Ensure isolation level is applied to subsequent transactions after se…

…tting

src/main/java/io/asyncer/r2dbc/mysql/MySqlConnection.java

@@ -129,7 +129,7 @@ public final class MySqlConnection implements Connection, Lifecycle, ConnectionS
 
     private final MySqlConnectionMetadata metadata;
 
-    private final IsolationLevel sessionLevel;
+    private volatile IsolationLevel sessionLevel;
 
     private final QueryCache queryCache;
 
@@ -303,13 +303,22 @@ public IsolationLevel getTransactionIsolationLevel() {
         return currentLevel;
     }
 
+    /**
+     * Gets session transaction isolation level(Only for testing).
+     *
+     * @return session transaction isolation level.
+     */
+    IsolationLevel getSessionTransactionIsolationLevel() {
+        return sessionLevel;
+    }
+
     @Override
     public Mono<Void> setTransactionIsolationLevel(IsolationLevel isolationLevel) {
         requireNonNull(isolationLevel, "isolationLevel must not be null");
 
-        // Set next transaction isolation level.
-        return QueryFlow.executeVoid(client, "SET TRANSACTION ISOLATION LEVEL " + isolationLevel.asSql())
-            .doOnSuccess(ignored -> setIsolationLevel(isolationLevel));
+        // Set subsequent transaction isolation level.
+        return QueryFlow.executeVoid(client, "SET SESSION TRANSACTION ISOLATION LEVEL " + isolationLevel.asSql())
+            .doOnSuccess(ignored -> this.sessionLevel = isolationLevel);
     }
 
     @Override

src/main/java/io/asyncer/r2dbc/mysql/message/client/TextQueryMessage.java

@@ -19,6 +19,7 @@
 import io.asyncer.r2dbc.mysql.ConnectionContext;
 import io.netty.buffer.ByteBuf;
 import io.netty.buffer.ByteBufAllocator;
+import java.util.Objects;
 import reactor.core.publisher.Mono;
 
 import java.nio.charset.Charset;
@@ -67,6 +68,23 @@ public Mono<ByteBuf> encode(ByteBufAllocator allocator, ConnectionContext contex
         });
     }
 
+    @Override
+    public boolean equals(Object o) {
+        if (this == o) {
+            return true;
+        }
+        if (o == null || getClass() != o.getClass()) {
+            return false;
+        }
+        TextQueryMessage that = (TextQueryMessage) o;
+        return Objects.equals(sql, that.sql);
+    }
+
+    @Override
+    public int hashCode() {
+        return Objects.hash(sql);
+    }
+
     @Override
     public String toString() {
         return "TextQueryMessage{sql=REDACTED}";

src/test/java/io/asyncer/r2dbc/mysql/ConnectionIntegrationTest.java

@@ -139,6 +139,31 @@ void transactionDefinitionIsolationLevel() {
             }));
     }
 
+    @Test
+    void shouldApplyIsolationLevelForSubsequentTransactions() {
+        complete(connection -> {
+            Mono<Void> setTransactionIsolationLevel =
+                connection.setTransactionIsolationLevel(READ_COMMITTED);
+
+            Mono<Void> beginTransaction =
+                connection.beginTransaction(MySqlTransactionDefinition.builder()
+                    .isolationLevel(SERIALIZABLE)
+                    .build());
+
+            Mono<Void> rollbackTransaction = connection.rollbackTransaction();
+
+            return setTransactionIsolationLevel
+                .then(beginTransaction)
+                .doOnSuccess(ignored ->
+                    assertThat(connection.getTransactionIsolationLevel()).isEqualTo(SERIALIZABLE)
+                )
+                .then(rollbackTransaction)
+                .doOnSuccess(ignored ->
+                    assertThat(connection.getTransactionIsolationLevel()).isEqualTo(READ_COMMITTED)
+                );
+        });
+    }
+
     @Test
     void transactionDefinition() {
         // The WITH CONSISTENT SNAPSHOT phrase can only be used with the REPEATABLE READ isolation level.

src/test/java/io/asyncer/r2dbc/mysql/MySqlConnectionTest.java

@@ -19,13 +19,21 @@
 import io.asyncer.r2dbc.mysql.cache.Caches;
 import io.asyncer.r2dbc.mysql.client.Client;
 import io.asyncer.r2dbc.mysql.codec.Codecs;
+import io.asyncer.r2dbc.mysql.message.client.ClientMessage;
+import io.asyncer.r2dbc.mysql.message.client.TextQueryMessage;
 import io.r2dbc.spi.IsolationLevel;
 import org.assertj.core.api.ThrowableTypeAssert;
 import org.junit.jupiter.api.Test;
+import reactor.core.publisher.Flux;
+import reactor.test.StepVerifier;
 
 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.eq;
+import static org.mockito.ArgumentMatchers.same;
 import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
 
 /**
  * Unit tests for {@link MySqlConnection}.
@@ -125,6 +133,18 @@ void badSetTransactionIsolationLevel() {
         assertThatIllegalArgumentException().isThrownBy(() -> noPrepare.setTransactionIsolationLevel(null));
     }
 
+    @Test
+    void shouldSetTransactionIsolationLevelSuccessfully() {
+        ClientMessage message = new TextQueryMessage("SET SESSION TRANSACTION ISOLATION LEVEL SERIALIZABLE");
+        when(client.exchange(eq(message), any())).thenReturn(Flux.empty());
+
+        noPrepare.setTransactionIsolationLevel(IsolationLevel.SERIALIZABLE)
+            .as(StepVerifier::create)
+            .verifyComplete();
+
+        assertThat(noPrepare.getSessionTransactionIsolationLevel()).isEqualTo(IsolationLevel.SERIALIZABLE);
+    }
+
     @SuppressWarnings("ConstantConditions")
     @Test
     void badValidate() {