Package org.apache.cayenne.query

Class ObjectSelect<T>

    • Field Detail

      • metaData

        protected org.apache.cayenne.query.ObjectSelectMetadata metaData

    • Constructor Detail

      • ObjectSelect

        protected ObjectSelect()

    • Method Detail

      • query

        public static <T> ObjectSelect<T> query​(Class<T> entityType)
        Creates a ObjectSelect that selects objects of a given persistent class.

      • query

        public static <T> ObjectSelect<T> query​(Class<T> entityType,
                                        Expression expression)
        Creates a ObjectSelect that selects objects of a given persistent class and uses provided expression for its qualifier.

      • query

        public static <T> ObjectSelect<T> query​(Class<T> entityType,
                                        Expression expression,
                                        List<Ordering> orderings)
        Creates a ObjectSelect that selects objects of a given persistent class and uses provided expression for its qualifier.

      • dataRowQuery

        public static ObjectSelect<DataRow> dataRowQuery​(Class<?> entityType)
        Creates a ObjectSelect that fetches data for an ObjEntity determined from a provided class.

      • dataRowQuery

        public static ObjectSelect<DataRow> dataRowQuery​(Class<?> entityType,
                                                 Expression expression)
        Creates a ObjectSelect that fetches data for an ObjEntity determined from a provided class and uses provided expression for its qualifier.

      • query

        public static <T> ObjectSelect<T> query​(Class<T> resultType,
                                        String entityName)
        Creates a ObjectSelect that fetches data for ObjEntity determined from provided "entityName", but fetches the result of a provided type. This factory method is most often used with generic classes that by themselves are not enough to resolve the entity to fetch.

      • dbQuery

        public static ObjectSelect<DataRow> dbQuery​(String dbEntityName)
        Creates a ObjectSelect that fetches DataRows for a DbEntity determined from provided "dbEntityName".

      • dbQuery

        public static ObjectSelect<DataRow> dbQuery​(String dbEntityName,
                                            Expression expression)
        Creates a ObjectSelect that fetches DataRows for a DbEntity determined from provided "dbEntityName" and uses provided expression for its qualifier.
        Returns:
        this object

      • columnQuery

        public static <E> ColumnSelect<E> columnQuery​(Class<?> entityType,
                                              Property<E> column)
        Creates a ColumnSelect that will fetch single property that can be resolved against a given ObjEntity class.
        Parameters:
        entityType - base persistent class that will be used as a root for this query
        column - single column to select

      • columnQuery

        public static ColumnSelect<Object[]> columnQuery​(Class<?> entityType,
                                                 Property<?>... columns)
        Creates a ColumnSelect that will fetch multiple columns of a given ObjEntity
        Parameters:
        entityType - base persistent class that will be used as a root for this query
        columns - columns to select

      • entityType

        public ObjectSelect<T> entityType​(Class<?> entityType)
        Sets the type of the entity to fetch without changing the return type of the query.
        Returns:
        this object

      • entityName

        public ObjectSelect<T> entityName​(String entityName)
        Sets the ObjEntity name to fetch without changing the return type of the query. This form is most often used for generic entities that don't map to a distinct class.
        Returns:
        this object

      • dbEntityName

        public ObjectSelect<T> dbEntityName​(String dbEntityName)
        Sets the DbEntity name to fetch without changing the return type of the query. This form is most often used for generic entities that don't map to a distinct class.
        Returns:
        this object

      • where

        public ObjectSelect<T> where​(String expressionString,
                             Object... parameters)
        Appends a qualifier expression of this query, using provided expression String and an array of position parameters. This is an equivalent to calling "and".
        Returns:
        this object

      • having

        public ObjectSelect<T> having​(Expression expression)
        Appends a having qualifier expression of this query. An equivalent to and(Expression...) that can be used a syntactic sugar.
        Returns:
        this object
        Since:
        4.2

      • having

        public ObjectSelect<T> having​(String expressionString,
                              Object... parameters)
        Appends a having qualifier expression of this query, using provided expression String and an array of position parameters. This is an equivalent to calling "and".
        Returns:
        this object
        Since:
        4.2

      • and

        public ObjectSelect<T> and​(Expression... expressions)
        AND's provided expressions to the existing WHERE clause expression.
        Returns:
        this object

      • or

        public ObjectSelect<T> or​(Expression... expressions)
        OR's provided expressions to the existing WHERE clause expression.
        Returns:
        this object

      • orderBy

        public ObjectSelect<T> orderBy​(String property)
        Add an ascending ordering on the given property. If there is already an ordering on this query then add this ordering with a lower priority.
        Parameters:
        property - the property to sort on
        Returns:
        this object

      • orderBy

        public ObjectSelect<T> orderBy​(String property,
                               SortOrder sortOrder)
        Add an ordering on the given property. If there is already an ordering on this query then add this ordering with a lower priority.
        Parameters:
        property - the property to sort on
        sortOrder - the direction of the ordering
        Returns:
        this object

      • orderBy

        public ObjectSelect<T> orderBy​(Ordering... orderings)
        Add one or more orderings to this query.
        Returns:
        this object

      • prefetch

        public ObjectSelect<T> prefetch​(String path,
                                int semantics)
        Merges a prefetch path with specified semantics into the query prefetch tree.
        Returns:
        this object

      • limit

        public ObjectSelect<T> limit​(int fetchLimit)
        Resets query fetch limit - a parameter that defines max number of objects that should be ever be fetched from the database.

