Config

trait Config extends ConfigMergeable

An immutable map from config paths to config values. Paths are dot-separated expressions such as foo.bar.baz. Values are as in JSON (booleans, strings, numbers, lists, or objects), represented by [[ConfigValue]] instances. Values accessed through the Config interface are never null.

An immutable map from config paths to config values. Paths are dot-separated expressions such as foo.bar.baz. Values are as in JSON (booleans, strings, numbers, lists, or objects), represented by [[ConfigValue]] instances. Values accessed through the Config interface are never null.

Config is an immutable object and thus safe to use from multiple threads. There's never a need for "defensive copies."

Fundamental operations on a Config include getting configuration values, resolving substitutions with resolve(), and merging configs using withFallback(ConfigMergeable).

All operations return a new immutable Config rather than modifying the original instance.

Examples

You can find an example app and library on GitHub. Also be sure to read the package-summary.html#package_description package overview]] which describes the big picture as shown in those examples.

Paths, keys, and Config vs. ConfigObject

Config is a view onto a tree of [[ConfigObject]]; the corresponding object tree can be found through [[Config#root]]. ConfigObject is a map from config keys, rather than paths, to config values. Think of ConfigObject as a JSON object and Config as a configuration API.

The API tries to consistently use the terms "key" and "path." A key is a key in a JSON object; it's just a string that's the key in a map. A "path" is a parseable expression with a syntax and it refers to a series of keys. Path expressions are described in the spec for Human-Optimized Config Object Notation. In brief, a path is period-separated so "a.b.c" looks for key c in object b in object a in the root object. Sometimes double quotes are needed around special characters in path expressions.

The API for a Config is in terms of path expressions, while the API for a ConfigObject is in terms of keys. Conceptually, Config is a one-level map from paths to values, while a ConfigObject is a tree of nested maps from keys to values.

Use ConfigUtil.joinPath(String*) and ConfigUtil.splitPath(String) to convert between path expressions and individual path elements (keys).

Another difference between Config and ConfigObject is that conceptually, ConfigValues with a [[ConfigValue#valueType valueType]] of [[ConfigValueType#NULL NULL]] exist in a ConfigObject, while a Config treats null values as if they were missing. (With the exception of two methods: [[Config#hasPathOrNull]] and [[Config#getIsNull]] let you detect null values.)

Getting configuration values

The "getters" on a Config all work in the same way. They never return null, nor do they return a ConfigValue with [[ConfigValue#valueType valueType]] of [[ConfigValueType#NULL NULL]]. Instead, they throw [[ConfigException.Missing]] if the value is completely absent or set to null. If the value is set to null, a subtype of ConfigException.Missing called [[ConfigException.Null]] will be thrown. [[ConfigException.WrongType]] will be thrown anytime you ask for a type and the value has an incompatible type. Reasonable type conversions are performed for you though.

Iteration

If you want to iterate over the contents of a Config, you can get its ConfigObject with [[#root]], and then iterate over the ConfigObject (which implements java.util.Map). Or, you can use [[#entrySet]] which recurses the object tree for you and builds up a Set of all path-value pairs where the value is not null.

'''Resolving substitutions'''

''Substitutions'' are the ${foo.bar} syntax in config files, described in the <a href= "https://github.com/lightbend/config/blob/master/HOCON.md#substitutions"

specification. Resolving substitutions replaces these references with real values.

Before using a Config it's necessary to call resolve() to handle substitutions (though ConfigFactory.load() and similar methods will do the resolve for you already).

Merging

The full Config for your application can be constructed using the associative operation withFallback(ConfigMergeable). If you use ConfigFactory.load() (recommended), it merges system properties over the top of application.conf over the top of reference.conf, using withFallback. You can add in additional sources of configuration in the same way (usually, custom layers should go either just above or just below application.conf, keeping reference.conf at the bottom and system properties at the top).

Serialization

Convert a Config to a JSON or HOCON string by calling root to get the ConfigObject and then call render on the root object, myConfig.root.render. There's also a variant render(ConfigRenderOptions) inherited from ConfigValue which allows you to control the format of the rendered string. (See [[ConfigRenderOptions]].) Note that Config does not remember the formatting of the original file, so if you load, modify, and re-save a config file, it will be substantially reformatted.

