/
DataDispatcher.java
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/
DataDispatcher.java
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package com.colintmiller.simplenosql.threading;
import android.content.Context;
import android.os.Process;
import com.colintmiller.simplenosql.DataComparator;
import com.colintmiller.simplenosql.NoSQLEntity;
import com.colintmiller.simplenosql.NoSQLQuery;
import com.colintmiller.simplenosql.db.DataStore;
import com.colintmiller.simplenosql.db.DataStoreType;
import com.colintmiller.simplenosql.db.SimpleDataStoreFactory;
import java.util.Collections;
import java.util.List;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.locks.ReadWriteLock;
import java.util.concurrent.locks.ReentrantReadWriteLock;
/**
* Provides a thread for performing data operations based on a queue of operations.
*
* Queries are processed from the given queue and dispatched based on their operation
* type. Retrieval queries have their results posted to the supplied callback in the
* query. All operations also notify any observers. Both callback and observer
* notification are handled by the {@link com.colintmiller.simplenosql.threading.QueryDelivery}
* class which will post those results via the UI thread (or possibly a supplied thread).
*/
public class DataDispatcher extends Thread {
private boolean hasQuit = false;
private BlockingQueue<NoSQLQuery<?>> queue;
private Context context;
private QueryDelivery delivery;
private ConcurrentHashMap<String, ReadWriteLock> locks;
private SimpleDataStoreFactory dataStoreFactory;
public DataDispatcher(
BlockingQueue<NoSQLQuery<?>> queue,
Context context,
QueryDelivery delivery,
ConcurrentHashMap<String, ReadWriteLock> locks,
DataStoreType type) {
this.queue = queue;
this.context = context;
this.delivery = delivery;
this.locks = locks;
this.dataStoreFactory = new SimpleDataStoreFactory(type);
}
/**
* Forces the dispatcher to quit immediately. Any unprocessed queries in the queue
* will not be processed.
*/
public void quit() {
hasQuit = true;
interrupt();
}
@Override
public void run() {
Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND);
NoSQLQuery<?> query;
// The exit for this loop is an InterruptedException
while (true) {
try {
query = queue.take();
} catch (InterruptedException e) {
if (hasQuit) {
return;
}
continue;
}
if (query.isCanceled()) {
// TODO: Add Logging of canceled request.
continue;
}
DataStore dataStore = dataStoreFactory.getDataStore(
context,
query.getSerializer(),
query.getDeserializer());
switch (query.getOperation()) {
case SAVE:
save(query, dataStore);
break;
case DELETE:
delete(query, dataStore);
break;
case RETRIEVE:
retrieve(query, dataStore);
break;
default:
throw new IllegalStateException("Should not have a null operation");
}
delivery.notifyObservers(query.getObservers());
}
}
private <T> void save(NoSQLQuery<T> query, DataStore dataStore) {
obtainWriteLock(query.getBucketId());
for (NoSQLEntity<T> entity : query.getEntities()) {
dataStore.saveEntity(entity);
}
releaseWriteLock(query.getBucketId());
}
private <T> void delete(NoSQLQuery<T> query, DataStore dataStore) {
String bucket = query.getBucketId();
obtainWriteLock(bucket);
if (bucket != null && query.getEntityId() != null) {
dataStore.deleteEntity(bucket, query.getEntityId());
} else if (bucket != null) {
dataStore.deleteBucket(bucket);
}
releaseWriteLock(bucket);
}
private <T> void retrieve(NoSQLQuery<T> query, DataStore dataStore) {
String bucket = query.getBucketId();
obtainReadLock(bucket);
if (bucket != null && query.getEntityId() != null) {
List<NoSQLEntity<T>> entityList = dataStore.getEntities(bucket, query.getEntityId(), query.getClazz(), query.getFilter());
sortAndDeliver(entityList, query);
} else if (bucket != null) {
List<NoSQLEntity<T>> entityList = dataStore.getEntities(bucket, query.getClazz(), query.getFilter());
sortAndDeliver(entityList, query);
}
releaseReadLock(bucket);
}
private <T> void sortAndDeliver(List<NoSQLEntity<T>> entities, NoSQLQuery<T> query) {
DataComparator<T> comparator = query.getComparator();
if (comparator != null) {
Collections.sort(entities, comparator);
}
delivery.performCallback(query.getCallback(), entities);
}
private void obtainReadLock(String bucket) {
if (bucket != null) {
ReadWriteLock lock = getReadWriteLock(bucket);
lock.readLock().lock();
}
}
private void releaseReadLock(String bucket) {
if (bucket != null) {
ReadWriteLock lock = getReadWriteLock(bucket);
lock.readLock().unlock();
}
}
private void obtainWriteLock(String bucket) {
if (bucket != null) {
ReadWriteLock lock = getReadWriteLock(bucket);
lock.writeLock().lock();
}
}
private void releaseWriteLock(String bucket) {
if (bucket != null) {
ReadWriteLock lock = getReadWriteLock(bucket);
lock.writeLock().unlock();
}
}
private ReadWriteLock getReadWriteLock(String bucket) {
if (!locks.containsKey(bucket)) {
ReadWriteLock newLock = new ReentrantReadWriteLock();
ReadWriteLock possibleLock = locks.putIfAbsent(bucket, newLock);
// if a value already exists (from another thread) we need to use that one
if (possibleLock != null) {
return possibleLock;
}
return newLock;
}
return locks.get(bucket);
}
}