Expose details of HeaderMissingException as properties

src/main/java/com/poiji/exception/HeaderMissingException.java

@@ -1,12 +1,29 @@
 package com.poiji.exception;
 
+import java.util.Set;
+
 /**
  * Exception thrown if namedHeaderMandatory is set in the options, but a header specified in an @ExcelCellName
  * is missing in the sheet.
  */
 @SuppressWarnings("serial")
 public class HeaderMissingException extends PoijiException {
-    public HeaderMissingException(String message) {
+
+    private final Set<Integer> missingExcelCellHeaders;
+    private final Set<String> missingExcelCellNameHeaders;
+
+    public HeaderMissingException(String message, Set<Integer> missingExcelCellHeaders,
+                                  Set<String> missingExcelCellNameHeaders) {
         super(message);
+        this.missingExcelCellHeaders = Set.copyOf(missingExcelCellHeaders);
+        this.missingExcelCellNameHeaders = Set.copyOf(missingExcelCellNameHeaders);
+    }
+
+    public Set<Integer> getMissingExcelCellHeaders() {
+        return missingExcelCellHeaders;
+    }
+
+    public Set<String> getMissingExcelCellNameHeaders() {
+        return missingExcelCellNameHeaders;
     }
 }

src/main/java/com/poiji/util/AnnotationUtil.java

@@ -77,7 +77,7 @@ public static <T> void validateMandatoryNameColumns(PoijiOptions options,
                                                 .forEach(missingMessage::append);
                                 message += missingMessage;
                         }
-                        throw new HeaderMissingException(message);
+                        throw new HeaderMissingException(message, missingExcelCellHeaders, missingExcelCellNameHeaders);
                 }
         }
 }

src/test/java/com/poiji/deserialize/MandatoryNamedColumnsExceptionTest.java

@@ -10,6 +10,10 @@
 
 import java.io.File;
 import java.util.Arrays;
+import java.util.Set;
+
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.fail;
 
 @RunWith(Parameterized.class)
 public class MandatoryNamedColumnsExceptionTest {
@@ -28,10 +32,17 @@ public static Iterable<Object[]> queries() {
         });
     }
 
-    @Test(expected = HeaderMissingException.class)
+    @Test
     public void testExcelMandatoryColumn() {
-        Poiji.fromExcel(new File(path), PersonByNameWithMissingColumn.class, PoijiOptions.PoijiOptionsBuilder
-                .settings()
-                .build());
+        try {
+            Poiji.fromExcel(new File(path), PersonByNameWithMissingColumn.class, PoijiOptions.PoijiOptionsBuilder
+                    .settings()
+                    .build());
+        } catch (HeaderMissingException e) {
+            assertEquals(Set.of(6), e.getMissingExcelCellHeaders());
+            assertEquals(Set.of("This column will be missing"), e.getMissingExcelCellNameHeaders());
+            return;
+        }
+        fail("Expected exception: " + HeaderMissingException.class.getName());
     }
 }