org.apache.lucene.util.InfoStream Maven / Gradle / Ivy
/*
* Licensed to the Apache Software Foundation (ASF) under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The ASF licenses this file to You 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.apache.lucene.util;
import org.apache.lucene.index.IndexWriter; // javadocs
import org.apache.lucene.index.SegmentInfos; // javadocs
import java.io.Closeable;
/**
* Debugging API for Lucene classes such as {@link IndexWriter}
* and {@link SegmentInfos}.
*
* NOTE: Enabling infostreams may cause performance degradation
* in some components.
*
* @lucene.internal
*/
public abstract class InfoStream implements Closeable {
/** Instance of InfoStream that does no logging at all. */
public static final InfoStream NO_OUTPUT = new NoOutput();
private static final class NoOutput extends InfoStream {
@Override
public void message(String component, String message) {
assert false: "message() should not be called when isEnabled returns false";
}
@Override
public boolean isEnabled(String component) {
return false;
}
@Override
public void close() {}
}
/** prints a message */
public abstract void message(String component, String message);
/** returns true if messages are enabled and should be posted to {@link #message}. */
public abstract boolean isEnabled(String component);
private static InfoStream defaultInfoStream = NO_OUTPUT;
/** The default {@code InfoStream} used by a newly instantiated classes.
* @see #setDefault */
public static synchronized InfoStream getDefault() {
return defaultInfoStream;
}
/** Sets the default {@code InfoStream} used
* by a newly instantiated classes. It cannot be {@code null},
* to disable logging use {@link #NO_OUTPUT}.
* @see #getDefault */
public static synchronized void setDefault(InfoStream infoStream) {
if (infoStream == null) {
throw new IllegalArgumentException("Cannot set InfoStream default implementation to null. "+
"To disable logging use InfoStream.NO_OUTPUT");
}
defaultInfoStream = infoStream;
}
}