As an alternative to render, the toString method produces a debug-output-oriented representation (which is not valid JSON).

Java serialization is supported as well for Config and all subtypes of ConfigValue.

This is an interface but don't implement it yourself

Do not implement Config; it should only be implemented by the config library. Arbitrary implementations will not work because the library internals assume a specific concrete implementation. Also, this interface is likely to grow new methods over time, so third-party implementations will break.

class Object
trait Matchable
class Any

Value members

Abstract methods

def atKey(key: String): Config

Places the config inside a Config at the given key. See also atPath. Note that a key is NOT a path expression (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Places the config inside a Config at the given key. See also atPath. Note that a key is NOT a path expression (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
key

key to store this config at.

Returns

a Config instance containing this config at the given key.

def atPath(path: String): Config

Places the config inside another Config at the given path.

Places the config inside another Config at the given path.

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

path expression to store this config at.

Returns

a { @code Config} instance containing this config at the given path.

@varargs
def checkValid(reference: Config, restrictToPaths: String*): Unit

Validates this config against a reference config, throwing an exception if it is invalid. The purpose of this method is to "fail early" with a comprehensive list of problems; in general, anything this method can find would be detected later when trying to use the config, but it's often more user-friendly to fail right away when loading the config.

Validates this config against a reference config, throwing an exception if it is invalid. The purpose of this method is to "fail early" with a comprehensive list of problems; in general, anything this method can find would be detected later when trying to use the config, but it's often more user-friendly to fail right away when loading the config.

Using this method is always optional, since you can "fail late" instead.

You must restrict validation to paths you "own" (those whose meaning are defined by your code module). If you validate globally, you may trigger errors about paths that happen to be in the config but have nothing to do with your module. It's best to allow the modules owning those paths to validate them. Also, if every module validates only its own stuff, there isn't as much redundant work being done.

If no paths are specified in checkValid's parameter list, validation is for the entire config.

If you specify paths that are not in the reference config, those paths are ignored. (There's nothing to validate.)

Here's what validation involves:

  • All paths found in the reference config must be present in this config or an exception will be thrown.

Some changes in type from the reference config to this config will cause an exception to be thrown. Not all potential type problems are detected, in particular it's assumed that strings are compatible with everything except objects and lists. This is because string types are often "really" some other type (system properties always start out as strings, or a string like "5ms" could be used with getDuration(String)). Also, it's allowed to set any type to null or override null with any type.

Any unresolved substitutions in this config will cause a validation failure; both the reference config and this config should be resolved before validation. If the reference config is unresolved, it's a bug in the caller of this method.

If you want to allow a certain setting to have a flexible type (or otherwise want validation to be looser for some settings), you could either remove the problematic setting from the reference config provided to this method, or you could intercept the validation exception and screen out certain problems. Of course, this will only work if all other callers of this method are careful to restrict validation to their own paths, as they should be.

If validation fails, the thrown exception contains a list of all problems found. See [[ConfigException.ValidationFailed#problems]]. The exception's getMessage will have all the problems concatenated into one huge string, as well.

Again, checkValid can't guess every domain-specific way a setting can be invalid, so some problems may arise later when attempting to use the config. checkValid is limited to reporting generic, but common, problems such as missing settings and blatant type incompatibilities.

Value Params
reference

a reference configuration

restrictToPaths

only validate values underneath these paths that your code module owns and understands

Throws
ConfigException.BugOrBroken

if the reference config is unresolved or caller otherwise misuses the API

ConfigException.NotResolved

if this config is not resolved

ConfigException.ValidationFailed

if there are any validation issues

def entrySet: Set[Entry[String, ConfigValue]]

Returns the set of path-value pairs, excluding any null values, found by recursing [[#root the root object]]. Note that this is very different from root.entrySet which returns the set of immediate-child keys in the root object and includes null values.

