Develop Reference

Connection to MongoDB using Morphia (Java)

I am developing a Java Restful web application and planning to use MongoDB with Morphia as ODM . As I am new to MongoDB, I needed a few suggestions.
The best way to handle db connections is to make use of db connection pool, which mongoClient takes care of.
Morphia morphia = new Morphia();
ServerAddress addr = new ServerAddress("127.0.0.1", 27017);
String databaseName = "test";
MongoClient mongoClient = new MongoClient(addr);
Datastore datastore = morphia.createDatastore(mongoClient, databaseName);
So I need to reuse the above datastore and not create a new instance upon every request as it can waste a lot of resources and affect performance. Should I be implementing the above as singleton class? Can someone help me through this?
Also can someone explain as to how I can set up configuration for db connections such as max connections per host, connection timeout in Morphia using MongoClientOptions?

Check out the config in this demo github.com/xeraa/morphia-demo
/**
* MongoDB providing the database connection for main.
*/
public class MongoDB {
public static final String DB_HOST = "127.0.0.1";
public static final int DB_PORT = 27017;
public static final String DB_NAME = "morphia_demo";
private static final Logger LOG = Logger.getLogger(MongoDB.class.getName());
private static final MongoDB INSTANCE = new MongoDB();
private final Datastore datastore;
private MongoDB() {
MongoClientOptions mongoOptions = MongoClientOptions.builder()
.socketTimeout(60000) // Wait 1m for a query to finish, https://jira.mongodb.org/browse/JAVA-1076
.connectTimeout(15000) // Try the initial connection for 15s, http://blog.mongolab.com/2013/10/do-you-want-a-timeout/
.maxConnectionIdleTime(600000) // Keep idle connections for 10m, so we discard failed connections quickly
.readPreference(ReadPreference.primaryPreferred()) // Read from the primary, if not available use a secondary
.build();
MongoClient mongoClient;
mongoClient = new MongoClient(new ServerAddress(DB_HOST, DB_PORT), mongoOptions);
mongoClient.setWriteConcern(WriteConcern.SAFE);
datastore = new Morphia().mapPackage(BaseEntity.class.getPackage().getName())
.createDatastore(mongoClient, DB_NAME);
datastore.ensureIndexes();
datastore.ensureCaps();
LOG.info("Connection to database '" + DB_HOST + ":" + DB_PORT + "/" + DB_NAME + "' initialized");
}
public static MongoDB instance() {
return INSTANCE;
}
// Creating the mongo connection is expensive - (re)use a singleton for performance reasons.
// Both the underlying Java driver and Datastore are thread safe.
public Datastore getDatabase() {
return datastore;
}
}

you can like this:
private MongoClient mongoClient = null;
private String mongoUrl="xxxx";//You can also use spring injection，#Value(value = "${db.mongo.url}")
private static final Morphia MORPHIA = new Morphia();
public Datastore getMORPHIADB(String dbName) {
if (mongoClient == null) {
//初始化
init();
}
return MORPHIA.createDatastore(mongoClient, dbName);
}
#PostConstruct
public void init() {
try {
//此处其它参数我们不做配置,采用默认配置MongoClientOptions.Builder里面配置连接池的参数
MongoClientOptions.Builder options = new MongoClientOptions.Builder()
.connectionsPerHost(30); //连接池大小(默认初始化为100个,原来老版本是10个)
MongoClientURI mongoClientURI = new MongoClientURI(mongoUrl, options);
mongoClient = new MongoClient(mongoClientURI);
} catch (MongoClientException e) {
LOGGER.error("建立MongoClient异常");
}
}
#PreDestroy
public synchronized void closeConnection() {
if (mongoClient != null) {
mongoClient.close();
}
}
when need use, you can like this:
private Datastore datastore = mongoConnService.getMORPHIADB("xxx");

Java MongoDB connection pool

I am using Java with MongoDB. Here I am opening MongoClient in each method. I only need to open it once through out the class and close it once.
public class A
{
public String name()
{
MongoClient mongo = new MongoClient(host, port);
DB db = mongo.getDB(database);
DBCollection coll = db.getCollection(collection);
BasicDBObject doc = new BasicDBObject("john", e.getName())
}
public String age()
{
MongoClient mongo = new MongoClient(host, port);
DB db = mongo.getDB(database);
DBCollection coll = db.getCollection(collection);
BasicDBObject doc = new BasicDBObject("age", e.getAge())
}
}

You can use a Singleton pattern to guarantee only one instance of MongoClient class per application. Once you obtain the instance of MongoClient, you can perform your operations and don't need to explicitly manage operations like MongoClient.close, as this object manages connection pooling automatically.
In your example, you can initialize the MongoClient in a static variable.

