Module io.helidon.config

Package io.helidon.config

Interface ConfigValue<T>

Type Parameters:

T - type of the value

public interface ConfigValue<T>

A typed value of a Config node.

You can use accessor methods on Config to obtain this value, such as Config.as(Class). A typed value that has all the methods of Optional - including the ones added in JDK9 and newer. In addition it has methods to access config values as supplier().

See Also:

• Config.as(Class)
• Config.as(Function)
• Config.as(io.helidon.common.GenericType)

Method Summary

Modifier and Type	Method	Description
<N> ConfigValue<N>	as(Function<T,N> mapper)	Convert this ConfigValue to a different type using a mapper function.
Optional<T>	asOptional()	Returns a typed value as Optional.
default Optional<T>	filter(Predicate<? super T> predicate)	If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.
default <U> Optional<U>	flatMap(Function<? super T,Optional<U>> mapper)	If a value is present, apply the provided Optional-bearing mapping function to it, return that result, otherwise return an empty Optional.
default T	get()	Typed value of the represented Config node.
default void	ifPresent(Consumer<? super T> consumer)	If a value is present, invoke the specified consumer with the value, otherwise do nothing.
default void	ifPresentOrElse(Consumer<T> action, Runnable emptyAction)	If a value is present, performs the given action with the value, otherwise performs the given empty-based action.
default boolean	isPresent()	Return true if there is a value present, otherwise false.
Config.Key	key()	Returns the fully-qualified key of the originating Config node.
default <U> Optional<U>	map(Function<? super T,? extends U> mapper)	If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result.
default String	name()	Returns the last token of the fully-qualified key for the originating Config node.
Supplier<Optional<T>>	optionalSupplier()	Returns a Supplier of an Optional<T> of the configuration node.
default Optional<T>	or(Supplier<? extends Optional<T>> supplier)	If the underlying Optional does not have a value, set it to the Optional produced by the supplying function.
default T	orElse(T other)	Return the value if present, otherwise return other.
default T	orElseGet(Supplier<? extends T> other)	Return the value if present, otherwise invoke other and return the result of that invocation.
default <X extends Throwable> T	orElseThrow(Supplier<? extends X> exceptionSupplier)	Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.
default Stream<T>	stream()	If a value is present, returns a sequential Stream containing only that value, otherwise returns an empty Stream.
Supplier<T>	supplier()	Returns a supplier of a typed value.
Supplier<T>	supplier(T defaultValue)	Returns a supplier of a typed value with a default.

Method Details

key

Config.Key key()

Returns the fully-qualified key of the originating Config node.

The fully-qualified key is a sequence of tokens derived from the name of each node along the path from the config root to the current node. Tokens are separated by . (the dot character). See name() for more information on the format of each token.

Returns:

current config node key

See Also:

• name()

name

default String name()

Returns the last token of the fully-qualified key for the originating Config node.

The name of a node is the last token in its fully-qualified key.

The exact format of the name depends on the Type of the containing node:

• from a Config.Type.OBJECT node the token for a child is the name of the object member;
• from a Config.Type.LIST node the token for a child is a zero-based index of the element, an unsigned base-10 integer value with no leading zeros.

The ABNF syntax of config key is:

 config-key = *1( key-token *( "." key-token ) )
  key-token = *( unescaped / escaped )
  unescaped = %x00-2D / %x2F-7D / %x7F-10FFFF
            ; %x2E ('.') and %x7E ('~') are excluded from 'unescaped'
    escaped = "~" ( "0" / "1" )
            ; representing '~' and '.', respectively
 

Returns:

current config node key

See Also:

• key()
• Config.Key.name()

asOptional

Optional<T> asOptional()
                throws ConfigMappingException

Returns a typed value as Optional. Returns a empty for nodes without a value. As this class implements all methods of Optional, this is only a utility method if an actual Optional instance is needed.

Returns:

value as type instance as Optional, empty in case the node does not have a direct value

Throws:

ConfigMappingException - in case the value cannot be converted to the expected type

See Also:

• get()

get

default T get()
       throws MissingValueException,
ConfigMappingException

Typed value of the represented Config node. Throws MissingValueException if the node is Config.Type.MISSING type.

Returns:

direct value of this node converted to the expected type

Throws:

MissingValueException - in case the node is Config.Type.MISSING.

ConfigMappingException - in case the value cannot be converted to the expected type

as

<N> ConfigValue<N> as(Function<T,N> mapper)

Convert this ConfigValue to a different type using a mapper function.

Type Parameters:

N - type of the returned ConfigValue

Parameters:

mapper - mapper to map the type of this ConfigValue to a type of the returned ConfigValue

Returns:

a new value with the new type

supplier

Supplier<T> supplier()

Returns a supplier of a typed value. The value provided from the supplier is the latest value available. E.g. in case there is a file config source that is being watched and a value is changed, this supplier would return the latest value, whereas get() would return the original value.

Note that Supplier.get() can throw a ConfigMappingException or MissingValueException as the get() method.

Returns:

a supplier of a typed value

supplier

Supplier<T> supplier(T defaultValue)

Returns a supplier of a typed value with a default. The value provided from the supplier is the latest value available. E.g. in case there is a file config source that is being watched and a value is changed, this supplier would return the latest value, whereas orElse(Object) would return the original value.

