Allow ignorable rows between the header row and the data rows

core/src/main/java/com/sciencesakura/dbsetup/spreadsheet/Import.java

@@ -171,8 +171,11 @@ public void execute(Connection connection, BinderConfiguration configuration) th
      * <ul>
      *   <li>{@code include([])}</li>
      *   <li>{@code exclude([])}</li>
+     *   <li>{@code resolver(i -> i)}</li>
      *   <li>{@code left(0)}</li>
      *   <li>{@code top(0)}</li>
+     *   <li>{@code margin(0, 0)}</li>
+     *   <li>{@code skipAfterHeader(0)}</li>
      * </ul>
      *
      * @author sciencesakura
@@ -185,6 +188,7 @@ public static final class Builder {
         Function<String, String> resolver = Function.identity();
         int left;
         int top;
+        int skipAfterHeader;
         final Map<String, Map<String, Object>> defaultValues = new HashMap<>();
         final Map<String, Map<String, ValueGenerator<?>>> valueGenerators = new HashMap<>();
         private boolean built;
@@ -197,6 +201,7 @@ private Builder(URL location) {
          * Build a new {@code Import} instance.
          *
          * @return the new {@code Import} instance
+         * @throws IllegalStateException if this method was called more than once on the same instance
          */
         public Import build() {
             if (built) {
@@ -278,8 +283,7 @@ public Builder exclude(@NotNull Pattern... patterns) {
          */
         public Builder resolver(@NotNull Map<String, String> resolver) {
             requireNonNull(resolver, "resolver must not be null");
-            this.resolver = resolver::get;
-            return this;
+            return resolver(resolver::get);
         }
 
         /**
@@ -301,6 +305,7 @@ public Builder resolver(@NotNull Function<String, String> resolver) {
          *
          * @param left the 0-based column index, must be non-negative
          * @return the reference to this object
+         * @throws IllegalArgumentException if the specified value is negative
          */
         public Builder left(int left) {
             if (left < 0) {
@@ -318,6 +323,7 @@ public Builder left(int left) {
          *
          * @param top the 0-based row index, must be non-negative
          * @return the reference to this object
+         * @throws IllegalArgumentException if the specified value is negative
          */
         public Builder top(int top) {
             if (top < 0) {
@@ -336,11 +342,30 @@ public Builder top(int top) {
          * @param left the 0-based column index, must be non-negative
          * @param top  the 0-based row index, must be non-negative
          * @return the reference to this object
+         * @throws IllegalArgumentException if the specified value is negative
          */
         public Builder margin(int left, int top) {
             return left(left).top(top);
         }
 
+        /**
+         * Specifies the number of rows to skip after the header row.
+         * <p>
+         * By default {@code 0} is used.
+         * </p>
+         *
+         * @param n the number of rows to skip after the header row, must be non-negative
+         * @return the reference to this object
+         * @throws IllegalArgumentException if the specified value is negative
+         */
+        public Builder skipAfterHeader(int n) {
+            if (n < 0) {
+                throw new IllegalArgumentException("skipAfterHeader must be greater than or equal to 0");
+            }
+            this.skipAfterHeader = n;
+            return this;
+        }
+
         /**
          * Specifies the default value for the given pair of table and column.
          *

core/src/main/java/com/sciencesakura/dbsetup/spreadsheet/OperationBuilder.java

@@ -78,6 +78,7 @@ static Operation build(Import.Builder builder) {
                         .columns(columns(row, builder.left, width, evaluator));
                 setDefaultValues(ib, builder.defaultValues, tableName);
                 setValueGenerators(ib, builder.valueGenerators, tableName);
+                rowIndex += builder.skipAfterHeader;
                 while ((row = sheet.getRow(++rowIndex)) != null) {
                     ib.values(values(row, builder.left, width, evaluator));
                 }

core/src/test/java/com/sciencesakura/dbsetup/spreadsheet/ImportTest.java

@@ -142,6 +142,7 @@ void import_with_default_settings() {
   }
 
   @Nested
+  @SuppressWarnings("ConstantConditions")
   class ExcelFile {
 
     @Test
@@ -181,6 +182,7 @@ void throw_dsre_if_header_row_contains_error() {
   }
 
   @Nested
+  @SuppressWarnings("ConstantConditions")
   class TableNames {
 
     @BeforeEach
@@ -408,6 +410,7 @@ void throws_npe_if_pattern_to_include_contains_null() {
   }
 
   @Nested
+  @SuppressWarnings("ConstantConditions")
   class TableMapping {
 
     @BeforeEach
@@ -610,6 +613,23 @@ void left_is_two_and_top_is_three() {
           .value("name").isEqualTo("Bob");
     }
 
+    @Test
+    void margin_between_header_and_data() {
+      var changes = new Changes(source).setStartPointNow();
+      var operation = excel("Margin/margin_between_header_and_data.xlsx").skipAfterHeader(1).build();
+      new DbSetup(destination, operation).launch();
+      assertThat(changes.setEndPointNow())
+          .hasNumberOfChanges(2)
+          .changeOfCreationOnTable("table_11")
+          .rowAtEndPoint()
+          .value("id").isEqualTo(1)
+          .value("name").isEqualTo("Alice")
+          .changeOfCreationOnTable("table_12")
+          .rowAtEndPoint()
+          .value("id").isEqualTo(2)
+          .value("name").isEqualTo("Bob");
+    }
+
     @Test
     void throw_dsre_if_header_row_is_not_found_1() {
       assertThatThrownBy(() -> excel("Margin/no_margin.xlsx").top(8).build())
@@ -637,9 +657,17 @@ void throws_iae_if_top_is_negative() {
           .isInstanceOf(IllegalArgumentException.class)
           .hasMessage("top must be greater than or equal to 0");
     }
+
+    @Test
+    void throws_iae_if_margin_between_header_and_data_is_negative() {
+      assertThatThrownBy(() -> excel("Margin/no_margin.xlsx").skipAfterHeader(-1))
+          .isInstanceOf(IllegalArgumentException.class)
+          .hasMessage("skipAfterHeader must be greater than or equal to 0");
+    }
   }
 
   @Nested
+  @SuppressWarnings("ConstantConditions")
   class WithDefaultValue {
 
     @BeforeEach
@@ -709,6 +737,7 @@ void throws_npe_if_column_is_null() {
   }
 
   @Nested
+  @SuppressWarnings("ConstantConditions")
   class WithGeneratedValue {
 
     @BeforeEach