【ODPS】TableTunnel单线程简单下载事例

ODPS Tunnel是ODPS的数据通道，用户能够通过Tunnel向ODPS中上传或者下载数据。眼下Tunnel仅支持表（不包含视图View）数据的上传下载。

主要接口	描写叙述
TableTunnel	訪问ODPS Tunnel服务的入口类。用户能够通过公网或者阿里云内网环境对ODPS 及其Tunnel进行訪问。 当用户在阿里云内网环境中。使用Tunnel内网连接下载数据时。ODPS不会将该操作产生的流量计入计费。 此外内网地址仅对杭州域的云产品有效。
TableTunnel.UploadSession	表示一个向ODPS表中上传数据的会话。
TableTunnel.DownloadSession	表示一个向ODPS表中下载数据的会话。

接口定义：

    public class DownloadSession {
        DownloadSession(Configuration conf, String projectName, String tableName,
            String partitionSpec) throws TunnelException
        DownloadSession(Configuration conf, String projectName, String tableName,
            String partitionSpec, String downloadId) throws TunnelException
        public String getId()
        public long getRecordCount()
        public TableSchema getSchema()
        public DownloadSession.Status getStatus()
        public RecordReader openRecordReader(long start, long count)
        public RecordReader openRecordReader(long start, long count, boolean compress)
    }

Download对象：

• 生命周期：从创建Download实例到下载结束
• 创建Download实例，能够通过调用构造方法创建。也能够通过TableTunnel创建。
  • 请求方式：同步
  • Server端会为该Download创建一个session。生成唯一downloadId标识该Download，client能够通过getId获取
  • 该操作开销较大，server端会对数据文件创建索引。当文件数非常多时，该时间会比較长。
  • 同一时候server端会返回总Record数。能够依据总Record数启动多个并发同一时候下载
• 下载数据：
  • 请求方式：异步
  • 调用openRecordReader方法，生成RecordReader实例，当中參数start标识本次下载的record的起始位置。从0開始。取值范围是 >= 0, count标识本次下载的记录数，取值范围是>0。
• 查看下载：
  • 请求方式：同步
  • 调用getStatus能够获取当前Download状态
• 4种状态说明：
  • UNKNOWN, server端刚创建一个session时设置的初始值
  • NORMAL, 创建Download对象成功
  • CLOSED, 下载结束后
  • EXPIRED, 下载超时

说明：分区表下载必须指定分区

事例源代码：

package bysql;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.util.Date;
import com.aliyun.odps.Column;
import com.aliyun.odps.Odps;
import com.aliyun.odps.PartitionSpec;
import com.aliyun.odps.TableSchema;
import com.aliyun.odps.account.Account;
import com.aliyun.odps.account.AliyunAccount;
import com.aliyun.odps.data.Record;
import com.aliyun.odps.data.RecordReader;
import com.aliyun.odps.tunnel.TableTunnel;
import com.aliyun.odps.tunnel.TunnelException;

public class DownloadSample {

	private static final String ACCESS_ID = "<your access id>";
	private static final String ACCESS_KEY = "<your access Key>";
	private static final String PROJECT_NAME = "<your project>";
	private static final String TUNNEL_URL = "<your tunnel endpoint>";
	private static final String ODPS_URL = "<your odps endpoint>";

	public static void main(String args[]) throws Exception {
		String tableName = "point_z";//表名

		/* 先构建阿里云帐号 */
		Account account = new AliyunAccount(ACCESS_ID, ACCESS_KEY);


		/* Odps类是ODPS SDK的入口 */
		Odps odps = new Odps(account);
		odps.setDefaultProject(PROJECT_NAME);// 指定默认使用的Project名称
		odps.setEndpoint(ODPS_URL);// 设置ODPS服务的地址
		
		/*訪问ODPS Tunnel服务的入口类*/
		TableTunnel tunnel = new TableTunnel(odps);
		tunnel.setEndpoint(TUNNEL_URL);//设置TunnelServer地址

		try {
			/*此处表point_z为分区表。下载时必须指定分区
			 * 指定下载分区
			 * */
			PartitionSpec partitionSpec = new PartitionSpec();
			partitionSpec.set("z", "1");
			
			System.out.println("開始下载数据.........");
			File file = new File("G:\"+tableName+"(单线程).txt");//下载文件
			if (file.exists()){
				file.delete();
			}
			file.createNewFile();
			long startTime = System.currentTimeMillis();
			
			/*在分区表上创建下载会话(分区表必须指定分区，非分区表不用)*/
			TableTunnel.DownloadSession downloadSession = tunnel
					.createDownloadSession(PROJECT_NAME, tableName,partitionSpec);

			long count = downloadSession.getRecordCount();
			System.out.println("RecordCount is: " + count);

			RecordReader recordReader = downloadSession.openRecordReader(0,
					count);
			Record record;
			while ((record = recordReader.read()) != null) {
				consumeRecord(record, downloadSession.getSchema(),file);			
			}
			recordReader.close();
			long endTime = System.currentTimeMillis();
	        System.out.println("总共耗时：" + (endTime - startTime) + " ms");
			System.out.println("-------------------------------------------------");
		} catch (TunnelException e) {
			e.printStackTrace();
		} catch (IOException e1) {
			e1.printStackTrace();
		}
	}

	private static void consumeRecord(Record record, TableSchema schema,File file)
			throws IOException {
		BufferedWriter out = new BufferedWriter(new OutputStreamWriter(
				new FileOutputStream(file, true), "utf-8"));
		String writeStr="";
        String str = null;
		for (int i = 0; i < schema.getColumns().size(); i++) {
			Column column = schema.getColumn(i);
			String colValue = null;
			switch (column.getType()) {
			case BIGINT: {
				Long v = record.getBigint(i);
				colValue = v == null ? null : v.toString();
				break;
			}
			case BOOLEAN: {
				Boolean v = record.getBoolean(i);
				colValue = v == null ? null : v.toString();
				break;
			}
			case DATETIME: {
				Date v = record.getDatetime(i);
				colValue = v == null ? null : v.toString();
				break;
			}
			case DOUBLE: {
				Double v = record.getDouble(i);
				colValue = v == null ?
 null : v.toString();
				break;
			}
			case STRING: {
				String v = record.getString(i);
				colValue = v == null ? null : v.toString();
				break;
			}
			default:
				throw new RuntimeException("Unknown column type: "
						+ column.getType());
			}
			str = colValue == null ?
 "null" : colValue;
			if (i != schema.getColumns().size()-1){
            	str = schema.getColumn(i).getName()+":"+str+",        ";
            }else{
            	str = schema.getColumn(i).getName()+":"+str;
            }
            writeStr =writeStr+str; 
		}
		str =str +System.getProperty("line.separator");
		writeStr =writeStr +System.getProperty("line.separator");
		out.write(writeStr);
		out.close();
	}

}