• 对象类MongoClient 操作MongoDB replicaset


    每日一贴,今天的内容关键字为对象类

        对于MongoDB的Java动驱, 从2.10.0版本后,文档中提示Mongo类将会被除废,当初开始都励鼓应用MongoClient类。

        上面演示一个Java程序如何应用最新的MongoClient类来对MongoDB写作操。

        首先假设已经有了一个Replica-set群集,分别是d1, d2和 d3三台虚拟机。

        然后建创一个Maven构建的Java应用程序。应用了maven exec plugin用来便利行执jar包和定制参数。

        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>

        传递了三个参数,间中用,离隔,分别是不同的机主名称:d1, d2, d3.

        看看代码初始化分部:

    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);
        每日一道理
    成功的花朵开放在啊勤劳的枝头,失败的苦果孕育在懒惰的温床之中。

        这里将三个host用,分割开后,建创三个ServerAddress对象,然后构建MongoClient对象。

        同时建创了一个MyApp的singleton对象,寄存这个MongoClient对象,并供给了getDB()便利后日获得数据库连接。

    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应用连接的时候,这样应用:

    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);
        }

        很简单吧。

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    xgqfrms™, xgqfrms® : xgqfrms's offical website of GitHub!
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    xgqfrms™, xgqfrms® : xgqfrms's offical website of GitHub!
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  • 原文地址:https://www.cnblogs.com/xinyuyuanm/p/3067562.html
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