Package net.java.ao

Class EntityManager

java.lang.Object
net.java.ao.EntityManager
public class EntityManager extends Object

The root control class for the entire ActiveObjects API. EntityManager is the source of all RawEntity objects, as well as the dispatch layer between the entities, the pluggable table name converters, and the database abstraction layers. This is the entry point for any use of the API.

EntityManager is designed to be used in an instance fashion with each instance corresponding to a single database. Thus, rather than a singleton instance or a static factory method, EntityManager does have a proper constructor. Any static instance management is left up to the developer using the API.

Author:
Daniel Spiewak

  • Constructor Details

  • Method Details

    • migrate

      public void migrate(Class<? extends RawEntity<?>>... entities) throws SQLException
      Convenience method to create the schema for the specified entities using the current settings (table/field name converter and database provider).
      Parameters:
      entities - the "list" of entity classes to consider for migration.
      Throws:
      SQLException
      See Also:

    • migrateDestructively

      public void migrateDestructively(Class<? extends RawEntity<?>>... entities) throws SQLException
      Convenience method to create the schema for the specified entities using the current settings (table/field name converter and database provider). Note that if the given entities do not include the full set of entities, or those entities have removed any fields, then the corresponding tables or columns will be dropped, and any data they contained will be lost. Use this at your own risk.
      Parameters:
      entities - the "list" of entity classes to consider for migration.
      Throws:
      SQLException
      See Also:

    • flushAll

      @Deprecated public void flushAll()
      Deprecated.
      since 0.23. EntityManager now no longer caches entities. use flush(RawEntity[]) to flush values for individual entities

    • flushEntityCache

      @Deprecated public void flushEntityCache()
      Deprecated.
      since 0.23. EntityManager now no longer caches entities. use flush(RawEntity[]) to flush values for individual entities

    • flush

      @Deprecated public void flush(RawEntity<?>... entities)
      Deprecated.
      since 0.25. Entities and values now no longer cached.

    • get

      public <T extends RawEntity<K>, K> T[] get(Class<T> type, K... keys) throws SQLException

      Returns an array of entities of the specified type corresponding to the varargs primary keys. If an in-memory reference already exists to a corresponding entity (of the specified type and key), it is returned rather than creating a new instance.

      If the entity is known to exist in the database, then no checks are performed and the method returns extremely quickly. However, for any key which has not already been verified, a query to the database is performed to determine whether or not the entity exists. If the entity does not exist, then null is returned.

      Parameters:
      type - The type of the entities to retrieve.
      keys - The primary keys corresponding to the entities to retrieve. All keys must be typed according to the generic type parameter of the entity's RawEntity inheritence (if inheriting from Entity, this is Integer or int). Thus, the keys array is type-checked at compile time.
      Returns:
      An array of entities of the given type corresponding with the specified primary keys. Any entities which are non-existent will correspond to a null value in the resulting array.
      Throws:
      SQLException

    • peer

      protected <T extends RawEntity<K>, K> T[] peer(EntityInfo<T,K> entityInfo, K... keys) throws SQLException
      Throws:
      SQLException

    • getAndInstantiate

      protected <T extends RawEntity<K>, K> T getAndInstantiate(EntityInfo<T,K> entityInfo, K key)
      Creates a new instance of the entity of the specified type corresponding to the given primary key. This is used by get(Class, Object[])} to create the entity.
      Parameters:
      entityInfo - The type of the entity to create.
      key - The primary key corresponding to the entity instance required.
      Returns:
      An entity instance of the specified type and primary key.

    • get

      public <T extends RawEntity<K>, K> T get(Class<T> type, K key) throws SQLException
      Cleverly overloaded method to return a single entity of the specified type rather than an array in the case where only one ID is passed. This method meerly delegates the call to the overloaded get method and functions as syntactical sugar.
      Parameters:
      type - The type of the entity instance to retrieve.
      key - The primary key corresponding to the entity to be retrieved.
      Returns:
      An entity instance of the given type corresponding to the specified primary key, or null if the entity does not exist in the database.
      Throws:
      SQLException
      See Also:

    • peer

      protected <T extends RawEntity<K>, K> T peer(EntityInfo<T,K> entityInfo, K key) throws SQLException
      Throws:
      SQLException

    • create

      public <T extends RawEntity<K>, K> T create(Class<T> type, DBParam... params) throws SQLException

      Creates a new entity of the specified type with the optionally specified initial parameters. This method actually inserts a row into the table represented by the entity type and returns the entity instance which corresponds to that row.

      The DBParam object parameters are designed to allow the creation of entities which have non-null fields which have no defalut or auto-generated value. Insertion of a row without such field values would of course fail, thus the need for db params. The db params can also be used to set the values for any field in the row, leading to more compact code under certain circumstances.

