Package org.apache.cayenne.query

Class ColumnSelect<T>

java.lang.Object
org.apache.cayenne.query.IndirectQuery
org.apache.cayenne.query.FluentSelect<T>
org.apache.cayenne.query.ColumnSelect<T>
All Implemented Interfaces:
Serializable, Query, Select<T>
public class ColumnSelect<T>
extends FluentSelect<T>

A helper builder for queries selecting individual properties based on the root object.

It can be used to select properties of the object itself, properties of related entities or some function calls (including aggregate functions).

Usage examples: 

 
      // select list of names:
      List<String> names = ObjectSelect.columnQuery(Artist.class, Artist.ARTIST_NAME).select(context);

      // select count:
      long count = ObjectSelect.columnQuery(Artist.class, Property.COUNT).selectOne();

      // select only required properties of an entity:
      List<Object[]> data = ObjectSelect.columnQuery(Artist.class, Artist.ARTIST_NAME, Artist.DATE_OF_BIRTH)
                                  .where(Artist.ARTIST_NAME.like("Picasso%))
                                  .select(context);

Note: this class can't be instantiated directly. Use ObjectSelect.

Since:
4.0
See Also:
ObjectSelect.columnQuery(Class, Property), Serialized Form

  • Constructor Details

    • ColumnSelect

      protected ColumnSelect()

    • ColumnSelect

      protected ColumnSelect​(ObjectSelect<T> select)
      Copy constructor to convert ObjectSelect to ColumnSelect

  • Method Details

    • createReplacementQuery

      protected Query createReplacementQuery​(EntityResolver resolver)
      Description copied from class: FluentSelect
      Translates self to a SelectQuery.
      Overrides:
      createReplacementQuery in class FluentSelect<T>

    • entityType

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

    • where

      public ColumnSelect<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

    • and

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

    • or

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

    • orderBy

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

    • orderBy

      public ColumnSelect<T> orderBy​(Collection<Ordering> orderings)
      Adds a list of orderings to this query.
      Returns:
      this object

    • prefetch

      public ColumnSelect<T> prefetch​(PrefetchTreeNode prefetch)
      Merges prefetch into the query prefetch tree.
      Returns:
      this object

    • prefetch

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

    • limit

      public ColumnSelect<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 ColumnSelect<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 ColumnSelect<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 ColumnSelect<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)

    • cacheStrategy

      public ColumnSelect<T> cacheStrategy​(QueryCacheStrategy strategy)

    • cacheStrategy

      public ColumnSelect<T> cacheStrategy​(QueryCacheStrategy strategy, String cacheGroup)

    • cacheGroup

      public ColumnSelect<T> cacheGroup​(String cacheGroup)

    • localCache

      public ColumnSelect<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 ColumnSelect<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 ColumnSelect<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 ColumnSelect<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);

    • columns

      public ColumnSelect<Object[]> columns​(Property<?> firstProperty, Property<?>... otherProperties)

      Add properties to select.

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

       
 List<Object[]> columns = ObjectSelect.columnQuery(Artist.class, Artist.ARTIST_NAME)
                                    .columns(Artist.ARTIST_SALARY, Artist.DATE_OF_BIRTH)
                                    .select(context);
      Parameters:
      firstProperty - first property
      otherProperties - array of properties to select
      See Also:
      column(Property), columns(Collection)

    • columns

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

      Add properties to select.

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

      Parameters:
      properties - collection of properties, must contain at least one element
      See Also:
      columns(Property, Property[])

    • column

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

    • count

      public ColumnSelect<Object[]> count()

      Shortcut for columns(Property, Property[]) columns}(Property.COUNT)

    • count

      public ColumnSelect<Object[]> count​(Property<?> property)

      Select COUNT(property)

      Can return different result than COUNT(*) as it will count only non null values

      See Also:
      count()

    • min

      public ColumnSelect<Object[]> min​(Property<?> property)

      Select minimum value of property

      See Also:
      columns(Property, Property[])

    • max

      public ColumnSelect<Object[]> max​(Property<?> property)

      Select maximum value of property

      See Also:
      columns(Property, Property[])

    • avg

      public ColumnSelect<Object[]> avg​(Property<?> property)

      Select average value of property

      See Also:
      columns(Property, Property[])

    • sum

      public <E extends Number> ColumnSelect<Object[]> sum​(Property<E> property)

      Select sum of values

      See Also:
      columns(Property, Property[])

    • having

      public ColumnSelect<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

    • having

      public ColumnSelect<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

    • and

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

    • or

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

    • distinct

      public ColumnSelect<T> distinct()
      Explicitly request distinct in query.

    • suppressDistinct

      public ColumnSelect<T> suppressDistinct()
      Explicitly suppress distinct in query.

    • getColumns

      public Collection<Property<?>> getColumns()

    • getHaving

      public Expression getHaving()
      Returns a HAVING clause Expression of this query.

    • 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.