Documentation

Application Framework

Linkki Converter Registry

Typically, each UI component is designed to handle a specific data type. However, with the LinkkiConverterRegistry in linkki, developers can customize conversions between model data types and presentation types. This feature expands the capabilities of UI components to support a broader range of value types beyond their defaults.

Default Converters in LinkkiConverterRegistry

Following converters are registered by default in the LinkkiConverterRegistry:

Table 1. Default Converters
Converter	Description
`DateToLongConverter`	Calculates the number of milliseconds since `January 1, 1970, 00:00:00 GMT`. `1000L` would be `Thu Jan 01 01:00:01 CET 1970` and vice versa.
`DateToSqlDateConverter`	Calculates the number on milliseconds since `January 1, 1970, 00:00:00 GMT` but in sql form. `1000L` would be `1970-01-01` and vice versa.
`LocalDateTimeToDateConverter`	Converts `LocalDateTime` to `Date`. Makes it possible to use `Date` for UI components that uses `LocalDateTime`, such as `@UIDateTimeField`.
`LocalDateToDateConverter`	Converts `LocalDate` to `Date`. Makes it possible to use `Date` for UI components that uses `LocalDate`, such as `@UIDateField`.
`LocalDateToStringConverter`	Converts `LocalDate` to `String` using the locale specific format. Makes ot possible to use `LocalDate` in `String`-valued components such as `@UILabel`.
`LocalDateTimeToStringConverter`	Converts `LocalDateTime` to `String` using the locale specific format. Makes it possible to use `LocalDateTime` in `String`-valued components such as `@UILabel`.
`StringToBigDecimalConverter`	Converts a `String` to a number of type `BigDecimal`. Makes it possible to use `BigDecimal` in `String`-valued components such as `@UILabel`.
`StringToBigIntegerConverter`	Converts a `String` to a number of type `BigInteger`. Makes it possible to use `BigInteger` in `String`-valued components such as `@UILabel`.
`StringToBooleanConverter`	Convert a `String` ("true" or "false") to `Boolean`. Makes it possible to use `Boolean` in `String`-valued components such as `@UILabel`.
`StringToDateConverter`	Converts a `Date` to a `String` using the locale specific format similar to the one used by a Vaadin DatePicker. Makes it possible to use `Date` in `String`-valued components such as `@UILabel`.
`StringToDoubleConverter`	Converts a `String` to a number of type `Double`. Makes it possible to use `Double` in `String`-valued components such as `@UILabel`.
`StringToFloatConverter`	Converts a `String` to a number of type `Float`. Makes it possible to use `Float` in `String`-valued components such as `@UILabel`.
`StringToIntegerConverter`	Converts a `String` to a number of type `Integer`. Makes it possible to use `Integer` in `String`-valued components such as `@UILabel`.
`StringToLongConverter`	Converts a `String` to a number of type `Long`. Makes it possible to use `Long` in `String`-valued components such as `@UILabel`.
`StringToGregorianCalendarConverter`	Converts `GregorianCalendar` to `String` and vice versa, taking locale-specific date formats into account. Makes it possible to use `GregorianCalendar` in `String`-valued components such as `@UILabel`.

Custom date formats

Custom date formats for a specific Locale or language code can be registered with DateFormats#register(…). All converters that come with linkki respect these formats. It is recommended to also respect these date formats in custom converters.

Custom converters

It possible to use custom converters in linkki, e.g. for data types that are not handled by default, or to change the conversion of a certain data type.

Implementing custom converters

All converters must implement the interface Converter<Presentation, Model>. PRESENTATION is the type needed by the UI component and MODEL is the type in the PMO. This interface defines two methods to converter between the two types.

When converting to model, it is possible to check the validity of the input before the value is pushed to the PMO. This can be achieved by returning an error in the result of convertToModel. In this case, an error message is shown in the UI indicating that the input is not valid. The value of the UI component is restored to its previous value.

Registering custom converters

The converter registry is defined in the Application Configuration.

By implementing ApplicationConfig#getConverterRegistry() additional custom converters can be registered. If the registry is initiated with a custom converter which has the same types as an existing one, the custom converter is used with higher priority.