      Unless within a transaction, this method will commit to the database immediately and exactly once per call. Thus, care should be taken in the creation of large numbers of entities. There doesn't seem to be a more efficient way to create large numbers of entities, however one should still be aware of the performance implications.

      This method delegates the action INSERT action to DatabaseProvider.insertReturningKey(net.java.ao.EntityManager, java.sql.Connection, java.lang.Class<T>, java.lang.Class<K>, java.lang.String, boolean, java.lang.String, net.java.ao.DBParam...). This is necessary because not all databases support the JDBC RETURN_GENERATED_KEYS constant (e.g. PostgreSQL and HSQLDB). Thus, the database provider itself is responsible for handling INSERTion and retrieval of the correct primary key value.

      Parameters:
      type - The type of the entity to INSERT.
      params - An optional varargs array of initial values for the fields in the row. These values will be passed to the database within the INSERT statement.
      Returns:
      The new entity instance corresponding to the INSERTed row.
      Throws:
      SQLException
      See Also:

    • create

      public <T extends RawEntity<K>, K> T create(Class<T> type, Map<String,Object> params) throws SQLException
      Creates and INSERTs a new entity of the specified type with the given map of parameters. This method merely delegates to the create(Class, DBParam...) method. The idea behind having a separate convenience method taking a map is in circumstances with large numbers of parameters or for people familiar with the anonymous inner class constructor syntax who might be more comfortable with creating a map than with passing a number of objects.
      Parameters:
      type - The type of the entity to INSERT.
      params - A map of parameters to pass to the INSERT.
      Returns:
      The new entity instance corresponding to the INSERTed row.
      Throws:
      SQLException
      See Also:

    • create

      public <T extends RawEntity<K>, K> void create(Class<T> type, List<Map<String,Object>> rows) throws SQLException
      Creates and INSERTs a batch of new entities represented by rows of the given type. Each entity corresponds to a single row.
      Parameters:
      type - The type of the entity to INSERT.
      rows - A list of rows to be INSERTed. A row is represented as a map from column name to its value. All rows must have the same columns.
      Throws:
      SQLException

    • delete

      public void delete(RawEntity<?>... entities) throws SQLException

      Deletes the specified entities from the database. DELETE statements are called on the rows in the corresponding tables. The entity instances themselves are not invalidated, but it doesn't even make sense to continue using the instance without a row with which it is paired.

      This method does attempt to group the DELETE statements on a per-type basis. Thus, if you pass 5 instances of EntityA and two instances of EntityB, the following SQL prepared statements will be invoked:

      DELETE FROM entityA WHERE id IN (?,?,?,?,?);
 DELETE FROM entityB WHERE id IN (?,?);

      Thus, this method scales very well for large numbers of entities grouped into types. However, the execution time increases linearly for each entity of unique type.

      Parameters:
      entities - A varargs array of entities to delete. Method returns immediately if length == 0.
      Throws:
      SQLException

    • deleteWithSQL

      public <K> int deleteWithSQL(Class<? extends RawEntity<K>> type, String criteria, Object... parameters) throws SQLException

      Deletes rows from the table corresponding to type. In contrast to delete(RawEntity[]), this method allows you to delete rows without creating entities for them first.

      Example:

      manager.deleteWithSQL(Person.class, "name = ?", "Charlie")

      The SQL in criteria is not parsed or modified in any way by ActiveObjects, and is simply appended to the DELETE statement in a WHERE clause. The above example would cause an SQL statement similar to the following to be executed:

      DELETE FROM people WHERE name = 'Charlie';

      If criteria is null, this method deletes all rows from the table corresponding to type.

      This method does not attempt to determine the set of entities affected by the statement.

      Parameters:
      type - The entity type corresponding to the table to delete from.
      criteria - An optional SQL fragment specifying which rows to delete.
      parameters - A varargs array of parameters to be passed to the executed prepared statement. The length of this array must match the number of parameters (denoted by the '?' char) in criteria.
      Returns:
      The number of rows deleted from the table.
      Throws:
      SQLException
      See Also:

    • find

      public <T extends RawEntity<K>, K> T[] find(Class<T> type) throws SQLException
      Returns all entities of the given type. This actually peers the call to the find(Class, Query) method.
      Parameters:
      type - The type of entity to retrieve.
      Returns:
      An array of all entities which correspond to the given type.
      Throws:
      SQLException

    • find

      public <T extends RawEntity<K>, K> T[] find(Class<T> type, String criteria, Object... parameters) throws SQLException

      Convenience method to select all entities of the given type with the specified, parameterized criteria. The criteria String specified is appended to the SQL prepared statement immediately following the WHERE.

