使用Morphia（Java）连接到MongoDB

Question

我正在开发一个Java的Restful Web应用程序，并计划将MongoDB与吗啡用作ODM。由于我是MongoDB的新手，我需要一些建议。

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处理db连接的最佳方法是使用db连接池，mongoClient负责处理。

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); 

所以我需要重用上面的数据存储，而不是在每次请求时创建一个新实例，因为它会浪费大量资源并影响性能。我应该将上述实现为单例类吗？有人能帮我解决这个问题吗？

Answer 1

你可以像这样：

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();
    }
}

当需要使用时，您可以这样做：private Datastore Datastore=mongoConnService。getMORPHIADB（“xxx”）；

Answer 2

查看这个演示github中的配置。com/xeraa/morphia演示

    /**
     * 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;
      }
    }