org.springframework.data.redis.connection.lettuce.LettuceScanCursor Maven / Gradle / Ivy
/*
* Copyright 2017 the original author or authors.
*
* 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 org.springframework.data.redis.connection.lettuce;
import java.util.Collection;
import org.springframework.data.redis.core.ScanCursor;
import org.springframework.data.redis.core.ScanIteration;
import org.springframework.data.redis.core.ScanOptions;
import org.springframework.lang.Nullable;
/**
* Lettuce-specific {@link ScanCursor} extension that maintains the cursor state that is required for stateful-scanning
* across a Redis Cluster.
*
* The cursor state uses Lettuce's stateful {@link io.lettuce.core.ScanCursor} to keep track of scanning progress.
*
* @author Mark Paluch
* @author Christoph Strobl
* @since 2.1
*/
abstract class LettuceScanCursor extends ScanCursor {
private @Nullable io.lettuce.core.ScanCursor state;
/**
* Creates a new {@link LettuceScanCursor} given {@link ScanOptions}.
*
* @param options must not be {@literal null}.
*/
LettuceScanCursor(ScanOptions options) {
super(options);
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.core.ScanCursor#doScan(long, org.springframework.data.redis.core.ScanOptions)
*/
@Override
protected ScanIteration doScan(long cursorId, ScanOptions options) {
if (state == null && cursorId == 0) {
return scanAndProcessState(io.lettuce.core.ScanCursor.INITIAL, options);
}
if (state != null) {
if (isMatchingCursor(cursorId)) {
return scanAndProcessState(state, options);
}
}
throw new IllegalArgumentException(String.format("Current scan %s state and cursor %d do not match!",
state != null ? state.getCursor() : "(none)", cursorId));
}
/*
* (non-Javadoc)
* @see org.springframework.data.redis.core.ScanCursor#isFinished(long)
*/
@Override
protected boolean isFinished(long cursorId) {
return state != null && isMatchingCursor(cursorId) ? state.isFinished() : super.isFinished(cursorId);
}
private ScanIteration scanAndProcessState(io.lettuce.core.ScanCursor scanCursor, ScanOptions options) {
LettuceScanIteration iteration = doScan(scanCursor, options);
state = iteration.cursor;
return iteration;
}
private boolean isMatchingCursor(long cursorId) {
return state != null && state.getCursor().equals(Long.toString(cursorId));
}
/**
* Perform the actual scan operation given {@link io.lettuce.core.ScanCursor} and {@link ScanOptions}.
*
* @param cursor must not be {@literal null}.
* @param options must not be {@literal null}.
* @return never {@literal null}
*/
protected abstract LettuceScanIteration doScan(io.lettuce.core.ScanCursor cursor, ScanOptions options);
/**
* Lettuce-specific extension to {@link ScanIteration} keeping track of the original
* {@link io.lettuce.core.ScanCursor} object.
*
* @author Mark Paluch
*/
static class LettuceScanIteration extends ScanIteration {
private final io.lettuce.core.ScanCursor cursor;
LettuceScanIteration(io.lettuce.core.ScanCursor cursor, Collection items) {
super(Long.parseLong(cursor.getCursor()), items);
this.cursor = cursor;
}
}
}