      • offset

        public ObjectSelect<T> offset​(int fetchOffset)
        Resets query fetch offset - a parameter that defines how many objects should be skipped when reading data from the database.

      • pageSize

        public ObjectSelect<T> pageSize​(int pageSize)
        Resets query page size. A non-negative page size enables query result pagination that saves memory and processing time for large lists if only parts of the result are ever going to be accessed.

      • statementFetchSize

        public ObjectSelect<T> statementFetchSize​(int size)
        Sets fetch size of the PreparedStatement generated for this query. Only non-negative values would change the default size.
        See Also:
        Statement.setFetchSize(int)

      • localCache

        public ObjectSelect<T> localCache​(String cacheGroup)
        Instructs Cayenne to look for query results in the "local" cache when running the query. This is a short-hand notation for: 

         query.cacheStrategy(QueryCacheStrategy.LOCAL_CACHE, cacheGroup);

      • localCache

        public ObjectSelect<T> localCache()
        Instructs Cayenne to look for query results in the "local" cache when running the query. This is a short-hand notation for: 

         query.cacheStrategy(QueryCacheStrategy.LOCAL_CACHE);

      • sharedCache

        public ObjectSelect<T> sharedCache​(String cacheGroup)
        Instructs Cayenne to look for query results in the "shared" cache when running the query. This is a short-hand notation for: 

         query.cacheStrategy(QueryCacheStrategy.SHARED_CACHE, cacheGroup);

      • sharedCache

        public ObjectSelect<T> sharedCache()
        Instructs Cayenne to look for query results in the "shared" cache when running the query. This is a short-hand notation for: 

         query.cacheStrategy(QueryCacheStrategy.SHARED_CACHE);

      • fetchDataRows

        public ObjectSelect<DataRow> fetchDataRows()
        Forces query to fetch DataRows. This automatically changes whatever result type was set previously to "DataRow".
        Returns:
        this object

      • columns

        public ColumnSelect<Object[]> columns​(Property<?>... properties)

        Select only specific properties.

        Can be any properties that can be resolved against root entity type (root entity's properties, function call expressions, properties of relationships, etc).

         
 List<Object[]> columns = ObjectSelect.query(Artist.class)
                                    .columns(Artist.ARTIST_NAME, Artist.DATE_OF_BIRTH)
                                    .select(context);
        Parameters:
        properties - array of properties to select
        See Also:
        column(Property)

      • column

        public <E> ColumnSelect<E> column​(Property<E> property)

        Select one specific property.

        Can be any property that can be resolved against root entity type (root entity's property, function call expression, property of relationships, etc)

        If you need several columns use columns(Property[]) method.

         
 List<String> names = ObjectSelect.query(Artist.class)
                                  .column(Artist.ARTIST_NAME)
                                  .select(context);

        Parameters:
        property - single property to select
        See Also:
        columns(Property[])

      • distinct

        public ObjectSelect<T> distinct()
        Returns:
        this
        Since:
        4.2

      • selectCount

        public long selectCount​(ObjectContext context)

        Quick way to select count of records

        Usage: 

         
     long count = ObjectSelect.query(Artist.class)
                      .where(Artist.ARTIST_NAME.like("a%"))
                      .selectCount(context);

        Parameters:
        context - to perform query
        Returns:
        count of rows

      • selectFirst

        public T selectFirst​(ObjectContext context)
        Description copied from interface: Select
        Selects a single object using provided context. The query itself can match any number of objects, but will return only the first one. It returns null if no objects were matched.

        If it matched more than one object, the first object from the list is returned. This makes 'selectFirst' different from Select.selectOne(ObjectContext), which would throw in this situation. 'selectFirst' is useful e.g. when the query is ordered and we only want to see the first object (e.g. "most recent news article"), etc.

        Selecting the first object via "Select.selectFirst(ObjectContext)" is more comprehensible than selecting via "ObjectContext.selectFirst(Select)", because implementations of "Select" set fetch size limit to one.

        Specified by:
        selectFirst in interface Select<T>

      • getBaseMetaData

        protected org.apache.cayenne.query.BaseQueryMetadata getBaseMetaData()
        Specified by:
        getBaseMetaData in class CacheableQuery

      • createQuery

        public Query createQuery​(Map<String,​?> parameters)
        This method is intended for internal use in a MappedSelect.
        Specified by:
        createQuery in interface ParameterizedQuery
        Parameters:
        parameters - to apply
        Returns:
        this query with parameters applied to the where qualifier
        Since:
        4.2