Module io.helidon.config

Package io.helidon.config

Class MergedConfig

java.lang.Object

io.helidon.config.MergedConfig

All Implemented Interfaces:

Config, Config

public class MergedConfig
extends Object
implements Config

Configuration that merges two Config instances, primary and fallback. When a property is not present in the primary configuration, fallback is used.

When a key is present in both the primary and fallback configurations, the value from the primary configuration takes precedence.

Nested Class Summary

Nested classes/interfaces inherited from interface io.helidon.config.Config

Config.Builder, Config.Context, Config.Key, Config.Type

Field Summary

Fields inherited from interface io.helidon.config.Config

GENERIC_TYPE

Method Summary

Modifier and Type	Method	Description
<T> ConfigValue<T>	as(GenericType<T> genericType)	Typed value as a ConfigValue for a generic type.
<T> ConfigValue<T>	as(Class<T> type)	Typed value as a ConfigValue.
<T> ConfigValue<T>	as(Function<Config,T> mapper)	Typed value as a ConfigValue created from factory method.
<T> ConfigValue<List<T>>	asList(Class<T> type)	Returns list of specified type.
<T> ConfigValue<List<T>>	asList(Function<Config,T> mapper)	Returns this node as a list converting each list value using the provided mapper.
ConfigValue<Map<String,String>>	asMap()	Transform all leaf nodes (values) into Map instance.
ConfigValue<List<Config>>	asNodeList()	Returns a list of child Config nodes if the node is Type#OBJECT.
<T> T	convert(Class<T> type, String value)	Convert a String to a specific type.
static Config	create(Config primary, Config fallback)	Creates a new MergedConfig that merges the specified configurations.
Config	detach()	Returns a copy of the Config node with no parent.
Config	get(Config.Key key)	Returns the single sub-node for the specified sub-key.
boolean	hasValue()	Returns true if this configuration node has a direct value.
Config.Key	key()	Returns the fully-qualified key of the Config node.
ConfigMapper	mapper()	Only mappers from the primary config are considered.
Config	root()	Get the root of the configuration tree.
Instant	timestamp()	Returns when the configuration tree was created.
Stream<Config>	traverse(Predicate<Config> predicate)	Traverses over merged configs like Config.traverse().
Config.Type	type()	Provides the Config.Type of the Config node.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface io.helidon.common.config.Config

get

Methods inherited from interface io.helidon.config.Config

asBoolean, asDouble, asInt, asLong, asNode, asString, context, exists, get, ifExists, isLeaf, isList, isObject, map, mapList, name, onChange, traverse

Method Details

create

public static Config create(Config primary,
 Config fallback)

Creates a new MergedConfig that merges the specified configurations.

Parameters:

primary - the primary configuration, which has precedence in the case of duplicate keys

fallback - the fallback configuration, queried for keys not found in the primary one

Returns:

a merged Config instance

timestamp

public Instant timestamp()

Description copied from interface: Config

Returns when the configuration tree was created.

Each config node of single Config tree returns same timestamp.

Specified by:

timestamp in interface Config

Returns:

timestamp of created instance of whole configuration tree.

See Also:

• Config.context()
• Config.Context.timestamp()

key

public Config.Key key()

Description copied from interface: Config

Returns the fully-qualified key of the 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 Config.name() for more information on the format of each token.

Specified by:

key in interface Config

Specified by:

key in interface Config

Returns:

current config node key

See Also:

• Config.name()

root

public Config root()

Description copied from interface: Config

Get the root of the configuration tree. In case this node is part of detached tree, this method returns the node that was detached.

Specified by:

root in interface Config

Specified by:

root in interface Config

Returns:

root of this configuration tree

get

public Config get(Config.Key key)

Description copied from interface: Config

Returns the single sub-node for the specified sub-key.

Specified by:

get in interface Config

Parameters:

key - sub-key of requested sub-node

Returns:

config node for specified sub-key, never returns null.

See Also:

• Config.get(String)

detach

public Config detach()

Description copied from interface: Config

Returns a copy of the Config node with no parent.

The returned node acts as a root node for the subtree below it. Its key is the empty string; "". The original config node is unchanged, and the original and the copy point to the same children.

Consider the following configuration:

 app:
      name: Example 1
      page-size: 20
 logging:
      app.level = INFO
      level = WARNING
 

The Config instances name1 and name2 represents same data and in fact refer to the same object:

 Config name1 = config
                  .get("app")
                  .get("name");
 Config name2 = config
                  .get("app")
                  .detach()               //DETACHED node
                  .get("name");

 assert name1.asString() == "Example 1";
 assert name2.asString() == "Example 1";  //DETACHED node
 

The only difference is the key each node returns:

 assert name1.key() == "app.name";
 assert name2.key() == "name";            //DETACHED node
 

See Config.asMap() for example of config detaching.

Specified by:

detach in interface Config

Specified by:

detach in interface Config

Returns:

returns detached Config instance of same config node

type

public Config.Type type()

Description copied from interface: Config

Provides the Config.Type of the Config node.

