com.netflix.spectator.api

Class Functions

java.lang.Object

com.netflix.spectator.api.Functions

public final class Functions
extends Object

Common functions for use with gauges.

Field Summary

Fields

Modifier and Type	Field and Description
static DoubleFunction<AtomicLong>	AGE Age function based on the system clock.
static ValueFunction<Collection<?>>	COLLECTION_SIZE Deprecated. Use Collection::size instead.
static DoubleFunction<? extends Number>	IDENTITY Identity function that just returns the passed in value if it implements the Number interface.
static ValueFunction<Map<?,?>>	MAP_SIZE Deprecated. Use Map::size instead.

Method Summary

Modifier and Type	Method and Description
static DoubleFunction<AtomicLong>	age(Clock clock) Returns a function that computes the age in seconds.
static <T> java.util.function.ToDoubleFunction<T>	invokeMethod(Method method) Returns a function that invokes a method on the object via reflection.
static java.util.function.Predicate<Meter>	nameEquals(String name) Returns a predicate that matches if the {code}id.name(){code} value for the input meter is equal to {code}name{code}.

Methods inherited from class java.lang.Object

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

Field Detail

IDENTITY

public static final DoubleFunction<? extends Number> IDENTITY

Identity function that just returns the passed in value if it implements the Number interface.

COLLECTION_SIZE

@Deprecated
public static final ValueFunction<Collection<?>> COLLECTION_SIZE

Deprecated. Use Collection::size instead.

Returns the size of the collection.

MAP_SIZE

@Deprecated
public static final ValueFunction<Map<?,?>> MAP_SIZE

Deprecated. Use Map::size instead.

Returns the size of the map.

AGE

public static final DoubleFunction<AtomicLong> AGE

Age function based on the system clock. See age(Clock) for more details.

Method Detail

age

public static DoubleFunction<AtomicLong> age(Clock clock)

Returns a function that computes the age in seconds. The value passed into the function should be a timestamp in milliseconds since the epoch. Typically this will be the return value from calling System.currentTimeMillis().

Parameters:

clock - Clock used to get the current time for comparing with the passed in value.

Returns:

Function that computes the age.

invokeMethod

public static <T> java.util.function.ToDoubleFunction<T> invokeMethod(Method method)

Returns a function that invokes a method on the object via reflection. If an exception of any kind occurs then NaN will be returned and the exception will be logged. The method must have an empty parameter list and return a primitive number value or a subclass of Number. The method will be set accessible so that private methods can be used.

Parameters:

method - Method to execute on the passed in object.

Returns:

Value returned by the method or NaN if an exception is thrown.

nameEquals

public static java.util.function.Predicate<Meter> nameEquals(String name)

Returns a predicate that matches if the {code}id.name(){code} value for the input meter is equal to {code}name{code}. Example of usage:

 long numberOfMatches = registry.stream().filter(Functions.nameEquals("foo")).count();
 

Parameters:

name - The name to use for finding matching meter instances. Cannot be null.

Returns:

A predicate function that can be used to filter a stream.