ServerLegacyKeyJoin.java
/*
** Module : ServerLegacyKeyJoin.java
** Abstract : Natural join helper implementation for server-side queries,
** which uses the "legacy foreign key" fields to perform join.
**
** Copyright (c) 2004-2024, Golden Code Development Corporation.
**
** -#- -I- --Date-- --JPRM-- -----------------------------------Description-----------------------------------
** 001 SVL 20080421 @38154 Created initial version. Natural join helper
** for server-side joins using legacy keys.
** 002 ECF 20080822 @39563 Added isServerJoin(). Reports whether join
** occurs at database server or within P2J
** runtime environment.
** 003 SVL 20140210 Use HQLExpression instead of HQL string.
** 004 EVL 20160223 Javadoc fixes to make compatible with Oracle Java 8 for Solaris 10.
** 005 ECF 20200906 New ORM implementation.
** OM 20221103 New class names for FQLPreprocessor, FQLExpression, FQLBundle, and FQLCache.
** 006 OM 20230404 The join navigation key may contain null/unknown values.
** 007 OM 20240102 Correctly map the properties of local/inverse buffers.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program is distributed in the hope that it will be useful,
** but WITHOUT ANY WARRANTY; without even the implied warranty of
** MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
** GNU Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
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** work or Appropriate Legal Notices displayed by works containing the covered
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**
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**
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** attribution required in this license.
*/
package com.goldencode.p2j.persist;
import java.util.*;
import com.goldencode.p2j.persist.orm.*;
/**
* 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
* fields which compose the "legacy foreign key" relation, and does not have
* a query substitution parameter. For instance, given the three table
* relationship:
* <pre>
* Person [one-to-many] ---> PersonAddress [many-to-one] ---> Address
* </pre>
* and the following multi-table join in Progress
* <pre>
* for each person,
* each person-address of person,
* each address of person-address:
* ...
* </pre>
* the first join (<code>person-address of person</code>) is represented as
* follows:
* <pre>
* personAddress.siteId = person.siteId and
* personAddress.empNum = person.empNum
* </pre>
* where <code>PersonAddress</code> is the local DMO and Person the foreign
* DMO; and the second join (<code>address of person-address</code>) is
* represented as follows:
* <pre>
* address.addrId = personAddress.addrId
* </pre>
* where <code>Address</code> is the local DMO and PersonAddress the foreign
* DMO.
*/
final class ServerLegacyKeyJoin
extends AbstractJoin
{
/**
* Constructor.
*
* @param local
* Local record buffer (the refering end of the join).
* @param inverse
* Inverse record buffer (the referent end of the join).
*/
ServerLegacyKeyJoin(RecordBuffer local, final RecordBuffer inverse)
{
super(local, inverse);
}
/**
* Report whether the join represented by this object takes place at the
* database server, or within runtime code.
*
* @return <code>true</code> if the join happens at the server;
* <code>false</code> if it happens in the runtime.
*/
protected boolean isServerJoin()
{
return true;
}
/**
* Generate the FQL where clause snippet 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.
*
* @param local
* Local record buffer (the refering end of the join).
* @param inverse
* Inverse record buffer (the referent end of the join).
* @param info
* Relation descriptor object.
* @param dereference
* {@code true} if the local DMO contains a reference to the foreign record, which must be
* dereferenced in the FQL query; {@code false} if the local DMO <i>is</i> the foreign record,
* referenced by the inverse DMO.
*
* @return 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 {@code null} and the second
* (NOT_NULL_FIELD) is used when the join field is not unknown.
*/
protected FQLExpression[][] generateFQL(RecordBuffer local,
RecordBuffer inverse,
RelationInfo info,
boolean dereference)
{
List<FQLExpression> wcListNotNulls = new ArrayList<>();
List<FQLExpression> wcListNulls = new ArrayList<>();
boolean switched = local.getDMOImplementationClass() != info.getLocalClass();
Iterator<String> localProperties = switched ? info.foreignProperties() : info.localProperties();
Iterator<String> foreignProperties = switched ? info.localProperties() : info.foreignProperties();
try
{
boolean first = true;
while (localProperties.hasNext() && foreignProperties.hasNext())
{
FQLExpression wcNotNull = new FQLExpression();
FQLExpression wcNull = new FQLExpression();
if (!first)
{
wcNotNull.append(" and ");
wcNull.append(" and ");
}
else
{
first = false;
}
StringBuilder bufLocal = new StringBuilder();
DBUtils.composePropertyName(local, localProperties.next(), bufLocal);
StringBuilder bufForeign = new StringBuilder();
DBUtils.composePropertyName(inverse, foreignProperties.next(), bufForeign);
wcNotNull.append(bufLocal.toString()).append(" = ").append(bufForeign.toString());
wcNull.append(bufLocal.toString()).append(" is null");
wcListNotNulls.add(wcNotNull);
wcListNulls.add(wcNull);
}
}
catch (PersistenceException e)
{
// RelationInfo contains incorrect information
throw new IllegalArgumentException(e);
}
// collect result and construct the 2-dimensional return array
int len = wcListNotNulls.size();
FQLExpression[][] ret = new FQLExpression[len][2];
for (int i = 0; i < len; i++)
{
ret[i][NULL_FIELD] = wcListNulls.get(i);
ret[i][NOT_NULL_FIELD] = wcListNotNulls.get(i);
}
return ret;
}
/**
* Get the values of DMO instance fields which will be used as the query substitution
* parameters. Since this implementation utilizes no query substitution parameters, this method
* always returns {@code null}.
*
* @param info
* Not used.
* @param dereference
* Not used.
*
* @return {@code null}.
*/
@Override
protected List<FqlType> getParameterTypes(RelationInfo info, boolean dereference)
{
return null;
}
}