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## javax.jdo
Interface Transaction

    public interface Transaction

The JDO `Transaction` interface provides for initiation and completion of transactions under user control. It is a sub-interface of the `PersistenceManager` that deals with options and transaction demarcation.

Transaction options include whether optimistic concurrency control should be used for the current transaction, whether instances may hold values in the cache outside transactions, and whether values should be retained in the cache after transaction completion. These options are valid for both managed and non-managed transactions.

Transaction initiation and completion methods have similar semantics to `javax.transaction.UserTransaction` when used outside a managed environment. When used in a managed environment, transaction initiation and completion methods may only be used with bean-managed transaction semantics.

Version:
  2.2

Method Summary
`void` | `begin()` Begin a transaction.
`void` | `commit()` Commit the current transaction.
`java.lang.String` | `getIsolationLevel()` Get the value for transaction isolation level for this transaction.
`boolean` | `getNontransactionalRead()` If `true`, allows persistent instances to be read without a transaction active.
`boolean` | `getNontransactionalWrite()` If `true`, allows persistent instances to be written without a transaction active.
`boolean` | `getOptimistic()` Optimistic transactions do not hold data store locks until commit time.
`PersistenceManager` | `getPersistenceManager()` The `Transaction` instance is always associated with exactly one `PersistenceManager`.
`boolean` | `getRestoreValues()` Return the current value of the restoreValues property.
`boolean` | `getRetainValues()` If `true`, at commit time instances retain their field values.
`boolean` | `getRollbackOnly()` Returns the rollback-only status of the transaction.
`Synchronization` | `getSynchronization()` The user-specified `Synchronization` instance for this `Transaction` instance.
`boolean` | `isActive()` Returns whether there is a transaction currently active.
`void` | `rollback()` Roll back the current transaction.
`void` | `setIsolationLevel(java.lang.String level)` Set the value for transaction isolation level for this transaction.
`void` | `setNontransactionalRead(boolean nontransactionalRead)` If `true`, allow persistent instances to be read without a transaction active.
`void` | `setNontransactionalWrite(boolean nontransactionalWrite)` If `true`, allow persistent instances to be written without a transaction active.
`void` | `setOptimistic(boolean optimistic)` Optimistic transactions do not hold data store locks until commit time.
`void` | `setRestoreValues(boolean restoreValues)` If `true`, at rollback, fields of newly persistent instances are restored to their values as of the beginning of the transaction, and the instances revert to transient.
`void` | `setRetainValues(boolean retainValues)` If `true`, at commit instances retain their values and the instances transition to persistent-nontransactional.
`void` | `setRollbackOnly()` Sets the rollback-only status of the transaction to `true`.
`void` | `setSynchronization(Synchronization sync)` The user can specify a `Synchronization` instance to be notified on transaction completions.

Method Detail

### begin

    void begin()

  Begin a transaction. The type of transaction is determined by the setting of the Optimistic flag.

  Throws:
    `JDOUserException` - if transactions are managed by a container in the managed environment, or if the transaction is already active.
  See Also:
    `setOptimistic(boolean)`, `getOptimistic()`

### commit

    void commit()

  Commit the current transaction.

  Throws:
    `JDOUserException` - if transactions are managed by a container in the managed environment, or if the transaction is not active.

### rollback

    void rollback()

  Roll back the current transaction.

  Throws:
    `JDOUserException` - if transactions are managed by a container in the managed environment, or if the transaction is not active.

### isActive

    boolean isActive()

  Returns whether there is a transaction currently active.

  Returns:
    `true` if the transaction is active.

### getRollbackOnly

    boolean getRollbackOnly()

  Returns the rollback-only status of the transaction. When begun, the rollback-only status is false. Either the application or the JDO implementation may set this flag using setRollbackOnly.

  Returns:
    `true` if the transaction has been marked for rollback.
  Since:
    2.0

### setRollbackOnly

    void setRollbackOnly()

  Sets the rollback-only status of the transaction to `true`. After this flag is set to `true`, the transaction can no longer be committed, and any attempt to commit the transaction will throw `JDOFatalDataStoreException`.

  ``
  Since:
    2.0

### setNontransactionalRead

    void setNontransactionalRead(boolean nontransactionalRead)

  If `true`, allow persistent instances to be read without a transaction active. If an implementation does not support this option, a `JDOUnsupportedOptionException` is thrown.

