[TAP] Fix the VOTable's FITS serialization.

Until now, the generated VOTable file was un-readable even by
STIL/STILTS/TOPCAT. To fix this, it was needed to temporary store the table to
format into FITS so that STIL can read it at least 2 times.

_This commit fixes the GitHub issue #43 ._

src/tap/formatter/VOTableFormat.java

@@ -16,7 +16,7 @@ package tap.formatter;
  * You should have received a copy of the GNU Lesser General Public License
  * along with TAPLibrary.  If not, see <http://www.gnu.org/licenses/>.
  *
- * Copyright 2012-2017 - UDS/Centre de Données astronomiques de Strasbourg (CDS)
+ * Copyright 2012-2019 - UDS/Centre de Données astronomiques de Strasbourg (CDS)
  *                       Astronomisches Rechen Institut (ARI)
  */
 
@@ -29,6 +29,9 @@ import java.util.HashSet;
 import java.util.Iterator;
 import java.util.Map;
 
+import adql.db.DBColumn;
+import adql.db.DBType;
+import adql.db.DBType.DBDatatype;
 import tap.ServiceConnection;
 import tap.TAPException;
 import tap.TAPExecutionReport;
@@ -44,13 +47,11 @@ import uk.ac.starlink.table.ColumnInfo;
 import uk.ac.starlink.table.DescribedValue;
 import uk.ac.starlink.table.RowSequence;
 import uk.ac.starlink.table.StarTable;
+import uk.ac.starlink.table.StoragePolicy;
 import uk.ac.starlink.votable.DataFormat;
 import uk.ac.starlink.votable.VOSerializer;
 import uk.ac.starlink.votable.VOStarTable;
 import uk.ac.starlink.votable.VOTableVersion;
-import adql.db.DBColumn;
-import adql.db.DBType;
-import adql.db.DBType.DBDatatype;
 
 /**
  * <p>Format any given query (table) result into VOTable.</p>
@@ -85,7 +86,7 @@ import adql.db.DBType.DBDatatype;
  * </p>
  *
  * @author Gr&eacute;gory Mantelet (CDS;ARI)
- * @version 2.1 (07/2017)
+ * @version 2.2 (03/2019)
  */
 public class VOTableFormat implements OutputFormat {
 
@@ -336,7 +337,15 @@ public class VOTableFormat implements OutputFormat {
 		table.setName("result_" + execReport.jobID);
 
 		/* Prepares the object that will do the serialization work. */
-		VOSerializer voser = VOSerializer.makeSerializer(votFormat, votVersion, table);
+		VOSerializer voser = null;
+		/* if FITS, copy the table on disk (or in memory if the table is short):
+		 * (note: this is needed because STIL needs at least 2 passes on this
+		 *        table to format it correctly in FITS format) */
+		if (votFormat == DataFormat.FITS)
+			voser = VOSerializer.makeSerializer(votFormat, votVersion, StoragePolicy.PREFER_DISK.copyTable(table));
+		// otherwise, just use the default VOTable serializer:
+		else
+			voser = VOSerializer.makeSerializer(votFormat, votVersion, table);
 		BufferedWriter out = new BufferedWriter(new OutputStreamWriter(output));
 
 		/* Write header. */
@@ -743,7 +752,8 @@ public class VOTableFormat implements OutputFormat {
 				}
 
 				@Override
-				public void close() throws IOException{}
+				public void close() throws IOException{
+				}
 			};
 		}
 	}