Interface Query
- All Superinterfaces:
Serializable
Query
interface allows applications to obtain persistent
instances, values, and aggregate data
from the data store.
The PersistenceManager
is the factory for Query
instances. There may be many Query
instances associated with a
PersistenceManager
. Multiple queries might be executed
simultaneously by different threads, but the implementation might choose to
execute them serially. In either case, the implementation must be thread
safe.
There are three required elements in a Query
: the class of
the results, the candidate collection of instances, and the filter.
There are optional elements: parameter declarations, variable declarations, import statements, ordering and grouping specifications, result and result class, the range of results, and flags indicating whether the query result is unique and whether the query can be modified.
The query namespace is modeled after methods in Java:
setClass
corresponds to the class definitiondeclareParameters
corresponds to formal parameters of a methoddeclareVariables
corresponds to local variables of a methodsetFilter
andsetOrdering
correspond to the method body
There are two namespaces in queries. Type names have their own namespace that is separate from the namespace for fields, variables and parameters.
The method setClass
introduces the name of the candidate
class in the type namespace. The method declareImports
introduces the names of the imported class or interface types in the type
namespace. Imported type names must be unique. When used (e.g. in a parameter
declaration, cast expression, etc.) a type name must be the name of the
candidate class, the name of a class or interface imported by method
declareImports
, or denote a class or interface from the same
package as the candidate class.
The method setClass
introduces the names of the candidate
class fields.
The method declareParameters
introduces the names of the
parameters. A name introduced by declareParameters
hides the
name of a candidate class field of the same name. Parameter names must be
unique.
The method declareVariables
introduces the names of the
variables. A name introduced by declareVariables
hides the name
of a candidate class field if equal. Variable names must be unique and must
not conflict with parameter names.
The result of the query by default is a list of result class instances,
but might be specified via setResult
. The class of the result
by default is the candidate class, but might be specified via
setResultClass
.
A hidden field may be accessed using the 'this' qualifier:
this.fieldName
.
The Query
interface provides methods which execute the query
based on the parameters given. They return a single instance or a
List
of result class instances which the
user can iterate to get results. The signature
of the execute
methods specifies that they return an
Object
which must be cast to the appropriate result by the user.
Any parameters passed to the execute
methods are used only
for this execution, and are not remembered for future execution.
- Version:
- 2.1
-
Field Summary
FieldsModifier and TypeFieldDescriptionstatic final String
The string constant used as the first argument toPersistenceManager.newQuery(String,Object)
to identify that the created query should obey the JDOQL syntax and semantic rules.static final String
The string constant used as the first argument toPersistenceManager.newQuery(String,Object)
to identify that the created query should use SQL semantics. -
Method Summary
Modifier and TypeMethodDescriptionvoid
addExtension
(String key, Object value) Add a vendor-specific extension to this query.void
addSubquery
(Query sub, String variableDeclaration, String candidateCollectionExpression) Add a subquery to this query.void
addSubquery
(Query sub, String variableDeclaration, String candidateCollectionExpression, String parameter) Add a subquery to this query.void
addSubquery
(Query sub, String variableDeclaration, String candidateCollectionExpression, String... parameters) Add a subquery to this query.void
addSubquery
(Query sub, String variableDeclaration, String candidateCollectionExpression, Map parameters) Add a subquery to this query.void
Close a query result and release any resources associated with it.void
closeAll()
Close all query results associated with thisQuery
instance, and release all resources associated with them.void
compile()
Verify the elements of the query and provide a hint to the query to prepare and optimize an execution plan.void
declareImports
(String imports) Set the import statements to be used to identify the fully qualified name of variables or parameters.void
declareParameters
(String parameters) Declare the list of parameters query execution.void
