我们先看HConnection的getTable方法描述:
Retrieve an HTableInterface implementation for access to a table. The returned HTableInterface is not thread safe, a new
instance should be created for each using thread. This is a lightweight operation, pooling or caching of the returned
HTableInterface is neither required nor desired. Note that the HConnection needs to be unmanaged (created
withHConnectionManager.createConnection(Configuration) ).
上面说HTable的的父类HTableInterface是非线程安全的,针对每个线程建议都应该创建一个新的HTableInterface实例,这个创建过程是轻量的,缓存HTableInterface对象既不是必须的也不是推荐的!
然后再联想到只要HTable使用的Configuration是同一个,那么它们一定是共用一个HConnection的,HConnection才是HBase客户端到Hbase集群的真正的连接。
再想想HTablePool的作用,无非就是HTable的连接池,里面维护的HTable应该来说都是使用的同一个HConnecion。
既然HTable的创建是轻量级的,使用同一个Confuguration的HTable都会共用一个HConnection,那么HTablePool就显得那么多余!
所以Hbase抛弃了HTablePool,我们唯一要做的就是保证HConnection实例是唯一的,全局共享的。然后针对HTableInterface对象最好在每次操作HBase表的时候根据HConnection对象来重新创建,使用完成之后及时关闭即可!
通过HConnection的getTable()方法就能够获取到用户操作HBase表的HTableInterface对象了。
下面是一个使用HConnection的getTable()方法获取HTableInterface对象的例子
public void addUser(User user) throws IOException
{
HTableInterface usersTable = conn.getTable(TABLE_NAME);
Put put = makePut(user);
usersTable.put(put);
usersTable.close();
log.info("Add a User:"+user.name+" successfully");
}
至于HConnection对象如何创建,HBase推荐使用的方法是:
Create a new HConnection instance using the passed conf instance.
Note: This bypasses the usual HConnection life cycle management done bygetConnection(Configuration) . The caller is
responsible for callingCloseable.close() on the returned connection instance. This is the recommended way to create
HConnections. HConnection connection = HConnectionManager.createConnection(conf); HTableInterface table =
connection.getTable("mytable"); table.get(...); ... table.close(); connection.close();
下面是单例创建:
public class HBaseUtils {
private static final String QUORUM = "192.168.1.100";
private static final String CLIENTPORT = "2181";
private static Configuration conf = null;
private static HConnection conn = null;
/**
* 获取全局唯一的Configuration实例
* @return
*/
public static synchronized Configuration getConfiguration()
{
if(conf == null)
{
conf = HBaseConfiguration.create();
conf.set("hbase.zookeeper.quorum", QUORUM);
conf.set("hbase.zookeeper.property.clientPort", CLIENTPORT);
}
return conf;
}
/**
* 获取全局唯一的HConnection实例
* @return
* @throws ZooKeeperConnectionException
*/
public static synchronized HConnection getHConnection() throws ZooKeeperConnectionException
{
if(conn == null)
{
/*
* * 创建一个HConnection
* HConnection connection = HConnectionManager.createConnection(conf);
* HTableInterface table = connection.getTable("mytable");
* table.get(...); ...
* table.close();
* connection.close();
* */
conn = HConnectionManager.createConnection(getConfiguration());
}
return conn;
}
}