ExcelExporter: Add predicate to OneQueryStrategy

Extends the exporter strategy to export a query document with exactly
one query by an alternate constructor that allows configuring a field
predicate that is passed on to .addSheet().

This allows for single-query document with filtered fields.

src/main/java/de/quinscape/automaton/runtime/export/excel/ExcelExporter.java

@@ -3,20 +3,22 @@
 import de.quinscape.automaton.runtime.export.ExportResult;
 import de.quinscape.automaton.runtime.export.GraphQLExporter;
 import de.quinscape.automaton.runtime.export.GraphQLQueryContext;
+import de.quinscape.automaton.runtime.util.SchemaReference;
 import de.quinscape.domainql.DomainQL;
 import org.apache.poi.hssf.usermodel.HSSFWorkbook;
 import org.slf4j.Logger;
 import org.slf4j.LoggerFactory;
 
 import java.io.ByteArrayOutputStream;
 import java.io.IOException;
+import java.util.function.Predicate;
 
 
 /**
  * GraphQLExport implementation for Excel sheets. Can be configured via builder including a strategy of how many
  * queries to export into how many excel sheets.
  *
- * @see #newExporter(DomainQL) 
+ * @see #newExporter(DomainQL)
  */
 public class ExcelExporter
     implements GraphQLExporter<byte[]>
@@ -27,14 +29,15 @@ public class ExcelExporter
     public final static String EXCEL_MEDIA_TYPE = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
 
 
-
     private final DomainQL domainQL;
+
     private final String metaHeadingName;
 
     private final String mediaType;
 
     private final ExportStrategy exportStrategy;
 
+
     ExcelExporter(
         DomainQL domainQL,
         ExportStrategy exportStrategy,
@@ -48,6 +51,7 @@ public class ExcelExporter
         this.mediaType = mediaType;
     }
 
+
     @Override
     public ExportResult<byte[]> export(GraphQLQueryContext ctx) throws IOException
     {
@@ -74,7 +78,6 @@ public ExportResult<byte[]> export(GraphQLQueryContext ctx) throws IOException
     }
 
 
-
     /**
      * Expects a single result that is converted into an Excel sheet name with a configured name, exporting the Excel
      * file under a configured name.
@@ -84,28 +87,57 @@ public static class OneQueryStrategy
     {
         public final static OneQueryStrategy DEFAULT = new OneQueryStrategy(
             "Automaton Export",
-            "automaton-$now.xlsx");
+            "automaton-$now.xlsx"
+        );
+
+        private final static Predicate<SchemaReference> ALL_FILES = ref -> true;
 
         private final String sheetName;
+
         private final String fileName;
 
+        private final Predicate<SchemaReference> fieldPredicate;
 
+
+        /**
+         * Creates a new OneQueryStrategy with the given sheet name and the given file name and a predicate to filter
+         * the fields.
+         *
+         * @param sheetName sheet name
+         * @param fileName  filename (with optional "$now" placeholder)
+         */
         public OneQueryStrategy(String sheetName, String fileName)
+        {
+            this(sheetName, fileName, ALL_FILES);
+        }
+
+
+        /**
+         * Creates a new OneQueryStrategy with the given sheet name and the given file name and a predicate to filter
+         * the fields.
+         *
+         * @param sheetName      sheet name
+         * @param fileName       filename (with optional "$now" placeholder)
+         * @param fieldPredicate field predicate
+         */
+        public OneQueryStrategy(String sheetName, String fileName, Predicate<SchemaReference> fieldPredicate)
         {
             this.sheetName = sheetName;
             this.fileName = fileName;
+            this.fieldPredicate = fieldPredicate;
         }
 
 
         @Override
         public String generateExport(ExcelExporterContext ctx, GraphQLQueryContext queryContext)
         {
             final GraphQLQueryContext.MethodResult mr = queryContext.getOnlyResult();
-            ctx.addSheet(sheetName, mr);
+            ctx.addSheet(sheetName, mr, fieldPredicate);
             return fileName;
         }
     }
 
+
     public static ExcelExporterBuilder newExporter(DomainQL domainQL)
     {
         return new ExcelExporterBuilder(domainQL);