com.goldencode.p2j.persist

Class ServerJoin

java.lang.Object

com.goldencode.p2j.persist.AbstractJoin

com.goldencode.p2j.persist.ServerJoin

final class ServerJoin
extends AbstractJoin

An implementation of a natural join helper used by query types which perform the join on the database server. The FQL query string snippet created by this class joins the local DMO with the inverse DMO using the aliases of each, and does not have a query substitution parameter. For instance, given the three table relationship:

    Person [one-to-many] ---> PersonAddress [many-to-one] ---> Address
 

and the following multi-table join in Progress

    for each person,
        each person-address of person,
        each address of person-address:
       ...
 

the first join (person-address of person) is represented as follows:

    personAddress.personRecord = person
 

where PersonAddress is the local DMO and Person the foreign DMO; and the second join (address of person-address) is represented as follows:

    address = personAddress.addressRecord
 

where Address is the local DMO and PersonAddress the foreign DMO.

Field Summary

Fields inherited from class com.goldencode.p2j.persist.AbstractJoin

inverse, NOT_NULL_FIELD, NULL_FIELD

Constructor Summary

Constructors

Constructor and Description
ServerJoin(RecordBuffer local, RecordBuffer inverse) Constructor.

Method Summary

Modifier and Type	Method and Description
protected FQLExpression[][]	generateFQL(RecordBuffer local, RecordBuffer inverse, RelationInfo info, boolean dereference) Generate the FQL where clause snippets which will be inserted into the overall FQL statement executed by the enclosing query.
protected java.util.List<FqlType>	getParameterTypes(RelationInfo info, boolean dereference) Determine the type of the query substitution parameters, if any.
protected boolean	isServerJoin() Report whether the join represented by this object takes place at the database server, or within runtime code.

Methods inherited from class com.goldencode.p2j.persist.AbstractJoin

getFQL, getInverse, getInverseInterface, getParameters, getParameterTypes, getUnresolvedParameters, raiseJoinError, setup

Methods inherited from class java.lang.Object

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

Constructor Detail

ServerJoin

ServerJoin(RecordBuffer local,
           RecordBuffer inverse)

Constructor.

Parameters:

local - Local record buffer (the refering end of the join).

inverse - Inverse record buffer (the referent end of the join).

Method Detail

isServerJoin

protected boolean isServerJoin()

Report whether the join represented by this object takes place at the database server, or within runtime code.

Specified by:

isServerJoin in class AbstractJoin

Returns:

true if the join happens at the server; false if it happens in the runtime.

generateFQL

protected FQLExpression[][] generateFQL(RecordBuffer local,
                                        RecordBuffer inverse,
                                        RelationInfo info,
                                        boolean dereference)

Generate the FQL where clause snippets which will be inserted into the overall FQL statement executed by the enclosing query. See the class description for additional details on the composition of the clause.

Specified by:

generateFQL in class AbstractJoin

Parameters:

local - Local record buffer (the refering end of the join).

inverse - Inverse record buffer (the referent end of the join).

info - Relation descriptor object.

dereference - true if the local DMO contains a reference to the foreign record, which must be dereferenced in the FQL query; false if the local DMO is the foreign record, referenced by the inverse DMO.

Returns:

FQL where clause snippets used to perform the join. A bi-dimensional array of clauses are used. The first dimension is the size of the join (aka the number of fields paired) and the second is always two: the first (NULL_FIELD) is used when the joined field is null and the second (NOT_NULL_FIELD) is used when the join field is not unknown.

getParameterTypes

protected java.util.List<FqlType> getParameterTypes(RelationInfo info,
                                                    boolean dereference)

Determine the type of the query substitution parameters, if any. Since this implementation utilizes no query substitution parameter, this method always returns null.

Specified by:

getParameterTypes in class AbstractJoin

Parameters:

info - Not used.

dereference - Not used.

Returns:

null.