      Example:

      manager.find(Person.class, "name LIKE ? OR age > ?", "Joe", 9);

      This actually delegates the call to the find(Class, Query) method, properly parameterizing the Query object.

      Parameters:
      type - The type of the entities to retrieve.
      criteria - A parameterized WHERE statement used to determine the results.
      parameters - A varargs array of parameters to be passed to the executed prepared statement. The length of this array must match the number of parameters (denoted by the '?' char) in the criteria.
      Returns:
      An array of entities of the given type which match the specified criteria.
      Throws:
      SQLException

    • findSingleEntity

      public <T extends RawEntity<K>, K> T findSingleEntity(Class<T> type, String criteria, Object... parameters) throws SQLException

      Convenience method to select a single entity of the given type with the specified, parameterized criteria. The criteria String specified is appended to the SQL prepared statement immediately following the WHERE.

      Example:

      manager.findSingleEntity(Person.class, "name LIKE ? OR age > ?", "Joe", 9);

      This actually delegates the call to the find(Class, String, Object...) method, properly parameterizing the Object object.

      Parameters:
      type - The type of the entities to retrieve.
      criteria - A parameterized WHERE statement used to determine the results.
      parameters - A varargs array of parameters to be passed to the executed prepared statement. The length of this array must match the number of parameters (denoted by the '?' char) in the criteria.
      Returns:
      A single entity of the given type which match the specified criteria or null if none returned
      Throws:
      SQLException

    • find

      public <T extends RawEntity<K>, K> T[] find(Class<T> type, Query query) throws SQLException

      Selects all entities matching the given type and Query. By default, the entities will be created based on the values within the primary key field for the specified type (this is usually the desired behavior).

      Example:

      manager.find(Person.class, Query.select().where("name LIKE ? OR age > ?", "Joe", 9).limit(10));

      This method delegates the call to find(Class, String, Query), passing the primary key field for the given type as the String parameter.

      Note that in the case of calling this function with a Query with select fields, the first field will be passed to find(Class, String, Query). If this is not the intention, a direct call to find(Class, String, Query) should be made instead, with the primary key field specified and present in the select fields.

      Parameters:
      type - The type of the entities to retrieve.
      query - The Query instance to be used to determine the results.
      Returns:
      An array of entities of the given type which match the specified query.
      Throws:
      SQLException

    • find

      public <T extends RawEntity<K>, K> T[] find(Class<T> type, String field, Query query) throws SQLException

      Selects all entities of the specified type which match the given Query. This method creates a PreparedStatement using the Query instance specified against the table represented by the given type. This query is then executed (with the parameters specified in the query). The method then iterates through the result set and extracts the specified field, mapping an entity of the given type to each row. This array of entities is returned.

      Parameters:
      type - The type of the entities to retrieve.
      field - The field value to use in the creation of the entities. This is usually the primary key field of the corresponding table.
      query - The Query instance to use in determining the results.
      Returns:
      An array of entities of the given type which match the specified query.
      Throws:
      SQLException

    • findWithSQL

      public <T extends RawEntity<K>, K> T[] findWithSQL(Class<T> type, String keyField, String sql, Object... parameters) throws SQLException

      Executes the specified SQL and extracts the given key field, wrapping each row into a instance of the specified type. The SQL itself is executed as a PreparedStatement with the given parameters.

      Example:

      manager.findWithSQL(Person.class, "personID", "SELECT personID FROM chairs WHERE position < ? LIMIT ?",
 10,
 5);

      The SQL is not parsed or modified in any way by ActiveObjects. As such, it is possible to execute database-specific queries using this method without realizing it. For example, the above query will not run on MS SQL Server or Oracle, due to the lack of a LIMIT clause in their SQL implementation. As such, be extremely careful about what SQL is executed using this method, or else be conscious of the fact that you may be locking yourself to a specific DBMS.

      Parameters:
      type - The type of the entities to retrieve.
      keyField - The field value to use in the creation of the entities. This is usually the primary key field of the corresponding table.
      sql - The SQL statement to execute.
      parameters - A varargs array of parameters to be passed to the executed prepared statement. The length of this array must match the number of parameters (denoted by the '?' char) in the criteria.
      Returns:
      An array of entities of the given type which match the specified query.
      Throws:
      SQLException

    • stream

      public <T extends RawEntity<K>, K> void stream(Class<T> type, EntityStreamCallback<T,K> streamCallback) throws SQLException

      Optimised read for large datasets. This method will stream all rows for the given type to the given callback.

      Please see stream(Class, Query, EntityStreamCallback) for details / limitations.

