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

Field Summary

Fields inherited from class org.apache.cayenne.query.FluentSelect

cacheGroup, cacheStrategy, dbEntityName, entityName, entityType, limit, offset, orderings, pageSize, prefetches, statementFetchSize, where

Fields inherited from class org.apache.cayenne.query.IndirectQuery

dataMap, lastResolver, name, replacementQuery

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	ColumnSelect()
protected	ColumnSelect(ObjectSelect<T> select) Copy constructor to convert ObjectSelect to ColumnSelect

Method Summary

Modifier and Type	Method and Description
ColumnSelect<T>	and(Collection<Expression> expressions) AND's provided expressions to the existing WHERE or HAVING clause expression.
ColumnSelect<T>	and(Expression... expressions) AND's provided expressions to the existing WHERE clause expression.
ColumnSelect<Object[]>	avg(Property<?> property) Select average value of property
ColumnSelect<T>	cacheGroup(String cacheGroup)
ColumnSelect<T>	cacheStrategy(QueryCacheStrategy strategy)
ColumnSelect<T>	cacheStrategy(QueryCacheStrategy strategy, String cacheGroup)
protected <E> ColumnSelect<E>	column(Property<E> property)
ColumnSelect<Object[]>	columns(Collection<Property<?>> properties) Add properties to select.
ColumnSelect<Object[]>	columns(Property<?> firstProperty, Property<?>... otherProperties) Add properties to select.
ColumnSelect<Object[]>	count() Shortcut for columns(Property, Property[]) columns}(Property.COUNT)
ColumnSelect<Object[]>	count(Property<?> property) Select COUNT(property)
protected Query	createReplacementQuery(EntityResolver resolver) Translates self to a SelectQuery.
ColumnSelect<T>	dbEntityName(String dbEntityName) Sets the DbEntity name to fetch without changing the return type of the query.
ColumnSelect<T>	distinct() Explicitly request distinct in query.
ColumnSelect<T>	entityName(String entityName) Sets the ObjEntity name to fetch without changing the return type of the query.
ColumnSelect<T>	entityType(Class<?> entityType) Sets the type of the entity to fetch without changing the return type of the query.
Collection<Property<?>>	getColumns()
Expression	getHaving() Returns a HAVING clause Expression of this query.
ColumnSelect<T>	having(Expression expression) Appends a having qualifier expression of this query.
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.
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.
ColumnSelect<T>	localCache() Instructs Cayenne to look for query results in the "local" cache when running the query.
ColumnSelect<T>	localCache(String cacheGroup) Instructs Cayenne to look for query results in the "local" cache when running the query.
ColumnSelect<Object[]>	max(Property<?> property) Select maximum value of property
ColumnSelect<Object[]>	min(Property<?> property) Select minimum value of property
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.
ColumnSelect<T>	or(Collection<Expression> expressions) OR's provided expressions to the existing WHERE or HAVING clause expression.
ColumnSelect<T>	or(Expression... expressions) OR's provided expressions to the existing WHERE clause expression.
ColumnSelect<T>	orderBy(Collection<Ordering> orderings) Adds a list of orderings to this query.
ColumnSelect<T>	orderBy(Ordering... orderings) Add one or more orderings to this query.
ColumnSelect<T>	orderBy(String property) Add an ascending ordering on the given property.
ColumnSelect<T>	orderBy(String property, SortOrder sortOrder) Add an ordering on the given property.
ColumnSelect<T>	pageSize(int pageSize) Resets query page size.
ColumnSelect<T>	prefetch(PrefetchTreeNode prefetch) Merges prefetch into the query prefetch tree.
ColumnSelect<T>	prefetch(String path, int semantics) Merges a prefetch path with specified semantics into the query prefetch tree.
T	selectFirst(ObjectContext context) Selects a single object using provided context.
ColumnSelect<T>	sharedCache() Instructs Cayenne to look for query results in the "shared" cache when running the query.
ColumnSelect<T>	sharedCache(String cacheGroup) Instructs Cayenne to look for query results in the "shared" cache when running the query.
ColumnSelect<T>	statementFetchSize(int size) Sets fetch size of the PreparedStatement generated for this query.
<E extends Number> ColumnSelect<Object[]>	sum(Property<E> property) Select sum of values
ColumnSelect<T>	suppressDistinct() Explicitly suppress distinct in query.
ColumnSelect<T>	where(Expression expression) Appends a qualifier expression of this query.
ColumnSelect<T>	where(String expressionString, Object... parameters) Appends a qualifier expression of this query, using provided expression String and an array of position parameters.

Methods inherited from class org.apache.cayenne.query.FluentSelect

batchIterator, getCacheGroup, getCacheStrategy, getDbEntityName, getEntityName, getEntityType, getLimit, getOffset, getOrderings, getPageSize, getPrefetches, getStatementFetchSize, getWhere, iterate, iterator, select, selectOne

Methods inherited from class org.apache.cayenne.query.IndirectQuery

createSQLAction, getDataMap, getMetaData, getName, getReplacementQuery, route, setDataMap, setName

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface org.apache.cayenne.query.Query

createSQLAction, getDataMap, getMetaData, getName, route

Constructor Detail

ColumnSelect

protected ColumnSelect()

ColumnSelect

protected ColumnSelect(ObjectSelect<T> select)

Copy constructor to convert ObjectSelect to ColumnSelect

Method Detail

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.