Module org.eclipse.persistence.core
Package org.eclipse.persistence.queries

Class ReadObjectQuery

java.lang.Object
org.eclipse.persistence.queries.DatabaseQuery
org.eclipse.persistence.queries.ReadQuery
org.eclipse.persistence.queries.ObjectBuildingQuery
org.eclipse.persistence.queries.ObjectLevelReadQuery
org.eclipse.persistence.queries.ReadObjectQuery
All Implemented Interfaces:
Serializable, Cloneable
public class ReadObjectQuery extends ObjectLevelReadQuery

Purpose: Concrete class for all read queries involving a single object.

Responsibilities: Return a single object for the query. Implements the inheritance feature when dealing with abstract descriptors.

Since:
TOPLink/Java 1.0
See Also:

  • Field Details

    • selectionObject

      protected transient Object selectionObject
      Object that can be used in place of a selection criteria.

    • selectionId

      protected Object selectionId
      Key that can be used in place of a selection criteria.

    • shouldLoadResultIntoSelectionObject

      protected boolean shouldLoadResultIntoSelectionObject
      Can be used to refresh a specific non-cached instance from the database.

  • Constructor Details

    • ReadObjectQuery

      public ReadObjectQuery()
      PUBLIC: Return a new read object query. A reference class must be specified before execution. It is better to provide the class and expression builder on construction to esnure a single expression builder is used. If no selection criteria is specified this will reads the first object found in the database.

    • ReadObjectQuery

      public ReadObjectQuery(Class<?> classToRead)
      PUBLIC: Return a new read object query. By default, the query has no selection criteria. Executing this query without selection criteria will always result in a database access to read the first instance of the specified Class found in the database. This is true no matter how cache usage is configured and even if an instance of the specified Class exists in the cache. Executing a query with selection criteria allows you to avoid a database access if the selected instance is in the cache. For this reason, you may whish to use a ReadObjectQuery constructor that takes selection criteria, such as: ReadObjectQuery(Class, Call), ReadObjectQuery(Class, Expression), ReadObjectQuery(Class, ExpressionBuilder), ReadObjectQuery(ExpressionBuilder), ReadObjectQuery(Object), or ReadObjectQuery(Object, QueryByExamplePolicy).

    • ReadObjectQuery

      public ReadObjectQuery(Class<?> classToRead, Expression selectionCriteria)
      PUBLIC: Return a new read object query for the class and the selection criteria.

    • ReadObjectQuery

      public ReadObjectQuery(Class<?> classToRead, ExpressionBuilder builder)
      PUBLIC: Return a new read object query for the class. The expression builder must be used for all associated expressions used with the query.

    • ReadObjectQuery

      public ReadObjectQuery(Class<?> classToRead, Call call)
      PUBLIC: Return a new read object query. The call represents a database interaction such as SQL, Stored Procedure.

    • ReadObjectQuery

      public ReadObjectQuery(Call call)
      PUBLIC: Return a new read object query. The call represents a database interaction such as SQL, Stored Procedure.

    • ReadObjectQuery

      public ReadObjectQuery(Object objectToRead)
      PUBLIC: Return a query to read the object with the same primary key as the provided object. Note: This is not a query by example object, only the primary key will be used for the selection criteria.

    • ReadObjectQuery

      public ReadObjectQuery(Object exampleObject, QueryByExamplePolicy policy)
      PUBLIC: Return a query by example query to find an object matching the attributes of the example object.

    • ReadObjectQuery

      public ReadObjectQuery(ExpressionBuilder builder)
      PUBLIC: The expression builder should be provide on creation to ensure only one is used.

  • Method Details

    • cacheResult

      public void cacheResult(Object object)
      INTERNAL:

      This method is called by the object builder when building an original. It will cause the original to be cached in the query results if the query is set to do so.

      Specified by:
      cacheResult in class ReadQuery

    • checkCacheByExactPrimaryKey

      public void checkCacheByExactPrimaryKey()
      PUBLIC: The cache will be checked only if the query contains exactly the primary key. Queries can be configured to use the cache at several levels. Other caching option are available.
      See Also:

    • checkCacheByPrimaryKey

      public void checkCacheByPrimaryKey()
      PUBLIC: This is the default, the cache will be checked only if the query contains the primary key. Queries can be configured to use the cache at several levels. Other caching option are available.
      See Also:

    • checkCacheThenDatabase

      public void checkCacheThenDatabase()
      PUBLIC: The cache will be checked completely, then if the object is not found or the query too complex the database will be queried. Queries can be configured to use the cache at several levels. Other caching option are available.
      See Also:

    • checkDescriptor

      public void checkDescriptor(AbstractSession session) throws QueryException
      INTERNAL: Ensure that the descriptor has been set.
      Overrides:
      checkDescriptor in class ObjectLevelReadQuery
      Parameters:
      session - Current session.
      Throws:
      QueryException

    • checkEarlyReturnLocal

      protected Object checkEarlyReturnLocal(AbstractSession session, AbstractRecord translationRow)
      INTERNAL: The cache check is done before the prepare as a hit will not require the work to be done.
      Specified by:
      checkEarlyReturnLocal in class ObjectLevelReadQuery

    • checkCustomQueryFlag

      protected Boolean checkCustomQueryFlag(AbstractSession session, AbstractRecord translationRow)
      INTERNAL: Check and return custom query flag. Custom query flag value is initialized when stored value is null. Called from ObjectLevelReadQuery.checkForCustomQuery(AbstractSession, AbstractRecord) to retrieve custom query flag.
      Specified by:
      checkCustomQueryFlag in class ObjectLevelReadQuery
      Parameters:
      session - Current session.
      translationRow - Database record.
      Returns:
      Current custom query flag. Value will never be null.

