Package org.jgrapes.util

Class JsonConfigurationStore

java.lang.Object

org.jgrapes.core.internal.ComponentVertex

org.jgrapes.core.Component

org.jgrapes.util.JsonConfigurationStore

All Implemented Interfaces:

Iterable<ComponentType>, Channel, ComponentType, Eligible, Manager

public class JsonConfigurationStore
extends Component

This component provides a store for an application’s configuration backed by a JSON file.

The JSON object described by this file represents the root directory. If an entry does not start with a slash, it represents the key of a key value pair. If it does starts with a slash, the value is another JSON object that describes the respective subdirectory.

The component reads the initial values from File passed to the constructor. During application bootstrap, it intercepts the Start event using a handler with priority 999999. When receiving this event, it fires all known preferences values on the channels of the start event as a InitialPreferences event, using a new EventPipeline and waiting for its completion. Then, allows the intercepted Start event to continue.

Components that depend on configuration values define handlers for ConfigurationUpdate events and adapt themselves to the values received. Note that due to the intercepted Start event, the initial preferences values are received before the Start event, so components’ configurations can be rearranged before they actually start doing something.

Besides initially publishing the stored preferences values, the component also listens for ConfigurationUpdate events on its channel and updates the JSON file (may be suppressed).

Nested Class Summary

Nested classes/interfaces inherited from interface org.jgrapes.core.Channel

Channel.Default

Field Summary

Fields inherited from interface org.jgrapes.core.Channel

BROADCAST, SELF

Constructor Summary

Constructors

Constructor	Description
JsonConfigurationStore(Channel componentChannel, File file)	Creates a new component with its channel set to the given channel and the given file.
JsonConfigurationStore(Channel componentChannel, File file, boolean update)	Creates a new component with its channel set to the given channel and the given file.

Method Summary

Modifier and Type	Method	Description
void	onConfigurationUpdate(ConfigurationUpdate event)	Merges and saves configuration updates.
void	onStart(Start event)	Intercepts the Start event and fires a ConfigurationUpdate event.

Methods inherited from class org.jgrapes.core.Component

channel, component, defaultCriterion, isEligibleFor, setName

Methods inherited from class org.jgrapes.core.internal.ComponentVertex

activeEventPipeline, addHandler, attach, children, componentPath, componentVertex, detach, fire, initComponentsHandlers, iterator, name, newEventPipeline, newEventPipeline, parent, registerAsGenerator, root, toString, unregisterAsGenerator

Methods inherited from class java.lang.Object

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

Methods inherited from interface java.lang.Iterable

forEach, spliterator

Methods inherited from interface org.jgrapes.core.Manager

stream

Constructor Details

JsonConfigurationStore

public JsonConfigurationStore(Channel componentChannel,
 File file)
                       throws IOException

Creates a new component with its channel set to the given channel and the given file.

Parameters:

componentChannel - the channel

file - the file used to store the JSON

Throws:

org.jdrupes.json.JsonDecodeException

IOException

JsonConfigurationStore

public JsonConfigurationStore(Channel componentChannel,
 File file,
 boolean update)
                       throws IOException

Creates a new component with its channel set to the given channel and the given file.

Parameters:

componentChannel - the channel

file - the file used to store the JSON

Throws:

org.jdrupes.json.JsonDecodeException

IOException

Method Details

onStart

@Handler(priority=999999,
         channels=Channel.class)
public void onStart(Start event)
             throws BackingStoreException,
InterruptedException

Intercepts the Start event and fires a ConfigurationUpdate event.

Parameters:

event - the event

Throws:

BackingStoreException - the backing store exception

InterruptedException - the interrupted exception

onConfigurationUpdate

@Handler(dynamic=true)
public void onConfigurationUpdate(ConfigurationUpdate event)
                           throws IOException

Merges and saves configuration updates.

Parameters:

event - the event

Throws:

IOException - Signals that an I/O exception has occurred.