Fix missing class issue with H2 version 2.0.202

With older versions H2 returned a proprietary  instance of `TimestampWithTimeZone` from `ResultSet.getObject()`.
We used to support the conversion of that to an `OffsetDateTime`.

With the most recent versions `TimestampWithTimeZone` is no longer part of the H2 driver, and we only register the converter when we encounter older versions of H2.

Closes #1114
See https://github.com/h2database/h2database/pull/1359

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/dialect/H2TimestampWithTimeZoneToOffsetDateTimeConverter.java

@@ -0,0 +1,63 @@
+/*
+ * Copyright 2021 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.data.jdbc.core.dialect;
+
+import java.time.OffsetDateTime;
+import java.time.ZoneOffset;
+
+import org.h2.api.TimestampWithTimeZone;
+import org.springframework.core.convert.converter.Converter;
+import org.springframework.data.convert.ReadingConverter;
+
+/**
+ * Converter converting from an H2 internal representation of a timestamp with time zone to an OffsetDateTime.
+ *
+ * Only required for H2 versions < 2.0
+ * 
+ * @author Jens Schauder
+ * @since 2.7
+ */
+@ReadingConverter
+public enum H2TimestampWithTimeZoneToOffsetDateTimeConverter
+		implements Converter<TimestampWithTimeZone, OffsetDateTime> {
+
+	INSTANCE;
+
+	@Override
+	public OffsetDateTime convert(TimestampWithTimeZone source) {
+
+		long nanosInSecond = 1_000_000_000;
+		long nanosInMinute = nanosInSecond * 60;
+		long nanosInHour = nanosInMinute * 60;
+
+		long hours = (source.getNanosSinceMidnight() / nanosInHour);
+
+		long nanosInHours = hours * nanosInHour;
+		long nanosLeft = source.getNanosSinceMidnight() - nanosInHours;
+		long minutes = nanosLeft / nanosInMinute;
+
+		long nanosInMinutes = minutes * nanosInMinute;
+		nanosLeft -= nanosInMinutes;
+		long seconds = nanosLeft / nanosInSecond;
+
+		long nanosInSeconds = seconds * nanosInSecond;
+		nanosLeft -= nanosInSeconds;
+		ZoneOffset offset = ZoneOffset.ofTotalSeconds(source.getTimeZoneOffsetSeconds());
+
+		return OffsetDateTime.of(source.getYear(), source.getMonth(), source.getDay(), (int) hours, (int) minutes,
+				(int) seconds, (int) nanosLeft, offset);
+	}
+}

spring-data-jdbc/src/main/java/org/springframework/data/jdbc/core/dialect/JdbcH2Dialect.java

@@ -15,15 +15,10 @@
  */
 package org.springframework.data.jdbc.core.dialect;
 
-import java.time.OffsetDateTime;
-import java.time.ZoneOffset;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
 
-import org.h2.api.TimestampWithTimeZone;
-import org.springframework.core.convert.converter.Converter;
-import org.springframework.data.convert.ReadingConverter;
 import org.springframework.data.relational.core.dialect.Db2Dialect;
 import org.springframework.data.relational.core.dialect.H2Dialect;
 
@@ -43,39 +38,26 @@ public class JdbcH2Dialect extends H2Dialect {
 	@Override
 	public Collection<Object> getConverters() {
 
-		List<Object> converters = new ArrayList<>(super.getConverters());
-		converters.add(TimestampWithTimeZoneToOffsetDateTimeConverter.INSTANCE);
-		return converters;
-	}
-
-	@ReadingConverter
-	enum TimestampWithTimeZoneToOffsetDateTimeConverter implements Converter<TimestampWithTimeZone, OffsetDateTime> {
-
-		INSTANCE;
+		final Collection<Object> originalConverters = super.getConverters();
 
-		@Override
-		public OffsetDateTime convert(TimestampWithTimeZone source) {
+		if (isH2belowVersion2()) {
 
-			long nanosInSecond = 1_000_000_000;
-			long nanosInMinute = nanosInSecond * 60;
-			long nanosInHour = nanosInMinute * 60;
-
-			long hours = (source.getNanosSinceMidnight() / nanosInHour);
+			List<Object> converters = new ArrayList<>(originalConverters);
+			converters.add(H2TimestampWithTimeZoneToOffsetDateTimeConverter.INSTANCE);
+			return converters;
+		}
 
-			long nanosInHours = hours * nanosInHour;
-			long nanosLeft = source.getNanosSinceMidnight() - nanosInHours;
-			long minutes = nanosLeft / nanosInMinute;
+		return originalConverters;
+	}
 
-			long nanosInMinutes = minutes * nanosInMinute;
-			nanosLeft -= nanosInMinutes;
-			long seconds = nanosLeft / nanosInSecond;
+	static boolean isH2belowVersion2() {
 
-			long nanosInSeconds = seconds * nanosInSecond;
-			nanosLeft -= nanosInSeconds;
-			ZoneOffset offset = ZoneOffset.ofTotalSeconds(source.getTimeZoneOffsetSeconds());
+		try {
 
-			return OffsetDateTime.of(source.getYear(), source.getMonth(), source.getDay(), (int) hours, (int) minutes,
-					(int) seconds, (int) nanosLeft, offset);
+			JdbcH2Dialect.class.getClassLoader().loadClass("org.h2.api.TimestampWithTimeZone");
+			return true;
+		}  catch (ClassNotFoundException e) {
+			return false;
 		}
 	}
 }

spring-data-jdbc/src/test/java/org/springframework/data/jdbc/core/dialect/JdbcH2DialectTests.java

@@ -33,7 +33,7 @@ class JdbcH2DialectTests {
 	@Test
 	void TimestampWithTimeZone2OffsetDateTimeConverterConvertsProperly() {
 
-		JdbcH2Dialect.TimestampWithTimeZoneToOffsetDateTimeConverter converter = JdbcH2Dialect.TimestampWithTimeZoneToOffsetDateTimeConverter.INSTANCE;
+		H2TimestampWithTimeZoneToOffsetDateTimeConverter converter = H2TimestampWithTimeZoneToOffsetDateTimeConverter.INSTANCE;
 		long dateValue = 123456789;
 		long timeNanos = 987654321;
 		int timeZoneOffsetSeconds = 4 * 60 * 60;