Move documentation example for transactions to the Java repo.

JAVA-3152

Author: jstewart148

driver-sync/src/examples/documentation/TransactionExample.java

@@ -0,0 +1,157 @@
+/*
+ * Copyright 2018 MongoDB, Inc.
+ *
+ * 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 documentation;
+
+import com.mongodb.ConnectionString;
+import com.mongodb.MongoClientSettings;
+import com.mongodb.client.MongoClient;
+import com.mongodb.MongoCommandException;
+import com.mongodb.MongoException;
+import com.mongodb.ReadConcern;
+import com.mongodb.ReadPreference;
+import com.mongodb.TransactionOptions;
+import com.mongodb.WriteConcern;
+import com.mongodb.client.ClientSession;
+import com.mongodb.client.MongoClients;
+import com.mongodb.client.MongoCollection;
+import com.mongodb.client.model.Filters;
+import com.mongodb.client.model.Updates;
+import org.bson.Document;
+import org.junit.After;
+import org.junit.Before;
+import org.junit.Test;
+
+import static com.mongodb.ClusterFixture.isDiscoverableReplicaSet;
+import static com.mongodb.ClusterFixture.isSharded;
+import static com.mongodb.ClusterFixture.serverVersionAtLeast;
+import static com.mongodb.client.Fixture.getMongoClientSettingsBuilder;
+import static org.junit.Assume.assumeTrue;
+
+public class TransactionExample {
+    private MongoClient client;
+
+    @Before
+    public void setUp() {
+        assumeTrue(canRunTest());
+        MongoClientSettings.Builder builder = getMongoClientSettingsBuilder()
+                .applyConnectionString(new ConnectionString(
+                        "mongodb://localhost,localhost:27018,localhost:27019/?serverSelectionTimeoutMS=5000"));
+        client = MongoClients.create(builder.build());
+
+        createCollection(client, "hr", "employees");
+        createCollection(client, "reporting", "events");
+    }
+
+    @After
+    public void cleanUp() {
+        if (client != null) {
+            client.close();
+        }
+    }
+
+    @Test
+    public void updateEmployeeInfoWithRetry() {
+        runTransactionWithRetry(new Runnable() {
+            @Override
+            public void run() {
+                updateEmployeeInfo();
+            }
+        });
+    }
+
+    private void runTransactionWithRetry(final Runnable transactional) {
+        while (true) {
+            try {
+                transactional.run();
+                break;
+            } catch (MongoException e) {
+                System.out.println("Transaction aborted. Caught exception during transaction.");
+
+                if (e.hasErrorLabel(MongoException.TRANSIENT_TRANSACTION_ERROR_LABEL)) {
+                    System.out.println("TransientTransactionError, aborting transaction and retrying ...");
+                } else {
+                    throw e;
+                }
+            }
+        }
+    }
+
+    private void commitWithRetry(final ClientSession clientSession) {
+        while (true) {
+            try {
+                clientSession.commitTransaction();
+                System.out.println("Transaction committed");
+                break;
+            } catch (MongoException e) {
+                // can retry commit
+                if (e.hasErrorLabel(MongoException.UNKNOWN_TRANSACTION_COMMIT_RESULT_LABEL)) {
+                    System.out.println("UnknownTransactionCommitResult, retrying commit operation ...");
+                } else {
+                    System.out.println("Exception during commit ...");
+                    throw e;
+                }
+            }
+        }
+    }
+
+    private void updateEmployeeInfo() {
+        MongoCollection<Document> employeesCollection = client.getDatabase("hr").getCollection("employees");
+        MongoCollection<Document> eventsCollection = client.getDatabase("reporting").getCollection("events");
+
+        TransactionOptions txnOptions = TransactionOptions.builder()
+                .readPreference(ReadPreference.primary())
+                .readConcern(ReadConcern.MAJORITY)
+                .writeConcern(WriteConcern.MAJORITY)
+                .build();
+
+        ClientSession clientSession = client.startSession();
+        try {
+            clientSession.startTransaction(txnOptions);
+
+            employeesCollection.updateOne(clientSession,
+                    Filters.eq("employee", 3),
+                    Updates.set("status", "Inactive"));
+            eventsCollection.insertOne(clientSession,
+                    new Document("employee", 3).append("status", new Document("new", "Inactive").append("old", "Active")));
+
+            commitWithRetry(clientSession);
+        } finally {
+            clientSession.close();
+        }
+    }
+
+    private void createCollection(final MongoClient client, final String dbName, final String collectionName) {
+        try {
+            client.getDatabase(dbName).createCollection(collectionName);
+        } catch (MongoCommandException e) {
+            if (!e.getErrorCodeName().equals("NamespaceExists")) {
+                throw e;
+            }
+        }
+    }
+
+    private boolean canRunTest() {
+        if (isSharded()) {
+            return serverVersionAtLeast(4, 1);
+        } else if (isDiscoverableReplicaSet()) {
+            return serverVersionAtLeast(4, 0);
+        } else {
+            return false;
+        }
+    }
+}