任何人都可以解释如何通过shell加载regionCoprocessor.i无法获得有关加载和部署Coprocessor.Thanks in advance
的正确信息答案 0 :(得分:1)
请按照以下步骤操作:
第1步:创建界面并扩展org.apache.hadoop.hbase.ipc.CoprocessorProtocol
步骤2:在进行协处理器调用后,在要执行的界面中定义方法
第3步:创建HTable
第4步:使用所有必需参数调用HTable.coprocessorExec()
方法
请找到以下示例:
在这个例子中,我们试图获得注册号在我们感兴趣的某个范围内的学生名单。
创建接口协议:
public interface CoprocessorTestProtocol extends org.apache.hadoop.hbase.ipc.CoprocessorProtocol{
List<Student> getStudentList(byte[] startRegistrationNumber, byte[] endRegistrationNumber) throws IOException;
}
示例学生班级:
public class Student implements Serializable{
byte[] registrationNumber;
String name;
public void setRegistrationNumber(byte[] registrationNumber){
this.registrationNumber = registrationNumber;
}
public byte[] getRegistrationNumber(){
return this.registrationNumber;
}
public void setName(String name){
this.name = name;
}
public int getName(){
return this.name;
}
public String toString(){
return "Student[ registration number = " + Bytes.toInt(this.getRegistrationNumber()) + " name = " + this.getName() + " ]"
}
}
模型类: [编写从HBase获取数据的业务逻辑]
public class MyModel extends org.apache.hadoop.hbase.coprocessor.BaseEndpointCoprocessor implements CoprocessorTestProtocol{
@Override
List<Student> getStudentList(byte[] startRegistrationNumber, byte[] endRegistrationNumber){
Scan scan = new Scan();
scan.setStartRow(startRegistrationNumber);
scan.setStopRow(endRegistrationNumber);
InternalScanner scanner = ((RegionCoprocessorEnvironment) getEnvironment()).getRegion().getScanner(scan);
List<KeyValue> currentTempObj = new ArrayList<KeyValue>();
List<Student> studentList = new ArrayList<Student>();
try{
Boolean hasNext = false;
Student student;
do{
currentTempObj.clear();
hasNext = scanner.next(currentTempObj);
if(!currentTempObj.isEmpty()){
student = new Student();
for(KeyValue keyValue: currentTempObj){
bytes[] qualifier = keyValue.getQualifier();
if(Arrays.equals(qualifier, Bytes.toBytes("registrationNumber")))
student.setRegistrationNumber(keyValue.getValue());
else if(Arrays.equals(qualifier, Bytes.toBytes("name")))
student.setName(Bytes.toString(keyValue.getValue()));
}
StudentList.add(student);
}
}while(hasNext);
}catch (Exception e){
// catch the exception the way you want
}
finally{
scanner.close();
}
}
}
客户端类: [对协处理器的调用]
public class MyClient{
if (args.length < 2) {
System.out.println("Usage : startRegistrationNumber endRegistrationNumber");
return;
}
public List<Student> displayStudentInfo(int startRegistrationNumber, int endRegistrationNumber){
final byte[] startKey=Bytes.toBytes(startRegistrationNumber);
final byte[] endKey=Bytes.toBytes(endRegistrationNumber);
String zkPeers = SystemInfo.getHBaseZkConnectString();
Configuration configuration=HBaseConfiguration.create();
configuration.set(HConstants.ZOOKEEPER_QUORUM, zkPeers);
HTableInterface table = new HTable(configuration, TABLE_NAME);
Map<byte[],List<Student>> allRegionOutput;
allRegionOutput = table.coprocessorExec(CoprocessorTestProtocol.class, startKey,endKey,
new Batch.Call<CoprocessorTestProtocol, List<Student>>() {
public List<Student> call(CoprocessorTestProtocol instance)throws IOException{
return instance.getStudentList(startKey, endKey);
}
});
table.close();
List<Student> anotherList = new ArrayList<Student>();
for (List<Student> studentData: allRegionOutput.values()){
anotherList.addAll(studentData);
}
return anotherList;
}
public static void main(String args){
if (args.length < 2) {
System.out.println("Usage : startRegistrationNumber endRegistrationNumber");
return;
}
int startRegistrationNumber = args[0];
int endRegistrationNumber = args[1];
for (Student student : displayStudentInfo(startRegistrationNumber, endRegistrationNumber)){
System.out.println(student);
}
}
}
请注意:请在示例中对Scanner.next(Object)
方法进行特殊说明。这将返回boolean并将当前对象存储在Object
参数