Hello Ivanceras,
Data type for primary keys (PKs)
--------------------------------
When I use Key as Encoded String for my PKs, the data type of the PK
is java.lang.String! I give a snippet below to demonstrate this for
me:
@PersistenceCapable(identityType = IdentityType.APPLICATION,
detachable = "true")
public class NoticePageHome implements Serializable
{
private static final long serialVersionUID = 1L;
/*
//////////////////////////////////////////////////////////////////////////////
// This block is required since this entity has an entity group
root.
// It does not work with MySQL, so we use an alternative for that
database.
// We have the getter method for getting the encoded key here for
convenience.
//
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
@Extension(vendorName="datanucleus", key="gae.encoded-pk",
value="true")
private String sEncodedKey;
@Persistent
@Extension(vendorName="datanucleus", key="gae.pk-id", value="true")
private Long loID;
public String getEncodedKey()
{
return sEncodedKey;
}
//
//////////////////////////////////////////////////////////////////////////////
*/
//////////////////////////////////////////////////////////////////////////////
// This block is required for MySQL only, and will not work
// for Google BigTable.
//
@PrimaryKey
@Persistent(valueStrategy = IdGeneratorStrategy.IDENTITY)
private Long loID;
//
//////////////////////////////////////////////////////////////////////////////
/*
Data fields, getters and setters...
*/
Please note:
1. I switch PK blocks depending on whether I am using GAE or MySQL.
2. Using GAE (with Key as Encoded String), I have both the String
encoded key and the Long ID produced automatically by GAE.
3. I trust that this PK method would be easily portable to non-GAE
datastores, should the need ever arise in the future.
I would prefer to use BigTable as much as possible, but I need to use
MySQL when running my Apache Wicket web app in development mode, which
is useful to catch silly mark-up mismatch bugs, amongst others.
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