Note that Supplier.get() can throw a ConfigMappingException as the orElse(Object) method.

Parameters:

defaultValue - a value to be returned if the supplied value represents a Config node that has no direct value

Returns:

a supplier of a typed value

optionalSupplier

Supplier<Optional<T>> optionalSupplier()

Returns a Supplier of an Optional<T> of the configuration node. Supplier returns a empty if the node does not have a direct value.

Returns:

a supplier of the value as an Optional typed instance, empty in case the node does not have a direct value

See Also:

• asOptional()
• supplier()

or

default Optional<T> or(Supplier<? extends Optional<T>> supplier)

If the underlying Optional does not have a value, set it to the Optional produced by the supplying function.

Parameters:

supplier - the supplying function that produces an Optional

Returns:

returns current value using asOptional() if present, otherwise value produced by the supplying function.

Throws:

NullPointerException - if the supplying function is null or produces a null result

isPresent

default boolean isPresent()

Return true if there is a value present, otherwise false.

Copied from Optional. You can get real optional from asOptional().

Returns:

true if there is a value present, otherwise false

See Also:

• Optional.isPresent()

ifPresentOrElse

default void ifPresentOrElse(Consumer<T> action,
 Runnable emptyAction)

If a value is present, performs the given action with the value, otherwise performs the given empty-based action.

Parameters:

action - the action to be performed, if a value is present

emptyAction - the empty-based action to be performed, if no value is present

Throws:

NullPointerException - if a value is present and the given action is null, or no value is present and the given empty-based action is null.

ifPresent

default void ifPresent(Consumer<? super T> consumer)

If a value is present, invoke the specified consumer with the value, otherwise do nothing.

Copied from Optional. You can get real optional from asOptional().

Parameters:

consumer - block to be executed if a value is present

Throws:

NullPointerException - if value is present and consumer is null

See Also:

• Optional.ifPresent(Consumer)

filter

default Optional<T> filter(Predicate<? super T> predicate)

If a value is present, and the value matches the given predicate, return an Optional describing the value, otherwise return an empty Optional.

Copied from Optional. You can get real optional from asOptional().

Parameters:

predicate - a predicate to apply to the value, if present

Returns:

an Optional describing the value of this Optional if a value is present and the value matches the given predicate, otherwise an empty Optional

Throws:

NullPointerException - if the predicate is null

See Also:

• Optional.filter(Predicate)

map

default <U> Optional<U> map(Function<? super T,? extends U> mapper)

If a value is present, apply the provided mapping function to it, and if the result is non-null, return an Optional describing the result. Otherwise return an empty Optional.

Type Parameters:

U - The type of the result of the mapping function

Parameters:

mapper - a mapping function to apply to the value, if present

Returns:

an Optional describing the result of applying a mapping function to the value of this Optional, if a value is present, otherwise an empty Optional

Throws:

NullPointerException - if the mapping function is null

Copied from Optional. You can get real optional from asOptional().

See Also:

• Optional.map(Function)

flatMap

default <U> Optional<U> flatMap(Function<? super T,Optional<U>> mapper)

If a value is present, apply the provided Optional-bearing mapping function to it, return that result, otherwise return an empty Optional. This method is similar to map(Function), but the provided mapper is one whose result is already an Optional, and if invoked, flatMap does not wrap it with an additional Optional.

Copied from Optional. You can get real optional from asOptional().

Type Parameters:

U - The type parameter to the Optional returned by

Parameters:

mapper - a mapping function to apply to the value, if present the mapping function

Returns:

the result of applying an Optional-bearing mapping function to the value of this Optional, if a value is present, otherwise an empty Optional

Throws:

NullPointerException - if the mapping function is null or returns a null result

See Also:

• Optional.flatMap(Function)

orElse

default T orElse(T other)

Return the value if present, otherwise return other.

Copied from Optional. You can get real optional from asOptional().

Parameters:

other - the value to be returned if there is no value present, may be null

Returns:

the value, if present, otherwise other

See Also:

• Optional.orElse(Object)

orElseGet

default T orElseGet(Supplier<? extends T> other)

Return the value if present, otherwise invoke other and return the result of that invocation.

Copied from Optional. You can get real optional from asOptional().

Parameters:

other - a Supplier whose result is returned if no value is present

Returns:

the value if present otherwise the result of other.get()

Throws:

NullPointerException - if value is not present and other is null

See Also:

• Optional.orElseGet(Supplier)

orElseThrow

default <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier)
                                     throws X

Return the contained value, if present, otherwise throw an exception to be created by the provided supplier.

Copied from Optional. You can get real optional from asOptional().

Type Parameters:

X - Type of the exception to be thrown

Parameters:

exceptionSupplier - The supplier which will return the exception to be thrown

Returns:

the present value

Throws:

X - if there is no value present

NullPointerException - if no value is present and exceptionSupplier is null

See Also:

• Optional.orElseThrow(Supplier)

stream

default Stream<T> stream()

If a value is present, returns a sequential Stream containing only that value, otherwise returns an empty Stream.

Returns:

the optional value as a Stream