Openshift can't connect to mongoDB from java code, time out

I've got a MongoDB cartridge installed on openshift and i'm having troubles with connecting to it from java code. Ip address, port and credentials are taken from openshift's RockMongo cartridge. The following method invocation:
public Document insert(String audio, String username) {
Document document = new Document();
document.put("username", username);
document.put("audio", audio);
document.put("timestamp", new Date());
collection.insertOne(document);
return document;
}
and this mongo client configuration:
private static MongoClient build() throws UnknownHostException {
if (mongoClient == null) {
mongoClient = new MongoClient(
new MongoClientURI( "mongodb://admin:password#X.X.X.X:27017/dbName"));
}
return mongoClient;
}
public static MongoCollection<Document> getCollection(String collectionName) {
try {
build();
} catch (UnknownHostException e) {
}
MongoDatabase db = mongoClient.getDatabase(dbName);
MongoCollection<Document> collection = db.getCollection(collectionName);
return collection;
}
results in INFO: No server chosen by PrimaryServerSelector from cluster description ClusterDescription, and exception: Timed out after 30000 ms while waiting for a server that matches PrimaryServerSelector.
EDIT: I can't connect with mongoDB service on openshift via mongo terminal application either: "exception: connect failed", so I think it's openshift configuration issue. Port forwarding and the service itself are started

I suppose you have not correctly configure cluster (message in logs told about this problem), I'm not sure how OpenShift Cratridge works, but I recommend you to check if it has mondo-db correctly started. Check it via ssh client and run mongo-db command to check its status and if started. Take a look on this question: Java MongoClient cannot connect to primary, I suppose it give you some idea how to check where you have problem.

java mongodb repairdatabase ()

Is there a way to call MongoDB's db.repairDatabase() function from the java driver?
I tried the following :
db.command("repairDatabase",1);
but I had an errmsg with "bad option"

I tried the following and it worked without error:
#Test
public void shouldNotErrorWhenCallingRepairDatabase() throws UnknownHostException {
// given
MongoClient mongoClient = new MongoClient();
DB database = mongoClient.getDB("database");
// when
CommandResult result = database.command(new BasicDBObject("repairDatabase", 1));
// then
assertThat(result, is(notNullValue()));
assertThat(result.ok(), is(true));
}
Can you post more information on the error please?

How do I change my java code to use replset? with Spring Data and MongoDB

I would like to know how to change my java code to support replset with spring-data and MongoDB.
I have 3 MongoDB servers running.. example:
./mongod --dbpath=/home/jsmith/tmp/db1 --replSet=spring --port=27017
./mongod --dbpath=/home/jsmith/tmp/db2 --replSet=spring --port=27027
./mongod --dbpath=/home/jsmith/tmp/db3 --replSet=spring --port=27037
if I do rs.status() I can see that if the db on 27017 goes down then one of the others become primary so I know that mongoDB is working right but in my java code if I try to run it I get the following error:
Exception in thread "main" org.springframework.dao.DataAccessResourceFailureException: can't call something : /127.0.0.1:27017/demo
Its looking only on port 27017
here is my mongodbconfig:
#Configuration
#EnableMongoRepositories
#ComponentScan(basePackageClasses = {MongoDBApp.class})
#PropertySource("classpath:application.properties")
public class MongoConfiguration extends AbstractMongoConfiguration {
#Override
protected String getDatabaseName() {
return "demo";
}
#Override
public Mongo mongo() throws Exception {
return new Mongo(new ArrayList<ServerAddress>() {{ add(new ServerAddress("127.0.0.1", 27017)); add(new ServerAddress("127.0.0.1", 27027)); add(new ServerAddress("127.0.0.1", 27037)); }});
}
#Override
protected String getMappingBasePackage() {
return "com.xxxx.mongodb.example.domain";
}
}
how do I change it to support replset? but if its reading and one of the servers goes down I get a error.. anyway to make in reconnect?

The URI method should work, or there's a clearer way to initialise the replica set using a list of servers:
final List<ServerAddress> seeds = Arrays.asList(new ServerAddress("127.0.0.1", 27017),
new ServerAddress("127.0.0.1", 27027),
new ServerAddress("127.0.0.1", 27037));
final Mongo mongo = new Mongo(seeds);

This is how I do it:
String mongoURI="mongodb://myUsrName:pass#mongoServer-001.company.com:27017,mongoServer-002.company.com:27017,mongoServer-003.company.com:27017/myDBname?waitqueuemultiple=1500&w=1&maxpoolsize=40&safe=true";
MongoURI uri = new MongoURI(mongoURI);
Mongo mongo = new Mongo(uri);
I specify the 3 servers in the URI (along with extra parameters like max pool size).
The third server (mongoServer-003) is the arbiter and it doesn't store any info. The arbiter helps in the election of the primary server when the current primary goes down. Take a look at this article.
With this configuration, the app can keep working even if the primary server goes down.

You can also do it the CustomEditorConfigurer and a class that implements PropertyEditorRegistrar.
So you your configuration class needs this:
#Bean
public static CustomEditorConfigurer customEditorConfigurer(){
CustomEditorConfigurer configurer = new CustomEditorConfigurer();
configurer.setPropertyEditorRegistrars(
new PropertyEditorRegistrar[]{new ServerAddressPropertyEditorRegistrar()});
return configurer;
}
#Override
protected String getDatabaseName() {
return authenticationDb;
}
#Override
#Bean
public MongoClient mongoClient() {
MongoClient mongoClient = new MongoClient(Arrays.asList(new ServerAddress(host, port)), mongoCredentials(), mongoClientOptions());
return mongoClient;
}
public final class ServerAddressPropertyEditorRegistrar implements PropertyEditorRegistrar {
#Override
public void registerCustomEditors(PropertyEditorRegistry registry) {
registry.registerCustomEditor(ServerAddress[].class, new ServerAddressPropertyEditor());
}
}