Returns the set of path-value pairs, excluding any null values, found by recursing [[#root the root object]]. Note that this is very different from root.entrySet which returns the set of immediate-child keys in the root object and includes null values.

Entries contain path expressions meaning there may be quoting and escaping involved. Parse path expressions with [[ConfigUtil#splitPath]].

Because a Config is conceptually a single-level map from paths to values, there will not be any [[ConfigObject]] values in the entries (that is, all entries represent leaf nodes). Use [[ConfigObject]] rather than Config if you want a tree. (OK, this is a slight lie: Config entries may contain [[ConfigList]] and the lists may contain objects. But no objects are directly included as entry values.)

Returns

set of paths with non-null values, built up by recursing the entire tree of { @link ConfigObject} and creating an entry for each leaf value.

def getAnyRef(path: String): AnyRef

Gets the value at the path as an unwrapped Java boxed value ( java.lang.Boolean java.lang.Integer, and so on - see [[ConfigValue#unwrapped]]).

Gets the value at the path as an unwrapped Java boxed value ( java.lang.Boolean java.lang.Integer, and so on - see [[ConfigValue#unwrapped]]).

Value Params
path

path expression

Returns

the unwrapped value at the requested path

Throws
ConfigException.Missing

if value is absent or null

def getAnyRefList(path: String): List[_ <: AnyRef]

Gets a list value with any kind of elements. Throws if the path is unset or null or not a list. Each element is "unwrapped" (see [[ConfigValue#unwrapped]]).

Gets a list value with any kind of elements. Throws if the path is unset or null or not a list. Each element is "unwrapped" (see [[ConfigValue#unwrapped]]).

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list

def getBoolean(path: String): Boolean
Value Params
path

path expression

Returns

the boolean value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to boolean

def getBooleanList(path: String): List[Boolean]

Gets a list value with boolean elements. Throws if the path is unset or null or not a list or contains values not convertible to boolean.

Gets a list value with boolean elements. Throws if the path is unset or null or not a list or contains values not convertible to boolean.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of booleans

def getBytes(path: String): Long

Gets a value as a size in bytes (parses special strings like "128M"). If the value is already a number, then it's left alone; if it's a string, it's parsed understanding unit suffixes such as "128K", as documented in the the spec.

Gets a value as a size in bytes (parses special strings like "128M"). If the value is already a number, then it's left alone; if it's a string, it's parsed understanding unit suffixes such as "128K", as documented in the the spec.

Value Params
path

path expression

Returns

the value at the requested path, in bytes

Throws
ConfigException.BadValue

if value cannot be parsed as a size in bytes

ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to Long or String

def getBytesList(path: String): List[Long]

Gets a list value with elements representing a size in bytes. Throws if the path is unset or null or not a list or contains values not convertible to memory sizes.

Gets a list value with elements representing a size in bytes. Throws if the path is unset or null or not a list or contains values not convertible to memory sizes.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of memory sizes

def getConfig(path: String): Config
Value Params
path

path expression

Returns

the nested Config value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a Config

def getConfigList(path: String): List[_ <: Config]

Gets a list value with Config elements. Throws if the path is unset or null or not a list or contains values not convertible to Config.

Gets a list value with Config elements. Throws if the path is unset or null or not a list or contains values not convertible to Config.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of configs

def getDouble(path: String): Double
Value Params
path

path expression

Returns

the floating-point value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a double

def getDoubleList(path: String): List[Double]

Gets a list value with double elements. Throws if the path is unset or null or not a list or contains values not convertible to double.

Gets a list value with double elements. Throws if the path is unset or null or not a list or contains values not convertible to double.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of doubles

def getDuration(path: String, unit: TimeUnit): Long

Gets a value as a duration in a specified java.util.concurrent.TimeUnit. If the value is already a number, then it's taken as milliseconds and then converted to the requested TimeUnit; if it's a string, it's parsed understanding units suffixes like "10m" or "5ns" as documented in the <a the HOCON spec.

Gets a value as a duration in a specified java.util.concurrent.TimeUnit. If the value is already a number, then it's taken as milliseconds and then converted to the requested TimeUnit; if it's a string, it's parsed understanding units suffixes like "10m" or "5ns" as documented in the <a the HOCON spec.

