ライブラリをSLF4Jに依存させたくないけど、SLF4Jがある場合は使いたい場合の小技
Reactorで使われていたのでメモ。ライブラリを作る時にコピって使いたい小技。
Logger.java
/*
* Copyright (c) 2011-2016 Pivotal Software Inc, All Rights Reserved.
*
* 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.example.logging;
/**
* Logger interface designed for internal Reactor usage.
*/
public interface Logger {
/**
* Return the name of this <code>Logger</code> instance.
* @return name of this logger instance
*/
String getName();
/**
* Is the logger instance enabled for the TRACE level?
*
* @return True if this Logger is enabled for the TRACE level,
* false otherwise.
*/
boolean isTraceEnabled();
/**
* Log a message at the TRACE level.
*
* @param msg the message string to be logged
*/
void trace(String msg);
/**
* Log a message at the TRACE level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the TRACE level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for TRACE.</p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
void trace(String format, Object... arguments);
/**
* Log an exception (throwable) at the TRACE level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
void trace(String msg, Throwable t);
/**
* Is the logger instance enabled for the DEBUG level?
*
* @return True if this Logger is enabled for the DEBUG level,
* false otherwise.
*/
boolean isDebugEnabled();
/**
* Log a message at the DEBUG level.
*
* @param msg the message string to be logged
*/
void debug(String msg);
/**
* Log a message at the DEBUG level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the DEBUG level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for DEBUG. </p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
void debug(String format, Object... arguments);
/**
* Log an exception (throwable) at the DEBUG level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
void debug(String msg, Throwable t);
/**
* Is the logger instance enabled for the INFO level?
*
* @return True if this Logger is enabled for the INFO level,
* false otherwise.
*/
boolean isInfoEnabled();
/**
* Log a message at the INFO level.
*
* @param msg the message string to be logged
*/
void info(String msg);
/**
* Log a message at the INFO level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the INFO level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for INFO. </p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
void info(String format, Object... arguments);
/**
* Log an exception (throwable) at the INFO level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
void info(String msg, Throwable t);
/**
* Is the logger instance enabled for the WARN level?
*
* @return True if this Logger is enabled for the WARN level,
* false otherwise.
*/
boolean isWarnEnabled();
/**
* Log a message at the WARN level.
*
* @param msg the message string to be logged
*/
void warn(String msg);
/**
* Log a message at the WARN level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the WARN level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for WARN. </p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
void warn(String format, Object... arguments);
/**
* Log an exception (throwable) at the WARN level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
void warn(String msg, Throwable t);
/**
* Is the logger instance enabled for the ERROR level?
*
* @return True if this Logger is enabled for the ERROR level,
* false otherwise.
*/
boolean isErrorEnabled();
/**
* Log a message at the ERROR level.
*
* @param msg the message string to be logged
*/
void error(String msg);
/**
* Log a message at the ERROR level according to the specified format
* and arguments.
* <p/>
* <p>This form avoids superfluous string concatenation when the logger
* is disabled for the ERROR level. However, this variant incurs the hidden
* (and relatively small) cost of creating an <code>Object[]</code> before invoking the method,
* even if this logger is disabled for ERROR. </p>
*
* @param format the format string
* @param arguments a list of 3 or more arguments
*/
void error(String format, Object... arguments);
/**
* Log an exception (throwable) at the ERROR level with an
* accompanying message.
*
* @param msg the message accompanying the exception
* @param t the exception (throwable) to log
*/
void error(String msg, Throwable t);
}
Loggers.java
/*
* Copyright (c) 2011-2016 Pivotal Software Inc, All Rights Reserved.
*
* 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.example.logging;
import java.util.logging.Level;
import java.util.regex.Matcher;
/**
* Expose static methods to get a logger depending on the environment (SLF4J or
* {@link java.util.logging.Logger}).
*/
public abstract class Loggers {
private final static LoggerFactory LOGGER_FACTORY;
static {
LoggerFactory loggerFactory;
String name = LoggerFactory.class.getName();
try {
loggerFactory = new Slf4JLoggerFactory();
loggerFactory.getLogger(name).debug("Using Slf4j logging framework");
}
catch (Throwable t) {
loggerFactory = new JdkLoggerFactory();
loggerFactory.getLogger(name).debug("Using JDK logging framework");
}
LOGGER_FACTORY = loggerFactory;
}
/**
* Try getting an appropriate
* {@link Logger} whether SLF4J is not present on the classpath or fallback to {@link java.util.logging.Logger}.
*
* @param name the category or logger name to assign
*
* @return a new {@link Logger} instance
*/
public static Logger getLogger(String name) {
return LOGGER_FACTORY.getLogger(name);
}
/**
* Try getting an appropriate
* {@link Logger} whether SLF4J is not present on the classpath or fallback to {@link java.util.logging.Logger}.
*
* @param cls the source {@link Class} to derive the name from.
