How to replace offset and max with page number in grails paginate tag?

Question

Grails Paginate tag generates links with max and offset params. Example

/?max=30&offset=0
/?max=30&offset=30

Say we have constant max equals 30.

Is there any possibility to make it generate page numbers instead?

/?page=1
/?page=2

Answer 1

This is my solution

In controller:

params.max = 30
if(params.long('page')) {
    params.offset = (params.long('page') - 1) * params.max
}

In tag lib:

static namespace = "my"

private final static Pattern OFFSET_PATTERN = Pattern.compile("offset=(\\d+)");

def paginate = { attrs, body ->
    String str = g.paginate(attrs) // using grails gsp paginate tag
    // make sure we delete max param with & (before or after)
    str = str.replaceAll(/&max=\d+/, '').replaceAll(/max=\d+&/, '')
    while (true) {
        Matcher matcher = OFFSET_PATTERN.matcher(str)
        if (matcher.find()) {
            long pageNum = (matcher.group(1) as long)/params.long('max') + 1
            // replace offset=0 with page=1, offset=30 with page=2, etc
            str = matcher.replaceFirst('page=' + pageNum)
        } else {
            break;
        }
    }
    out << str
}

So we can use my.paginate in our gsp views the same way we use standard grails gsp paginate tag. Looking forward your feedbacks and improvements

Answer 2

You could change the controller itself. Something along the line of:

def myMethod() {
    params.max = 30
    params.offset = (params.max * params.page) - params.max //todo - make sure page is bigger than one :-)
    def listOfItemsYouWantToShow = MyPerfectDomainClass.list(params)
    ....
}

not tested, but should work.

The view tag should be also changed, just like the first comment.