转换字符串到时间戳

我有一个问题，而我试图转换一个 String到一个 TimeStamp。我有一个数组，日期的格式为 yyyy-MM-dd，我想改变它的格式为 yyyy-MM-dd HH:mm:ss.SSS。所以，我用这个代码:

final String OLD_FORMAT = "yyyy-MM-dd";
final String NEW_FORMAT = "yyyy-MM-dd HH:mm:ss.SSS";
String oldDateString = createdArray[k];
String newDateString;
                

final DateFormat formatter = new SimpleDateFormat(OLD_FORMAT);
final Date d = formatter.parse(oldDateString);
((SimpleDateFormat) formatter).applyPattern(NEW_FORMAT);
newDateString = formatter.format(d);
System.out.println(newDateString);
                

final Timestamp ts = Timestamp.valueOf(newDateString);
System.out.println(ts);

我得到了下面的结果。

2009-10-2000.00.00.000

2009-10-2000.00.00.0

但是当我试图简单地做

final String text = "2011-10-02 18:48:05.123";
ts = Timestamp.valueOf(text);
System.out.println(ts);

我得到了正确的结果:

2011年10月2日18:48:05.123

你知道我做错了什么吗？

谢谢你的帮助。

585895 次浏览
小开

First, convert your date string to date, then convert it to timestamp by using the following set of line:

final Date date = new Date();
final Timestamp timestamp = new Timestamp(date.getTime()); // Instead of date, put your converted date
final Timestamp myTimeStamp = timestamp;
小开

Follow these steps for a correct result:

try {
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd hh:mm:ss.SSS");
Date parsedDate = dateFormat.parse(yourString);
Timestamp timestamp = new java.sql.Timestamp(parsedDate.getTime());
} catch(Exception e) { //this generic but you can control another types of exception
// look the origin of excption
}

Please note that .parse(String) might throw a ParseException.

小开

can you try it once...

String dob="your date String";
String dobis=null;
final DateFormat df = new SimpleDateFormat("yyyy-MMM-dd");
final Calendar c = Calendar.getInstance();
try {
if(dob!=null && !dob.isEmpty() && dob != "")
{
c.setTime(df.parse(dob));
int month=c.get(Calendar.MONTH);
month=month+1;
dobis=c.get(Calendar.YEAR)+"-"+month+"-"+c.get(Calendar.DAY_OF_MONTH);
}


}
小开

I'm sure the solution is that your oldDateString is something like "2009-10-20". Obviously this does not contain any time data lower than days. If you format this string with your new formatter where should it get the minutes, seconds and milliseconds from?

So the result is absolutely correct: 2009-10-20 00:00:00.000

What you'll need to solve this, is the original timestamp (incl. time data) before your first formatting.

小开 
import java.sql.Timestamp;
import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;


public class Util {
public static Timestamp convertStringToTimestamp(String strDate) {
try {
DateFormat formatter = new SimpleDateFormat("dd/MM/yyyy");
// you can change format of date
Date date = formatter.parse(strDate);
Timestamp timeStampDate = new Timestamp(date.getTime());


return timeStampDate;
} catch (ParseException e) {
System.out.println("Exception :" + e);
return null;
}
}
}
小开 
DateFormat formatter;
formatter = new SimpleDateFormat("dd/MM/yyyy");
Date date = (Date) formatter.parse(str_date);
java.sql.Timestamp timeStampDate = new Timestamp(date.getTime());
小开 
DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd");


Date date = formatter.parse(dateString);


Timestamp timestamp = new Timestamp(date.getTime());


System.out.println(timestamp);
小开

I should like to contribute the modern answer. When this question was asked in 2013, using the Timestamp class was right, for example for storing a date-time into your database. Today the class is long outdated. The modern Java date and time API came out with Java 8 in the spring of 2014, three and a half years ago. I recommend you use this instead.

Depending on your situation an exact requirements, there are two natural replacements for Timestamp:

  • Instant is a point on the time-line. For most purposes I would consider it safest to use this. An Instant is independent of time zone and will usually work well even in situations where your client device and your database server run different time zones.
  • LocalDateTime is a date and time of day without time zone, like 2011-10-02 18:48:05.123 (to quote the question).

A modern JDBC driver (JDBC 4.2 or higher) and other modern tools for database access will be happy to store either an Instant or a LocalDateTime into your database column of datatype timestamp. Both classes and the other date-time classes I am using in this answer belong to the modern API known as java.time or JSR-310.

