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A lightweight Java library for writing elegant OSGi bundle activators
package domino.java.internal;
/**
* Use this factory to get an instance of {@link Logger}.
*
* The instance will use SLF4J as underlying logging API, it it can be detected
* on the classpath. Else, it will fall back to use Java Util Logging.
*
* The enhanced placeholder syntax of SLF4J is always supported.
*
*/
public class LoggerFactory {
/**
* All log messages will be pass through SLF4j as-is.
*/
public static class Slf4jLogger implements Logger {
private final org.slf4j.Logger underlying;
public Slf4jLogger(final Class clazz) {
underlying = org.slf4j.LoggerFactory.getLogger(clazz);
}
public boolean isErrorEnabled() {
return underlying.isErrorEnabled();
}
public boolean isWarnEnabled() {
return underlying.isWarnEnabled();
}
public boolean isInfoEnabled() {
return underlying.isInfoEnabled();
}
public boolean isDebugEnabled() {
return underlying.isDebugEnabled();
}
public boolean isTraceEnabled() {
return underlying.isTraceEnabled();
}
public void error(final String msg, final Object... args) {
underlying.error(msg, args);
}
public void warn(final String msg, final Object... args) {
underlying.warn(msg, args);
}
public void info(final String msg, final Object... args) {
underlying.info(msg, args);
}
public void debug(final String msg, final Object... args) {
underlying.debug(msg, args);
}
public void trace(final String msg, final Object... args) {
underlying.trace(msg, args);
}
@Override
public String toString() {
return getClass().getSimpleName() + "(" + underlying + ")";
}
}
/**
* All log messages will be pre-processed before given to the JUL logger to
* support SLF4J-style placeholders and arguments semantics.
*/
public static class JavaUtilLogger implements Logger {
private final java.util.logging.Logger underlying;
public JavaUtilLogger(final Class clazz) {
underlying = java.util.logging.Logger.getLogger(clazz.getName());
}
protected Object[] formattedMsgAndCause(final String msg, final Object... args) {
final String formattedMsg;
final Throwable thrown;
if (args != null && args.length > 0) {
final int l;
if (args[args.length - 1] instanceof Throwable) {
l = args.length - 1;
thrown = (Throwable) args[args.length - 1];
} else {
l = args.length;
thrown = null;
}
if (l > 0) {
final StringBuilder strBuilder = new StringBuilder();
boolean braceOpen = false;
int argNr = 0;
for (int i = 0; i < msg.length(); ++i) {
final char charAt = msg.charAt(i);
if (argNr < l) {
if (braceOpen) {
braceOpen = false;
if (charAt == '}') {
// instead, insert next arg
strBuilder.append(args[argNr]);
++argNr;
continue;
} else {
strBuilder.append("{");
}
} else if (charAt == '{') {
braceOpen = true;
continue;
}
}
strBuilder.append(charAt);
}
if (braceOpen) {
strBuilder.append("{");
}
formattedMsg = strBuilder.toString();
} else {
formattedMsg = msg;
}
} else {
formattedMsg = msg;
thrown = null;
}
return new Object[] { formattedMsg, thrown };
}
private void log(final java.util.logging.Level level, final String msg, final Object... args) {
if (underlying.isLoggable(level)) {
final Object[] formattedMsgAndCause = formattedMsgAndCause(msg, args);
final String formattedMsg = (String) formattedMsgAndCause[0];
final Throwable thrown = (Throwable) formattedMsgAndCause[1];
underlying.log(level, formattedMsg, thrown);
}
}
public boolean isErrorEnabled() {
return underlying.isLoggable(java.util.logging.Level.SEVERE);
}
public boolean isWarnEnabled() {
return underlying.isLoggable(java.util.logging.Level.WARNING);
}
public boolean isInfoEnabled() {
return underlying.isLoggable(java.util.logging.Level.INFO);
}
public boolean isDebugEnabled() {
return underlying.isLoggable(java.util.logging.Level.FINE);
}
public boolean isTraceEnabled() {
return underlying.isLoggable(java.util.logging.Level.FINER);
}
public void error(final String msg, final Object... args) {
log(java.util.logging.Level.SEVERE, msg, args);
}
public void warn(final String msg, final Object... args) {
log(java.util.logging.Level.WARNING, msg, args);
}
public void info(final String msg, final Object... args) {
log(java.util.logging.Level.INFO, msg, args);
}
public void debug(final String msg, final Object... args) {
log(java.util.logging.Level.FINE, msg, args);
}
public void trace(final String msg, final Object... args) {
log(java.util.logging.Level.FINER, msg, args);
}
@Override
public String toString() {
return getClass().getSimpleName() + "(" + underlying + ")";
}
}
public static class DummyLogger implements Logger {
public boolean isErrorEnabled() {
return false;
}
public boolean isWarnEnabled() {
return false;
}
public boolean isInfoEnabled() {
return false;
}
public boolean isDebugEnabled() {
return false;
}
public boolean isTraceEnabled() {
return false;
}
public void error(final String msg, final Object... args) {
}
public void warn(final String msg, final Object... args) {
}
public void info(final String msg, final Object... args) {
}
public void debug(final String msg, final Object... args) {
}
public void trace(final String msg, final Object... args) {
}
@Override
public String toString() {
return getClass().getSimpleName();
}
}
private static transient volatile boolean slf4ClassTestedButUnavailable = false;
public static Logger getLogger(final Class clazz) {
// synchronization would be too costly.
// There is no problem in trying multiple times before giving up.
if (!slf4ClassTestedButUnavailable) {
try {
return new Slf4jLogger(clazz);
} catch (final NoClassDefFoundError e) {
slf4ClassTestedButUnavailable = true;
}
}
return new JavaUtilLogger(clazz);
}
}