Bindable Types

Generally any type that can be converted from a String representation to a Java type via the ConversionService API can be bound to.

This includes most common Java types, however additional TypeConverter instances can be registered by creating @Singleton beans of type TypeConverter.

The handling of nullability deserves special mention. Consider for example the following example:

    @Get("/headerInferred")
    public String headerInferred(@Header String contentType) {
        // ...
    }

    @Get("/headerInferred")
    String headerInferred(@Header String contentType) {
        // ...
    }

    @Get("/headerInferred")
    fun headerInferred(@Header contentType: String): String {
        // ...
    }

In this case, if the HTTP header Content-Type is not present in the request, the route is considered invalid, since it cannot be satisfied, and a HTTP 400 BAD REQUEST is returned.

To make the Content-Type header optional, you can instead write:

    @Get("/headerNullable")
    public String headerNullable(@Nullable @Header String contentType) {
        // ...
    }

    @Get("/headerNullable")
    String headerNullable(@Nullable @Header String contentType) {
        // ...
    }

    @Get("/headerNullable")
    fun headerNullable(@Header contentType: String?): String? {
        // ...
    }

A null string is passed if the header is absent from the request.

Additionally, any DateTime that conforms to RFC-1123 can be bound to a parameter. Alternatively the format can be customized with the Format annotation:

    @Get("/date")
    public String date(@Header ZonedDateTime date) {
        // ...
    }
    @Get("/dateFormat")
    public String dateFormat(@Format("dd/MM/yyyy hh:mm:ss a z") @Header ZonedDateTime date) {
        // ...
    }

    @Get("/date")
    String date(@Header ZonedDateTime date) {
        // ...
    }
    @Get("/dateFormat")
    String dateFormat(@Format("dd/MM/yyyy hh:mm:ss a z") @Header ZonedDateTime date) {
        // ...
    }

    @Get("/date")
    fun date(@Header date: ZonedDateTime): String {
        // ...
    }
    @Get("/dateFormat")
    fun dateFormat(@Format("dd/MM/yyyy hh:mm:ss a z") @Header date: ZonedDateTime): String {
        // ...
    }