TransactionalLock (Apache Jena ARQ)

java.lang.Object
- org.apache.jena.sparql.core.TransactionalLock

All Implemented Interfaces:

Transactional

Direct Known Subclasses:

TxnDataset2Graph
```
public class TransactionalLock
extends Object
implements Transactional
```
An implementation of Transactional that provides MRSW locking but no abort. This is often the best you can do for a system that does not itself provide transactions.

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

Method Summary

All Methods Static 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`	`commit()` Commit a transaction - finish the transaction and make any changes permanent (if a "write" transaction)
`static TransactionalLock`	`create(Lock lock)` Create a Transactional using the given lock
`static TransactionalLock`	`createMRPlusSW()` Create a Transactional using a MR+SW (Multiple Reader AND a Single Writer) lock
`static TransactionalLock`	`createMRSW()` Create a Transactional using a MRSW (Multiple Reader OR a Single Writer) lock
`static TransactionalLock`	`createMutex()` Create a Transactional using a mutex (exclusive - one at a time) lock
`void`	`end()` Finish the transaction - if a write transaction and commit() has not been called, then abort
`boolean`	`isInTransaction()` Say whether inside a transaction.
`boolean`	`isTransactionMode(ReadWrite mode)`
`boolean`	`promote(Transactional.Promote txnType)` Attempt to promote a transaction from "read" mode to "write" and the transaction.
`ReadWrite`	`transactionMode()` Return the current mode of the transaction - "read" or "write".
`TxnType`	`transactionType()` Return the transaction type used in `begin(TxnType)`.

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

- Method Detail
  - create
```
public static TransactionalLock create(Lock lock)
```
    Create a Transactional using the given lock
  - createMRPlusSW
```
public static TransactionalLock createMRPlusSW()
```
    Create a Transactional using a MR+SW (Multiple Reader AND a Single Writer) lock
  - createMRSW
```
public static TransactionalLock createMRSW()
```
    Create a Transactional using a MRSW (Multiple Reader OR a Single Writer) lock
  - createMutex
```
public static TransactionalLock createMutex()
```
    Create a Transactional using a mutex (exclusive - one at a time) lock
  - 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
  - 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
  - promote
```
public boolean promote(Transactional.Promote txnType)
```
    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
  - isTransactionMode
```
public boolean isTransactionMode(ReadWrite mode)
```
  - 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

Class TransactionalLock

Nested Class Summary

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

Method Summary

Methods inherited from class java.lang.Object

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

Method Detail

create

createMRPlusSW

createMRSW

createMutex

begin

begin

transactionMode

transactionType

promote

commit

abort

isInTransaction

isTransactionMode

end