/
SinglePERequest.java
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/
SinglePERequest.java
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/*
* Copyright (c) 2010 Yahoo! Inc. All rights reserved.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing,
* software distributed under the License is distributed on an
* "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND,
* either express or implied. See the License for the specific
* language governing permissions and limitations under the
* License. See accompanying LICENSE file.
*/
package io.s4.message;
import io.s4.dispatcher.partitioner.CompoundKeyInfo;
import io.s4.dispatcher.partitioner.Hasher;
import io.s4.dispatcher.partitioner.KeyInfo;
import io.s4.processor.ProcessingElement;
import io.s4.util.MethodInvoker;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.List;
import org.springframework.util.StringUtils;
/**
* A request for a value from a particular PE.
*/
public class SinglePERequest extends Request {
private final List<String> target;
private final List<String> query;
public SinglePERequest(List<String> target, List<String> query, RInfo info) {
this.target = target;
this.query = query;
this.rinfo = info;
}
public SinglePERequest(List<String> target, List<String> query) {
this.target = target;
this.query = query;
this.rinfo = null;
}
public SinglePERequest() {
this.target = Collections.<String> emptyList();
this.query = Collections.<String> emptyList();
this.rinfo = null;
}
public String toString() {
return "target:" + target + " query:" + query + " info:" + rinfo;
}
/**
* Fields used to target a particular PE.
*
* @return list of targeting values. Order matters.
*/
public List<String> getTarget() {
return target;
}
/**
* List of field names that have to be read form target PE.
*
* @return list of field name strings.
*/
public List<String> getQuery() {
return query;
}
/**
* Evaluate Request on a particular PE.
*
* @param pe
* @return Response object.
*/
public Response evaluate(ProcessingElement pe) {
HashMap<String, Object> results = new HashMap<String, Object>();
HashMap<String, String> exceptions = new HashMap<String, String>();
for (String q : query) {
// requests for getters should be of the form $field. Responds with
// pe.getField()
if (q.startsWith("$")) {
try {
Object res = MethodInvoker.invokeGetter(pe, q.substring(1));
results.put(q, res);
} catch (Exception e) {
exceptions.put(q, e.toString());
}
}
}
return new Response(results, exceptions, this);
}
public List<CompoundKeyInfo> partition(Hasher h, String delim, int partCount) {
List<String> valueList = this.getTarget();
if (valueList == null)
return null;
// First, build the key
KeyInfo keyInfo = new KeyInfo();
// special kay name to denote request
keyInfo.addElementToPath("#req");
// for value, concatenate list of values from Request's target field.
String stringValue = StringUtils.collectionToDelimitedString(valueList,
delim);
keyInfo.setValue(stringValue);
// partition id is derived form string value, as usual
int partitionId = (int) (h.hash(stringValue) % partCount);
CompoundKeyInfo partitionInfo = new CompoundKeyInfo();
partitionInfo.addKeyInfo(keyInfo);
partitionInfo.setCompoundValue(stringValue);
partitionInfo.setPartitionId(partitionId);
List<CompoundKeyInfo> partitionInfoList = new ArrayList<CompoundKeyInfo>();
partitionInfoList.add(partitionInfo);
return partitionInfoList;
}
}