#58 - Add sample for usage of server-side JavaScript.

Use a server-side script to simulate putIfAbsent(…) as contracted by the Map interface. The operation will be atomic since MongoDB will put a lock on database until the script is finished.

mongodb/example/src/main/java/example/springdata/mongodb/customer/Customer.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 the original author or authors.
+ * Copyright 2014-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,6 @@
 
 import lombok.Data;
 
-import org.bson.types.ObjectId;
 import org.springframework.data.mongodb.core.mapping.Document;
 import org.springframework.util.Assert;
 
@@ -30,9 +29,7 @@
 @Document
 public class Customer {
 
-	private ObjectId id;
-	private String firstname, lastname;
-
+	private String id, firstname, lastname;
 	private Address address;
 
 	/**

mongodb/example/src/main/java/example/springdata/mongodb/customer/CustomerRepository.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014 the original author or authors.
+ * Copyright 2014-2015 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -17,7 +17,6 @@
 
 import java.util.List;
 
-import org.bson.types.ObjectId;
 import org.springframework.data.domain.Sort;
 import org.springframework.data.geo.Distance;
 import org.springframework.data.geo.GeoResults;
@@ -29,7 +28,7 @@
  * 
  * @author Oliver Gierke
  */
-public interface CustomerRepository extends CrudRepository<Customer, ObjectId> {
+public interface CustomerRepository extends CrudRepository<Customer, String> {
 
 	/**
 	 * Derived query using dynamic sort information.
@@ -41,7 +40,7 @@ public interface CustomerRepository extends CrudRepository<Customer, ObjectId> {
 	List<Customer> findByLastname(String lastname, Sort sort);
 
 	/**
-	 * Showcase for a repository query using geo-spatial functionality.
+	 * Show case for a repository query using geo-spatial functionality.
 	 * 
 	 * @param point
 	 * @param distance

mongodb/example/src/test/java/example/springdata/mongodb/advanced/ServersideScriptTests.java

@@ -0,0 +1,116 @@
+/*
+ * Copyright 2015 the original author or authors.
+ *
+ * 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 example.springdata.mongodb.advanced;
+
+import static org.hamcrest.core.Is.*;
+import static org.hamcrest.core.IsNull.*;
+import static org.junit.Assert.*;
+
+import example.springdata.mongodb.customer.Customer;
+import example.springdata.mongodb.util.RequiresMongoDB;
+
+import java.util.Map;
+
+import org.junit.Before;
+import org.junit.ClassRule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.test.SpringApplicationConfiguration;
+import org.springframework.data.mongodb.core.MongoOperations;
+import org.springframework.data.mongodb.core.script.ExecutableMongoScript;
+import org.springframework.data.mongodb.core.script.NamedMongoScript;
+import org.springframework.data.util.Version;
+import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
+
+import com.mongodb.BasicDBObject;
+import com.mongodb.DBObject;
+
+/**
+ * @author Christoph Strobl
+ */
+@RunWith(SpringJUnit4ClassRunner.class)
+@SpringApplicationConfiguration(classes = ApplicationConfiguration.class)
+public class ServersideScriptTests {
+
+	@ClassRule public static RequiresMongoDB mongodbAvailable = RequiresMongoDB.atLeast(new Version(2, 6));
+
+	@Autowired AdvancedRepository repository;
+	@Autowired MongoOperations operations;
+
+	@Before
+	public void setUp() {
+
+		if (!operations.collectionExists(Customer.class)) {
+			operations.createCollection(Customer.class);
+		}
+
+		// just make sure we remove everything properly
+		operations.getCollection("system.js").remove(new BasicDBObject());
+		repository.deleteAll();
+	}
+
+	/**
+	 * Store and call an arbitrary JavaScript function (in this case a simple echo script) via its name.
+	 */
+	@Test
+	public void saveAndCallScriptViaName() {
+
+		operations.scriptOps()
+				.register(new NamedMongoScript("echoScript", new ExecutableMongoScript("function(x) { return x; }")));
+
+		Object o = operations.scriptOps().call("echoScript", "Hello echo...!");
+		assertThat(o, is((Object) "Hello echo...!"));
+	}
+
+	/**
+	 * Use a script execution to create an atomic put-if-absent operation that fulfills the contract of
+	 * {@link Map#putIfAbsent(Object, Object)}
+	 */
+	@Test
+	public void complexScriptExecutionSimulatingPutIfAbsent() {
+
+		Customer ned = new Customer("Ned", "Stark");
+		ned.setId("ned-stark");
+
+		// #1: on first insert null has to be returned
+		assertThat(operations.scriptOps().execute(createExecutablePutIfAbsentScript(ned)), nullValue());
+
+		// #2: change the firstname and put the object again, we expect a return value.
+		ned.setFirstname("Eddard");
+		assertThat(operations.scriptOps().execute(createExecutablePutIfAbsentScript(ned)), notNullValue());
+
+		// #3: make sure the entity has not been altered by #2
+		assertThat(repository.findOne(ned.getId()).getFirstname(), is("Ned"));
+		assertThat(repository.count(), is(1L));
+	}
+
+	private ExecutableMongoScript createExecutablePutIfAbsentScript(Customer customer) {
+
+		String collectionName = operations.getCollectionName(Customer.class);
+		Object id = operations.getConverter().getMappingContext().getPersistentEntity(Customer.class)
+				.getIdentifierAccessor(customer).getIdentifier();
+
+		DBObject dbo = new BasicDBObject();
+		operations.getConverter().write(customer, dbo);
+
+		String scriptString = String.format(
+				"object  =  db.%1$s.findOne('{\"_id\": \"%2$s\"}'); if (object == null) { db.%1s.insert(%3$s); return null; } else { return object; }",
+				collectionName, id, dbo);
+
+		return new ExecutableMongoScript(scriptString);
+	}
+}