Class TxnCounter

  • All Implemented Interfaces:
    Transactional

    public class TxnCounter
    extends java.lang.Object
    implements Transactional
    A MR+SW transactional Counter
    • Constructor Summary

      Constructors 
      Constructor Description
      TxnCounter​(long x)  
    • Method Summary

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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
    • Constructor Detail

      • TxnCounter

        public TxnCounter​(long x)
    • Method Detail

      • 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
      • 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.