com.sleepycat.persist
Class PrimaryIndex<PK,E>

java.lang.Object
  extended by com.sleepycat.persist.BasicIndex<PK,E>
      extended by com.sleepycat.persist.PrimaryIndex<PK,E>
All Implemented Interfaces:
EntityIndex<PK,E>

public class PrimaryIndex<PK,E>
extends BasicIndex<PK,E>

The primary index for an entity class and its primary key.

PrimaryIndex objects are thread-safe. Multiple threads may safely call the methods of a shared PrimaryIndex object.

PrimaryIndex implements EntityIndex to map the primary key type (PK) to the entity type (E).

The Entity annotation may be used to define an entity class and the PrimaryKey annotation may be used to define a primary key as shown in the following example.

 @Entity
 class Employee {

     @PrimaryKey
     long id;

     String name;

     Employee(long id, String name) {
         this.id = id;
         this.name = name;
     }

     private Employee() {} // For bindings
 }

To obtain the PrimaryIndex for a given entity class, call EntityStore.getPrimaryIndex, passing the primary key class and the entity class. For example:

 EntityStore store = new EntityStore(...);

 PrimaryIndex<Long, Employee> primaryIndex =
     store.getPrimaryIndex(Long.class, Employee.class);

Note that Long.class is passed as the primary key class, but the primary key field has the primitive type long. When a primitive primary key field is used, the corresponding primitive wrapper class is used to access the primary index. For more information on key field types, see PrimaryKey.

The PrimaryIndex provides the primary storage and access methods for the instances of a particular entity class. Entities are inserted and updated in the PrimaryIndex by calling a method in the family of put(E) methods. The put(E) method will insert the entity if no entity with the same primary key already exists. If an entity with the same primary key does exist, it will update the entity and return the existing (old) entity. For example:

 Employee oldEntity;
 oldEntity = primaryIndex.put(new Employee(1, "Jane Smith"));    // Inserts an entity
 assert oldEntity == null;
 oldEntity = primaryIndex.put(new Employee(2, "Joan Smith"));    // Inserts an entity
 assert oldEntity == null;
 oldEntity = primaryIndex.put(new Employee(2, "Joan M. Smith")); // Updates an entity
 assert oldEntity != null;

The putNoReturn(E) method can be used to avoid the overhead of returning the existing entity, when the existing entity is not important to the application. The return type of putNoReturn(E) is void. For example:

 primaryIndex.putNoReturn(new Employee(1, "Jane Smith"));    // Inserts an entity
 primaryIndex.putNoReturn(new Employee(2, "Joan Smith"));    // Inserts an entity
 primaryIndex.putNoReturn(new Employee(2, "Joan M. Smith")); // Updates an entity

The putNoOverwrite(E) method can be used to ensure that an existing entity is not overwritten. putNoOverwrite(E) returns true if the entity was inserted, or false if an existing entity exists and no action was taken. For example:

 boolean inserted;
 inserted = primaryIndex.putNoOverwrite(new Employee(1, "Jane Smith"));    // Inserts an entity
 assert inserted;
 inserted = primaryIndex.putNoOverwrite(new Employee(2, "Joan Smith"));    // Inserts an entity
 assert inserted;
 inserted = primaryIndex.putNoOverwrite(new Employee(2, "Joan M. Smith")); // No action was taken!
 assert !inserted;

Primary key values must be unique, in other words, each instance of a given entity class must have a distinct primary key value. Rather than assigning the unique primary key values yourself, a sequence can be used to assign sequential integer values automatically, starting with the value 1 (one). A sequence is defined using the PrimaryKey.sequence() annotation property. For example:

 @Entity
 class Employee {

     @PrimaryKey(sequence="ID")
     long id;

     String name;

     Employee(String name) {
         this.name = name;
     }

     private Employee() {} // For bindings
 }

The name of the sequence used above is "ID". Any name can be used. If the same sequence name is used in more than one entity class, the sequence will be shared by those classes, in other words, a single sequence of integers will be used for all instances of those classes. See PrimaryKey.sequence() for more information.

Any method in the family of put(E) methods may be used to insert entities where the primary key is assigned from a sequence. When the put(E) method returns, the primary key field of the entity object will be set to the assigned key value. For example:

 Employee employee;
 employee = new Employee("Jane Smith");
 primaryIndex.putNoReturn(employee);    // Inserts an entity
 assert employee.id == 1;
 employee = new Employee("Joan Smith");
 primaryIndex.putNoReturn(employee);    // Inserts an entity
 assert employee.id == 2;

This begs the question: How do you update an existing entity, without assigning a new primary key? The answer is that the put(E) methods will only assign a new key from the sequence if the primary key field is zero or null (for reference types). If an entity with a non-zero and non-null key field is passed to a put(E) method, any existing entity with that primary key value will be updated. For example:

 Employee employee;
 employee = new Employee("Jane Smith");
 primaryIndex.putNoReturn(employee);    // Inserts an entity
 assert employee.id == 1;
 employee = new Employee("Joan Smith");
 primaryIndex.putNoReturn(employee);    // Inserts an entity
 assert employee.id == 2;
 employee.name = "Joan M. Smith";
 primaryIndex.putNoReturn(employee);    // Updates an existing entity
 assert employee.id == 2;

Since PrimaryIndex implements the EntityIndex interface, it shares the common index methods for retrieving and deleting entities, opening cursors and using transactions. See EntityIndex for more information on these topics.

