Properly handle null row in sommon select mapper

Author: jeffgbutler

Diff for: src/main/java/org/mybatis/dynamic/sql/util/mybatis3/CommonSelectMapper.java

@@ -22,6 +22,7 @@
 import java.util.function.Function;
 
 import org.apache.ibatis.annotations.SelectProvider;
+import org.jspecify.annotations.Nullable;
 import org.mybatis.dynamic.sql.select.render.SelectStatementProvider;
 import org.mybatis.dynamic.sql.util.SqlProviderAdapter;
 
@@ -58,7 +59,7 @@ public interface CommonSelectMapper {
      * @return A Map containing the row values.
      */
     @SelectProvider(type = SqlProviderAdapter.class, method = "select")
-    Map<String, Object> selectOneMappedRow(SelectStatementProvider selectStatement);
+    @Nullable Map<String, Object> selectOneMappedRow(SelectStatementProvider selectStatement);
 
     /**
      * Select a single row of values and then convert the values to a custom type. This is similar
@@ -74,9 +75,10 @@ public interface CommonSelectMapper {
      * @param <R> the datatype of the converted object
      * @return the converted object
      */
-    default <R> R selectOne(SelectStatementProvider selectStatement,
+    default <R> @Nullable R selectOne(SelectStatementProvider selectStatement,
                             Function<Map<String, Object>, R> rowMapper) {
-        return rowMapper.apply(selectOneMappedRow(selectStatement));
+        var result = selectOneMappedRow(selectStatement);
+        return result == null ? null : rowMapper.apply(result);
     }
 
     /**
@@ -122,7 +124,7 @@ default <R> List<R> selectMany(SelectStatementProvider selectStatement,
      *     column is null
      */
     @SelectProvider(type = SqlProviderAdapter.class, method = "select")
-    BigDecimal selectOneBigDecimal(SelectStatementProvider selectStatement);
+    @Nullable BigDecimal selectOneBigDecimal(SelectStatementProvider selectStatement);
 
     /**
      * Retrieve a single {@link java.math.BigDecimal} from a result set. The result set must have
@@ -157,7 +159,7 @@ default <R> List<R> selectMany(SelectStatementProvider selectStatement,
      *     column is null
      */
     @SelectProvider(type = SqlProviderAdapter.class, method = "select")
-    Double selectOneDouble(SelectStatementProvider selectStatement);
+    @Nullable Double selectOneDouble(SelectStatementProvider selectStatement);
 
     /**
      * Retrieve a single {@link java.lang.Double} from a result set. The result set must have
@@ -192,7 +194,7 @@ default <R> List<R> selectMany(SelectStatementProvider selectStatement,
      *     column is null
      */
     @SelectProvider(type = SqlProviderAdapter.class, method = "select")
-    Integer selectOneInteger(SelectStatementProvider selectStatement);
+    @Nullable Integer selectOneInteger(SelectStatementProvider selectStatement);
 
     /**
      * Retrieve a single {@link java.lang.Integer} from a result set. The result set must have
@@ -227,7 +229,7 @@ default <R> List<R> selectMany(SelectStatementProvider selectStatement,
      *     column is null
      */
     @SelectProvider(type = SqlProviderAdapter.class, method = "select")
-    Long selectOneLong(SelectStatementProvider selectStatement);
+    @Nullable Long selectOneLong(SelectStatementProvider selectStatement);
 
     /**
      * Retrieve a single {@link java.lang.Long} from a result set. The result set must have
@@ -262,7 +264,7 @@ default <R> List<R> selectMany(SelectStatementProvider selectStatement,
      *     column is null
      */
     @SelectProvider(type = SqlProviderAdapter.class, method = "select")
-    String selectOneString(SelectStatementProvider selectStatement);
+    @Nullable String selectOneString(SelectStatementProvider selectStatement);
 
     /**
      * Retrieve a single {@link java.lang.String} from a result set. The result set must have

Diff for: src/test/java/examples/animal/data/CommonSelectMapperTest.java

@@ -106,13 +106,29 @@ void testGeneralSelectOneWithRowMapper() {
 
             AnimalData animal = mapper.selectOne(selectStatement, rowMapper);
 
+            assertThat(animal).isNotNull();
             assertThat(animal.getId()).isEqualTo(1);
             assertThat(animal.getAnimalName()).isEqualTo("Lesser short-tailed shrew");
             assertThat(animal.getBodyWeight()).isEqualTo(0.14);
             assertThat(animal.getBrainWeight()).isEqualTo(0.005);
         }
     }
 
+    @Test
+    void testGeneralSelectOneWithRowMapperAndNullRow() {
+        try (SqlSession sqlSession = sqlSessionFactory.openSession()) {
+            CommonSelectMapper mapper = sqlSession.getMapper(CommonSelectMapper.class);
+            SelectStatementProvider selectStatement = select(id, animalName, bodyWeight, brainWeight)
+                    .from(animalData)
+                    .where(id, isEqualTo(-237))
+                    .build()
+                    .render(RenderingStrategies.MYBATIS3);
+
+            AnimalData animal = mapper.selectOne(selectStatement, rowMapper);
+            assertThat(animal).isNull();
+        }
+    }
+
     @Test
     void testGeneralSelectMany() {
         try (SqlSession sqlSession = sqlSessionFactory.openSession()) {