Specified by:

type in interface Config

Returns:

the Type of the configuration node

hasValue

public boolean hasValue()

Description copied from interface: Config

Returns true if this configuration node has a direct value.

This may be a value node (e.g. a leaf) or object node or a list node (e.g. a branch with value). The application can invoke methods such as Config.as(Class) on nodes that have value.

Specified by:

hasValue in interface Config

Specified by:

hasValue in interface Config

Returns:

true if the node has direct value, false otherwise.

traverse

public Stream<Config> traverse(Predicate<Config> predicate)

Traverses over merged configs like Config.traverse(). Every config node exising in both primary and fallback configs is merged.

Specified by:

traverse in interface Config

Parameters:

predicate - predicate evaluated on each visited Config node to continue or stop visiting the node

Returns:

stream of deepening depth-first sub nodes

convert

public <T> T convert(Class<T> type,
 String value)
              throws ConfigMappingException

Description copied from interface: Config

Convert a String to a specific type. This is a helper method to allow for processing of default values that cannot be typed (e.g. in annotations).

Specified by:

convert in interface Config

Type Parameters:

T - type

Parameters:

type - type of the property

value - String value

Returns:

instance of the correct type

Throws:

ConfigMappingException - in case the String provided cannot be converted to the type expected

See Also:

• Config.as(Class)

mapper

public ConfigMapper mapper()

Only mappers from the primary config are considered.

Specified by:

mapper in interface Config

Returns:

mapper from primary config

as

public <T> ConfigValue<T> as(GenericType<T> genericType)

Description copied from interface: Config

Typed value as a ConfigValue for a generic type. If appropriate mapper exists, returns a properly typed generic instance.

Example:

 
 ConfigValue<Map<String, Integer>> myMapValue = config.as(new GenericType<Map<String, Integer>>(){});
 myMapValue.ifPresent(map -> {
      Integer port = map.get("service.port");
  }
 
 

Specified by:

as in interface Config

Type Parameters:

T - type of the returned value

Parameters:

genericType - a (usually anonymous) instance of generic type to prevent type erasure

Returns:

properly typed config value

as

public <T> ConfigValue<T> as(Class<T> type)

Description copied from interface: Config

Typed value as a ConfigValue.

Specified by:

as in interface Config

Specified by:

as in interface Config

Type Parameters:

T - type

Parameters:

type - type class

Returns:

typed value

See Also:

• OptionalValue.map(Function)
• ConfigValue.supplier()
• ConfigValue.get()
• OptionalValue.orElse(Object)

as

public <T> ConfigValue<T> as(Function<Config,T> mapper)

Description copied from interface: Config

Typed value as a ConfigValue created from factory method. To convert from String, you can use config.asString().as(Function).

Specified by:

as in interface Config

Type Parameters:

T - type

Parameters:

mapper - method to create an instance from config

Returns:

typed value

asList

public <T> ConfigValue<List<T>> asList(Class<T> type)
                                throws ConfigMappingException

Description copied from interface: Config

Returns list of specified type.

Specified by:

asList in interface Config

Specified by:

asList in interface Config

Type Parameters:

T - type of list elements

Parameters:

type - type class

Returns:

a typed list with values

Throws:

ConfigMappingException - in case of problem to map property value.

asList

public <T> ConfigValue<List<T>> asList(Function<Config,T> mapper)
                                throws ConfigMappingException

Description copied from interface: Config

Returns this node as a list converting each list value using the provided mapper.

Specified by:

asList in interface Config

Type Parameters:

T - type of list elements

Parameters:

mapper - mapper to convert each list node into a typed value

Returns:

a typed list with values

Throws:

ConfigMappingException - in case the mapper fails to map the values

asNodeList

public ConfigValue<List<Config>> asNodeList()
                                     throws ConfigMappingException

Description copied from interface: Config

Returns a list of child Config nodes if the node is Type#OBJECT. Returns a list of element nodes if the node is Type#LIST. Throws MissingValueException if the node is Type#MISSING. Otherwise, if node is Type#VALUE, it throws ConfigMappingException.

Specified by:

asNodeList in interface Config

Specified by:

asNodeList in interface Config

Returns:

a list of Type#OBJECT members or a list of Type#LIST members

Throws:

ConfigMappingException

asMap

public ConfigValue<Map<String,String>> asMap()
                                      throws MissingValueException

Description copied from interface: Config

Transform all leaf nodes (values) into Map instance.

Fully qualified key of config node is used as a key in returned Map. Detach config node before transforming to Map in case you want to cut current Config node key prefix.

Let's say we work with following configuration:

 app:
      name: Example 1
      page-size: 20
 logging:
      app.level = INFO
      level = WARNING
 

Map app1 contains two keys: app.name, app.page-size.

 Map<String, String> app1 = config.get("app").asMap();
 

Detaching app config node returns new Config instance with "reset" local root.

 Map<String, String> app2 = config.get("app").detach().asMap();
 

Map app2 contains two keys without app prefix: name, page-size.

Specified by:

asMap in interface Config

Specified by:

asMap in interface Config

Returns:

new Map instance that contains all config leaf node values

Throws:

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

See Also:

• Config.traverse()
• Config.detach()