org.hawkular.bus.common

Class AbstractMessage

java.lang.Object

org.hawkular.bus.common.AbstractMessage

All Implemented Interfaces:

BasicMessage

Direct Known Subclasses:

ObjectMessage, SimpleBasicMessage

public abstract class AbstractMessage
extends Object
implements BasicMessage

Basic information that is sent over the message bus. The message ID is assigned by the messaging framework and so typically is not explicitly set. The correlation ID is a message ID of another message that was sent previously. This is usually left unset unless this message needs to be correlated with another. As an example, when a process is stopped, you can correlate the "Stopped" event with the "Stopping" event so you can later determine how long it took for the process to stop. The headers are normally those out-of-band properties that are sent with the message.

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	AbstractMessage()

Method Summary

Modifier and Type	Method and Description
protected static com.fasterxml.jackson.databind.ObjectMapper	buildObjectMapperForDeserialization() This is static, so really there is no true overriding it in subclasses.
protected com.fasterxml.jackson.databind.ObjectMapper	buildObjectMapperForSerialization()
static <T extends BasicMessage> BasicMessageWithExtraData<T>	fromJSON(InputStream in, Class<T> clazz) Convenience static method that reads a JSON string from the given stream and converts the JSON string to a particular message object.
static <T extends BasicMessage> T	fromJSON(String json, Class<T> clazz) Convenience static method that converts a JSON string to a particular message object.
MessageId	getCorrelationId() If this message is correlated with another message, this will be that other message's ID.
Map<String,String>	getHeaders() The headers that were shipped along side of the message when the message was received.
MessageId	getMessageId() Returns the message ID that was assigned to this message by the messaging infrastructure.
void	setCorrelationId(MessageId correlationId)
void	setHeaders(Map<String,String> headers) Sets headers that will be sent with the message when the message gets delivered.
void	setMessageId(MessageId messageId)
String	toJSON() Converts this message to its JSON string representation.
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

AbstractMessage

protected AbstractMessage()

Method Detail

fromJSON

public static <T extends BasicMessage> T fromJSON(String json,
                                                  Class<T> clazz)

Convenience static method that converts a JSON string to a particular message object.

Parameters:

json - the JSON string

clazz - the class whose instance is represented by the JSON string

Returns:

the message object that was represented by the JSON string

fromJSON

public static <T extends BasicMessage> BasicMessageWithExtraData<T> fromJSON(InputStream in,
                                                                             Class<T> clazz)

Convenience static method that reads a JSON string from the given stream and converts the JSON string to a particular message object. The input stream will remain open so the caller can stream any extra data that might appear after it. Because of the way the JSON parser works, some extra data might have been read from the stream that wasn't part of the JSON message but was part of the extra data that came with it. Because of this, the caller should no longer use the given stream but instead read the extra data via the returned object (see BasicMessageWithExtraData.getBinaryData()) since it will handle this condition properly.

Parameters:

in - input stream that has a JSON string at the head.

clazz - the class whose instance is represented by the JSON string

Returns:

a POJO that contains a message object that was represented by the JSON string found in the stream. This returned POJO will also contain a BinaryData object that you can use to stream any additional data that came in the given input stream.

buildObjectMapperForDeserialization

protected static com.fasterxml.jackson.databind.ObjectMapper buildObjectMapperForDeserialization()

This is static, so really there is no true overriding it in subclasses. However, fromJSON will do the proper reflection in order to invoke the proper method for the class that is being deserialized. So subclasses that want to provide their own ObjectMapper will define their own method that matches the signature of this method and it will be used.

Returns:

object mapper to be used for deserializing JSON.

toJSON

public String toJSON()

Converts this message to its JSON string representation.

Specified by:

toJSON in interface BasicMessage

Returns:

JSON encoded data that represents this message.

buildObjectMapperForSerialization

protected com.fasterxml.jackson.databind.ObjectMapper buildObjectMapperForSerialization()

Returns:

object mapper to be used to serialize a message to JSON

getMessageId

public MessageId getMessageId()

Returns the message ID that was assigned to this message by the messaging infrastructure. This could be null if the message has not been sent yet.

Specified by:

getMessageId in interface BasicMessage

Returns:

message ID assigned to this message by the messaging framework

setMessageId

public void setMessageId(MessageId messageId)

Specified by:

setMessageId in interface BasicMessage

getCorrelationId

public MessageId getCorrelationId()

If this message is correlated with another message, this will be that other message's ID. This could be null if the message is not correlated with another message.

Specified by:

getCorrelationId in interface BasicMessage

Returns:

the message ID of the correlated message

setCorrelationId

public void setCorrelationId(MessageId correlationId)

Specified by:

setCorrelationId in interface BasicMessage

getHeaders

public Map<String,String> getHeaders()

The headers that were shipped along side of the message when the message was received. The returned map is an unmodifiable read-only view of the properties. Will never return null but may return an empty map.

Specified by:

getHeaders in interface BasicMessage

Returns:

a read-only view of the name/value properties that came with the message as separate headers.

setHeaders

public void setHeaders(Map<String,String> headers)

Sets headers that will be sent with the message when the message gets delivered. This completely replaces any existing headers already associated with this message. Note that the given name/value pairs will be copied to an internal map. If the given map is null or empty, this message's internal map will be destroyed and getHeaders() will return an empty map. Note that the header values are all expected to be strings.

Specified by:

setHeaders in interface BasicMessage

Parameters:

headers - name/value properties

toString

public String toString()

Overrides:

toString in class Object