UiMessageHandler (ONOS Java API (1.12.0))

java.lang.Object
- org.onosproject.ui.UiMessageHandler

```
public abstract class UiMessageHandler
extends java.lang.Object
```
Abstraction of an entity capable of processing JSON messages from the user interface client.
The message structure is:
```
 {
     "event": "event-type",
     "payload": {
         arbitrary JSON object structure
     }
 }
 
```
On initialization the handler will create and cache RequestHandler instances, each of which are bound to a particular event-type. On arrival of a new message, the event-type is determined, and the message dispatched to the corresponding RequestHandler's process method.
For convenience the implementation includes methods to obtain JSON generating objects (mapper, objectNode, arrayNode) as well as a JsonCodecContext for preparing and digesting messages to the UI client.

Constructor Summary

Constructors
Constructor and Description

UiMessageHandler()

Constructors
Constructor and Description
`UiMessageHandler()`

Method Summary

All Methods Instance Methods Abstract Methods Concrete Methods
Modifier and Type	Method and Description
`protected com.fasterxml.jackson.databind.node.ArrayNode`	`arrayNode()` Returns a freshly minted array node.
`void`	`cacheLionBundle(LionBundle bundle)` Invoked during initialization to cache any requested localization bundles in the handler's context, so that it may subsequently look up localization strings when composing data for the client.
`UiConnection`	`connection()` Returns the user interface connection with which this handler was primed.
`protected abstract java.util.Collection<RequestHandler>`	`createRequestHandlers()` Subclasses must create and return the collection of request handlers for the message types they handle.
`void`	`destroy()` Destroys the message handler context.
`ServiceDirectory`	`directory()` Returns the service directory with which this handler was primed.
`protected <T> T`	`get(java.lang.Class<T> serviceClass)` Returns an implementation of the specified service class.
`protected CodecContext`	`getJsonCodecContext()` Obtain a CodecContext to be used in encoding and decoding objects that have a registered JsonCodec for their class.
`protected LionBundle`	`getLionBundle(java.lang.String id)` Returns the localization bundle with the given identifier, if we requested to have it cached during initialization; null otherwise.
`void`	`init(UiConnection connection, ServiceDirectory directory)` Initializes the handler with the user interface connection and service directory context.
`java.util.Set<java.lang.String>`	`messageTypes()` Returns the set of message types which this handler is capable of processing.
`protected com.fasterxml.jackson.databind.node.ObjectNode`	`objectNode()` Returns a freshly minted object node.
`void`	`process(com.fasterxml.jackson.databind.node.ObjectNode message)` Processes a JSON message from the user interface client.
`java.util.Set<java.lang.String>`	`requiredLionBundles()` Returns the set of identifiers for localization bundles that the message handler would like injected into itself, so that it can use those bundles in composing localized data to ship to the client.
`protected void`	`sendMessage(com.fasterxml.jackson.databind.node.ObjectNode data)` Sends the specified data to the client.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Constructor Detail
  - UiMessageHandler
```
public UiMessageHandler()
```
- Method Detail
  - createRequestHandlers
```
protected abstract java.util.Collection<RequestHandler> createRequestHandlers()
```
    Subclasses must create and return the collection of request handlers for the message types they handle.
    Note that request handlers should be stateless. When we are destroyed, we will simply drop our references to them and allow them to be garbage collected.
    
    Returns:
    
    the message handler instances
  - messageTypes
```
public java.util.Set<java.lang.String> messageTypes()
```
    Returns the set of message types which this handler is capable of processing.
    
    Returns:
    
    set of message types
  - process
```
public void process(com.fasterxml.jackson.databind.node.ObjectNode message)
```
    Processes a JSON message from the user interface client.
    
    Parameters:
    
    message - JSON message
  - init
```
public void init(UiConnection connection,
                 ServiceDirectory directory)
```
    Initializes the handler with the user interface connection and service directory context.
    
    Parameters:
    
    connection - user interface connection
    
    directory - service directory
  - destroy
```
public void destroy()
```
    Destroys the message handler context.
  - connection
```
public UiConnection connection()
```
    Returns the user interface connection with which this handler was primed.
    
    Returns:
    
    user interface connection
  - directory
```
public ServiceDirectory directory()
```
    Returns the service directory with which this handler was primed.
    
    Returns:
    
    service directory
  - get
```
protected <T> T get(java.lang.Class<T> serviceClass)
```
    Returns an implementation of the specified service class.
    
    Type Parameters:
    
    T - type of service
    
    Parameters:
    
    serviceClass - service class
    
    Returns:
    
    implementation class
    
    Throws:
    
    ServiceNotFoundException - if no implementation found
  - requiredLionBundles
```
public java.util.Set<java.lang.String> requiredLionBundles()
```
    Returns the set of identifiers for localization bundles that the message handler would like injected into itself, so that it can use those bundles in composing localized data to ship to the client.
    This default implementation returns an empty set.
    Subclasses that wish to have localization bundles injected should override this method and return the set of bundle identifiers.
    
    Returns:
    
    the set of identifiers of required localization bundles
  - cacheLionBundle
```
public void cacheLionBundle(LionBundle bundle)
```
    Invoked during initialization to cache any requested localization bundles in the handler's context, so that it may subsequently look up localization strings when composing data for the client.
    
    Parameters:
    
    bundle - the bundle to cache
  - getLionBundle
```
protected LionBundle getLionBundle(java.lang.String id)
```
    Returns the localization bundle with the given identifier, if we requested to have it cached during initialization; null otherwise.
    
    Parameters:
    
    id - the lion bundle identifier
    
    Returns:
    
    the associated lion bundle
  - objectNode
```
protected com.fasterxml.jackson.databind.node.ObjectNode objectNode()
```
    Returns a freshly minted object node.
    
    Returns:
    
    new object node
  - arrayNode
```
protected com.fasterxml.jackson.databind.node.ArrayNode arrayNode()
```
    Returns a freshly minted array node.
    
    Returns:
    
    new array node
  - sendMessage
```
protected void sendMessage(com.fasterxml.jackson.databind.node.ObjectNode data)
```
    Sends the specified data to the client. It is expected that the data is in the prescribed JSON format for events to the client.
    
    Parameters:
    
    data - data to be sent
  - getJsonCodecContext
```
protected CodecContext getJsonCodecContext()
```
    Obtain a CodecContext to be used in encoding and decoding objects that have a registered JsonCodec for their class. This method instantiates a private inner class which is returned on subsequent calls.
    
    Returns:
    
    a CodecContext.

Class UiMessageHandler

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

UiMessageHandler

Method Detail

createRequestHandlers

messageTypes

process

init

destroy

connection

directory

get

requiredLionBundles

cacheLionBundle

getLionBundle

objectNode

arrayNode

sendMessage

getJsonCodecContext