org.apache.tapestry5.services
Interface Environment

All Known Implementing Classes:

EnvironmentImpl

public interface Environment

Provides access to environment objects, which are almost always provided to enclosed components by enclosing components. Environmental services are a form of very late binding.

The Environment acts like a collection of stacks. Each stack contains environmental objects of a given type. Most often, a stack has zero or one elements, but on occasion, a particular component will push an override onto the stack for the benefit of the components it encloses.

See Also:

Environmental, EnvironmentalShadowBuilder

Method Summary

void	clear() Deprecated. Deprecated in 5.3 with no replacement.
void	cloak() Hides all current environment values, making the Environment object appear empty, until a call to decloak()} restores the original state.
void	decloak() Restores state previously hidden by cloak()}.
<T> T	peek(Class<T> type) Peeks at the current top of the indicated stack.
<T> T	peekRequired(Class<T> type) Peeks at the current top of the indicated stack (which must have a non-null value).
<T> T	pop(Class<T> type) Removes and returns the top environmental object of the selected type.
<T> T	push(Class<T> type, T instance) Pushes a new service onto the stack.

Method Detail

peek

<T> T peek(Class<T> type)

Peeks at the current top of the indicated stack.

Type Parameters:

T - the type of environmental object

Parameters:

type - class used to select the object

Returns:

the current object of that type, or null if no service of that type has been added

peekRequired

<T> T peekRequired(Class<T> type)

Peeks at the current top of the indicated stack (which must have a non-null value).

Type Parameters:

T - the type of environmental object

Parameters:

type - class used to select the object

Returns:

the current object of the specified type

Throws:

RuntimeException - if no service of that type has been added

pop

<T> T pop(Class<T> type)

Removes and returns the top environmental object of the selected type.

Type Parameters:

T - the type of environmental object

Parameters:

type - class used to select the object

Returns:

the object just removed

Throws:

NoSuchElementException - if the environmental stack (for the specified type) is empty

push

<T> T push(Class<T> type,
           T instance)

Pushes a new service onto the stack. The old service at the top of the stack is returned (it may be null).

Type Parameters:

T - the type of environmental object

Parameters:

type - class used to select the object

instance - the service object

Returns:

the previous top service

clear

void clear()

Deprecated. Deprecated in 5.3 with no replacement.

Clears all stacks; no longer used by Tapestry.

cloak

void cloak()

Hides all current environment values, making the Environment object appear empty, until a call to decloak()} restores the original state.

Since:

5.3

decloak

void decloak()

Restores state previously hidden by cloak()}.

Since:

5.3