com.google.appengine.api.datastore
Enum ImplicitTransactionManagementPolicy
- java.lang.Object
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- java.lang.Enum<ImplicitTransactionManagementPolicy>
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- com.google.appengine.api.datastore.ImplicitTransactionManagementPolicy
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- All Implemented Interfaces:
- java.io.Serializable, java.lang.Comparable<ImplicitTransactionManagementPolicy>
public enum ImplicitTransactionManagementPolicy extends java.lang.Enum<ImplicitTransactionManagementPolicy>
Describes the various policies the datastore can follow for implicit transaction management. When deciding which policy to use, keep the following in mind: The datastore will automatically retry operations that fail due to concurrent updates to the same entity group if the operation is not part of a transaction. The datastore will not retry operations that fail due to concurrent updates to the same entity group if the operation is part of a transaction, and will instead immediately throw aConcurrentModificationException
. If your application needs to perform any sort of intelligent merging when concurrent attempts are made to update the same entity group you probably wantAUTO
, otherwiseNONE
is probably acceptable.See
DatastoreService
for a list of operations that perform implicit transaction management.
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Enum Constant Summary
Enum Constants Enum Constant and Description AUTO
If a current transaction exists, use it, otherwise create one.NONE
If a current transaction exists, use it, otherwise execute without a transaction.
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Method Summary
All Methods Static Methods Concrete Methods Modifier and Type Method and Description static ImplicitTransactionManagementPolicy
valueOf(java.lang.String name)
Returns the enum constant of this type with the specified name.static ImplicitTransactionManagementPolicy[]
values()
Returns an array containing the constants of this enum type, in the order they are declared.
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Enum Constant Detail
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NONE
public static final ImplicitTransactionManagementPolicy NONE
If a current transaction exists, use it, otherwise execute without a transaction.
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AUTO
public static final ImplicitTransactionManagementPolicy AUTO
If a current transaction exists, use it, otherwise create one. The transaction will be committed before the method returns if the datastore operation completes successfully and rolled back if the datastore operation does not complete successfully. No matter the type or quantity of entities provided, only one transaction will be created. This means that if you pass entities that belong to multiple entity groups into one of these methods and you have this policy enabled, you will receive an exception because transactions do not function across entity groups.
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Method Detail
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values
public static ImplicitTransactionManagementPolicy[] values()
Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:for (ImplicitTransactionManagementPolicy c : ImplicitTransactionManagementPolicy.values()) System.out.println(c);
- Returns:
- an array containing the constants of this enum type, in the order they are declared
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valueOf
public static ImplicitTransactionManagementPolicy valueOf(java.lang.String name)
Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)- Parameters:
name
- the name of the enum constant to be returned.- Returns:
- the enum constant with the specified name
- Throws:
java.lang.IllegalArgumentException
- if this enum type has no constant with the specified namejava.lang.NullPointerException
- if the argument is null
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