JdbcTemplate: add queryOne method

src/main/java/ghast/database/JdbcOperations.java

@@ -2,6 +2,7 @@ package ghast.database;
 
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 
 public interface JdbcOperations {
 
@@ -9,6 +10,8 @@ public interface JdbcOperations {
 
 	<T> T query(String sql, ResultSetExtractor<T> rse) throws DataAccessException;
 
+	<T> Optional<T> queryOne(String sql, ResultSetExtractor<T> rse) throws DataAccessException;
+
 	<T> List<T> queryList(String sql, RowMapper<T> rowMapper) throws DataAccessException;
 
 	Map<String, Object> queryForMap(String sql) throws DataAccessException;

src/main/java/ghast/database/JdbcTemplate.java

@@ -59,6 +59,17 @@ public class JdbcTemplate implements JdbcOperations {
 		}
 	}
 
+	@Override
+	public <T> Optional<T> queryOne(String sql, ResultSetExtractor<T> rse) throws DataAccessException {
+		return query(sql, rs -> {
+			if (rs.next()) {
+				return Optional.ofNullable(rse.extractData(rs));
+			} else {
+				return Optional.empty();
+			}
+		});
+	}
+
 	@Override
 	public <T> List<T> queryList(String sql, final RowMapper<T> rowMapper) throws DataAccessException {
 		return query(sql, rs -> {

src/test/java/ghast/database/JdbcTemplateTest.java

@@ -17,6 +17,7 @@ import java.sql.SQLException;
 import java.text.MessageFormat;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.StringJoiner;
 import java.util.logging.Logger;
 import java.util.stream.Collectors;
@@ -99,6 +100,17 @@ class JdbcTemplateTest {
 		assertEquals(DATA[0][1], value);
 	}
 
+	@Test
+	void testQuery_Simple_Optional() {
+		String sql = MessageFormat.format("SELECT {2} FROM {0} WHERE {1} LIKE ''{3}''",
+				TABLE_NAME, COLUMN_NAME, COLUMN_VALUE, DATA[0][0]);
+
+		Optional<Integer> optValue = jdbcTemplate.queryOne(sql, rs -> rs.getInt(1));
+
+		assertTrue(optValue.isPresent());
+		assertEquals(DATA[0][1], optValue.get());
+	}
+
 	@Test
 	void testQuery_Simple_List() {
 		String sql = MessageFormat.format("SELECT {2} FROM {0} WHERE {1} LIKE ''{3}'' OR {1} LIKE ''{4}''",