Value Params
path

path expression

unit

convert the return value to this time unit

Returns

the duration value at the requested path, in the given TimeUnit

Throws
ConfigException.BadValue

if value cannot be parsed as a number of the given TimeUnit

ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to Long or String

Since

1.2.0

def getDuration(path: String): Duration

Gets a value as a java.time.Duration. If the value is already a number, then it's taken as milliseconds; if it's a string, it's parsed understanding units suffixes like "10m" or "5ns" as documented in the the spec. This method never returns null.

Gets a value as a java.time.Duration. If the value is already a number, then it's taken as milliseconds; if it's a string, it's parsed understanding units suffixes like "10m" or "5ns" as documented in the the spec. This method never returns null.

Value Params
path

path expression

Returns

the duration value at the requested path

Throws
ConfigException.BadValue

if value cannot be parsed as a number of the given TimeUnit

ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to Long or String

Since

1.3.0

def getDurationList(path: String, unit: TimeUnit): List[Long]

Gets a list, converting each value in the list to a duration, using the same rules as getDuration(String, TimeUnit).

Gets a list, converting each value in the list to a duration, using the same rules as getDuration(String, TimeUnit).

Value Params
path

a path expression

unit

time units of the returned values

Returns

list of durations, in the requested units

Since

1.2.0

def getDurationList(path: String): List[Duration]

Gets a list, converting each value in the list to a duration, using the same rules as getDuration(String).

Gets a list, converting each value in the list to a duration, using the same rules as getDuration(String).

Value Params
path

a path expression

Returns

list of durations

Since

1.3.0

def getInt(path: String): Int

Gets the integer at the given path. If the value at the path has a fractional (floating point) component, it will be discarded and only the integer part will be returned (it works like a "narrowing primitive conversion" in the Java language specification).

Gets the integer at the given path. If the value at the path has a fractional (floating point) component, it will be discarded and only the integer part will be returned (it works like a "narrowing primitive conversion" in the Java language specification).

Value Params
path

path expression

Returns

the 32-bit integer value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to an int (for example it is out of range, or it's a boolean value)

def getIntList(path: String): List[Integer]

Gets a list value with int elements. Throws if the path is unset or null or not a list or contains values not convertible to int.

Gets a list value with int elements. Throws if the path is unset or null or not a list or contains values not convertible to int.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of ints

def getIsNull(path: String): Boolean

Checks whether a value is set to null at the given path, but throws an exception if the value is entirely unset. This method will not throw if [[#hasPathOrNull]] returned true for the same path, so to avoid any possible exception check hasPathOrNull first. However, an exception for unset paths will usually be the right thing (because a reference.conf should exist that has the path set, the path should never be unset unless something is broken).

Checks whether a value is set to null at the given path, but throws an exception if the value is entirely unset. This method will not throw if [[#hasPathOrNull]] returned true for the same path, so to avoid any possible exception check hasPathOrNull first. However, an exception for unset paths will usually be the right thing (because a reference.conf should exist that has the path set, the path should never be unset unless something is broken).

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

the path expression

Returns

true if the value exists and is null, false if it exists and is not null

Throws
ConfigException.BadPath

if the path expression is invalid

ConfigException.Missing

if value is not set at all

def getList(path: String): ConfigList

Gets a list value (with any element type) as a [[ConfigList]], which implements java.util.List. Throws if the path is unset or null.

Gets a list value (with any element type) as a [[ConfigList]], which implements java.util.List. Throws if the path is unset or null.

Value Params
path

the path to the list value.

Returns

the { @link ConfigList} at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a ConfigList

def getLong(path: String): Long

Gets the long integer at the given path. If the value at the path has a fractional (floating point) component, it will be discarded and only the integer part will be returned (it works like a "narrowing primitive conversion" in the Java language specification).

Gets the long integer at the given path. If the value at the path has a fractional (floating point) component, it will be discarded and only the integer part will be returned (it works like a "narrowing primitive conversion" in the Java language specification).