declareVariables
(String variables) Declare the unbound variables to be used in the query.long
Deletes all the instances of the candidate class that pass the filter.long
deletePersistentAll
(Object... parameters) Deletes all the instances of the candidate class that pass the filter.long
deletePersistentAll
(Map parameters) Deletes all the instances of the candidate class that pass the filter.execute()
Execute the query and return the filtered Collection.Execute the query and return the filteredCollection
.Execute the query and return the filteredCollection
.Execute the query and return the filteredCollection
.executeWithArray
(Object... parameters) Execute the query and return the filteredCollection
.executeWithMap
(Map parameters) Execute the query and return the filteredCollection
.Returns theFetchPlan
used by thisQuery
.boolean
Get the ignoreCache option setting.Get thePersistenceManager
associated with thisQuery
.boolean
The unmodifiable flag, when set, disallows further modification of the query, except for specifying the range, result class, and ignoreCache option.void
setCandidates
(Collection pcs) Set the candidateCollection
to query.void
setCandidates
(Extent pcs) Set the candidateExtent
to query.void
Set the class of the candidate instances of the query.void
setExtensions
(Map extensions) Set multiple extensions, or use null to clear all extensions.void
Set the filter for the query.void
setGrouping
(String group) Set the grouping expressions, optionally including a "having" clause.void
setIgnoreCache
(boolean ignoreCache) Set the ignoreCache option.void
setOrdering
(String ordering) Set the ordering specification for the resultCollection
.void
setRange
(long fromIncl, long toExcl) Set the range of results to return.void
Set the range of results to return.void
Specifies what type of data this query should return.void
setResultClass
(Class cls) Specify the type of object in which to return each element of the result of invokingexecute()
or one of its siblings.void
setUnique
(boolean unique) Specify that only the first result of the query should be returned, rather than a collection.void
The unmodifiable flag, when set, disallows further modification of the query, except for specifying the range, result class, and ignoreCache option.
-
Field Details
-
JDOQL
The string constant used as the first argument toPersistenceManager.newQuery(String,Object)
to identify that the created query should obey the JDOQL syntax and semantic rules.This is the default query language used when creating a query with any of the other
PersistenceManager.newQuery()
methods, exceptPersistenceManager.newQuery(Object)
, which uses the query language of the compiled query template object passed to that method.- Since:
- 2.0
- See Also:
-
SQL
The string constant used as the first argument toPersistenceManager.newQuery(String,Object)
to identify that the created query should use SQL semantics. This is only meaningful for relational JDO implementations.If this is used, the
Object
argument to thePersistenceManager.newQuery(String,Object)
method should be aString
containing a SQLSELECT
statement.- Since:
- 2.0
- See Also:
-
-
Method Details
-
setClass
Set the class of the candidate instances of the query.The class specifies the class of the candidates of the query. Elements of the candidate collection that are of the specified class are filtered before being put into the result
Collection
.- Parameters:
cls
- theClass
of the candidate instances.
-
setCandidates
Set the candidateExtent
to query.- Parameters:
pcs
- the candidateExtent
.
-
setCandidates
Set the candidateCollection
to query.- Parameters:
pcs
- the candidateCollection
.
-
setFilter
Set the filter for the query.The filter specification is a
String
containing a Boolean expression that is to be evaluated for each of the instances in the candidate collection. If the filter is not specified, then it defaults to "true", which has the effect of filtering the inputCollection
only for class type.An element of the candidate collection is returned in the result if:
- it is assignment compatible to the candidate
Class
of theQuery
; and - for all variables there exists a value for which the filter
expression evaluates to
true
.
The user may denote uniqueness in the filter expression by explicitly declaring an expression (for example,
e1 != e2
).Rules for constructing valid expressions follow the Java language, except for these differences:
- Equality and ordering comparisons between primitives and instances of wrapper classes are valid.
- Equality and ordering comparisons of
Date
fields andDate
parameters are valid. - White space (non-printing characters space, tab, carriage return, and line feed) is a separator and is otherwise ignored.
