TxnCounter (Apache Jena ARQ)

java.lang.Object
- org.apache.jena.system.TxnCounter

All Implemented Interfaces:

Transactional
```
public class TxnCounter
extends Object
implements Transactional
```
A MR+SW transactional Counter

Nested Class Summary
- Nested classes/interfaces inherited from interface org.apache.jena.sparql.core.Transactional
  Transactional.Promote

Constructor Summary

Constructors
Constructor and Description

TxnCounter(long x)

Constructors
Constructor and Description
`TxnCounter(long x)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`void`	`abort()` Abort a transaction - finish the transaction and undo any changes (if a "write" transaction)
`void`	`begin(ReadWrite readWrite)` Start either a READ or WRITE transaction.
`void`	`begin(TxnType txnType)` Start a transaction. READ or WRITE transactions start in that state and do not change for the lifetime of the transaction.
`void`	`begin(TxnType txnType, boolean canBlock)`
`void`	`commit()` Commit a transaction - finish the transaction and make any changes permanent (if a "write" transaction)
`void`	`dec()` Decrement the value inside a write transaction
`void`	`end()` Finish the transaction - if a write transaction and commit() has not been called, then abort
`long`	`get()` Return the current value.
`void`	`inc()` Increment the value inside a write transaction
`boolean`	`isInTransaction()` Say whether inside a transaction.
`boolean`	`promote(Transactional.Promote promoteMode)` Attempt to promote a transaction from "read" mode to "write" and the transaction.
`long`	`read()` Return the current value in a transaction.
`long`	`set(long x)` Set the value inside a write transaction, return the old value
`ReadWrite`	`transactionMode()` Return the current mode of the transaction - "read" or "write".
`TxnType`	`transactionType()` Return the transaction type used in `begin(TxnType)`.
`long`	`value()` Read the current global state (that is, the last committed value) outside a transaction.

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

Methods inherited from interface org.apache.jena.sparql.core.Transactional
begin, promote

- Constructor Detail
  - TxnCounter
```
public TxnCounter(long x)
```
- Method Detail
  - begin
```
public void begin(ReadWrite readWrite)
```
    Description copied from interface: Transactional
    
    Start either a READ or WRITE transaction.
    
    Specified by:
    
    begin in interface Transactional
  - begin
```
public void begin(TxnType txnType)
```
    Description copied from interface: Transactional
    Start a transaction.
    READ or WRITE transactions start in that state and do not change for the lifetime of the transaction.
    - WRITE: this guarantees a WRITE will complete if commit() is called. The same as begin(ReadWrite.WRITE).
    - READ: the transaction can not promote to WRITE,ensuring read-only access to the data. The same as begin(ReadWrite.READ).
    - READ_PROMOTE: the transaction will go from "read" to "write" if an update is attempted and if the dataset has not been changed by another write transaction. See also Transactional.promote().
    - READ_COMMITTED_PROMOTE: Use this with care. The promotion will succeed but changes from other transactions become visible.
    Read committed: at the point transaction attempts promotion from "read" to "write", the system checks if the dataset has change since the transaction started (called begin). If READ_PROMOTE, the dataset must not have changed; if READ_COMMITTED_PROMOTE any intermediate changes are visible but the application can not assume any data it has read in the transaction is the same as it was at the point the transaction started.
    This operation is optional and some implementations may throw a JenaTransactionException exception for some or all TxnType values.
    See Transactional.begin(ReadWrite) for a form that is required of implementations.
    Specified by:
    
    begin in interface Transactional
  - begin
```
public void begin(TxnType txnType,
                  boolean canBlock)
```
  - promote
```
public boolean promote(Transactional.Promote promoteMode)
```
    Description copied from interface: Transactional
    
    Attempt to promote a transaction from "read" mode to "write" and the transaction. This method allows the form of promotion to be specified. The transaction must not have been started with READ, which is read-only.
    An argument of READ_PROMOTE treats the promotion as if the transaction was started with READ_PROMOTE (any other writer commiting since the transaction started blocks promotion) and READ_COMMITTED_PROMOTE treats the promotion as if the transaction was started with READ_COMMITTED_PROMOTE (intemediate writer commits become visible).
    Returns "true" if the transaction is in write mode after the call. The method always succeeds of the transaction is already "write".
    This method returns true if a READ_PROMOTE or READ_COMMITTED_PROMOTE is promoted.
    This method returns false if a READ_PROMOTE can't be promoted - the transaction is still valid and in "read" mode.
    This method throws an exception if there is an attempt to promote a READ transaction.
    
    Specified by:
    
    promote in interface Transactional
  - commit
```
public void commit()
```
    Description copied from interface: Transactional
    
    Commit a transaction - finish the transaction and make any changes permanent (if a "write" transaction)
    
    Specified by:
    
    commit in interface Transactional
  - abort
```
public void abort()
```
    Description copied from interface: Transactional
    
    Abort a transaction - finish the transaction and undo any changes (if a "write" transaction)
    
    Specified by:
    
    abort in interface Transactional
  - isInTransaction
```
public boolean isInTransaction()
```
    Description copied from interface: Transactional
    
    Say whether inside a transaction.
    
    Specified by:
    
    isInTransaction in interface Transactional
  - transactionMode
```
public ReadWrite transactionMode()
```
    Description copied from interface: Transactional
    
    Return the current mode of the transaction - "read" or "write". If the caller is not in a transaction, this method returns null.
    
    Specified by:
    
    transactionMode in interface Transactional
  - transactionType
```
public TxnType transactionType()
```
    Description copied from interface: Transactional
    
    Return the transaction type used in begin(TxnType). If the caller is not in a transaction, this method returns null.
    
    Specified by:
    
    transactionType in interface Transactional
  - end
```
public void end()
```
    Description copied from interface: Transactional
    
    Finish the transaction - if a write transaction and commit() has not been called, then abort
    
    Specified by:
    
    end in interface Transactional
  - inc
```
public void inc()
```
    Increment the value inside a write transaction
  - dec
```
public void dec()
```
    Decrement the value inside a write transaction
  - set
```
public long set(long x)
```
    Set the value inside a write transaction, return the old value
  - read
```
public long read()
```
    Return the current value in a transaction. Must be inside a transaction.
    
    See Also:
    
    get()
  - get
```
public long get()
```
    Return the current value. If inside a transaction, return the transaction view of the value. If not in a transaction return the state value (effectively a read transaction, optimized by the fact that reading the TransInteger state is atomic).
  - value
```
public long value()
```
    Read the current global state (that is, the last committed value) outside a transaction.

Class TxnCounter

Nested Class Summary

Nested classes/interfaces inherited from interface org.apache.jena.sparql.core.Transactional

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Methods inherited from interface org.apache.jena.sparql.core.Transactional

Constructor Detail

TxnCounter

Method Detail

begin

begin

begin

promote

commit

abort

isInTransaction

transactionMode

transactionType

end

inc

dec

set

read

get

value