Value Params
path

path expression

Returns

the 64-bit long value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a long

def getLongList(path: String): List[Long]

Gets a list value with long elements. Throws if the path is unset or null or not a list or contains values not convertible to long.

Gets a list value with long elements. Throws if the path is unset or null or not a list or contains values not convertible to long.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of longs

def getMemorySize(path: String): ConfigMemorySize

Gets a value as an amount of memory (parses special strings like "128M"). If the value is already a number, then it's left alone; if it's a string, it's parsed understanding unit suffixes such as "128K", as documented in the the spec.

Gets a value as an amount of memory (parses special strings like "128M"). If the value is already a number, then it's left alone; if it's a string, it's parsed understanding unit suffixes such as "128K", as documented in the the spec.

Value Params
path

path expression

Returns

the value at the requested path, in bytes

Throws
ConfigException.BadValue

if value cannot be parsed as a size in bytes

ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to Long or String

Since

1.3.0

def getMemorySizeList(path: String): List[ConfigMemorySize]

Gets a list, converting each value in the list to a memory size, using the same rules as [[#getMemorySize]].

Gets a list, converting each value in the list to a memory size, using the same rules as [[#getMemorySize]].

Value Params
path

a path expression

Returns

list of memory sizes

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of memory sizes

Since

1.3.0

def getNumber(path: String): Number
Value Params
path

path expression

Returns

the numeric value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a number

def getNumberList(path: String): List[Number]

Gets a list value with number elements. Throws if the path is unset or null or not a list or contains values not convertible to number.

Gets a list value with number elements. Throws if the path is unset or null or not a list or contains values not convertible to number.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of numbers

def getObject(path: String): ConfigObject
Value Params
path

path expression

Returns

the { @link ConfigObject} value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to an object

def getObjectList(path: String): List[_ <: ConfigObject]

Gets a list value with object elements. Throws if the path is unset or null or not a list or contains values not convertible to ConfigObject.

Gets a list value with object elements. Throws if the path is unset or null or not a list or contains values not convertible to ConfigObject.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of objects

def getPeriod(path: String): Period

Gets a value as a java.time.Period. If the value is already a number, then it's taken as days; if it's a string, it's parsed understanding units suffixes like "10d" or "5w" as documented in the the spec. This method never returns null.

Gets a value as a java.time.Period. If the value is already a number, then it's taken as days; if it's a string, it's parsed understanding units suffixes like "10d" or "5w" as documented in the the spec. This method never returns null.

Value Params
path

path expression

Returns

the period value at the requested path

Throws
ConfigException.BadValue

if value cannot be parsed as a number of the given TimeUnit

ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to Long or String

Since

1.3.0

def getString(path: String): String
Value Params
path

path expression

Returns

the string value at the requested path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a string

def getStringList(path: String): List[String]

Gets a list value with string elements. Throws if the path is unset or null or not a list or contains values not convertible to string.

Gets a list value with string elements. Throws if the path is unset or null or not a list or contains values not convertible to string.

Value Params
path

the path to the list value.

Returns

the list at the path

Throws
ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to a list of strings

def getTemporal(path: String): TemporalAmount

Gets a value as a java.time.temporal.TemporalAmount. This method will first try get get the value as a java.time.Duration, and if unsuccessful, then as a java.time.Period. This means that values like "5m" will be parsed as 5 minutes rather than 5 months

Gets a value as a java.time.temporal.TemporalAmount. This method will first try get get the value as a java.time.Duration, and if unsuccessful, then as a java.time.Period. This means that values like "5m" will be parsed as 5 minutes rather than 5 months

Value Params
path

path expression

Returns

the temporal value at the requested path

Throws
ConfigException.BadValue

if value cannot be parsed as a TemporalAmount

ConfigException.Missing

if value is absent or null

ConfigException.WrongType

if value is not convertible to Long or String

def getValue(path: String): ConfigValue

Gets the value at the given path, unless the value is a null value or missing, in which case it throws just like the other getters. Use get on the [[Config#root]] object (or other object in the tree) if you want an unprocessed value.