      Parameters:
      type - The type of the entities to retrieve.
      streamCallback - The receiver of the data, will be passed one entity per returned row
      Throws:
      SQLException

    • stream

      public <T extends RawEntity<K>, K> void stream(Class<T> type, Query query, EntityStreamCallback<T,K> streamCallback) throws SQLException

      Selects all entities of the given type and feeds them to the callback, one by one. The entities are slim, read-only representations of the data. They only supports getters or designated Accessor methods. Calling setters or 

      save
      will result in an exception. Other method calls will be ignored. The proxies do not support lazy-loading of related entities.

      Only the fields specified in the Query are loaded. Since lazy loading is not supported, calls to unspecified getters will return null (or AO's defaults in case of primitives)

      This call is optimised for efficient read operations on large datasets. For best memory usage, do not buffer the entities passed to the callback but process and discard them directly.

      Unlike regular Entities, the read only implementations do not support flushing/refreshing. The data is a snapshot view at the time of query.

      Parameters:
      type - The type of the entities to retrieve.
      query -
      streamCallback - The receiver of the data, will be passed one entity per returned row
      Throws:
      SQLException

    • count

      public <K> int count(Class<? extends RawEntity<K>> type) throws SQLException
      Counts all entities of the specified type. This method is actually a delegate for: count(Class<? extends Entity>, Query)
      Parameters:
      type - The type of the entities which should be counted.
      Returns:
      The number of entities of the specified type.
      Throws:
      SQLException

    • count

      public <K> int count(Class<? extends RawEntity<K>> type, String criteria, Object... parameters) throws SQLException
      Counts all entities of the specified type matching the given criteria and parameters. This is a convenience method for: count(type, Query.select().where(criteria, parameters))
      Parameters:
      type - The type of the entities which should be counted.
      criteria - A parameterized WHERE statement used to determine the result set which will be counted.
      parameters - A varargs array of parameters to be passed to the executed prepared statement. The length of this array must match the number of parameters (denoted by the '?' char) in the criteria.
      Returns:
      The number of entities of the given type which match the specified criteria.
      Throws:
      SQLException

    • count

      public <K> int count(Class<? extends RawEntity<K>> type, Query query) throws SQLException
      Counts all entities of the specified type matching the given Query instance. The SQL runs as a SELECT COUNT(*) to ensure maximum performance.
      Parameters:
      type - The type of the entities which should be counted.
      query - The Query instance used to determine the result set which will be counted.
      Returns:
      The number of entities of the given type which match the specified query.
      Throws:
      SQLException

    • getFastCountEstimate

      public <K> int getFastCountEstimate(Class<? extends RawEntity<K>> type) throws SQLException, FailedFastCountException
      Gives an approximate count of all entities of the specified type to avoid performance issues.

      DO NOT use this API if you need an exact count. For a guaranteed accurate count, use count(Class).

      Accuracy may depend on how long the last DB cleanup job was run

      Parameters:
      type - The type of the entities which should be counted
      Returns:
      The approximate number of entities of the given type
      Throws:
      FailedFastCountException - means something went wrong while attempting to get a fast count
      SQLException
      Since:
      4.1 and 5.3 but not in 5.0 or 5.1

    • getNameConverters

      public NameConverters getNameConverters()

    • resolveEntityInfo

      protected <T extends RawEntity<K>, K> EntityInfo<T,K> resolveEntityInfo(Class<T> type)

    • getTableNameConverter

      public TableNameConverter getTableNameConverter()
      Retrieves the TableNameConverter instance used for name conversion of all entity types.

    • getFieldNameConverter

      public FieldNameConverter getFieldNameConverter()
      Retrieves the FieldNameConverter instance used for name conversion of all entity methods.

    • setPolymorphicTypeMapper

      public void setPolymorphicTypeMapper(PolymorphicTypeMapper typeMapper)
      Specifies the PolymorphicTypeMapper instance to use for all flag value conversion of polymorphic types. The default type mapper is an empty DefaultPolymorphicTypeMapper instance (thus using the fully qualified classname for all values).
      See Also:

    • getPolymorphicTypeMapper

      public PolymorphicTypeMapper getPolymorphicTypeMapper()
      Retrieves the PolymorphicTypeMapper instance used for flag value conversion of polymorphic types.
      See Also:

    • getProvider

      public DatabaseProvider getProvider()

      Retrieves the database provider used by this EntityManager for all database operations. This method can be used reliably to obtain a database provider and hence a Connection instance which can be used for JDBC operations outside of ActiveObjects. Thus:

      Connection conn = manager.getProvider().getConnection();
 try {
     // ...
 } finally {
     conn.close();
 }

    • getSchemaConfiguration

      public SchemaConfiguration getSchemaConfiguration()
      Retrieves SchemaConfiguration used by this entity manager.
      Returns:
      the SchemaConfiguration