*
* @return a new {@link Logger} instance
*/
public static Logger getLogger(Class<?> cls) {
return LOGGER_FACTORY.getLogger(cls.getName());
}
private interface LoggerFactory {
Logger getLogger(String name);
}
private static class Slf4JLoggerFactory implements LoggerFactory {
@Override
public Logger getLogger(String name) {
return new Slf4JLogger(org.slf4j.LoggerFactory.getLogger(name));
}
}
private static class Slf4JLogger implements Logger {
private final org.slf4j.Logger logger;
public Slf4JLogger(org.slf4j.Logger logger) {
this.logger = logger;
}
@Override
public String getName() {
return logger.getName();
}
@Override
public boolean isTraceEnabled() {
return logger.isTraceEnabled();
}
@Override
public void trace(String msg) {
logger.trace(msg);
}
@Override
public void trace(String format, Object... arguments) {
logger.trace(format, arguments);
}
@Override
public void trace(String msg, Throwable t) {
logger.trace(msg, t);
}
@Override
public boolean isDebugEnabled() {
return logger.isDebugEnabled();
}
@Override
public void debug(String msg) {
logger.debug(msg);
}
@Override
public void debug(String format, Object... arguments) {
logger.debug(format, arguments);
}
@Override
public void debug(String msg, Throwable t) {
logger.debug(msg, t);
}
@Override
public boolean isInfoEnabled() {
return logger.isInfoEnabled();
}
@Override
public void info(String msg) {
logger.info(msg);
}
@Override
public void info(String format, Object... arguments) {
logger.info(format, arguments);
}
@Override
public void info(String msg, Throwable t) {
logger.info(msg, t);
}
@Override
public boolean isWarnEnabled() {
return logger.isWarnEnabled();
}
@Override
public void warn(String msg) {
logger.warn(msg);
}
@Override
public void warn(String format, Object... arguments) {
logger.warn(format, arguments);
}
@Override
public void warn(String msg, Throwable t) {
logger.warn(msg, t);
}
@Override
public boolean isErrorEnabled() {
return logger.isErrorEnabled();
}
@Override
public void error(String msg) {
logger.error(msg);
}
@Override
public void error(String format, Object... arguments) {
logger.error(format, arguments);
}
@Override
public void error(String msg, Throwable t) {
logger.error(msg, t);
}
}
/**
* Wrapper over JDK logger
*/
private static class JdkLogger implements Logger {
private final java.util.logging.Logger logger;
public JdkLogger(java.util.logging.Logger logger) {
this.logger = logger;
}
@Override
public String getName() {
return logger.getName();
}
@Override
public boolean isTraceEnabled() {
return logger.isLoggable(Level.FINEST);
}
@Override
public void trace(String msg) {
logger.log(Level.FINEST, msg);
}
@Override
public void trace(String format, Object... arguments) {
logger.log(Level.FINEST, format(format, arguments));
}
@Override
public void trace(String msg, Throwable t) {
logger.log(Level.FINEST, msg, t);
}
@Override
public boolean isDebugEnabled() {
return logger.isLoggable(Level.FINE);
}
@Override
public void debug(String msg) {
logger.log(Level.FINE, msg);
}
@Override
public void debug(String format, Object... arguments) {
logger.log(Level.FINE, format(format, arguments));
}
@Override
public void debug(String msg, Throwable t) {
logger.log(Level.FINE, msg, t);
}
@Override
public boolean isInfoEnabled() {
return logger.isLoggable(Level.INFO);
}
@Override
public void info(String msg) {
logger.log(Level.INFO, msg);
}
@Override
public void info(String format, Object... arguments) {
logger.log(Level.INFO, format(format, arguments));
}
@Override
public void info(String msg, Throwable t) {
logger.log(Level.INFO, msg, t);
}
@Override
public boolean isWarnEnabled() {
return logger.isLoggable(Level.WARNING);
}
@Override
public void warn(String msg) {
logger.log(Level.WARNING, msg);
}
@Override
public void warn(String format, Object... arguments) {
logger.log(Level.WARNING, format(format, arguments));
}
@Override
public void warn(String msg, Throwable t) {
logger.log(Level.WARNING, msg, t);
}
@Override
public boolean isErrorEnabled() {
return logger.isLoggable(Level.SEVERE);
}
@Override
public void error(String msg) {
logger.log(Level.SEVERE, msg);
}
@Override
public void error(String format, Object... arguments) {
logger.log(Level.SEVERE, format(format, arguments));
}
@Override
public void error(String msg, Throwable t) {
logger.log(Level.SEVERE, msg, t);
}
private String format(String from, Object... arguments){
if(from != null) {
String computed = from;
if (arguments != null && arguments.length != 0) {
for (Object argument : arguments) {
computed = computed.replaceFirst("\\{\\}", Matcher.quoteReplacement(argument.toString()));
}
}
return computed;
}
return null;
}
}
private static class JdkLoggerFactory implements LoggerFactory {
@Override
public Logger getLogger(String name) {
return new JdkLogger(java.util.logging.Logger.getLogger(name));
}
}
Loggers(){}
}
使い方
private static final Logger log = Loggers.getLogger(Foo.class);