116 lines
4.1 KiB
Java
116 lines
4.1 KiB
Java
/* ====================================================================
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Licensed to the Apache Software Foundation (ASF) under one or more
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contributor license agreements. See the NOTICE file distributed with
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this work for additional information regarding copyright ownership.
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The ASF licenses this file to You under the Apache License, Version 2.0
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(the "License"); you may not use this file except in compliance with
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the License. You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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==================================================================== */
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package org.apache.poi.util;
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/**
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* A logger interface that strives to make it as easy as possible for
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* developers to write log calls, while simultaneously making those
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* calls as cheap as possible by performing lazy evaluation of the log
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* message.<p>
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*/
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@Internal
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public abstract class POILogger {
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public static final int DEBUG = 1;
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public static final int INFO = 3;
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public static final int WARN = 5;
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public static final int ERROR = 7;
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public static final int FATAL = 9;
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/** Short strings for numeric log level. Use level as array index. */
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protected static final String LEVEL_STRINGS_SHORT[] = {"?", "D", "?", "I", "?", "W", "?", "E", "?", "F", "?"};
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/** Long strings for numeric log level. Use level as array index. */
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protected static final String LEVEL_STRINGS[] = {"?0?", "DEBUG", "?2?", "INFO", "?4?", "WARN", "?6?", "ERROR", "?8?", "FATAL", "?10+?"};
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/**
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* package scope so it cannot be instantiated outside of the util
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* package. You need a POILogger? Go to the POILogFactory for one
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*/
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POILogger() {
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// no fields to initialize
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}
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abstract public void initialize(String cat);
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/**
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* Log a message
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*
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* @param level One of DEBUG, INFO, WARN, ERROR, FATAL
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* @param obj1 The object to log. This is converted to a string.
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*/
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abstract protected void _log(int level, Object obj1);
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/**
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* Log a message
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*
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* @param level One of DEBUG, INFO, WARN, ERROR, FATAL
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* @param obj1 The object to log. This is converted to a string.
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* @param exception An exception to be logged
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*/
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abstract protected void _log(int level, Object obj1, final Throwable exception);
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/**
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* Check if a logger is enabled to log at the specified level
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* This allows code to avoid building strings or evaluating functions in
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* the arguments to log.
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*
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* An example:
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* <code><pre>
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* if (logger.check(POILogger.INFO)) {
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* logger.log(POILogger.INFO, "Avoid concatenating " + " strings and evaluating " + functions());
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* }
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* </pre></code>
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*
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* @param level One of DEBUG, INFO, WARN, ERROR, FATAL
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*/
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abstract public boolean check(int level);
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/**
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* Log a message. Lazily appends Object parameters together.
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* If the last parameter is a {@link Throwable} it is logged specially.
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*
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* @param level One of DEBUG, INFO, WARN, ERROR, FATAL
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* @param objs the objects to place in the message
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*/
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public void log(int level, Object... objs) {
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if (!check(level)) return;
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StringBuilder sb = new StringBuilder(32);
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Throwable lastEx = null;
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for (int i=0; i<objs.length; i++) {
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if (i == objs.length-1 && objs[i] instanceof Throwable) {
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lastEx = (Throwable)objs[i];
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} else {
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sb.append(objs[i]);
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}
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}
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String msg = sb.toString();
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msg = msg.replaceAll("[\r\n]+", " "); // log forging escape
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// somehow this ambiguity works and doesn't lead to a loop,
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// but it's confusing ...
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if (lastEx == null) {
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_log(level, msg);
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} else {
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_log(level, msg, lastEx);
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}
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}
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}
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