Groovy String to Date

Question

I am coding this with Groovy

I am currently trying to convert a string that I have to a date without having to do anything too tedious.

String theDate = "28/09/2010 16:02:43";
def newdate = new Date().parse("d/M/yyyy H:m:s", theDate)

Output:

Tue Aug 10 16:02:43 PST 2010

The above code works just fine, however when my string changes to something like:

String testDate = "Tue Aug 10 16:02:43 PST 2010"
def newerdate = new Date().parse("d/M/yyyy H:m:s", testDate)

It tells me that "there is no such value for Tue". I tried to throw an 'E' in the parse for the date but it said the date was not able to be parsed.

Can someone explain how I should go about parsing the second example?

Answer 1

I think the best easy way in this case is to use parseToStringDate which a one of the Groovy JDK enhancements:

Parse a String matching the pattern EEE MMM dd HH:mm:ss zzz yyyy containing US-locale-constants only (e.g. Sat for Saturdays). Such a string is generated by the toString method of Date

Example:

println (Date.parseToStringDate("Tue Aug 10 16:02:43 PST 2010").format('MM-dd-yyyy'))​

Hope this helps.

Answer 2

Date#parse is deprecated . The alternative is :

java.text.DateFormat#parse 

thereFore :

 new SimpleDateFormat("E MMM dd H:m:s z yyyy", Locale.ARABIC).parse(testDate)

Note that SimpleDateFormat is an implementation of DateFormat

Answer 3

Below is the way we are going within our developing application.

import java.text.SimpleDateFormat

String newDateAdded = "2018-11-11T09:30:31"
SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss")
Date dateAdded = dateFormat.parse(newDateAdded)

println(dateAdded)

The output looks like

Sun Nov 11 09:30:31 GMT 2018

In your example, we could adjust a bit to meet your need. If I were you, I will do:

String datePattern = "d/M/yyyy H:m:s"
String theDate = "28/09/2010 16:02:43"
SimpleDateFormat df = new SimpleDateFormat(datePattern)
println df.parse(theDate)

I hope this would help you much.

Answer 4

The first argument to parse() is the expected format. You have to change that to Date.parse("E MMM dd H:m:s z yyyy", testDate) for it to work. (Note you don't need to create a new Date object, it's a static method)

If you don't know in advance what format, you'll have to find a special parsing library for that. In Ruby there's a library called Chronic, but I'm not aware of a Groovy equivalent. Edit: There is a Java port of the library called jChronic, you might want to check it out.

Answer 5

JChronic is your best choice. Here's an example that adds a .fromString() method to the Date class that parses just about anything you can throw at it:

Date.metaClass.'static'.fromString = { str ->
    com.mdimension.jchronic.Chronic.parse(str).beginCalendar.time
}

You can call it like this:

println Date.fromString("Tue Aug 10 16:02:43 PST 2010")
println Date.fromString("july 1, 2012")
println Date.fromString("next tuesday")

Answer 6

Googling around for Groovy ways to "cast" a String to a Date, I came across this article: http://www.goodercode.com/wp/intercept-method-calls-groovy-type-conversion/

The author uses Groovy metaMethods to allow dynamically extending the behavior of any class' asType method. Here is the code from the website.

class Convert {
    private from
    private to

    private Convert(clazz) { from = clazz }
    static def from(clazz) {
        new Convert(clazz)
    }

    def to(clazz) {
        to = clazz
        return this
    }

    def using(closure) {
        def originalAsType = from.metaClass.getMetaMethod('asType', [] as Class[])
        from.metaClass.asType = { Class clazz ->
            if( clazz == to ) {
                closure.setProperty('value', delegate)
                closure(delegate)
            } else {
                originalAsType.doMethodInvoke(delegate, clazz)
            }
        }
    }
}

They provide a Convert class that wraps the Groovy complexity, making it trivial to add custom as-based type conversion from any type to any other:

Convert.from( String ).to( Date ).using { new java.text.SimpleDateFormat('MM-dd-yyyy').parse(value) }

def christmas = '12-25-2010' as Date

It's a convenient and powerful solution, but I wouldn't recommend it to someone who isn't familiar with the tradeoffs and pitfalls of tinkering with metaClasses.