    • getReadQuery

      protected ObjectLevelReadQuery getReadQuery()
      INTERNAL: Get custom single object read query from query manager. Called from ObjectLevelReadQuery.checkForCustomQuery(AbstractSession, AbstractRecord) to retrieve custom read query.
      Specified by:
      getReadQuery in class ObjectLevelReadQuery
      Returns:
      Custom single object read query from query manager.

    • conformResult

      protected Object conformResult(Object result, UnitOfWorkImpl unitOfWork, AbstractRecord databaseRow, boolean buildDirectlyFromRows)
      INTERNAL: Conform the result in the UnitOfWork.

    • dontLoadResultIntoSelectionObject

      public void dontLoadResultIntoSelectionObject()
      PUBLIC: Do not refesh/load into the selection object, this is the default. This property allows for the selection object of the query to be refreshed or put into the TopLink cache. By default on a read or refresh the object in the cache is refreshed and returned or a new object is built from the database, in some cases such as EJB BMP it is desirable to refresh or load into the object passed into the read object query.

      Note: This forces the selection object into the cache a replaces any existing object that may already be there, this is a strict violation of object identity and other objects can still be refering to the old object.

    • execute

      public Object execute(AbstractSession session, AbstractRecord row) throws DatabaseException
      INTERNAL: Execute the query. If there are cached results return those. This must override the super to support result caching.
      Overrides:
      execute in class ObjectLevelReadQuery
      Parameters:
      session - the session in which the receiver will be executed.
      Returns:
      An object or vector, the result of executing the query.
      Throws:
      DatabaseException - - an error has occurred on the database

    • executeObjectLevelReadQuery

      protected Object executeObjectLevelReadQuery() throws DatabaseException
      INTERNAL: Execute the query. Do a cache lookup and build object from row if required.
      Specified by:
      executeObjectLevelReadQuery in class ObjectLevelReadQuery
      Returns:
      object - the first object found or null if none.
      Throws:
      DatabaseException - - an error has occurred on the database

    • executeObjectLevelReadQueryFromResultSet

      protected Object executeObjectLevelReadQueryFromResultSet() throws DatabaseException
      INTERNAL: Execute the query building the objects directly from the database result-set.
      Specified by:
      executeObjectLevelReadQueryFromResultSet in class ObjectLevelReadQuery
      Returns:
      object - the first object found or null if none.
      Throws:
      DatabaseException - - an error has occurred on the database

    • extractRemoteResult

      public Object extractRemoteResult(Transporter transporter)
      INTERNAL: Extract the correct query result from the transporter.
      Overrides:
      extractRemoteResult in class DatabaseQuery

    • getDefaultRedirector

      protected QueryRedirector getDefaultRedirector()
      INTERNAL: Returns the specific default redirector for this query type. There are numerous default query redirectors. See ClassDescriptor for their types.
      Overrides:
      getDefaultRedirector in class DatabaseQuery

    • getSelectionObject

      public Object getSelectionObject()
      PUBLIC: Return the selection object of the query. This can be used instead of a where clause expression for single object primary key queries. The selection object given should have a primary key defined, this primary key will be used to query the database instance of the same object. This is a basic form of query by example where only the primary key is required, it can be used for simple query forms, or testing.

    • isReadObjectQuery

      public boolean isReadObjectQuery()
      PUBLIC: Return if this is a read object query.
      Overrides:
      isReadObjectQuery in class DatabaseQuery

    • isPrimaryKeyQuery

      public boolean isPrimaryKeyQuery()
      INTERNAL: Return if the query is by primary key.
      Overrides:
      isPrimaryKeyQuery in class ObjectLevelReadQuery

    • loadResultIntoSelectionObject

      public void loadResultIntoSelectionObject()
      PUBLIC: Allow for the selection object of the query to be refreshed or put into the EclipseLink cache. By default on a read or refresh the object in the cache is refreshed and returned or a new object is built from the database, in some cases such as EJB BMP it is desirable to refresh or load into the object passed into the read object query.

      Note: This forces the selection object into the cache a replaces any existing object that may already be there, this is a strict violation of object identity and other objects can still be referring to the old object.