Gets the value at the given path, unless the value is a null value or missing, in which case it throws just like the other getters. Use get on the [[Config#root]] object (or other object in the tree) if you want an unprocessed value.

Value Params
path

path expression

Returns

the value at the requested path

Throws
ConfigException.Missing

if value is absent or null

def hasPath(path: String): Boolean

Checks whether a value is present and non-null at the given path. This differs in two ways from Map.containsKey as implemented by [[ConfigObject]]: it looks for a path expression, not a key; and it returns false for null values, while containsKey returns true indicating that the object contains a null value for the key.

Checks whether a value is present and non-null at the given path. This differs in two ways from Map.containsKey as implemented by [[ConfigObject]]: it looks for a path expression, not a key; and it returns false for null values, while containsKey returns true indicating that the object contains a null value for the key.

If a path exists according to [[#hasPath]], then [[#getValue]] will never throw an exception. However, the typed getters, such as [[#getInt]], will still throw if the value is not convertible to the requested type.

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

the path expression

Returns

true if a non-null value is present at the path

Throws
ConfigException.BadPath

if the path expression is invalid

def hasPathOrNull(path: String): Boolean

Checks whether a value is present at the given path, even if the value is null. Most of the getters on Config will throw if you try to get a null value, so if you plan to call [[#getValue]], [[#getInt]], or another getter you may want to use plain [[#hasPath]] rather than this method.

Checks whether a value is present at the given path, even if the value is null. Most of the getters on Config will throw if you try to get a null value, so if you plan to call [[#getValue]], [[#getInt]], or another getter you may want to use plain [[#hasPath]] rather than this method.

To handle all three cases (unset, null, and a non-null value) the code might look like:

if (config.hasPathOrNull(path)) {
 if (config.getIsNull(path)) {
   // handle null setting
 } else {
   // get and use non-null setting
 }
} else {
 // handle entirely unset path
}

However, the usual thing is to allow entirely unset paths to be a bug that throws an exception (because you set a default in your reference.conf), so in that case it's OK to call [[#getIsNull]] without checking hasPathOrNull first.

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

the path expression

Returns

true if a value is present at the path, even if the value is null

Throws
ConfigException.BadPath

if the path expression is invalid

def isEmpty: Boolean

Returns true if the Config's root object contains no key-value pairs.

Returns true if the Config's root object contains no key-value pairs.

Returns

true if the configuration is empty

def isResolved: Boolean

Checks whether the config is completely resolved. After a successful call to resolve() it will be completely resolved, but after calling resolve(ConfigResolveOptions) with allowUnresolved set in the options, it may or may not be completely resolved. A newly-loaded config may or may not be completely resolved depending on whether there were substitutions present in the file.

Checks whether the config is completely resolved. After a successful call to resolve() it will be completely resolved, but after calling resolve(ConfigResolveOptions) with allowUnresolved set in the options, it may or may not be completely resolved. A newly-loaded config may or may not be completely resolved depending on whether there were substitutions present in the file.

Returns

true if there are no unresolved substitutions remaining in this configuration.

Since

1.2.0

Gets the origin of the Config, which may be a file, or a file with a line number, or just a descriptive phrase.

Gets the origin of the Config, which may be a file, or a file with a line number, or just a descriptive phrase.

Returns

the origin of the Config for use in error messages

def resolve(): Config

Returns a replacement config with all substitutions (the ${foo.bar} syntax, see HOCON spec for resolved. Substitutions are looked up using this Config as the root object, that is, a substitution ${foo.bar} will be replaced with the result of getValue("foo.bar").

Returns a replacement config with all substitutions (the ${foo.bar} syntax, see HOCON spec for resolved. Substitutions are looked up using this Config as the root object, that is, a substitution ${foo.bar} will be replaced with the result of getValue("foo.bar").

This method uses [[ConfigResolveOptions#defaults]], there is another variant resolve(ConfigResolveOptions) which lets you specify non-default options.

