ExtensionHeader (openmessaging 1.0.0-beta-SNAPSHOT API)

```
@Optional
public interface ExtensionHeader
```
The ExtensionHeader interface contains extended properties for common implementations in current messaging and streaming field, such as the queue-based partitioning implementation, but the related properties in this interface are not mandatory.

Since:

OMS 1.0.0

Version:

OMS 1.0.0

Method Summary

All Methods Instance Methods Abstract Methods
Modifier and Type	Method and Description
`String`	`getCorrelationId()` See `setCorrelationId(String)`
`long`	`getDelayTime()` See `setDelayTime(long)`
`long`	`getExpireTime()` See `setExpireTime(long)`
`String`	`getMessageKey()` See `setMessageKey(String)`
`long`	`getOffset()` This method will return the `OFFSET` in the partition to which the message belongs to, but the premise is that the implementation of the server side is dependent on the partition or a queue-like storage mechanism.
`int`	`getPartiton()` This method will return the partition of this message belongs.
`String`	`getStoreHost()` See `setStoreHost(String)`
`long`	`getStoreTimestamp()` See `setStoreTimestamp(long)`
`String`	`getTraceId()` See `setTraceId(String)`
`String`	`getTransactionId()` See `setTransactionId(String)`
`ExtensionHeader`	`setCorrelationId(String correlationId)` A client can use the `CORRELATION_ID` field to link one message with another.
`ExtensionHeader`	`setDelayTime(long delayTime)` The `DELAY_TIME` header field contains a number that represents the delayed times in milliseconds.
`ExtensionHeader`	`setExpireTime(long expireTime)` The `EXPIRE_TIME` header field contains the expiration time, it represents a time-to-live value.
`ExtensionHeader`	`setMessageKey(String messageKey)` The `messagekey` header field contains the custom key of a message.
`ExtensionHeader`	`setOffset(long offset)` This method is only called by the server.
`ExtensionHeader`	`setPartition(int partition)` The `PARTITION` in extension header field contains the partition of target destination which the message is being sent.
`ExtensionHeader`	`setStoreHost(String storeHost)` The `STORE_HOST` header field contains the store host info of a message in server side.
`ExtensionHeader`	`setStoreTimestamp(long storeTimestamp)` The `STORE_TIMESTAMP` header field contains the store timestamp of a message in server side.
`ExtensionHeader`	`setTraceId(String traceId)` The `TRACE_ID` header field contains the trace ID of a message, which represents a global and unique identification, to associate key events in the whole lifecycle of a message, like sent by who, stored at where, and received by who.
`ExtensionHeader`	`setTransactionId(String transactionId)` This field `TRANSACTION_ID` is used in transactional message, and it can be used to trace a transaction.

- Method Detail
  - setPartition
```
ExtensionHeader setPartition(int partition)
```
    The PARTITION in extension header field contains the partition of target destination which the message is being sent.
    When a Message is set with this value, this message will be delivered to specified partition, but the premise is that the implementation of the server side is dependent on the partition or a queue-like storage mechanism.
    
    Parameters:
    
    partition - The specified partition will be sent to.
  - setOffset
```
ExtensionHeader setOffset(long offset)
```
    This method is only called by the server. and OFFSET represents this message offset in partition.
    
    Parameters:
    
    offset - The offset in the current partition, used to quickly get this message in the queue
  - setCorrelationId
```
ExtensionHeader setCorrelationId(String correlationId)
```
    A client can use the CORRELATION_ID field to link one message with another. A typical use is to link a response message with its request message.
  - setTransactionId
```
ExtensionHeader setTransactionId(String transactionId)
```
    This field TRANSACTION_ID is used in transactional message, and it can be used to trace a transaction.
    So the same TRANSACTION_ID will be appeared not only in prepare message, but also in commit message, and consumer received message also contains this field.
  - setStoreTimestamp
```
ExtensionHeader setStoreTimestamp(long storeTimestamp)
```
    The STORE_TIMESTAMP header field contains the store timestamp of a message in server side.
    When a message is sent, STORE_TIMESTAMP is ignored.
    When the send method returns it contains a server-assigned value.
    This filed is a long value, measured in milliseconds.
  - setStoreHost
```
ExtensionHeader setStoreHost(String storeHost)
```
    The STORE_HOST header field contains the store host info of a message in server side.
    When a message is sent, STORE_HOST is ignored.
    When the send method returns it contains a server-assigned value.
  - setMessageKey
```
ExtensionHeader setMessageKey(String messageKey)
```
    The messagekey header field contains the custom key of a message.
    This key is a customer identifier for a class of messages, and this key may be used for server to hash or dispatch messages, or even can use this key to implement order message.
  - setTraceId
```
ExtensionHeader setTraceId(String traceId)
```
    The TRACE_ID header field contains the trace ID of a message, which represents a global and unique identification, to associate key events in the whole lifecycle of a message, like sent by who, stored at where, and received by who.
    And, the messaging system only plays exchange role in a distributed system in most cases, so the TraceID can be used to trace the whole call link with other parts in the whole system.
  - setDelayTime
```
ExtensionHeader setDelayTime(long delayTime)
```
    The DELAY_TIME header field contains a number that represents the delayed times in milliseconds.
    The message will be delivered after delayTime milliseconds starting from BORN_TIMESTAMP . When this filed isn't set explicitly, this means this message should be delivered immediately.
  - setExpireTime
```
ExtensionHeader setExpireTime(long expireTime)
```
    The EXPIRE_TIME header field contains the expiration time, it represents a time-to-live value.
    The EXPIRE_TIME represents a relative valid interval that a message can be delivered in it. If the EXPIRE_TIME field is specified as zero, that indicates the message does not expire.
    
    When an undelivered message's expiration time is reached, the message should be destroyed. OMS does not define a notification of message expiration.
  - getPartiton
```
int getPartiton()
```
    This method will return the partition of this message belongs.
    
    Returns:
    
    The PARTITION to which the message belongs
  - getOffset
```
long getOffset()
```
    This method will return the OFFSET in the partition to which the message belongs to, but the premise is that the implementation of the server side is dependent on the partition or a queue-like storage mechanism.
    
    Returns:
    
    The offset of the partition to which the message belongs.
  - getCorrelationId
```
String getCorrelationId()
```
    See setCorrelationId(String)
    
    Returns:
    
    correlationId
  - getTransactionId
```
String getTransactionId()
```
    See setTransactionId(String)
    
    Returns:
    
    transactionId
  - getStoreTimestamp
```
long getStoreTimestamp()
```
    See setStoreTimestamp(long)
    
    Returns:
    
    storeTimestamp
  - getStoreHost
```
String getStoreHost()
```
    See setStoreHost(String)
    
    Returns:
    
    storeHost
  - getDelayTime
```
long getDelayTime()
```
    See setDelayTime(long)
    
    Returns:
    
    delayTime
  - getExpireTime
```
long getExpireTime()
```
    See setExpireTime(long)
    
    Returns:
    
    expireTime
  - getMessageKey
```
String getMessageKey()
```
    See setMessageKey(String)
    
    Returns:
    
    messageKey
  - getTraceId
```
String getTraceId()
```
    See setTraceId(String)
    
    Returns:
    
    traceId

Interface ExtensionHeader

Method Summary

Method Detail

setPartition

setOffset

setCorrelationId

setTransactionId

setStoreTimestamp

setStoreHost

setMessageKey

setTraceId

setDelayTime

setExpireTime

getPartiton

getOffset

getCorrelationId

getTransactionId

getStoreTimestamp

getStoreHost

getDelayTime

getExpireTime

getMessageKey

getTraceId