- The assignment operators
=
,+=
, etc. and pre- and post-increment and -decrement are not supported. Therefore, there are no side effects from evaluation of any expressions. - Methods, including object construction, are not supported, except
for
Collection.contains(Object o)
,Collection.isEmpty()
,String.startsWith(String s)
, andString.endsWith(String e)
. Implementations might choose to support non-mutating method calls as non-standard extensions. - Navigation through a
null
-valued field, which would throwNullPointerException
, is treated as if the filter expression returnedfalse
for the evaluation of the current set of variable values. Other values for variables might still qualify the candidate instance for inclusion in the result set. - Navigation through multi-valued fields (
Collection
types) is specified using a variable declaration and theCollection.contains(Object o)
method.
Identifiers in the expression are considered to be in the name space of the specified class, with the addition of declared imports, parameters and variables. As in the Java language,
this
is a reserved word which means the element of the collection being evaluated.Navigation through single-valued fields is specified by the Java language syntax of
field_name.field_name....field_name
.A JDO implementation is allowed to reorder the filter expression for optimization purposes.
- Parameters:
filter
- the query filter.
- it is assignment compatible to the candidate
-
declareImports
Set the import statements to be used to identify the fully qualified name of variables or parameters. Parameters and unbound variables might come from a different class from the candidate class, and the names need to be declared in an import statement to eliminate ambiguity. Import statements are specified as aString
with semicolon-separated statements.The
String
parameter to this method follows the syntax of the import statement of the Java language.- Parameters:
imports
- import statements separated by semicolons.
-
declareParameters
Declare the list of parameters query execution. The parameter declaration is aString
containing one or more query parameter declarations separated with commas. Each parameter named in the parameter declaration must be bound to a value when the query is executed.The
String
parameter to this method follows the syntax for formal parameters in the Java language.- Parameters:
parameters
- the list of parameters separated by commas.
-
declareVariables
Declare the unbound variables to be used in the query. Variables might be used in the filter, and these variables must be declared with their type. The unbound variable declaration is aString
containing one or more unbound variable declarations separated with semicolons. It follows the syntax for local variables in the Java language.- Parameters:
variables
- the variables separated by semicolons.
-
setOrdering
Set the ordering specification for the resultCollection
. The ordering specification is aString
containing one or more ordering declarations separated by commas.Each ordering declaration is the name of the field on which to order the results followed by one of the following words: "
ascending
" or "descending
".The field must be declared in the candidate class or must be a navigation expression starting with a field in the candidate class.
Valid field types are primitive types except
boolean
; wrapper types exceptBoolean
;BigDecimal
;BigInteger
;String
; andDate
.- Parameters:
ordering
- the ordering specification.
-
setIgnoreCache
void setIgnoreCache(boolean ignoreCache) Set the ignoreCache option. The default value for this option was set by thePersistenceManagerFactory
or thePersistenceManager
used to create thisQuery
. The ignoreCache option setting specifies whether the query should execute entirely in the back end, instead of in the cache. If this flag is set totrue
, an implementation might be able to optimize the query execution by ignoring changed values in the cache. For optimistic transactions, this can dramatically improve query response times.- Parameters:
ignoreCache
- the setting of the ignoreCache option.
-
getIgnoreCache
boolean getIgnoreCache()Get the ignoreCache option setting.- Returns:
- the ignoreCache option setting.
- See Also:
-
compile
void compile()Verify the elements of the query and provide a hint to the query to prepare and optimize an execution plan. -
execute
Object execute()Execute the query and return the filtered Collection.- Returns:
- the filtered
Collection
. - See Also:
-
execute
Execute the query and return the filteredCollection
.- Parameters:
p1
- the value of the first parameter declared.- Returns:
- the filtered
Collection
. - See Also:
-
execute
Execute the query and return the filteredCollection
.- Parameters:
p1
- the value of the first parameter declared.p2
- the value of the second parameter declared.- Returns:
- the filtered
Collection
. - See Also:
-
execute
Execute the query and return the filteredCollection
.- Parameters:
p1
- the value of the first parameter declared.p2
- the value of the second parameter declared.p3
- the value of the third parameter declared.- Returns:
- the filtered
Collection
. - See Also:
-
executeWithMap
Execute the query and return the filteredCollection
. The query is executed with the parameters set by theMap
values. EachMap
entry consists of a key which is the name of the parameter in thedeclareParameters
method, and a value which is the value used in theexecute
method. The keys in theMap
and the declared parameters must exactly match or aJDOUserException
is thrown.- Parameters:
parameters
- theMap
containing all of the parameters.- Returns:
- the filtered
Collection
. - See Also:
-
executeWithArray
Execute the query and return the filteredCollection
.The execution of the query obtains the values of the parameters and matches them against the declared parameters in order. The names of the declared parameters are ignored. The type of the declared parameters must match the type of the passed parameters, except that the passed parameters might need to be unwrapped to get their primitive values.