    • copyFromQuery

      public void copyFromQuery(DatabaseQuery query)
      INTERNAL: Copy all setting from the query. This is used to morph queries from one type to the other. By default this calls prepareFromQuery, but additional properties may be required to be copied as prepareFromQuery only copies properties that affect the SQL.
      Overrides:
      copyFromQuery in class ObjectLevelReadQuery

    • prepare

      protected void prepare() throws QueryException
      INTERNAL: Prepare the receiver for execution in a session.
      Overrides:
      prepare in class ObjectLevelReadQuery
      Throws:
      QueryException

    • prepareCustomQuery

      protected void prepareCustomQuery(DatabaseQuery customQuery)
      INTERNAL: Set the properties needed to be cascaded into the custom query including the translation row. This is used only for primary key queries, as the descriptor query manager stores a predefined query for this query to avoid having to re-prepare and allow for customization.
      Overrides:
      prepareCustomQuery in class ObjectBuildingQuery

    • prepareForExecution

      public void prepareForExecution() throws QueryException
      INTERNAL: Prepare the receiver for execution in a session.
      Overrides:
      prepareForExecution in class ReadQuery
      Throws:
      QueryException

    • prePrepare

      protected void prePrepare() throws QueryException
      INTERNAL: Prepare the receiver for execution in a session.
      Overrides:
      prePrepare in class ObjectLevelReadQuery
      Throws:
      QueryException

    • registerResultInUnitOfWork

      public Object registerResultInUnitOfWork(Object result, UnitOfWorkImpl unitOfWork, AbstractRecord arguments, boolean buildDirectlyFromRows)
      INTERNAL: All objects queried via a UnitOfWork get registered here. If the query went to the database.

      Involves registering the query result individually and in totality, and hence refreshing / conforming is done here.

      Specified by:
      registerResultInUnitOfWork in class ObjectLevelReadQuery
      Parameters:
      result - may be collection (read all) or an object (read one), or even a cursor. If in transaction the shared cache will be bypassed, meaning the result may not be originals from the parent but raw database rows.
      unitOfWork - the unitOfWork the result is being registered in.
      arguments - the original arguments/parameters passed to the query execution. Used by conforming
      buildDirectlyFromRows - If in transaction must construct a registered result from raw database rows.
      Returns:
      the final (conformed, refreshed, wrapped) UnitOfWork query result

    • remoteExecute

      protected Object remoteExecute()
      Overrides:
      remoteExecute in class DatabaseQuery

    • replaceValueHoldersIn

      public Map replaceValueHoldersIn(Object object, RemoteSessionController controller)
      INTERNAL: replace the value holders in the specified result object(s)
      Overrides:
      replaceValueHoldersIn in class DatabaseQuery

    • getQueryPrimaryKey

      protected Object getQueryPrimaryKey()
      INTERNAL: Return the primary key stored in this query
      Overrides:
      getQueryPrimaryKey in class ObjectBuildingQuery
      Returns:
      the selection id of this ReadObjectQuery
      See Also:

    • getSelectionId

      public Object getSelectionId()
      PUBLIC: Return Id of the object to be selected by the query.

    • clearSelectionId

      public void clearSelectionId()
      INTERNAL: Clear the selection id and object. This is done after cloning queries to prepare them in inheritance.

    • setSelectionId

      public void setSelectionId(Object id)
      PUBLIC: The Id of the object to be selected by the query. This will generate a query by primary key. This can be used instead of an Expression, SQL, or JPQL, or example object. The Id is the Id value for a singleton primary key, for a composite it is an instance of CacheId.
      See Also:

    • setSelectionObject

      public void setSelectionObject(Object selectionObject)
      PUBLIC: Used to set the where clause of the query. This can be used instead of a where clause expression for single object primary key queries. The selection object given should have a primary key defined, this primary key will be used to query the database instance of the same object. This is a basic form of query by example where only the primary key is required, it can be used for simple query forms, or testing.

    • setShouldLoadResultIntoSelectionObject

      public void setShouldLoadResultIntoSelectionObject(boolean shouldLoadResultIntoSelectionObject)
      PUBLIC: Allow for the selection object of the query to be refreshed or put into the EclipseLink cache. By default on a read or refresh the object in the cache is refreshed and returned or a new object is built from the database, in some cases such as EJB BMP it is desirable to refresh or load into the object passed into the read object query.

      Note: This forces the selection object into the cache a replaces any existing object that may already be there, this is a strict violation of object identity and other objects can still be referring to the old object.

    • shouldCheckCacheByExactPrimaryKey

      public boolean shouldCheckCacheByExactPrimaryKey()
      PUBLIC: Return if cache should be checked.

    • shouldCheckCacheByPrimaryKey

      public boolean shouldCheckCacheByPrimaryKey()
      PUBLIC: Return if cache should be checked.

    • shouldCheckCacheThenDatabase

      public boolean shouldCheckCacheThenDatabase()
      PUBLIC: Return if cache should be checked.

    • shouldLoadResultIntoSelectionObject

      public boolean shouldLoadResultIntoSelectionObject()
      PUBLIC: return true if the result should be loaded into the passed in selection Object

    • hasNonDefaultFetchGroup

      protected boolean hasNonDefaultFetchGroup()
      INTERNAL: Return if the query has an non-default fetch group defined for itself.