  Parameters:
    `nontransactionalRead` - the value of the nontransactionalRead property

### getNontransactionalRead

    boolean getNontransactionalRead()

  If `true`, allows persistent instances to be read without a transaction active.

  Returns:
    the value of the nontransactionalRead property

### setNontransactionalWrite

    void setNontransactionalWrite(boolean nontransactionalWrite)

  If `true`, allow persistent instances to be written without a transaction active. If an implementation does not support this option, a `JDOUnsupportedOptionException` is thrown.

  Parameters:
    `nontransactionalWrite` - the value of the nontransactionalRead property

### getNontransactionalWrite

    boolean getNontransactionalWrite()

  If `true`, allows persistent instances to be written without a transaction active.

  Returns:
    the value of the nontransactionalWrite property

### setRetainValues

    void setRetainValues(boolean retainValues)

  If `true`, at commit instances retain their values and the instances transition to persistent-nontransactional. If an implementation does not support this option, a `JDOUnsupportedOptionException` is thrown.

  Parameters:
    `retainValues` - the value of the retainValues property

### getRetainValues

    boolean getRetainValues()

  If `true`, at commit time instances retain their field values.

  Returns:
    the value of the retainValues property

### setRestoreValues

    void setRestoreValues(boolean restoreValues)

  If `true`, at rollback, fields of newly persistent instances are restored to their values as of the beginning of the transaction, and the instances revert to transient. Additionally, fields of modified instances of primitive types and immutable reference types are restored to their values as of the beginning of the transaction.

  If `false`, at rollback, the values of fields of newly persistent instances are unchanged and the instances revert to transient. Additionally, dirty instances transition to hollow. If an implementation does not support this option, a `JDOUnsupportedOptionException` is thrown.

  Parameters:
    `restoreValues` - the value of the restoreValues property

### getRestoreValues

    boolean getRestoreValues()

  Return the current value of the restoreValues property.

  Returns:
    the value of the restoreValues property

### setOptimistic

    void setOptimistic(boolean optimistic)

  Optimistic transactions do not hold data store locks until commit time. If an implementation does not support this option, a `JDOUnsupportedOptionException` is thrown.

  Parameters:
    `optimistic` - the value of the Optimistic flag.

### getOptimistic

    boolean getOptimistic()

  Optimistic transactions do not hold data store locks until commit time.

  Returns:
    the value of the Optimistic property.

### getIsolationLevel

    java.lang.String getIsolationLevel()

  Get the value for transaction isolation level for this transaction.

  Returns:
    the transaction isolation level
  Since:
    2.2
  See Also:
    `setIsolationLevel(String)`

### setIsolationLevel

    void setIsolationLevel(java.lang.String level)

  Set the value for transaction isolation level for this transaction. Transaction isolation levels are defined in javax.jdo.Constants. If the requested level is not available, but a higher level is available, the higher level is silently used. If the requested level is not available, and no higher level is available, then JDOUnsupportedOptionException is thrown. Five standard isolation levels are defined. Other isolation levels might be supported by an implementation but are not standard.

  Standard values in order of low to high are:

  - read-uncommitted
  - read-committed
  - repeatable-read
  - snapshot
  - serializable

  Parameters:
    `level` - the transaction isolation level
  Since:
    2.2
  See Also:
    `getIsolationLevel()`, `Constants.TX_READ_UNCOMMITTED`, `Constants.TX_READ_COMMITTED`, `Constants.TX_REPEATABLE_READ`, `Constants.TX_SNAPSHOT`, `Constants.TX_SERIALIZABLE`

### setSynchronization

    void setSynchronization(Synchronization sync)

  The user can specify a `Synchronization` instance to be notified on transaction completions. The `beforeCompletion` method is called prior to flushing instances to the data store.

  The `afterCompletion` method is called after performing state transitions of persistent and transactional instances, following the data store commit or rollback operation.

  Only one `Synchronization` instance can be registered with the `Transaction`. If the application requires more than one instance to receive synchronization callbacks, then the single application instance is responsible for managing them, and forwarding callbacks to them.

  Parameters:
    `sync` - the `Synchronization` instance to be notified; `null` for none

### getSynchronization

    Synchronization getSynchronization()

  The user-specified `Synchronization` instance for this `Transaction` instance.

  Returns:
    the user-specified `Synchronization` instance.

### getPersistenceManager

    PersistenceManager getPersistenceManager()

  The `Transaction` instance is always associated with exactly one `PersistenceManager`.

  Returns:
    the `PersistenceManager` for this `Transaction` instance

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