A given [[Config]] must be resolved before using it to retrieve config values, but ideally should be resolved one time for your entire stack of fallbacks (see [[Config#withFallback]]). Otherwise, some substitutions that could have resolved with all fallbacks available may not resolve, which will be potentially confusing for your application's users.

resolve should be invoked on root config objects, rather than on a subtree (a subtree is the result of something like config.getConfig("foo")). The problem with resolve on a subtree is that substitutions are relative to the root of the config and the subtree will have no way to get values from the root. For example, if you did config.getConfig("foo").resolve on the below config file, it would not work:

common-value = 10
foo {
 whatever = ${common-value}
}

Many methods on [[ConfigFactory]] such as ConfigFactory.load() automatically resolve the loaded Config on the loaded stack of config files.

Resolving an already-resolved config is a harmless no-op, but again, it is best to resolve an entire stack of fallbacks (such as all your config files combined) rather than resolving each one individually.

Returns

an immutable object with substitutions resolved

Throws
ConfigException

some other config exception if there are other problems

ConfigException.UnresolvedSubstitution

if any substitutions refer to nonexistent paths

Like resolve() but allows you to specify non-default options.

Like resolve() but allows you to specify non-default options.

Value Params
options

resolve options

Returns

the resolved Config (may be only partially resolved if options are set to allow unresolved)

def resolveWith(source: Config): Config

Like resolve() except that substitution values are looked up in the given source, rather than in this instance. This is a special-purpose method which doesn't make sense to use in most cases; it's only needed if you're constructing some sort of app-specific custom approach to configuration. The more usual approach if you have a source of substitution values would be to merge that source into your config stack using [[Config#withFallback]] and then resolve.

Like resolve() except that substitution values are looked up in the given source, rather than in this instance. This is a special-purpose method which doesn't make sense to use in most cases; it's only needed if you're constructing some sort of app-specific custom approach to configuration. The more usual approach if you have a source of substitution values would be to merge that source into your config stack using [[Config#withFallback]] and then resolve.

Note that this method does NOT look in this instance for substitution values. If you want to do that, you could either merge this instance into your value source using [[Config#withFallback]], or you could resolve multiple times with multiple sources (using [[ConfigResolveOptions#setAllowUnresolved]] so the partial resolves don't fail).

Value Params
source

configuration to pull values from

Returns

an immutable object with substitutions resolved

Throws
ConfigException

some other config exception if there are other problems

ConfigException.UnresolvedSubstitution

if any substitutions refer to paths which are not in the source

Since

1.2.0

Like resolveWith(Config) but allows you to specify non-default options.

Like resolveWith(Config) but allows you to specify non-default options.

Value Params
options

resolve options

source

source configuration to pull values from

Returns

the resolved Config (may be only partially resolved if options are set to allow unresolved)

Since

1.2.0

Gets the Config as a tree of [[ConfigObject]]. This is a constant-time operation (it is not proportional to the number of values in the Config).

Gets the Config as a tree of [[ConfigObject]]. This is a constant-time operation (it is not proportional to the number of values in the Config).

Returns

the root object in the configuration

override def withFallback(other: ConfigMergeable): Config
Definition Classes
def withOnlyPath(path: String): Config

Clone the config with only the given path (and its children) retained; all sibling paths are removed.

Clone the config with only the given path (and its children) retained; all sibling paths are removed.

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

path to keep

Returns

a copy of the config minus all paths except the one specified

def withValue(path: String, value: ConfigValue): Config

Returns a Config based on this one, but with the given path set to the given value. Does not modify this instance (since it's immutable). If the path already has a value, that value is replaced. To remove a value, use withoutPath.

Returns a Config based on this one, but with the given path set to the given value. Does not modify this instance (since it's immutable). If the path already has a value, that value is replaced. To remove a value, use withoutPath.

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

path expression for the value's new location

value

value at the new path

Returns

the new instance with the new map entry

def withoutPath(path: String): Config

Clone the config with the given path removed.

Clone the config with the given path removed.

Note that path expressions have a syntax and sometimes require quoting (see ConfigUtil$.joinPath and [[ConfigUtil#splitPath]]).

Value Params
path

path expression to remove

Returns

a copy of the config minus the specified path