It’s easiest to convert your string to LocalDateTime, so let’s take that first:

    DateTimeFormatter formatter
= DateTimeFormatter.ofPattern("uuuu-MM-dd HH:mm:ss.SSS");
String text = "2011-10-02 18:48:05.123";
LocalDateTime dateTime = LocalDateTime.parse(text, formatter);
System.out.println(dateTime);

This prints

2011-10-02T18:48:05.123

If your string was in yyyy-MM-dd format, instead do:

    String text = "2009-10-20";
LocalDateTime dateTime = LocalDate.parse(text).atStartOfDay();
System.out.println(dateTime);

This prints

2009-10-20T00:00

Or still better, take the output from LocalDate.parse() and store it into a database column of datatype date.

In both cases the procedure for converting from a LocalDateTime to an Instant is:

    Instant ts = dateTime.atZone(ZoneId.systemDefault()).toInstant();
System.out.println(ts);

I have specified a conversion using the JVM’s default time zone because this is what the outdated class would have used. This is fragile, though, since the time zone setting may be changed under our feet by other parts of your program or by other programs running in the same JVM. If you can, specify a time zone in the region/city format instead, for example:

    Instant ts = dateTime.atZone(ZoneId.of("Europe/Athens")).toInstant();
小开

The easy way to convert String to java.sql.Timestamp:

Timestamp t = new Timestamp(DateUtil.provideDateFormat().parse("2019-01-14T12:00:00.000Z").getTime());

DateUtil.java:

import java.text.SimpleDateFormat;
import java.util.TimeZone;


public interface DateUtil {


String ISO_DATE_FORMAT_ZERO_OFFSET = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";
String UTC_TIMEZONE_NAME = "UTC";


static SimpleDateFormat provideDateFormat() {
SimpleDateFormat simpleDateFormat = new SimpleDateFormat(ISO_DATE_FORMAT_ZERO_OFFSET);
simpleDateFormat.setTimeZone(TimeZone.getTimeZone(UTC_TIMEZONE_NAME));
return simpleDateFormat;
}
}
小开

Just for the sake of completeness, here is a solution with lambda and method reference:

ISO format?

Description: The following method

  • converts a String with the pattern yyyy-MM-dd into a Timestamp, if a valid input is given,
  • returns a null, if a null value is given,
  • throws a DateTimeParseException, if an invalid input is given

Code:

static Timestamp convertStringToTimestamp(String strDate) {
return Optional.ofNullable(strDate) // wrap the String into an Optional
.map(str -> LocalDate.parse(str).atStartOfDay()) // convert into a LocalDate and fix the hour:minute:sec to 00:00:00
.map(Timestamp::valueOf) // convert to Timestamp
.orElse(null); // if no value is present, return null
}


Validation: This method can be tested with those unit tests: (with Junit5 and Hamcrest)

@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenValidInput() {
// given
String strDate = "2020-01-30";


// when
final Timestamp result = convertStringToTimestamp(strDate);


// then
final LocalDateTime dateTime = LocalDateTime.ofInstant(result.toInstant(), ZoneId.systemDefault());
assertThat(dateTime.getYear(), is(2020));
assertThat(dateTime.getMonthValue(), is(1));
assertThat(dateTime.getDayOfMonth(), is(30));
}


@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenInvalidInput() {
// given
String strDate = "7770-91-30";


// when, then
assertThrows(DateTimeParseException.class, () -> convertStringToTimestamp(strDate));
}


@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenNullInput() {
// when
final Timestamp result = convertStringToTimestamp(null);


// then
assertThat(result, is(nullValue()));
}


Another format?

Usually, the string to parse comes with another format. A way to deal with it is to use a formatter to convert it to another format. Here is an example:

Input: 20200130 11:30

Pattern: yyyyMMdd HH:mm

Output: Timestamp of this input

Code:

static Timestamp convertStringToTimestamp(String strDate) {
final DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyyMMdd HH:mm");
return Optional.ofNullable(strDate) //
.map(str -> LocalDateTime.parse(str, formatter))
.map(Timestamp::valueOf) //
.orElse(null);
}

Test:

@Test
void convertStringToTimestamp_shouldReturnTimestamp_whenValidInput() {
// given
String strDate = "20200130 11:30";


// when
final Timestamp result = convertStringToTimestamp(strDate);


// then
final LocalDateTime dateTime = LocalDateTime.ofInstant(result.toInstant(), ZoneId.systemDefault());
assertThat(dateTime.getYear(), is(2020));
assertThat(dateTime.getMonthValue(), is(1));
assertThat(dateTime.getDayOfMonth(), is(30));
assertThat(dateTime.getHour(), is(11));
assertThat(dateTime.getMinute(), is(30));
}
小开

This is what I did:

Timestamp timestamp = Timestamp.valueOf(stringValue);

where stringValue can be any format of Date/Time.


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