java 8 or above, it is recommended to use java.time (https://docs.oracle.com/javase/8/docs/api/java/time/package-summary.html) instead of java.util.Date.

But if you really want to use Date, the below snippet should help you resolve the error and parse the string. Be wary of the zone calculation.

Date timestamp = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ssX").parse(time);

If you decide to switch to java.time, the below snippet would help

Instant instant = Instant.parse(time) ;
Date date = java.util.Date.from(instant);
Zsolo
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