Module org.microbean.loader

Package org.microbean.loader

Class EnvironmentVariableProvider

java.lang.Object

org.microbean.loader.spi.AbstractProvider

org.microbean.loader.EnvironmentVariableProvider

All Implemented Interfaces:

Provider

public class EnvironmentVariableProvider
extends AbstractProvider

An AbstractProvider that provides access to environment variables.

Author:

Laird Nelson

Constructor Summary

Constructors

Constructor	Description
EnvironmentVariableProvider()	Creates a new EnvironmentVariableProvider that uses flat keys.
EnvironmentVariableProvider(boolean flatKeys)	Creates a new EnvironmentVariableProvider.

Method Summary

Modifier and Type	Method	Description
protected Supplier<?>	find(Loader<?> requestor, Path<? extends Type> absolutePath)	If the supplied absolutePath has a size of 2 (the root plus a single name), returns a deterministic Supplier whose Supplier.get() method returns the environment variable with that name, or null in all other cases.
protected static final String	key(Path<?> path, boolean flat)	Returns a String representation of the supplied Path.
protected <T extends Type> Path<T>	path(Loader<?> requestor, Path<T> absolutePath)	Overrides the AbstractProvider.path(Loader, Path) method to return a (relative) Path consisting solely of the last element of the supplied absolutePath.

Methods inherited from class org.microbean.loader.spi.AbstractProvider

get, lowerBound

Methods inherited from class java.lang.Object

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

Constructor Details

EnvironmentVariableProvider

public EnvironmentVariableProvider()

Creates a new EnvironmentVariableProvider that uses flat keys.

See Also:

• EnvironmentVariableProvider(boolean)

EnvironmentVariableProvider

public EnvironmentVariableProvider(boolean flatKeys)

Creates a new EnvironmentVariableProvider.

Parameters:

flatKeys - whether the key for an environment variable is derived from a Path's last element's name only

Method Details

find

protected Supplier<?> find(Loader<?> requestor,
 Path<? extends Type> absolutePath)

If the supplied absolutePath has a size of 2 (the root plus a single name), returns a deterministic Supplier whose Supplier.get() method returns the environment variable with that name, or null in all other cases.

Specified by:

find in class AbstractProvider

Parameters:

requestor - the Loader requesting a Value; must not be null

absolutePath - an absolute Path; must not be null

Returns:

a deterministic Supplier whose Supplier.get() method returns the appropriate environment variable if the supplied absolutePath has a size of 2 (the root plus a single name) and there actually is a corresponding environment variable; null in all other cases

Throws:

NullPointerException - if requestor or absolutePath is null

See Also:

• AbstractProvider.find(Loader, Path)
• System.getenv(String)

Idempotency:

This method is idempotent and deterministic during the lifetime of a Java virtual machine instance.

Nullability:

This method may return null.

Thread Safety:

This method is safe for concurrent use by multiple threads.

path

protected <T extends Type> Path<T> path(Loader<?> requestor,
 Path<T> absolutePath)

Overrides the AbstractProvider.path(Loader, Path) method to return a (relative) Path consisting solely of the last element of the supplied absolutePath.

Overrides:

path in class AbstractProvider

Type Parameters:

T - the type of both the supplied and returned Paths

Parameters:

requestor - the Loader seeking a Value; must not be null

absolutePath - an absolute Path for which a Value is being sought; must not be null

Returns:

a Path that will be used to build a Value to be returned by the AbstractProvider.get(Loader, Path) method

See Also:

• AbstractProvider.path(Loader, Path)

Idempotency:

This method is, and its overrides must be, idempotent and deterministic.

Nullability:

This method does not, but overrides may, return null.

Thread Safety:

This method is, and its overrides must be, safe for concurrent use by multiple threads.

key

protected static final String key(Path<?> path,
 boolean flat)

Returns a String representation of the supplied Path.

Parameters:

path - the Path in question; must not be null

flat - whether the key is derived from the supplied Path's last element's name only

Returns:

a String representation of the supplied Path

Throws:

NullPointerException - if path is null

Idempotency:

This method is idempotent and deterministic.

Nullability:

This method never returns null.

Thread Safety:

This method is safe for concurrent use by multiple threads.