每日一貼,今天的內(nèi)容關(guān)鍵字為對(duì)象類

????對(duì)于MongoDB的Java動(dòng)驅(qū), 從2.10.0版本后，文檔中提示Mongo類將會(huì)被除廢，當(dāng)初開始都勵(lì)鼓應(yīng)用MongoClient類。

????上面演示一個(gè)Java程序如何應(yīng)用最新的MongoClient類來對(duì)MongoDB寫作操。

????首先假設(shè)已經(jīng)有了一個(gè)Replica-set群集，分別是d1, d2和 d3三臺(tái)虛擬機(jī)。

????然后建創(chuàng)一個(gè)Maven構(gòu)建的Java應(yīng)用程序。應(yīng)用了maven exec plugin用來便利行執(zhí)jar包和定制參數(shù)。

????看一下pom.xml：

    <build>

    <plugins>

      <plugin>

	<groupId>org.codehaus.mojo</groupId>

	<artifactId>exec-maven-plugin</artifactId>

	<version>1.2.1</version>

	<executions>

	  <execution>

	    <goals>

	      <goal>java</goal>

	    </goals>

	  </execution>

	</executions>

	<configuration>

	  <mainClass>org.freebird.dbtool.App</mainClass>

	  <arguments>

	    <argument>d1,d2,d3</argument>

	  </arguments>

	</configuration>

      </plugin>

    </plugins>

  </build>
  

????傳遞了三個(gè)參數(shù)，間中用,離隔，分別是不同的機(jī)主名稱：d1, d2, d3.

????看看代碼初始化分部：

    public static void main(String[] args) throws UnknownHostException {

	System.out.println(args[0]);

        String[] hosts = args[0].split(",");

        int portNumber = 27017;

        System.out.println(hosts[0]);

        System.out.println(hosts[1]);

        System.out.println(hosts[2]);

        

        MongoClient client = new MongoClient(Arrays.asList(new ServerAddress(hosts[0], portNumber),

                                      new ServerAddress(hosts[1], portNumber),

                                      new ServerAddress(hosts[2], portNumber)));

        MyApp.getInstance().setDbName("kaimei");

        MyApp.getInstance().setClient(client);
  

????這里將三個(gè)host用,分割開后，建創(chuàng)三個(gè)ServerAddress對(duì)象，然后構(gòu)建MongoClient對(duì)象。

????同時(shí)建創(chuàng)了一個(gè)MyApp的singleton對(duì)象，寄存這個(gè)MongoClient對(duì)象，并供給了getDB()便利后日獲得數(shù)據(jù)庫(kù)連接。

    public class MyApp {

    

    private MyApp() {

    }

    

    public static MyApp getInstance() {

        return MyAppHolder.INSTANCE;

    }

    

    private static class MyAppHolder {



        private static final MyApp INSTANCE = new MyApp();

    }

    

    @Getter @Setter

    String dbName;

    

    @Setter

    MongoClient client;

    

    public DB getDB() {

        return client.getDB(dbName);

    }

}
  

????后以在任何地方要需應(yīng)用連接的時(shí)候，這樣應(yīng)用：

    public static void bind(final String address, final String userId) {

	DB db = MyApp.getInstance().getDB();

	DBCollection collection = db.getCollection(DISPLAY_COLLECTION);

	DBObject condition = new BasicDBObject();

	condition.put("address", address);



	DBObject field = new BasicDBObject();

	field.put("user_id", new ObjectId(userId));

	DBObject set = new BasicDBObject();

	set.put("$set", field);

	collection.update(condition, set, false, false);

    }
  

????很簡(jiǎn)單吧。

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對(duì)象類MongoClient 操作MongoDB replica-set