DrivenValue

Type Parameters:

T - The type of the driven value

All Known Implementing Classes:

AbstractStaticDrivenValue, ExpressionDrivenStringValue, ExpressionDrivenValue, LockGuardedDrivenValue, LockGuardedDrivenValueCollection
```
public interface DrivenValue<T>
```
A DrivenValue contains a value which can change (driven by some source). It has startup() and shutdown() hooks to allow the implementation to prepare / tear down its instance. The value may be fetched by calling getAndClear() which will fetch the current value and reset its dirty state to false. Clients should always startup() before using the instance. Before fetching the latest value, isReady() must be checked and must return true. If isDirty() returns false, the last value fetched is the latest value which will be returned on the next call to getAndClear(). When finished with the instance, shutdown() must be called to clean up.

Method Summary

All Methods Instance Methods Abstract Methods Default Methods
Modifier and Type	Method	Description
`java.util.Optional<T>`	`getAndClear()`	Fetch the current driven value
`boolean`	`isDirty()`
`boolean`	`isReady()`
`default java.util.Collection<PropertyReference>`	`resolveReferences()`	Call before startup() to resolve and collect any references this value might depend on.
`void`	`shutdown()`	Lifecycle hook to shut down the driven value
`void`	`startup()`	Lifecycle hook to start up the driven value

- Method Detail
  - startup
```
void startup()
```
    Lifecycle hook to start up the driven value
  - shutdown
```
void shutdown()
```
    Lifecycle hook to shut down the driven value
  - resolveReferences
```
default java.util.Collection<PropertyReference> resolveReferences()
```
    Call before startup() to resolve and collect any references this value might depend on.
  - isReady
```
boolean isReady()
```
    Returns:
    
    true if the driven value is ready to fetch
  - isDirty
```
boolean isDirty()
```
    Returns:
    
    true if the driven value has changed since the last time it was fetched
  - getAndClear
```
@Nonnull
java.util.Optional<T> getAndClear()
```
    Fetch the current driven value
    
    Returns:
    
    An Optional containing the current driven value, if present, or an empty Optional if the driven value is null / not present.