refactor: refactor getGridHeaders return type

Close #155

Author: javier-godoy

src/main/java/com/flowingcode/vaadin/addons/gridexporter/BaseStreamResourceWriter.java

@@ -95,13 +95,13 @@ protected Stream<T> getDataStream(Query newQuery) {
     return stream;
   }
 
-  protected List<Pair<List<String>, Column<T>>> getGridHeaders(Grid<T> grid) {
+  protected List<GridHeader<T>> getGridHeaders(Grid<T> grid) {
     return exporter.getColumnsOrdered().stream()
-        .map(column -> ImmutablePair.of(getHeaderTexts(grid, column), column))
+        .map(column -> getGridHeader(grid, column))
         .collect(Collectors.toList());
   }
-  
-  private List<String> getHeaderTexts(Grid<T> grid, Column<T> column) {
+
+  private GridHeader<T> getGridHeader(Grid<T> grid, Column<T> column) {
       List<String> headerTexts = new ArrayList<>();
       List<HeaderRow> headerRows = grid.getHeaderRows();
       for (HeaderRow headerRow : headerRows) {
@@ -117,7 +117,7 @@ private List<String> getHeaderTexts(Grid<T> grid, Column<T> column) {
           });
           headerTexts.add(headerText);
       }
-      return headerTexts;
+      return new GridHeader(headerTexts, column);
   }
 
   protected List<Pair<String, Column<T>>> getGridFooters(Grid<T> grid) {

src/main/java/com/flowingcode/vaadin/addons/gridexporter/CsvStreamResourceWriter.java

@@ -61,7 +61,7 @@ public void accept(OutputStream out, VaadinSession session) throws IOException {
           .filter(this::isExportable)
           .collect(Collectors.toList()));
 
-      headers = getGridHeaders(grid).stream().map(Pair::getLeft).toArray(String[]::new);
+      headers = getGridHeaders(grid).stream().map(GridHeader::getHeaderTexts).toArray(String[]::new);
       data = obtainDataStream(grid.getDataProvider())
           .map(this::buildRow)
           .collect(Collectors.toList());

src/main/java/com/flowingcode/vaadin/addons/gridexporter/DocxStreamResourceWriter.java

@@ -129,8 +129,8 @@ private XWPFDocument createDoc() throws IOException {
             });
 
     List<Pair<String, Column<T>>> headers = getGridHeaders(grid).stream()
-        .map(pair -> 
-        Pair.of(pair.getLeft().get(0), pair.getRight())
+        .map(header -> Pair.of(header.getHeaderTexts().get(0),
+            header.getColumn())
         ).collect(Collectors.toList());
     XWPFTableCell cell = findCellWithPlaceHolder(table, exporter.headersPlaceHolder);
     if (cell != null) {

src/main/java/com/flowingcode/vaadin/addons/gridexporter/ExcelStreamResourceWriter.java

@@ -95,7 +95,7 @@ private Workbook createWorkbook(VaadinSession session) {
       }
 
       Cell cell = findCellWithPlaceHolder(sheet, exporter.headersPlaceHolder);
-      List<Pair<List<String>, Column<T>>> headers = getGridHeaders(grid);
+      List<GridHeader<T>> headers = getGridHeaders(grid);
 
       fillHeaderOrFooter(sheet, cell, headers, true);
       if (exporter.autoMergeTitle && titleCell != null && exporter.getColumns().size()>1) {
@@ -346,7 +346,7 @@ private void buildCell(Object value, Cell cell, Column<T> column, T item) {
     String excelFormat = getExcelFormat(column, item, provider);
     if (value == null) {
       PoiHelper.setBlank(cell);
-      if(excelFormat != null) {       
+      if(excelFormat != null) {
         applyExcelFormat(cell, excelFormat, cellStyles);
       }
     } else if (value instanceof Number) {
@@ -426,20 +426,20 @@ private Cell findCellWithPlaceHolder(Sheet sheet, String placeholder) {
 
   private void fillFooter(Sheet sheet, Cell headersOrFootersCell,
       List<Pair<String, Column<T>>> headersOrFooters, boolean isHeader) {
-    List<Pair<List<String>, Column<T>>> headersOrFootersCellSingleRow = headersOrFooters.stream()
-        .map(pair -> Pair.of(List.of(pair.getLeft()), pair.getRight())).collect(Collectors.toList());
+    List<GridHeader<T>> headersOrFootersCellSingleRow = headersOrFooters.stream()
+        .map(pair -> new GridHeader<>(List.of(pair.getLeft()), pair.getRight())).collect(Collectors.toList());
     fillHeaderOrFooter(sheet, headersOrFootersCell, headersOrFootersCellSingleRow, isHeader);
   }
   private void fillHeaderOrFooter(Sheet sheet, Cell headersOrFootersCell,
-      List<Pair<List<String>, Column<T>>> headersOrFooters, boolean isHeader) {
+      List<GridHeader<T>> headersOrFooters, boolean isHeader) {
     CellStyle style = headersOrFootersCell.getCellStyle();
-    
+
     int startRow = headersOrFootersCell.getRowIndex();
     int currentColumn = headersOrFootersCell.getColumnIndex();
     boolean shiftFirstTime = true;
-    for (Pair<List<String>, Column<T>> headerOrFooter : headersOrFooters) {
-      List<String> headerOrFooterTexts = headerOrFooter.getLeft();
-      Column<T> column = headerOrFooter.getRight();
+    for (GridHeader<T> headerOrFooter : headersOrFooters) {
+      List<String> headerOrFooterTexts = headerOrFooter.getHeaderTexts();
+      Column<T> column = headerOrFooter.getColumn();
       if (!isHeader) {
         ComponentUtil.setData(column, COLUMN_CELLSTYLE_MAP, null);
       }

src/main/java/com/flowingcode/vaadin/addons/gridexporter/GridHeader.java

@@ -0,0 +1,15 @@
+package com.flowingcode.vaadin.addons.gridexporter;
+
+import com.vaadin.flow.component.grid.Grid.Column;
+import java.util.List;
+import lombok.Getter;
+import lombok.RequiredArgsConstructor;
+
+@Getter
+@RequiredArgsConstructor
+final class GridHeader<T> {
+
+  private final List<String> headerTexts;
+  private final Column<T> column;
+
+}