Column Support Feat Docs

fesod-examples/fesod-sheet-examples/src/test/java/org/apache/fesod/sheet/examples/ExampleTestBase.java

@@ -28,6 +28,8 @@
 import java.nio.file.Path;
 import org.apache.poi.ss.usermodel.Workbook;
 import org.apache.poi.ss.usermodel.WorkbookFactory;
+import org.apache.poi.ss.usermodel.Sheet;
+import org.apache.poi.ss.usermodel.Row;
 
 /**
  * Base class for Fesod example integration tests.
@@ -87,6 +89,41 @@ protected static void assertValidExcelFile(File file, int minDataRows) {
         }
     }
 
+    /**
+     * Assert that the given file is a valid Excel workbook with at least the specified number of
+     * columns, scanning for the first non-empty row to determine the column count.
+     *
+     * @param file the Excel file to validate
+     * @param minColumns the minimum number of columns expected
+     */
+    protected static void assertValidExcelFileColumns(File file, int minColumns) {
+        int totalColumns = 0;
+        assertValidExcelFile(file);
+
+        try (FileInputStream fis = new FileInputStream(file);
+                Workbook workbook = WorkbookFactory.create(fis)) {
+
+            Sheet sheet = workbook.getSheetAt(0);
+
+            // find which row is not empty
+            for (int i = 0; i <= sheet.getLastRowNum(); i++) {
+                Row row = sheet.getRow(i);
+
+                if (row != null && row.getPhysicalNumberOfCells() > 0) {
+                    totalColumns = row.getLastCellNum();
+                    break;
+                }
+            }
+
+            assertTrue(
+                    totalColumns >= minColumns,
+                    "Expected at least " + minColumns + " columns, but found " + totalColumns
+                            + " total columns in the first data row of: " + file.getAbsolutePath());
+        } catch (IOException e) {
+            fail("Failed to read workbook for column count verification: " + e.getMessage());
+        }
+    }
+
     /**
      * Generate a temp output file path within the given directory.
      *

website/docs/sheet/read/simple.md

@@ -246,3 +246,33 @@ public void synchronousReadToMapList() {
     }
 }
 ```
+## Reading Specific Columns (Column Filtering)
+
+By default, Fesod reads all columns from a sheet. If you only want to process specific columns, you can use `.includeColumnIndexes(List<Integer>)`. This selects specific columns out of the entire sheet column set
+
+### Reading Specific Columns to Map List (Synchronous)
+
+When reading without a POJO template, the filtered columns are packed sequentially into the resulting `Map<Integer, String>`. The first targeted column is mapped to key `0`, the second to key `1`, and so on.
+
+```java
+@Test
+public void readSpecificColumnsToMapList() {
+    String fileName = "path/to/demo.xlsx";
+
+    // We only want to read Column A (Index 0) and Column C (Index 2)
+    List<Integer> targetColumns = Arrays.asList(0, 2);
+
+    List<Map<Integer, String>> list = FesodSheet.read(fileName)
+            .sheet()
+            .includeColumnIndexes(targetColumns)
+            .doReadSync();
+
+    for (Map<Integer, String> data : list) {
+        // Column Index 0 is mapped to key 0
+        String id = data.get(0); 
+        // Column Index 2 is mapped sequentially to key 1
+        String age = data.get(1); 
+
+        log.info("ID: {}, Age: {}", id, age);
+    }
+}