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MongoChangeStreamCursorImpl.java
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MongoChangeStreamCursorImpl.java
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/*
* Copyright 2008-present MongoDB, Inc.
*
* 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.
*/
package com.mongodb.client.internal;
import com.mongodb.ServerAddress;
import com.mongodb.ServerCursor;
import com.mongodb.client.MongoChangeStreamCursor;
import com.mongodb.internal.operation.AggregateResponseBatchCursor;
import com.mongodb.internal.operation.BatchCursor;
import com.mongodb.lang.Nullable;
import org.bson.BsonDocument;
import org.bson.RawBsonDocument;
import org.bson.codecs.Decoder;
import java.util.List;
import java.util.NoSuchElementException;
public class MongoChangeStreamCursorImpl<T> implements MongoChangeStreamCursor<T> {
private final AggregateResponseBatchCursor<RawBsonDocument> batchCursor;
private final Decoder<T> decoder;
private List<RawBsonDocument> curBatch;
private int curPos;
private BsonDocument resumeToken;
public MongoChangeStreamCursorImpl(final BatchCursor<RawBsonDocument> batchCursor, final Decoder<T> decoder,
@Nullable final BsonDocument initialResumeToken) {
this.batchCursor = (AggregateResponseBatchCursor<RawBsonDocument>) batchCursor;
this.decoder = decoder;
this.resumeToken = initialResumeToken;
}
@Override
public void remove() {
throw new UnsupportedOperationException("Cursors do not support removal");
}
@Override
public void close() {
batchCursor.close();
}
@Override
public boolean hasNext() {
return curBatch != null || batchCursor.hasNext();
}
@Override
public T next() {
if (!hasNext()) {
throw new NoSuchElementException();
}
if (curBatch == null) {
curBatch = batchCursor.next();
}
return getNextInBatch();
}
@Nullable
@Override
public T tryNext() {
if (curBatch == null) {
curBatch = batchCursor.tryNext();
}
if (curBatch == null) {
if (batchCursor.getPostBatchResumeToken() != null) {
resumeToken = batchCursor.getPostBatchResumeToken();
}
}
return curBatch == null ? null : getNextInBatch();
}
@Nullable
@Override
public ServerCursor getServerCursor() {
return batchCursor.getServerCursor();
}
@Override
public ServerAddress getServerAddress() {
return batchCursor.getServerAddress();
}
private T getNextInBatch() {
RawBsonDocument nextInBatch = curBatch.get(curPos);
resumeToken = nextInBatch.getDocument("_id");
if (curPos < curBatch.size() - 1) {
curPos++;
} else {
curBatch = null;
curPos = 0;
if (batchCursor.getPostBatchResumeToken() != null) {
resumeToken = batchCursor.getPostBatchResumeToken();
}
}
return nextInBatch.decode(decoder);
}
@Nullable
public BsonDocument getResumeToken() {
return resumeToken;
}
}