com.sun.jdo.spi.persistence.support.sqlstore

Interface RetrieveDesc

All Superinterfaces:

ActionDesc

All Known Implementing Classes:

RetrieveDescImpl

public interface RetrieveDesc
extends ActionDesc

This 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.

Field Summary

Fields inherited from interface com.sun.jdo.spi.persistence.support.sqlstore.ActionDesc

LOG_CREATE, LOG_DESTROY, LOG_NOOP, LOG_UPDATE, OP_ABS, OP_ADD, OP_AND, OP_APPROX, OP_AVG, OP_BETWEEN, OP_CONCAT, OP_COUNT, OP_COUNT_PC, OP_DISTINCT, OP_DIV, OP_EQ, OP_EQ_CLASS, OP_EQUIJOIN, OP_EXISTS, OP_FIELD, OP_FOR_UPDATE, OP_GE, OP_GT, OP_IN, OP_LE, OP_LEFTJOIN, OP_LENGTH, OP_LENGTHB, OP_LIKE, OP_LIKE_ESCAPE, OP_LOWER, OP_LT, OP_LTRIM, OP_MAX, OP_MAX_ROWS, OP_MAYBE_NULL, OP_MIN, OP_MOD, OP_MUL, OP_NE, OP_NONKEY, OP_NONREL_JOIN, OP_NOT, OP_NOTEXISTS, OP_NOTIN, OP_NOTNULL, OP_NULL, OP_NULL_COMPARISION_FUNCTION, OP_OR, OP_ORDERBY, OP_ORDERBY_DESC, OP_PARAMETER, OP_PARAMETER_COUNT, OP_POSITION, OP_POSITION_START, OP_RIGHTJOIN, OP_RTRIM, OP_RTRIMFIXED, OP_SOUNDEX, OP_SQRT, OP_SUB, OP_SUBSTR, OP_SUBSTRB, OP_SUBSTRING, OP_SUM, OP_UPPER, OP_VALUE

Method Summary

Modifier and Type	Method and Description
void	addConstraint(String name, int operation, Object value) Adds a constraint on the persistent field specified by name.
void	addConstraint(String name, int operator, RetrieveDesc foreignConstraint, String foreignFieldName) Adds a constraint on the field specified by name.
void	addConstraint(String name, RetrieveDesc foreignConstraint) Adds a constraint on the foreign field specified by name.
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.
void	addResult(String name, RetrieveDesc foreignConstraint, boolean projection) The addResult method is used to specify which fields should be returned in a persistent object.
void	setNavigationalId(Object navigationalId) Sets a navigational id on the retrieve descriptor.
void	setPrefetchEnabled(boolean prefetchEnabled) Sets the prefetchEnabled option.

Methods inherited from interface com.sun.jdo.spi.persistence.support.sqlstore.ActionDesc

getPersistenceCapableClass

Method Detail

addResult

void addResult(String name,
               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.

Parameters:

name - The name of the field to return.

foreignConstraint - RetrieveDesc describing fields and constraints for a referenced object.

projection - Specifies, if this is a projection.

addResult

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);

Parameters:

opCode - The operation code.

resultType - The object type returned by aggregate queries.

See Also:

FieldTypeEnumeration

addConstraint

void addConstraint(String name,
                   int operation,
                   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")
 

addConstraint

void addConstraint(String name,
                   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.

addConstraint

void addConstraint(String name,
                   int operator,
                   RetrieveDesc foreignConstraint,
                   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.

setNavigationalId

void setNavigationalId(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.

setPrefetchEnabled

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.

Parameters:

prefetchEnabled - the setting of the prefetchEnabled option.