io.openmessaging

Interface Message

All Known Subinterfaces:

BytesMessage

public interface Message

The Message interface is the root interface of all OMS messages, and the most commonly used OMS message is BytesMessage.

Most message-oriented middleware (MOM) products treat messages as lightweight entities that consist of header and body and is used by separate applications to exchange a piece of information, like Apache RocketMQ.

The header contains fields used by the messaging system that describes the message's meta information, like QoS level, origin, destination, and so on, while the body contains the application data being transmitted.

As for the header, OMS defines two kinds types: System Header and User Header, with respect to flexibility in vendor implementation and user usage.

• System Header, OMS defines some standard attributes that represent the characteristics of the message.
• User Header, some OMS vendors may require enhanced extra attributes of the message or some users may want to clarify some customized attributes to draw the body. OMS provides the improved scalability for these scenarios.

The body contains the application data being transmitted, which is generally ignored by the messaging system and simply transmitted to its destination.

In BytesMessage, the body is just a byte array, may be compressed and uncompressed in the transmitting process by the messaging system. The application is responsible for explaining the concrete content and format of the message body, OMS is never aware of that. The body part is placed in the implementation classes of Message.

Since:

OMS 1.0.0

Version:

OMS 1.0.0

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static interface	Message.BuiltinKeys

Method Summary

Modifier and Type	Method and Description
<T> T	getBody(Class<T> type) Get message body
Message	putSysHeaders(String key, double value) Puts a String-double KeyValue entry to the system headers of a Message.
Message	putSysHeaders(String key, int value) Puts a String-int KeyValue entry to the system headers of a Message.
Message	putSysHeaders(String key, long value) Puts a String-long KeyValue entry to the system headers of a Message.
Message	putSysHeaders(String key, String value) Puts a String-String KeyValue entry to the system headers of a Message.
Message	putUserHeaders(String key, double value) Puts a String-double KeyValue entry to the user headers of a Message.
Message	putUserHeaders(String key, int value) Puts a String-int KeyValue entry to the user headers of a Message.
Message	putUserHeaders(String key, long value) Puts a String-long KeyValue entry to the user headers of a Message.
Message	putUserHeaders(String key, String value) Puts a String-String KeyValue entry to the user headers of a Message.
KeyValue	sysHeaders() Returns all the system header fields of the Message object as a KeyValue.
KeyValue	userHeaders() Returns all the customized user header fields of the Message object as a KeyValue.

Method Detail

sysHeaders

KeyValue sysHeaders()

Returns all the system header fields of the Message object as a KeyValue.

Returns:

the system headers of a Message

See Also:

Message.BuiltinKeys

userHeaders

KeyValue userHeaders()

Returns all the customized user header fields of the Message object as a KeyValue.

Returns:

the user headers of a Message

putSysHeaders

Message putSysHeaders(String key,
                      int value)

Puts a String-int KeyValue entry to the system headers of a Message.

Parameters:

key - the key to be placed into the system headers

value - the value corresponding to key

putSysHeaders

Message putSysHeaders(String key,
                      long value)

Puts a String-long KeyValue entry to the system headers of a Message.

Parameters:

key - the key to be placed into the system headers

value - the value corresponding to key

putSysHeaders

Message putSysHeaders(String key,
                      double value)

Puts a String-double KeyValue entry to the system headers of a Message.

Parameters:

key - the key to be placed into the system headers

value - the value corresponding to key

putSysHeaders

Message putSysHeaders(String key,
                      String value)

Puts a String-String KeyValue entry to the system headers of a Message.

Parameters:

key - the key to be placed into the system headers

value - the value corresponding to key

putUserHeaders

Message putUserHeaders(String key,
                       int value)

Puts a String-int KeyValue entry to the user headers of a Message.

Parameters:

key - the key to be placed into the user headers

value - the value corresponding to key

putUserHeaders

Message putUserHeaders(String key,
                       long value)

Puts a String-long KeyValue entry to the user headers of a Message.

Parameters:

key - the key to be placed into the user headers

value - the value corresponding to key

putUserHeaders

Message putUserHeaders(String key,
                       double value)

Puts a String-double KeyValue entry to the user headers of a Message.

Parameters:

key - the key to be placed into the user headers

value - the value corresponding to key

putUserHeaders

Message putUserHeaders(String key,
                       String value)

Puts a String-String KeyValue entry to the user headers of a Message.

Parameters:

key - the key to be placed into the user headers

value - the value corresponding to key

getBody

<T> T getBody(Class<T> type)
       throws OMSMessageFormatException

Get message body

Type Parameters:

T - Generic type

Parameters:

type - Message body type

Returns:

message body

Throws:

OMSMessageFormatException - if the message body cannot be assigned to the specified type