/**
* Utility that does a discriminator candidate query for the specified candidate and subclasses
* and returns the class name of the instance that has the specified identity (if any).
*
* @param storeMgr RDBMS StoreManager
* @param ec execution context
* @param id The id
* @param cmd Metadata for the root candidate class
* @return Name of the class with this identity (or null if none found)
*/
public static String getClassNameForIdUsingDiscriminator(
RDBMSStoreManager storeMgr, ExecutionContext ec, Object id, AbstractClassMetaData cmd) {
// Check for input error
if (cmd == null || id == null) {
return null;
}
SQLExpressionFactory exprFactory = storeMgr.getSQLExpressionFactory();
ClassLoaderResolver clr = ec.getClassLoaderResolver();
DatastoreClass primaryTable = storeMgr.getDatastoreClass(cmd.getFullClassName(), clr);
// Form the query to find which one of these classes has the instance with this id
DiscriminatorStatementGenerator stmtGen =
new DiscriminatorStatementGenerator(
storeMgr, clr, clr.classForName(cmd.getFullClassName()), true, null, null);
stmtGen.setOption(SelectStatementGenerator.OPTION_RESTRICT_DISCRIM);
SelectStatement sqlStmt = stmtGen.getStatement();
// Select the discriminator
JavaTypeMapping discrimMapping = primaryTable.getDiscriminatorMapping(true);
SQLTable discrimSqlTbl =
SQLStatementHelper.getSQLTableForMappingOfTable(
sqlStmt, sqlStmt.getPrimaryTable(), discrimMapping);
sqlStmt.select(discrimSqlTbl, discrimMapping, null);
// Restrict to this id
JavaTypeMapping idMapping = primaryTable.getIdMapping();
JavaTypeMapping idParamMapping = new PersistableIdMapping((PersistableMapping) idMapping);
SQLExpression sqlFldExpr =
exprFactory.newExpression(sqlStmt, sqlStmt.getPrimaryTable(), idMapping);
SQLExpression sqlFldVal = exprFactory.newLiteralParameter(sqlStmt, idParamMapping, id, "ID");
sqlStmt.whereAnd(sqlFldExpr.eq(sqlFldVal), true);
// Perform the query
try {
ManagedConnection mconn = storeMgr.getConnection(ec);
SQLController sqlControl = storeMgr.getSQLController();
if (ec.getSerializeReadForClass(cmd.getFullClassName())) {
sqlStmt.addExtension(SQLStatement.EXTENSION_LOCK_FOR_UPDATE, true);
}
try {
PreparedStatement ps =
SQLStatementHelper.getPreparedStatementForSQLStatement(sqlStmt, ec, mconn, null, null);
String statement = sqlStmt.getSQLText().toSQL();
try {
ResultSet rs = sqlControl.executeStatementQuery(ec, mconn, statement, ps);
try {
if (rs != null) {
while (rs.next()) {
DiscriminatorMetaData dismd = discrimMapping.getTable().getDiscriminatorMetaData();
return RDBMSQueryUtils.getClassNameFromDiscriminatorResultSetRow(
discrimMapping, dismd, rs, ec);
}
}
} finally {
rs.close();
}
} finally {
sqlControl.closeStatement(mconn, ps);
}
} finally {
mconn.release();
}
} catch (SQLException sqe) {
NucleusLogger.DATASTORE.error("Exception thrown on querying of discriminator for id", sqe);
throw new NucleusDataStoreException(sqe.toString(), sqe);
}
return null;
}
