Adding and example for how to run multiple transactions within a single async session (neo4j#899)

Author: gjmwoods

examples/src/main/java/org/neo4j/docs/driver/AsyncRunMultipleTransactionExample.java

@@ -0,0 +1,88 @@
+/*
+ * Copyright (c) "Neo4j"
+ * Neo4j Sweden AB [http://neo4j.com]
+ *
+ * This file is part of Neo4j.
+ *
+ * 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
+ *
+ *     http://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.neo4j.docs.driver;
+
+// tag::async-result-consume-import[]
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.CompletionStage;
+
+import org.neo4j.driver.async.AsyncSession;
+import org.neo4j.driver.async.AsyncTransaction;
+import org.neo4j.driver.async.ResultCursor;
+import org.neo4j.driver.summary.ResultSummary;
+import org.neo4j.driver.summary.SummaryCounters;
+
+import static org.neo4j.driver.Values.parameters;
+// end::async-result-consume-import[]
+
+public class AsyncRunMultipleTransactionExample extends BaseApplication
+{
+    public AsyncRunMultipleTransactionExample( String uri, String user, String password )
+    {
+        super( uri, user, password );
+    }
+
+    // tag::async-multiple-tx[]
+    public CompletionStage<Integer> addEmployees( final String companyName )
+    {
+        AsyncSession session = driver.asyncSession();
+
+        return session.readTransactionAsync( AsyncRunMultipleTransactionExample::matchPersonNodes )
+                      .thenCompose( personNames -> session.writeTransactionAsync( tx -> createNodes( tx, companyName, personNames ) ) );
+    }
+
+    private static CompletionStage<List<String>> matchPersonNodes( AsyncTransaction tx )
+    {
+        return tx.runAsync( "MATCH (a:Person) RETURN a.name AS name" )
+                 .thenCompose( cursor -> cursor.listAsync( record -> record.get( "name" ).asString() ) );
+    }
+
+    private static CompletableFuture<Integer> createNodes( AsyncTransaction tx, String companyName, List<String> personNames )
+    {
+        CompletableFuture<Integer>[] nodeCreatedCounts = personNames.stream()
+                                                                    .map( personName -> createNode(
+                                                                            tx,
+                                                                            companyName,
+                                                                            personName ) )
+                                                                    .toArray(
+                                                                            size -> new CompletableFuture[size] );
+        return CompletableFuture.allOf( nodeCreatedCounts )
+                                .thenApply( ignored ->
+                                                    Arrays.stream(
+                                                            nodeCreatedCounts )
+                                                          .map( CompletableFuture::join )
+                                                          .reduce( 0,
+                                                                   Integer::sum ) );
+    }
+
+    private static CompletionStage<Integer> createNode( AsyncTransaction tx, String companyName, String personName )
+    {
+        return tx.runAsync( "MATCH (emp:Person {name: $person_name}) " +
+                            "MERGE (com:Company {name: $company_name}) " +
+                            "MERGE (emp)-[:WORKS_FOR]->(com)",
+                            parameters( "person_name", personName, "company_name", companyName ) )
+                 .thenCompose( ResultCursor::consumeAsync )
+                 .thenApply( ResultSummary::counters )
+                 .thenApply( SummaryCounters::nodesCreated );
+    }
+    // end::async-multiple-tx[]
+}

examples/src/test/java/org/neo4j/docs/driver/ExamplesIT.java

@@ -187,6 +187,25 @@ void testShouldAsyncRunResultConsumeExample() throws Exception
         }
     }
 
+    @Test
+    void testShouldAsyncRunMultipleTransactionExample() throws Exception
+    {
+        // Given
+        write( "CREATE (a:Person {name: 'Alice'})" );
+        write( "CREATE (a:Person {name: 'Bob'})" );
+        try ( AsyncRunMultipleTransactionExample example = new AsyncRunMultipleTransactionExample( uri, USER, PASSWORD ) )
+        {
+            // When
+            Integer nodesCreated = await( example.addEmployees("Acme") );
+
+            // Then
+            int employeeCount = readInt(
+                    "MATCH (emp:Person)-[WORKS_FOR]->(com:Company) WHERE com.name = 'Acme' RETURN count(emp)" );
+            assertThat( employeeCount, equalTo( 2 ) );
+            assertThat( nodesCreated, equalTo( 1 ) );
+        }
+    }
+
     @Test
     void testShouldRunConfigConnectionPoolExample() throws Exception
     {