The filter, import, declared parameters, declared variables, and ordering statements are verified for consistency.
Each element in the candidate
Collection
is examined to see that it is assignment compatible to theClass
of the query. It is then evaluated by the Boolean expression of the filter. The element passes the filter if there exist unique values for all variables for which the filter expression evaluates totrue
.- Parameters:
parameters
- theObject
array with all of the parameters.- Returns:
- the filtered
Collection
.
-
getPersistenceManager
PersistenceManager getPersistenceManager()Get thePersistenceManager
associated with thisQuery
.If this
Query
was restored from a serialized form, it has noPersistenceManager
, and this method returnsnull
.- Returns:
- the
PersistenceManager
associated with thisQuery
.
-
close
Close a query result and release any resources associated with it. The parameter is the return fromexecute(...)
and might have iterators open on it. Iterators associated with the query result are invalidated: they returnfalse
tohasNext()
and throwNoSuchElementException
tonext()
.- Parameters:
queryResult
- the result ofexecute(...)
on thisQuery
instance.
-
closeAll
void closeAll()Close all query results associated with thisQuery
instance, and release all resources associated with them. The query results might have iterators open on them. Iterators associated with the query results are invalidated: they returnfalse
tohasNext()
and throwNoSuchElementException
tonext()
. -
setGrouping
Set the grouping expressions, optionally including a "having" clause. When grouping is specified, each result expression must either be an expression contained in the grouping, or an aggregate evaluated once per group.- Parameters:
group
- a comma-delimited list of expressions, optionally followed by the "having" keyword and a boolean expression- Since:
- 2.0
-
setUnique
void setUnique(boolean unique) Specify that only the first result of the query should be returned, rather than a collection. The execute method will return null if the query result size is 0.- Parameters:
unique
- if true, only one element is returned- Since:
- 2.0
-
setResult
Specifies what type of data this query should return. If this is unset or set tonull
, this query returns instances of the query's candidate class. If set, this query will return expressions, including field values (projections) and aggregate function results.- Parameters:
data
- a comma-delimited list of expressions (fields, functions on fields, or aggregate functions) to return from this query- Since:
- 2.0
-
setResultClass
Specify the type of object in which to return each element of the result of invokingexecute()
or one of its siblings. If the result is not set or set to null, the result class defaults to the candidate class of the query. If the result consists of one expression, the result class defaults to the type of that expression. If the result consists of more than one expression, the result class defaults to Object[]. The result class may be specified to be one of the java.lang classes Character, Boolean, Byte, Short, Integer, Long, Float, Double, String, or Object[]; or one of the java.math classes BigInteger or BigDecimal; or the java.util class Date; or one of the java.sql classes Date, Time, or Timestamp; or a user-defined class.If there are multiple result expressions, the result class must be able to hold all elements of the result specification or a JDOUserException is thrown.
If there is only one result expression, the result class must be assignable from the type of the result expression or must be able to hold all elements of the result specification. A single value must be able to be coerced into the specified result class (treating wrapper classes as equivalent to their unwrapped primitive types) or by matching. If the result class does not satisfy these conditions, a JDOUserException is thrown.
