在我的前面一篇博客中，抄录了hbase官网的一段话，讲的是0.96.0以后版本中endpoint的实现机制由于引进了protobuf框架，有了比较彻底的改变。本文承接上面一篇博客，给出定制一个endpoint的过程。

下面是实现过程：

1、定义接口描述文件（该功能有protobuf提供出来）

option java_package = "coprocessor.endpoints.generated";option java_outer_classname = "RowCounterEndpointProtos";option java_generic_services = true;option java_generate_equals_and_hash = true;option optimize_for = SPEED;message CountRequest {}message CountResponse {  required int64 count = 1 [default = 0];}service RowCountService {  rpc getRowCount(CountRequest)    returns (CountResponse);  rpc getKeyValueCount(CountRequest)    returns (CountResponse);}

这个文件我直接拿的hbase提供的example中的例子。其中的语法应该有过类似经验的一看就清楚了，实在不清楚就请查查protobuf的帮助手册吧。

2、根据接口描述文件生成java接口类（该功能有protobuf提供出来）

有了接口描述文件，还需要生成java语言的接口类。这个需要借助protobuf提供的工具protoc。

$protoc --java_out=./ Examples.proto

简单解释下，protoc这个命令在你装了protobuf后就有了。Examples.proto这个是文件名，也就是刚才编写的那个接口描述文件。“--java_out”这个用来指定生成后的java类放的地方。

所以，这地方如果你没有装protobuf，你需要装一个，window和linux版都有，多说一句，如果你去装hadoop64位的编译环境的话，应该是要装protobuf。

3、实现接口

package coprocessor;import java.io.IOException;import java.util.ArrayList;import java.util.List;import org.apache.hadoop.hbase.Cell;import org.apache.hadoop.hbase.CellUtil;import org.apache.hadoop.hbase.Coprocessor;import org.apache.hadoop.hbase.CoprocessorEnvironment;import org.apache.hadoop.hbase.client.Scan;import org.apache.hadoop.hbase.coprocessor.CoprocessorException;import org.apache.hadoop.hbase.coprocessor.CoprocessorService;import org.apache.hadoop.hbase.coprocessor.RegionCoprocessorEnvironment;import org.apache.hadoop.hbase.filter.FirstKeyOnlyFilter;import org.apache.hadoop.hbase.protobuf.ResponseConverter;import org.apache.hadoop.hbase.regionserver.InternalScanner;import org.apache.hadoop.hbase.util.Bytes;import com.google.protobuf.RpcCallback;import com.google.protobuf.RpcController;import com.google.protobuf.Service;import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountRequest;import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountResponse;import coprocessor.endpoints.generated.RowCounterEndpointProtos.RowCountService;public class RowCounterEndpointExample extends RowCountService implements		Coprocessor, CoprocessorService {	private RegionCoprocessorEnvironment env;	public RowCounterEndpointExample() {	}	@Override	public Service getService() {		return this;	}	@Override	public void getRowCount(RpcController controller, CountRequest request,			RpcCallback
    
      done) {		Scan scan = new Scan();		scan.setFilter(new FirstKeyOnlyFilter());		CountResponse response = null;		InternalScanner scanner = null;		try {			scanner = env.getRegion().getScanner(scan);			List
     
       results = new ArrayList
      
       ();			boolean hasMore = false;			byte[] lastRow = null;			long count = 0;			do {				hasMore = scanner.next(results);				for (Cell kv : results) {					byte[] currentRow = CellUtil.cloneRow(kv);					if (lastRow == null || !Bytes.equals(lastRow, currentRow)) {						lastRow = currentRow;						count++;					}				}				results.clear();			} while (hasMore);			response = CountResponse.newBuilder().setCount(count).build();		} catch (IOException ioe) {			ResponseConverter.setControllerException(controller, ioe);		} finally {			if (scanner != null) {				try {					scanner.close();				} catch (IOException ignored) {				}			}		}		done.run(response);	}	@Override	public void getKeyValueCount(RpcController controller,			CountRequest request, RpcCallback
       
         done) {		CountResponse response = null;		InternalScanner scanner = null;		try {			scanner = env.getRegion().getScanner(new Scan());			List
        
          results = new ArrayList
         
          (); boolean hasMore = false; long count = 0; do { hasMore = scanner.next(results); for (Cell kv : results) { count++; } results.clear(); } while (hasMore); response = CountResponse.newBuilder().setCount(count).build(); } catch (IOException ioe) { ResponseConverter.setControllerException(controller, ioe); } finally { if (scanner != null) { try { scanner.close(); } catch (IOException ignored) { } } } done.run(response); } @Override public void start(CoprocessorEnvironment env) throws IOException { if (env instanceof RegionCoprocessorEnvironment) { this.env = (RegionCoprocessorEnvironment) env; } else { throw new CoprocessorException("Must be loaded on a table region!"); } } @Override public void stop(CoprocessorEnvironment env) throws IOException { // TODO Auto-generated method stub }}
         
        
       
      
     
    

4、注册接口（Hbase功能，通过配置文件或者表模式方式注册）

这部分，可以看hbase权威指南了，我就看这部分做的。

5、测试调用

package coprocessor;import java.io.IOException;import java.util.Map;import org.apache.hadoop.conf.Configuration;import org.apache.hadoop.hbase.HBaseConfiguration;import org.apache.hadoop.hbase.client.HTable;import org.apache.hadoop.hbase.client.coprocessor.Batch;import org.apache.hadoop.hbase.ipc.BlockingRpcCallback;import org.apache.hadoop.hbase.ipc.ServerRpcController;import org.apache.hadoop.hbase.util.Bytes;import com.google.protobuf.ServiceException;import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountRequest;import coprocessor.endpoints.generated.RowCounterEndpointProtos.CountResponse;import coprocessor.endpoints.generated.RowCounterEndpointProtos.RowCountService;import util.HBaseHelper;public class RowCounterEndpointClientExample {	public static void main(String[] args) throws ServiceException, Throwable {		Configuration conf = HBaseConfiguration.create();		HBaseHelper helper = HBaseHelper.getHelper(conf);		//helper.dropTable("testtable");		//helper.createTable("testtable", "colfam1", "colfam2");		System.out.println("Adding rows to table...");		helper.fillTable("testtable", 1, 10, 10, "colfam1", "colfam2");		HTable table = new HTable(conf, "testtable");		final CountRequest request = CountRequest.getDefaultInstance();				final Batch.Call
    
      call =new Batch.Call
     
      () {			public Long call(RowCountService counter)					throws IOException {				ServerRpcController controller = new ServerRpcController();				BlockingRpcCallback
      
        rpcCallback = new BlockingRpcCallback
       
        ();				counter.getRowCount(controller, request, rpcCallback);				CountResponse response = rpcCallback.get();				if (controller.failedOnException()) {					throw controller.getFailedOn();				}				return (response != null && response.hasCount()) ? response						.getCount() : 0;			}		};				Map
        
          results = table.coprocessorService(				RowCountService.class, null, null, call);				for(byte[] b : results.keySet()){			System.err.println(Bytes.toString(b) + ":" + results.get(b));		} 	}}