org.apache.log4j.helpers.MDCKeySetExtractor 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.log4j.helpers;
import org.apache.log4j.spi.LoggingEvent;
import org.apache.log4j.pattern.LogEvent;
import java.lang.reflect.Method;
import java.util.Set;
import java.io.ByteArrayOutputStream;
import java.io.ObjectOutputStream;
import java.io.ByteArrayInputStream;
import java.io.ObjectInputStream;
public final class MDCKeySetExtractor {
private final Method getKeySetMethod;
public static final MDCKeySetExtractor INSTANCE =
new MDCKeySetExtractor();
private MDCKeySetExtractor() {
//
// log4j 1.2.15 and later will have method to get names
// of all keys in MDC
//
Method getMethod = null;
try {
getMethod = LoggingEvent.class.getMethod(
"getPropertyKeySet", null);
} catch(Exception ex) {
getMethod = null;
}
getKeySetMethod = getMethod;
}
public Set getPropertyKeySet(final LoggingEvent event) throws Exception {
//
// MDC keys are not visible prior to log4j 1.2.15
//
Set keySet = null;
if (getKeySetMethod != null) {
keySet = (Set) getKeySetMethod.invoke(event, null);
} else {
//
// for 1.2.14 and earlier could serialize and
// extract MDC content
ByteArrayOutputStream outBytes = new ByteArrayOutputStream();
ObjectOutputStream os = new ObjectOutputStream(outBytes);
os.writeObject(event);
os.close();
byte[] raw = outBytes.toByteArray();
//
// bytes 6 and 7 should be the length of the original classname
// should be the same as our substitute class name
final String subClassName = LogEvent.class.getName();
if (raw[6] == 0 || raw[7] == subClassName.length()) {
//
// manipulate stream to use our class name
//
for (int i = 0; i < subClassName.length(); i++) {
raw[8 + i] = (byte) subClassName.charAt(i);
}
ByteArrayInputStream inBytes = new ByteArrayInputStream(raw);
ObjectInputStream is = new ObjectInputStream(inBytes);
Object cracked = is.readObject();
if (cracked instanceof LogEvent) {
keySet = ((LogEvent) cracked).getPropertyKeySet();
}
is.close();
}
}
return keySet;
}
}