RetrieveDescpublic interface RetrieveDesc implements ActionDescThis interface represents a retrieve descriptor used by an application
to retrieve container-managed entity beans from a persistent store. It
allows you specify which persistent fields an application wants to retrieve.
In addition, it allows an application to specify sophisticated constraints
on its object retrieval. |
| Methods Summary |
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| public void | addConstraint(java.lang.String name, int operation, java.lang.Object value)Adds a constraint on the persistent field specified by
name. The valid values for operation
are defined in ActionDesc. The parameter
value specifies the constraint value.
By default, multiple constraints are implicitly ANDed together.
If the applications want to OR together the constraints,
it can explicitly add OP_OR constraints. For example,
to OR together two constraints, an application can do the following:
addConstraint("field1", ActionDesc.OP_EQ, "field1Value");
addConstraint("field2", ActionDesc.OP_EQ, "field2Value");
addConstraint(null, ActionDesc.OP_OR, null);
The important thing to note about the above example is
that the constraints are processed in postfix order, so
the above example should be read as
(field1 == "field1Value") OR (field2 == "field2Value")
| | public void | addConstraint(java.lang.String name, com.sun.jdo.spi.persistence.support.sqlstore.RetrieveDesc foreignConstraint)Adds a constraint on the foreign field specified by
name. This method is used to specify a relationship
navigation on field name to the class represented by
the retrieve descriptor foreignConstraint.
If name is null, an unrelated constraint is added.
A constraint is unrelated, if there is neither a foreign field
nor a local field connecting to the retrieve descriptor
foreignConstraint.
| | public void | addConstraint(java.lang.String name, int operator, com.sun.jdo.spi.persistence.support.sqlstore.RetrieveDesc foreignConstraint, java.lang.String foreignFieldName)Adds a constraint on the field specified by name.
This method is useful e.g. for comparisons of local fields with field of a related object:
emp.addConstraint("lastName", ActionDesc.OP_EQ, mgr, lastName");
compares the employee's lastName field with the lastName field of the related manager.
| | public void | addResult(java.lang.String name, com.sun.jdo.spi.persistence.support.sqlstore.RetrieveDesc foreignConstraint, boolean projection)The addResult method is used to specify which fields should be
returned in a persistent object. If the field requested is a
reference to another persistent object then a RetrieveDesc may be
provided which describes which fields of the referenced object
should be returned and, optionally, constraints on it.
The parameter projection specifies, if the field
specified by name should be projected.
| | public void | addResult(int opCode, int resultType)The addResult method can be used to specify global
query attributes that don't end up in the where clause.
Aggregate functions and the distinct op code are examples for
those query options. The result type defines the object to be
returned by an aggregate query. In case of distinct the result
type should be FieldTypeEnumeration.NOT_ENUMERATED. The method
might be called twice, in case of a JDOQL query having both an
aggregate and distinct:
query.setResult("avg (distinct salary)");
->
retrieveDesc.addResult(OP_AVG, FieldTypeEnumeration.DOUBLE);
retrieveDesc.addResult(OP_DISTINCT, FieldTypeEnumeration.NOT_ENUMERATED);
retrieveDesc.addResult("salary", null, true);
| | public void | setNavigationalId(java.lang.Object navigationalId)Sets a navigational id on the retrieve descriptor.
This id will be used to discriminate different retrieve descriptors which
use the same navigational field.
| | public void | setPrefetchEnabled(boolean prefetchEnabled)Sets the prefetchEnabled option.
The prefetchEnabled option specifies whether prefetch of relationship
fields should be enabled for this retrieve descriptor. The prefetch
is enabled by default if such fields are part of DFG. A user needs
to explicitely disable prefetch for any particular query if the related
instances will not be used in this transaction.
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