Package org.eclipse.microprofile.config.spi

Interface Converter<T>


  • public interface Converter<T>

    Interface for converting configured values from String to any Java type.

    Converters for the following types are provided by default:

    • boolean and Boolean, values for true: (case insensitive) "true", "yes", "Y", "on", "1"
    • int and Integer
    • long and Long
    • float and Float, a dot '.' is used to separate the fractional digits
    • double and Double, a dot '.' is used to separate the fractional digits
    • java.lang.Class based on the result of Class.forName(java.lang.String)

    Custom Converters will get picked up via the ServiceLoader mechanism and and can be registered by providing a file
    META-INF/services/org.eclipse.microprofile.config.spi.Converter
    which contains the fully qualified Converter implementation class name as content.

    A Converter can specify a javax.annotation.Priority. If no priority is explicitly assigned, the value of 100 is assumed. If multiple Converters are registered for the same type, the one with the highest priority will be used. Highest number means highest priority.

    Custom Converters can also be registered programmatically via `ConfigBuilder#withConverters(Converter... converters)` or `ConfigBuilder#withConverter(Class type, int priority, Converter converter)`. All Built In Converters have a javax.annotation.Priority of 1 A Converter should handle null values returning either null or a valid Object of the specified type.

    Array Converters

    The implementation must support the Array converter for each built-in converters and custom converters. The delimiter for the config value is ",". The escape character is "\". e.g. myPets=dog,cat,dog\,cat

    For the property injection, List and Set should be supported as well.

    Usage:

    String[] myPets = config.getValue("myPet", String[].class);

    @Inject @ConfigProperty(name="myPets") private String[] myPets;

    @Inject @ConfigProperty(name="myPets") private List<String> myPets;

    @Inject @ConfigProperty(name="myPets") private Set<String> myPets;

    myPets will be "dog", "cat", "dog,cat"

    Implicit Converters

    If no explicit Converter and no built-in Converter could be found for a certain type, the Config provides an Implicit Converter, if

    • the target type T has a public static T of(String) method, or
    • the target type T has a public static T valueOf(String) method, or
    • the target type T has a public Constructor with a String parameter, or
    • the target type T has a public static T parse(CharSequence) method

    • Method Detail

      • convert

        T convert​(java.lang.String value)
        Configure the string value to a specified type
        Parameters:
        value - the string representation of a property value.
        Returns:
        the converted value or null
        Throws:
        java.lang.IllegalArgumentException - if the value cannot be converted to the specified type.