Add nextOrThrow methods to KiwiJdbc to advance a ResultSet

src/main/java/org/kiwiproject/jdbc/KiwiJdbc.java

@@ -1,13 +1,16 @@
 package org.kiwiproject.jdbc;
 
+import static com.google.common.base.Preconditions.checkState;
 import static java.util.Objects.isNull;
 import static org.apache.commons.lang3.StringUtils.isBlank;
 import static org.kiwiproject.base.KiwiPreconditions.checkArgumentNotNull;
+import static org.kiwiproject.base.KiwiStrings.format;
 
 import lombok.experimental.UtilityClass;
 import org.checkerframework.checker.nullness.qual.Nullable;
 import org.kiwiproject.base.KiwiPrimitives;
 import org.kiwiproject.base.KiwiPrimitives.BooleanConversionOption;
+import org.kiwiproject.base.KiwiStrings;
 
 import java.sql.PreparedStatement;
 import java.sql.ResultSet;
@@ -29,6 +32,51 @@
 @UtilityClass
 public class KiwiJdbc {
 
+    /**
+     * Attempt to call {@link ResultSet#next()} on the given ResultSet, and throw an {@link IllegalStateException}
+     * if the result set was not advanced.
+     *
+     * @param rs the ResultSet
+     * @throws SQLException          if a database access error occurs or this method is called on a closed result set
+     *                               (copied from {@link ResultSet#next()})
+     * @throws IllegalStateException if the result set was not advanced
+     */
+    public static void nextOrThrow(ResultSet rs) throws SQLException {
+        nextOrThrow(rs, "ResultSet.next() returned false");
+    }
+
+    /**
+     * Attempt to call {@link ResultSet#next()} on the given ResultSet, and throw an {@link IllegalStateException}
+     * if the result set was not advanced.
+     *
+     * @param rs      the ResultSet
+     * @param message the error message in case the result set cannot be advanced
+     * @throws SQLException          if a database access error occurs or this method is called on a closed result set
+     *                               (copied from {@link ResultSet#next()})
+     * @throws IllegalStateException if the result set was not advanced
+     */
+    public static void nextOrThrow(ResultSet rs, String message) throws SQLException {
+        checkState(rs.next(), message);
+    }
+
+    /**
+     * Attempt to call {@link ResultSet#next()} on the given ResultSet, and throw an {@link IllegalStateException}
+     * if the result set was not advanced.
+     *
+     * @param rs              the ResultSet
+     * @param messageTemplate the error message template in case the result set cannot be advanced, according to how
+     *                        {@link KiwiStrings#format(String, Object...)} handles placeholders
+     * @param args            the arguments to be substituted into the message template
+     * @throws SQLException          if a database access error occurs or this method is called on a closed result set
+     *                               (copied from {@link ResultSet#next()})
+     * @throws IllegalStateException if the result set was not advanced
+     */
+    public static void nextOrThrow(ResultSet rs, String messageTemplate, Object... args) throws SQLException {
+        if (!rs.next()) {
+            throw new IllegalStateException(format(messageTemplate, args));
+        }
+    }
+
     /**
      * Convert the timestamp column given by {@code columnName} in the {@link ResultSet} to milliseconds
      * from the epoch.

src/test/java/org/kiwiproject/jdbc/KiwiJdbcTest.java

@@ -1,14 +1,18 @@
 package org.kiwiproject.jdbc;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatCode;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.mockito.ArgumentMatchers.anyString;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.only;
 import static org.mockito.Mockito.verify;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 import static org.mockito.Mockito.when;
 
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.DisplayName;
 import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
@@ -37,6 +41,84 @@
 @DisplayName("KiwiJdbc")
 class KiwiJdbcTest {
 
+    @Nested
+    class NextOrThrow {
+
+        private ResultSet resultSet;
+
+        @BeforeEach
+        void setUp() {
+            resultSet = mock(ResultSet.class);
+        }
+
+        @Test
+        void shouldAdvanceResultSet() throws SQLException {
+            when(resultSet.next()).thenReturn(true);
+
+            assertThatCode(() -> KiwiJdbc.nextOrThrow(resultSet))
+                    .doesNotThrowAnyException();
+
+            verify(resultSet, only()).next();
+        }
+
+        @Test
+        void shouldAdvanceResultSet_WithCustomMessageArgument() throws SQLException {
+            when(resultSet.next()).thenReturn(true);
+
+            assertThatCode(() -> KiwiJdbc.nextOrThrow(resultSet, "failed to advance ResultSet"))
+                    .doesNotThrowAnyException();
+
+            verify(resultSet, only()).next();
+        }
+
+        @Test
+        void shouldAdvanceResultSet_WithCustomMessageTemplateAndArguments() throws SQLException {
+            when(resultSet.next()).thenReturn(true);
+
+            assertThatCode(() -> KiwiJdbc.nextOrThrow(resultSet, "{} with id {} was not found", "Order", "12345ABC"))
+                    .doesNotThrowAnyException();
+
+            verify(resultSet, only()).next();
+        }
+
+        @Test
+        void shouldThrowIllegalState_WhenNextReturnsFalse() throws SQLException {
+            when(resultSet.next()).thenReturn(false);
+
+            assertThatIllegalStateException()
+                    .isThrownBy(() -> KiwiJdbc.nextOrThrow(resultSet))
+                    .withMessage("ResultSet.next() returned false");
+
+            verify(resultSet, only()).next();
+        }
+
+        @Test
+        void shouldThrowIllegalState_WithCustomMessage_WhenNextReturnsFalse() throws SQLException {
+            when(resultSet.next()).thenReturn(false);
+
+            assertThatIllegalStateException()
+                    .isThrownBy(() -> KiwiJdbc.nextOrThrow(resultSet, "record was not found"))
+                    .withMessage("record was not found");
+
+            verify(resultSet, only()).next();
+        }
+
+        @ParameterizedTest
+        @ValueSource(strings = {
+                "{} with id {} was not found",
+                "%s with id %s was not found"
+        })
+        void shouldThrowIllegalState_WithCustomMessageTemplate_WhenNextReturnsFalse(String template) throws SQLException {
+            when(resultSet.next()).thenReturn(false);
+
+            assertThatIllegalStateException()
+                    .isThrownBy(() -> KiwiJdbc.nextOrThrow(resultSet, template, "Item", 42))
+                    .withMessage("Item with id 42 was not found");
+
+            verify(resultSet, only()).next();
+        }
+    }
+
     @Nested
     class EpochMillisFromTimestamp {