Note that when using an index, keys and values are stored and retrieved by value not by reference. In other words, if an entity object is stored and then retrieved, or retrieved twice, each object will be a separate instance. For example, in the code below the assertion will always fail.

 MyKey key = ...;
 MyEntity entity1 = new MyEntity(key, ...);
 index.put(entity1);
 MyEntity entity2 = index.get(key);
 assert entity1 == entity2; // always fails!
 

Author:
Mark Hayes

Field Summary
 
Fields inherited from class com.sleepycat.persist.BasicIndex
db, emptyRange, entityAdapter, keyAdapter, keyBinding, keyClass, locking, NO_RETURN_ENTRY, sortedDups, transactional
 
Constructor Summary
PrimaryIndex(Database database, Class<PK> keyClass, EntryBinding<PK> keyBinding, Class<E> entityClass, EntityBinding<E> entityBinding)
          Creates a primary index without using an EntityStore.
 
Method Summary
 E get(PK key)
          Gets an entity via a key of this index.
 E get(Transaction txn, PK key, LockMode lockMode)
          Gets an entity via a key of this index.
 Database getDatabase()
          Returns the underlying database for this index.
 EntityBinding<E> getEntityBinding()
          Returns the entity binding for this index.
 Class<E> getEntityClass()
          Returns the entity class for this index.
 EntryBinding<PK> getKeyBinding()
          Returns the primary key binding for this index.
 Class<PK> getKeyClass()
          Returns the primary key class for this index.
(package private)  boolean isUpdateAllowed()
           
 Map<PK,E> map()
          Returns a standard Java map based on this entity index.
 E put(E entity)
          Inserts an entity and returns null, or updates it if the primary key already exists and returns the existing entity.
 E put(Transaction txn, E entity)
          Inserts an entity and returns null, or updates it if the primary key already exists and returns the existing entity.
 boolean putNoOverwrite(E entity)
          Inserts an entity and returns true, or returns false if the primary key already exists.
 boolean putNoOverwrite(Transaction txn, E entity)
          Inserts an entity and returns true, or returns false if the primary key already exists.
 void putNoReturn(E entity)
          Inserts an entity, or updates it if the primary key already exists (does not return the existing entity).
 void putNoReturn(Transaction txn, E entity)
          Inserts an entity, or updates it if the primary key already exists (does not return the existing entity).
 SortedMap<PK,E> sortedMap()
          Returns a standard Java sorted map based on this entity index.
 
Methods inherited from class com.sleepycat.persist.BasicIndex
contains, contains, count, delete, delete, entities, entities, entities, entities, keys, keys, keys, keys
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

PrimaryIndex

public PrimaryIndex(Database database,
                    Class<PK> keyClass,
                    EntryBinding<PK> keyBinding,
                    Class<E> entityClass,
                    EntityBinding<E> entityBinding)
             throws DatabaseException
Creates a primary index without using an EntityStore.

This constructor is not normally needed and is provided for applications that wish to use custom bindings along with the Direct Persistence Layer. Normally, getPrimaryIndex is used instead.

Note that when this constructor is used directly, primary keys cannot be automatically assigned from a sequence. The key assignment feature requires knowledge of the primary key field, which is only available if an EntityStore is used. Of course, primary keys may be assigned from a sequence manually before calling the put methods in this class.

Parameters:
database - the primary database.
keyClass - the class of the primary key.
keyBinding - the binding to be used for primary keys.
entityClass - the class of the entities stored in this index.
entityBinding - the binding to be used for entities.
Throws:
DatabaseException - the base class for all BDB exceptions.
Method Detail

getDatabase

public Database getDatabase()
Returns the underlying database for this index.

Returns:
the database.

getKeyClass

public Class<PK> getKeyClass()
Returns the primary key class for this index.

Returns:
the key class.

getKeyBinding

public EntryBinding<PK> getKeyBinding()
Returns the primary key binding for this index.

Returns:
the key binding.

getEntityClass

public Class<E> getEntityClass()
Returns the entity class for this index.

Returns:
the entity class.

getEntityBinding

public EntityBinding<E> getEntityBinding()
Returns the entity binding for this index.

Returns:
the entity binding.

put

public E put(E entity)
      throws DatabaseException
Inserts an entity and returns null, or updates it if the primary key already exists and returns the existing entity.