A constructor of a result class specified in the setResult method will be used if the results specification matches the parameters of the constructor by position and type. If more than one constructor satisfies the requirements, the JDO implementation chooses one of them. If no constructor satisfies the results requirements, or if the result class is specified via the setResultClass method, the following requirements apply:
- A user-defined result class must have a no-args constructor and
one or more public
set
orput
methods or fields. - Each result expression must match one of:
- a public field that matches the name of the result expression and is of the type (treating wrapper types equivalent to primitive types) of the result expression;
- or if no public field matches the name and type, a public
setinvalid input: '<'/code method that returns void and matches the name of the result expression and takes a single parameter which is the exact type of the result expression;
- or if neither of the above applies,a public method must be found with the signature
void put(Object, Object)
. During processing of the results, the first argument is the name of the result expression and the second argument is the value from the query result. - or if neither of the above applies,a public method must be found with the signature
setinvalid input: '<'/code methods.
- Parameters:
cls
- the result class- Since:
- 2.0
- A user-defined result class must have a no-args constructor and
one or more public
-
setRange
void setRange(long fromIncl, long toExcl) Set the range of results to return. The execution of the query is modified to return only a subset of results. If the filter would normally return 100 instances, and fromIncl is set to 50, and toExcl is set to 70, then the first 50 results that would have been returned are skipped, the next 20 results are returned and the remaining 30 results are ignored. An implementation should execute the query such that the range algorithm is done at the data store.- Parameters:
fromIncl
- 0-based inclusive start indextoExcl
- 0-based exclusive end index, orLong.MAX_VALUE
for no limit.- Since:
- 2.0
-
setRange
Set the range of results to return. The parameter is a String containing a comma-separated fromIncl and toExcl. The fromIncl and toExcl can be either String representations of long values, or can be parameters identified with a leading ":". For example,setRange("50, 70");
orsetRange(":from, :to");
orsetRange("50, :to");
. The execution of the query is modified to return only a subset of results. If the filter would normally return 100 instances, and fromIncl is set to 50, and toExcl is set to 70, then the first 50 results that would have been returned are skipped, the next 20 results are returned and the remaining 30 results are ignored. An implementation should execute the query such that the range algorithm is done at the data store.- Parameters:
fromInclToExcl
- comma-separated fromIncl and toExcl values- Since:
- 2.0
- See Also:
-
addExtension
Add a vendor-specific extension to this query. The key and value are not standard. An implementation must ignore keys that are not recognized.- Parameters:
key
- the key of the extensionvalue
- the value of the extension- Since:
- 2.0
-
setExtensions
Set multiple extensions, or use null to clear all extensions. Map keys and values are not standard. An implementation must ignore entries that are not recognized.- Parameters:
extensions
- the map of extensions- Since:
- 2.0
- See Also:
-
getFetchPlan
FetchPlan getFetchPlan()Returns theFetchPlan
used by thisQuery
. Modifications of the returned fetch plan will not cause this query's owningPersistenceManager
'sFetchPlan
to be modified.- Returns:
- the fetch plan used by this query
- Since:
- 2.0
-
deletePersistentAll
Deletes all the instances of the candidate class that pass the filter.- Parameters:
parameters
- for the query- Returns:
- the number of instances of the candidate class that were deleted
- Since:
- 2.0
- See Also:
-
deletePersistentAll
Deletes all the instances of the candidate class that pass the filter.- Parameters:
parameters
- for the query- Returns:
- the number of instances of the candidate class that were deleted
- Since:
- 2.0
- See Also:
-
deletePersistentAll
long deletePersistentAll()Deletes all the instances of the candidate class that pass the filter. Returns the number of instances of the candidate class that were deleted, specifically not including the number of dependent and embedded instances.Dirty instances of affected classes in the cache are first flushed to the datastore. Instances in the cache or brought into the cache as a result of executing one of the
deletePersistentAll
methods undergo life cycle changes as ifdeletePersistent
were called on them.Specifically, if the class of deleted instances implements the delete callback interface, the corresponding callback methods are called on the deleted instances. Similarly, if there are lifecycle listeners registered for delete events on affected classes, the listener is called for each appropriate deleted instance.
