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Interface IContextLookup

All Known Subinterfaces:

IContextLookupChainLink

All Known Implementing Classes:

LookupChain

public interface IContextLookup

An interface for instances that can provide a ILookup capabilities for a given object.

This is useful in the case where lookup functionality is not intrinsic to an item or where an existing object cannot implement the interface or when an item needs to be decorated externally with new lookup functionality.

See Also:

ILookup, IContextLookup

Field Summary

Fields

Modifier and Type	Field and Description
static IContextLookup	EMPTY_CONTEXT_LOOKUP An ILookupContext instance that always returns null.

Method Summary

Modifier and Type	Method and Description
default <T> T	lookup(Class<T> type, Object item) Typesafe convenience method for the lookup(Object, Class) method.
static <T> T	lookup(Class<T> tType, Object context, IContextLookup lookup) Utility method that helps keeping code more clean when using IContextLookup lookup(Object, Class) calls.
static <T> T	lookup(Class<T> tType, Object context, IContextLookup lookup, T fallback) Utility method that helps keeping code more clean when using IContextLookup lookup(Object, Class) calls.
Object	lookup(Object item, Class type) Tries to create or retrieve an implementation of the given type for a given item.
default <T> T	safeLookup(Class<T> type, Object item) Typesafe convenience method for the lookup(Object, Class) method.

Field Detail

EMPTY_CONTEXT_LOOKUP

static final IContextLookup EMPTY_CONTEXT_LOOKUP

An ILookupContext instance that always returns null.

Method Detail

lookup

default <T> T lookup(Class<T> type,
                     Object item)

Typesafe convenience method for the lookup(Object, Class) method.

Type Parameters:

T - The type to query, this is passed to the lookup(Object, Class) method using typeof. The result of the query will be converted to this type.

Parameters:

item - The item to pass to the lookup(Object, Class) method.

Returns:

The result of the query, or null.

lookup

static <T> T lookup(Class<T> tType,
                    Object context,
                    IContextLookup lookup)

Utility method that helps keeping code more clean when using IContextLookup lookup(Object, Class) calls.

Type Parameters:

T - The type that is the target of the lookup.

Parameters:

context - The context object to pass to the lookup.

lookup - The actual lookup provider.

Returns:

The value returned by lookup which may be null.

lookup

static <T> T lookup(Class<T> tType,
                    Object context,
                    IContextLookup lookup,
                    T fallback)

Utility method that helps keeping code more clean when using IContextLookup lookup(Object, Class) calls.

Type Parameters:

T - The type that is the target of the lookup.

Parameters:

context - The context object to pass to the lookup.

lookup - The actual lookup provider.

fallback - The fallback value to use if the lookup yields null

Returns:

The value returned by lookup or fallback if the former yields null.

lookup

Object lookup(Object item,
              Class type)

Tries to create or retrieve an implementation of the given type for a given item.

Parameters:

item - the item to lookup a type for

type - the type to look up

Returns:

an implementation or null

See Also:

ILookup.lookup(Class)

safeLookup

default <T> T safeLookup(Class<T> type,
                         Object item)

Typesafe convenience method for the lookup(Object, Class) method.

Throws:

NoSuchElementException - If the context lookup did not yield a non-null result for the type.

Type Parameters:

T - The type to query, this is passed to the lookup(Object, Class) method using typeof. The result of the query will be converted to this type.

Parameters:

item - The item to pass to the lookup(Object, Class) method.

Returns:

The result of the query, never null.