If a PrimaryKey.sequence() is used and the primary key field of the given entity is null or zero, this method will assign the next value from the sequence to the primary key field of the given entity.

Auto-commit is used implicitly if the store is transactional.

Parameters:
entity - the entity to be inserted or updated.
Returns:
the existing entity that was updated, or null if the entity was inserted.
Throws:
OperationFailureException - if one of the Write Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

put

public E put(Transaction txn,
             E entity)
      throws DatabaseException
Inserts an entity and returns null, or updates it if the primary key already exists and returns the existing entity.

If a PrimaryKey.sequence() is used and the primary key field of the given entity is null or zero, this method will assign the next value from the sequence to the primary key field of the given entity.

Parameters:
txn - the transaction used to protect this operation, null to use auto-commit, or null if the store is non-transactional.
entity - the entity to be inserted or updated.
Returns:
the existing entity that was updated, or null if the entity was inserted.
Throws:
OperationFailureException - if one of the Write Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

putNoReturn

public void putNoReturn(E entity)
                 throws DatabaseException
Inserts an entity, or updates it if the primary key already exists (does not return the existing entity). This method may be used instead of put(Object) to save the overhead of returning the existing entity.

If a PrimaryKey.sequence() is used and the primary key field of the given entity is null or zero, this method will assign the next value from the sequence to the primary key field of the given entity.

Auto-commit is used implicitly if the store is transactional.

Parameters:
entity - the entity to be inserted or updated.
Throws:
OperationFailureException - if one of the Write Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

putNoReturn

public void putNoReturn(Transaction txn,
                        E entity)
                 throws DatabaseException
Inserts an entity, or updates it if the primary key already exists (does not return the existing entity). This method may be used instead of put(Transaction,Object) to save the overhead of returning the existing entity.

If a PrimaryKey.sequence() is used and the primary key field of the given entity is null or zero, this method will assign the next value from the sequence to the primary key field of the given entity.

Parameters:
txn - the transaction used to protect this operation, null to use auto-commit, or null if the store is non-transactional.
entity - the entity to be inserted or updated.
Throws:
OperationFailureException - if one of the Write Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

putNoOverwrite

public boolean putNoOverwrite(E entity)
                       throws DatabaseException
Inserts an entity and returns true, or returns false if the primary key already exists.

If a PrimaryKey.sequence() is used and the primary key field of the given entity is null or zero, this method will assign the next value from the sequence to the primary key field of the given entity.

Auto-commit is used implicitly if the store is transactional.

Parameters:
entity - the entity to be inserted.
Returns:
true if the entity was inserted, or false if an entity with the same primary key is already present.
Throws:
OperationFailureException - if one of the Write Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

putNoOverwrite

public boolean putNoOverwrite(Transaction txn,
                              E entity)
                       throws DatabaseException
Inserts an entity and returns true, or returns false if the primary key already exists.

If a PrimaryKey.sequence() is used and the primary key field of the given entity is null or zero, this method will assign the next value from the sequence to the primary key field of the given entity.

Parameters:
txn - the transaction used to protect this operation, null to use auto-commit, or null if the store is non-transactional.
entity - the entity to be inserted.
Returns:
true if the entity was inserted, or false if an entity with the same primary key is already present.
Throws:
OperationFailureException - if one of the Write Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

get

public E get(PK key)
      throws DatabaseException
Description copied from interface: EntityIndex
Gets an entity via a key of this index.

The operation will not be transaction protected, and LockMode.DEFAULT is used implicitly.

Parameters:
key - the key to search for.
Returns:
the value mapped to the given key, or null if the key is not present in the index.
Throws:
OperationFailureException - if one of the Read Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

get

public E get(Transaction txn,
             PK key,
             LockMode lockMode)
      throws DatabaseException
Description copied from interface: EntityIndex
Gets an entity via a key of this index.

Parameters:
txn - the transaction used to protect this operation, or null if the operation should not be transaction protected.
key - the key to search for.
lockMode - the lock mode to use for this operation, or null to use LockMode.DEFAULT.
Returns:
the value mapped to the given key, or null if the key is not present in the index.
Throws:
OperationFailureException - if one of the Read Operation Failures occurs.
EnvironmentFailureException - if an unexpected, internal or environment-wide failure occurs.
DatabaseException - the base class for all BDB exceptions.

map

public Map<PK,E> map()
Description copied from interface: EntityIndex
Returns a standard Java map based on this entity index. The StoredMap returned is defined by the Collections API. Stored collections conform to the standard Java collections framework interface.

Returns:
the map.

sortedMap

public SortedMap<PK,E> sortedMap()
Description copied from interface: EntityIndex
Returns a standard Java sorted map based on this entity index. The StoredSortedMap returned is defined by the Collections API. Stored collections conform to the standard Java collections framework interface.

Returns:
the map.

isUpdateAllowed

boolean isUpdateAllowed()
Specified by:
isUpdateAllowed in class BasicIndex<PK,E>


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