Before returning control to the application, instances of affected classes in the cache are refreshed to reflect whether they were deleted from the datastore.
- Returns:
- the number of instances of the candidate class that were deleted
- Since:
- 2.0
-
setUnmodifiable
void setUnmodifiable()The unmodifiable flag, when set, disallows further modification of the query, except for specifying the range, result class, and ignoreCache option. The unmodifiable flag can also be set in metadata.- Since:
- 2.0
-
isUnmodifiable
boolean isUnmodifiable()The unmodifiable flag, when set, disallows further modification of the query, except for specifying the range, result class, and ignoreCache option.- Returns:
- the current setting of the flag
- Since:
- 2.0
-
addSubquery
Add a subquery to this query.- Parameters:
sub
- the subquery to add to this QueryvariableDeclaration
- the name of the variable in the outer query to bind the results of the subquerycandidateCollectionExpression
- the candidate collection of the subquery as an expression using terms of the outer query- Since:
- 2.1
- See Also:
-
addSubquery
void addSubquery(Query sub, String variableDeclaration, String candidateCollectionExpression, String parameter) Add a subquery to this query. The String version of the method binds the named expression to the parameter implictly or explicitly declared in the subquery.- Parameters:
sub
- the subquery to add to this QueryvariableDeclaration
- the name of the variable to be used in this QuerycandidateCollectionExpression
- the candidate collection to apply to the subqueryparameter
- the expression from the outer query to bind the parameter in the subquery- Since:
- 2.1
- See Also:
-
addSubquery
void addSubquery(Query sub, String variableDeclaration, String candidateCollectionExpression, String... parameters) Add a subquery to this query. A subquery is composed as a Query and subsequently attached to a different query (the outer query) by calling this method. The query parameter instance is unmodified as a result of the addSubquery or subsequent execution of the outer query. Only some of the query parts are copied for use as the subquery. The parts copied include the candidate class, filter, parameter declarations, variable declarations, imports, ordering specification, uniqueness, result specification, and grouping specification. The association with a PersistenceManager, the candidate collection or extent, result class, and range limits are not used. The String parameters are trimmed of white space. The variableDeclaration parameter is the name of the variable containing the results of the subquery execution. If the same value of variableDeclaration is used to add multiple subqueries, the subquery replaces the previous subquery for the same named variable. If the subquery parameter is null, the variable is unset, effectively making the variable named in the variableDeclaration unbound. If the trimmed value is the empty String, or the parameter is null, then JDOUserException is thrown. The candidateCollectionExpression is the expression from the outer query that represents the candidates over which the subquery is evaluated. If the trimmed value is the empty String, or the parameter is null, then the candidate collection is the extent of the candidate class. The String... version of the method binds the named expressions in turn to parameters in the order in which they are declared in the subquery, or in the order they are found in the filter if not explicitly declared in the subquery.- Parameters:
sub
- the subquery to add to this QueryvariableDeclaration
- the name of the variable in the outer query to bind the results of the subquerycandidateCollectionExpression
- the candidate collection of the subquery as an expression using terms of the outer queryparameters
- the expressions from the outer query to bind the parameters in the subquery- Since:
- 2.1
-
addSubquery
void addSubquery(Query sub, String variableDeclaration, String candidateCollectionExpression, Map parameters) Add a subquery to this query. The Map version of the method treats the key of each map entry as the name of the parameter in the subquery, with or without the leading ":", and the value as the name of the expression in the outer query. If the trimmed expression is the empty String for either the parameter or the value of the String[], or for any map key or value, that expression is ignored.- Parameters:
sub
- the subquery to add to this QueryvariableDeclaration
- the name of the variable to be used in this QuerycandidateCollectionExpression
- the candidate collection to apply to the subqueryparameters
- the expressions from the outer query to bind the parameter in the subquery- Since:
- 2.1
- See Also:
-