Fix NullPointerException whith batching inserts

hibernate-reactive-core/src/main/java/org/hibernate/reactive/adaptor/impl/ResultSetAdaptor.java

@@ -44,6 +44,7 @@
 import io.vertx.sqlclient.PropertyKind;
 import io.vertx.sqlclient.Row;
 import io.vertx.sqlclient.RowSet;
+import io.vertx.sqlclient.Tuple;
 import io.vertx.sqlclient.desc.ColumnDescriptor;
 import io.vertx.sqlclient.impl.RowBase;
 
@@ -56,13 +57,71 @@
  */
 public class ResultSetAdaptor implements ResultSet {
 
-	private final Iterator<Row> iterator;
+	private final Iterator<? extends Row> iterator;
 
 	private final List<ColumnDescriptor> columnDescriptors;
 	private final List<String> columnNames;
 	private Row row;
 	private boolean wasNull;
 
+	public ResultSetAdaptor(Object id, Class<?> idClass, String columnName) {
+		requireNonNull( id );
+		this.iterator = List.of( new RowAdaptor( id, idClass, columnName ) ).iterator();
+		this.columnNames = columnName == null ? emptyList() : List.of( columnName );
+		this.columnDescriptors = List.of( toColumnDescriptor( idClass, columnName ) );
+	}
+
+	private static class RowAdaptor implements Row {
+		private final Object id;
+		private final Class<?> idClass;
+		private final String columnName;
+
+		public RowAdaptor(Object id, Class<?> idClass, String columnName) {
+			this.id = id;
+			this.idClass = idClass;
+			this.columnName = columnName;
+		}
+
+		@Override
+		public Object getValue(String column) {
+			return id;
+		}
+
+		@Override
+		public String getColumnName(int pos) {
+			return columnName;
+		}
+
+		@Override
+		public int getColumnIndex(String column) {
+			return 0;
+		}
+
+		@Override
+		public Object getValue(int pos) {
+			return id;
+		}
+
+		@Override
+		public Tuple addValue(Object value) {
+			return null;
+		}
+
+		@Override
+		public int size() {
+			return 1;
+		}
+
+		@Override
+		public void clear() {
+		}
+
+		@Override
+		public List<Class<?>> types() {
+			return List.of( idClass );
+		}
+	}
+
 	public ResultSetAdaptor(RowSet<Row> rows) {
 		requireNonNull( rows );
 		this.iterator = rows.iterator();
@@ -83,7 +142,11 @@ private ResultSetAdaptor(RowSet<Row> rows, Row row, String idColumnName, Class<?
 		requireNonNull( idColumnName );
 		this.iterator = List.of( row ).iterator();
 		this.columnNames = List.of( idColumnName );
-		ColumnDescriptor columnDescriptor = new ColumnDescriptor() {
+		this.columnDescriptors = List.of( toColumnDescriptor( idClass, idColumnName ) );
+	}
+
+	private static ColumnDescriptor toColumnDescriptor(Class<?> idClass, String idColumnName) {
+		return new ColumnDescriptor() {
 			@Override
 			public String name() {
 				return idColumnName;
@@ -104,7 +167,6 @@ public JDBCType jdbcType() {
 				return null;
 			}
 		};
-		this.columnDescriptors = List.of( columnDescriptor );
 	}
 
 	private static class RowFromId extends RowBase {

hibernate-reactive-core/src/main/java/org/hibernate/reactive/pool/BatchingConnection.java

@@ -12,6 +12,8 @@
 import java.util.concurrent.CompletionStage;
 
 
+import org.hibernate.reactive.adaptor.impl.ResultSetAdaptor;
+
 import io.vertx.sqlclient.spi.DatabaseMetadata;
 
 import static org.hibernate.reactive.util.impl.CompletionStages.voidFuture;
@@ -169,11 +171,7 @@ public CompletionStage<ResultSet> insertAndSelectIdentifierAsResultSet(
 			Class<?> idClass,
 			String idColumnName) {
 		return insertAndSelectIdentifier( sql, paramValues, idClass, idColumnName )
-				.thenApply( this::convertToResultSet );
-	}
-
-	private ResultSet convertToResultSet(Object o) {
-		return null;
+				.thenApply( id -> new ResultSetAdaptor( id, idClass, idColumnName ) );
 	}
 
 	public CompletionStage<ReactiveConnection.Result> select(String sql) {

hibernate-reactive-core/src/test/java/org/hibernate/reactive/IdentityGenerationWithBatchingTest.java

@@ -0,0 +1,107 @@
+/* Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright: Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.reactive;
+
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.List;
+
+import org.hibernate.cfg.AvailableSettings;
+import org.hibernate.cfg.Configuration;
+
+import org.junit.jupiter.api.Test;
+
+import io.vertx.junit5.VertxTestContext;
+import jakarta.persistence.Entity;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import jakarta.persistence.Table;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+
+public class IdentityGenerationWithBatchingTest extends BaseReactiveTest {
+
+	@Override
+	protected Collection<Class<?>> annotatedEntities() {
+		return List.of( Book.class );
+	}
+
+	@Override
+	protected Configuration constructConfiguration() {
+		Configuration configuration = super.constructConfiguration();
+		configuration.setProperty( AvailableSettings.STATEMENT_BATCH_SIZE, "5" );
+		return configuration;
+	}
+
+	@Test
+	public void test(VertxTestContext context) {
+		String[] titles = {
+				"Around the World in Eighty Days",
+				"The Book of M: A Novel",
+				"The Poppy War",
+				"The poetry home repair manual",
+				"Relish"
+		};
+		test( context, getMutinySessionFactory()
+				.withTransaction( s -> s.persistAll( asBooks( titles ) ) )
+				.chain( () -> getMutinySessionFactory().withSession( s -> s.createSelectionQuery( "from Book order by id ASC", Book.class ).getResultList() ) )
+				.invoke( results -> {
+					String[] resultTitles = results.stream().map( Book::getTitle ).toArray( String[]::new );
+					assertThat( resultTitles ).containsExactly( titles );
+					Long savedId = 0L;
+					for ( Book book : results ) {
+						assertThat( book.getId() ).isNotNull().isGreaterThan( savedId );
+						savedId = book.getId();
+					}
+				} )
+		);
+	}
+
+	private Book[] asBooks(String[] titles) {
+		return Arrays.asList( titles ).stream().map( Book::new ).toArray( Book[]::new );
+	}
+
+	@Entity(name = "Book")
+	@Table(name = "books")
+	static class Book {
+
+		@Id
+		@GeneratedValue(strategy = GenerationType.IDENTITY)
+		private Long id;
+
+		private String title;
+
+		public Book() {
+		}
+
+		public Book(String title) {
+			this.title = title;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public void setId(Long id) {
+			this.id = id;
+		}
+
+		public String getTitle() {
+			return title;
+		}
+
+		public void setTitle(String title) {
+			this.title = title;
+		}
+
+		@Override
+		public String toString() {
+			return id + ":" + title;
+		}
+	}
+}