Only start a new transaction if there's a delta for session updates with JDBC based repository

Avoids eagerly acquiring a connection or any other eager initialization that may happen alongside a transaction starting if there's no actual update to be made.

Author: ryanrupp

spring-session-jdbc/src/main/java/org/springframework/session/jdbc/JdbcIndexedSessionRepository.java

@@ -907,45 +907,57 @@ private void save() {
 				});
 			}
 			else {
-				JdbcIndexedSessionRepository.this.transactionOperations.executeWithoutResult((status) -> {
-					if (JdbcSession.this.changed) {
+				List<Runnable> deltaActions = new ArrayList<>();
+				if (JdbcSession.this.changed) {
+					deltaActions.add(() -> {
 						Map<String, String> indexes = JdbcIndexedSessionRepository.this.indexResolver
-							.resolveIndexesFor(JdbcSession.this);
+								.resolveIndexesFor(JdbcSession.this);
 						JdbcIndexedSessionRepository.this.jdbcOperations
-							.update(JdbcIndexedSessionRepository.this.updateSessionQuery, (ps) -> {
-								ps.setString(1, getId());
-								ps.setLong(2, getLastAccessedTime().toEpochMilli());
-								ps.setInt(3, (int) getMaxInactiveInterval().getSeconds());
-								ps.setLong(4, getExpiryTime().toEpochMilli());
-								ps.setString(5, indexes.get(PRINCIPAL_NAME_INDEX_NAME));
-								ps.setString(6, JdbcSession.this.primaryKey);
-							});
-					}
-					List<String> addedAttributeNames = JdbcSession.this.delta.entrySet()
+								.update(JdbcIndexedSessionRepository.this.updateSessionQuery, (ps) -> {
+									ps.setString(1, getId());
+									ps.setLong(2, getLastAccessedTime().toEpochMilli());
+									ps.setInt(3, (int) getMaxInactiveInterval().getSeconds());
+									ps.setLong(4, getExpiryTime().toEpochMilli());
+									ps.setString(5, indexes.get(PRINCIPAL_NAME_INDEX_NAME));
+									ps.setString(6, JdbcSession.this.primaryKey);
+								});
+					});
+				}
+
+				List<String> addedAttributeNames = JdbcSession.this.delta.entrySet()
 						.stream()
 						.filter((entry) -> entry.getValue() == DeltaValue.ADDED)
 						.map(Map.Entry::getKey)
 						.collect(Collectors.toList());
-					if (!addedAttributeNames.isEmpty()) {
-						insertSessionAttributes(JdbcSession.this, addedAttributeNames);
-					}
-					List<String> updatedAttributeNames = JdbcSession.this.delta.entrySet()
+				if (!addedAttributeNames.isEmpty()) {
+					deltaActions.add(() -> insertSessionAttributes(JdbcSession.this, addedAttributeNames));
+				}
+
+				List<String> updatedAttributeNames = JdbcSession.this.delta.entrySet()
 						.stream()
 						.filter((entry) -> entry.getValue() == DeltaValue.UPDATED)
 						.map(Map.Entry::getKey)
 						.collect(Collectors.toList());
-					if (!updatedAttributeNames.isEmpty()) {
-						updateSessionAttributes(JdbcSession.this, updatedAttributeNames);
-					}
-					List<String> removedAttributeNames = JdbcSession.this.delta.entrySet()
+				if (!updatedAttributeNames.isEmpty()) {
+					deltaActions.add(() -> updateSessionAttributes(JdbcSession.this, updatedAttributeNames));
+				}
+
+				List<String> removedAttributeNames = JdbcSession.this.delta.entrySet()
 						.stream()
 						.filter((entry) -> entry.getValue() == DeltaValue.REMOVED)
 						.map(Map.Entry::getKey)
 						.collect(Collectors.toList());
-					if (!removedAttributeNames.isEmpty()) {
-						deleteSessionAttributes(JdbcSession.this, removedAttributeNames);
-					}
-				});
+				if (!removedAttributeNames.isEmpty()) {
+					deltaActions.add(() -> deleteSessionAttributes(JdbcSession.this, removedAttributeNames));
+				}
+
+				if (!deltaActions.isEmpty()) {
+					JdbcIndexedSessionRepository.this.transactionOperations.executeWithoutResult((status) -> {
+						for (Runnable action : deltaActions) {
+							action.run();
+						}
+					});
+				}
 			}
 			clearChangeFlags();
 		}

spring-session-jdbc/src/test/java/org/springframework/session/jdbc/JdbcIndexedSessionRepositoryTests.java

@@ -23,6 +23,7 @@
 import java.util.List;
 import java.util.Map;
 import java.util.UUID;
+import java.util.function.Consumer;
 import java.util.function.Supplier;
 
 import org.junit.jupiter.api.BeforeEach;
@@ -48,20 +49,25 @@
 import org.springframework.session.SaveMode;
 import org.springframework.session.Session;
 import org.springframework.session.jdbc.JdbcIndexedSessionRepository.JdbcSession;
+import org.springframework.transaction.TransactionStatus;
+import org.springframework.transaction.support.TransactionCallback;
 import org.springframework.transaction.support.TransactionOperations;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.assertThatIllegalArgumentException;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.ArgumentMatchers.anyLong;
 import static org.mockito.ArgumentMatchers.eq;
 import static org.mockito.ArgumentMatchers.isA;
 import static org.mockito.ArgumentMatchers.matches;
 import static org.mockito.ArgumentMatchers.startsWith;
 import static org.mockito.BDDMockito.given;
 import static org.mockito.Mockito.atLeastOnce;
+import static org.mockito.Mockito.lenient;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.times;
 import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoInteractions;
 import static org.mockito.Mockito.verifyNoMoreInteractions;
 
 /**
@@ -78,12 +84,25 @@ class JdbcIndexedSessionRepositoryTests {
 	@Mock
 	private JdbcOperations jdbcOperations;
 
+	@Mock
+	private TransactionOperations transactionOperations;
+
 	private JdbcIndexedSessionRepository repository;
 
 	@BeforeEach
 	void setUp() {
+		// Mock transaction callbacks to the real consumer
+		lenient().doAnswer(answer -> {
+			answer.getArgument(0, Consumer.class).accept(mock(TransactionStatus.class));
+			return null;
+		}).when(transactionOperations).executeWithoutResult(any());
+
+		lenient().doAnswer(answer ->
+			answer.getArgument(0, TransactionCallback.class).doInTransaction(mock(TransactionStatus.class))
+		).when(transactionOperations).execute(any());
+
 		this.repository = new JdbcIndexedSessionRepository(this.jdbcOperations,
-				TransactionOperations.withoutTransaction());
+				transactionOperations);
 	}
 
 	@Test
@@ -467,6 +486,7 @@ void saveUpdatedAddAndRemoveAttribute() {
 
 		assertThat(session.isNew()).isFalse();
 		verifyNoMoreInteractions(this.jdbcOperations);
+		verifyNoMoreInteractions(this.transactionOperations);
 	}
 
 	@Test // gh-1070