Use filtered dataProvider contents when FileDownloader is called in Vaadin

Question

I'm trying to download a csv file after applying filters to the DataProvider.

For some reason the filtered results are shown in the Grid, but the downloaded csv file still contains all data.

@AutoView
class FinancialTransactionsView : VerticalLayout(), View {    
    private val grid: Grid<FinancialTransaction>
    private val yearField: ComboBox<Int>

    private val dataProvider = DataProvider.ofCollection(FinancialTransaction.findAll())
    private val fileDownloader: FileDownloader

    init {
        label("Financial Transactions") {
            styleName = ValoTheme.LABEL_H1
        }

        yearField = comboBox("Select Year") {
            setItems(listOf(2016, 2017, 2018))

            addSelectionListener {
                // Filter the data based on the selected year
                if (it.value != it.oldValue) setDataProvider()
            }
        }

        // Create FileDownloader and initialize with all contents in the DataProvider
        fileDownloader = FileDownloader(createCsvResource())

        val downloadButton = button("Download csv") {
            styleName = ValoTheme.BUTTON_PRIMARY

            onLeftClick {
                // The idea here is to assign values from the filtered DataProvider to the FileDownloader
                fileDownloader.fileDownloadResource = createCsvResource()
            }
        }

        fileDownloader.extend(downloadButton)
        fileDownloader.fileDownloadResource = createCsvResource()

        grid = grid(dataProvider = dataProvider) {

            expandRatio = 1f
            setSizeFull()
            addColumnFor(FinancialTransaction::companyId)
            addColumnFor(FinancialTransaction::fiscalYear)
            addColumnFor(FinancialTransaction::fiscalPeriod)
            addColumnFor(FinancialTransaction::currency)
            addColumnFor(FinancialTransaction::finalizedDebitAmountInCurrency)
            addColumnFor(FinancialTransaction::finalizedCreditAmountInCurrency)

            appendHeaderRow().generateFilterComponents(this, FinancialTransaction::class)
        }
    }

    private fun createCsvResource(): StreamResource {
        return StreamResource(StreamResource.StreamSource {

            val csv = dataProvider.items.toList().toCsv()

            try {
                return@StreamSource csv.byteInputStream()
            } catch (e: IOException) {
                e.printStackTrace()
                return@StreamSource null
            }
        }, "financial_transactions.csv")
    }

    private fun setDataProvider() {
        dataProvider.clearFilters()

        if (!yearField.isEmpty)
            dataProvider.setFilterByValue(FinancialTransaction::fiscalYear, yearField.value)
    }
}

toCsv() is an extension function List<FinancialTransaction> which returns a string containing csv data.

What can I do to get the filtered results in my csv file?

Answer 1

val csv = dataProvider.items.toList().toCsv()

I am not Kotlin guy, but I assume dataProvider.items is a shorthand to dataProvider.getItems() in Java, i.e. this method (and you use ListDataProvider)

https://vaadin.com/download/release/8.4/8.4.1/docs/api/com/vaadin/data/provider/ListDataProvider.html#getItems--

In Vaadin getItems() returns all items by passing all filters.

So instead you should do either of the following

dataProvider.fetch(..)

https://vaadin.com/download/release/8.4/8.4.1/docs/api/com/vaadin/data/provider/DataProvider.html#fetch-com.vaadin.data.provider.Query-

Where you give the filters you want to apply in the query, or

grid.getDataCommunicator.fetchItemsWithRange(..)

https://vaadin.com/download/release/8.4/8.4.1/docs/api/com/vaadin/data/provider/DataCommunicator.html#fetchItemsWithRange-int-int-

Which returns list of items with filters you have set applied, which I think is ideal for you