freemarker-core/src/main/java/freemarker/log/_Log4jOverSLF4JTester.java

/*
 * 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 freemarker.log;

/**
 * Don't use this class; it's only public to work around Google App Engine Java
 * compliance issues. FreeMarker developers only: treat this class as package-visible.
 */
public class _Log4jOverSLF4JTester {

    private static final String MDC_KEY = _Log4jOverSLF4JTester.class.getName();

    /**
     * Returns if Log4j-over-SLF4J is actually working. Sometimes the API classes are present, but there's no SLF4J
     * implementation around.
     */
    public static final boolean test() {
        org.apache.log4j.MDC.put(MDC_KEY, "");
        try {
            return org.slf4j.MDC.get(MDC_KEY) != null;
        } finally {
            org.apache.log4j.MDC.remove(MDC_KEY);
        }
    }

}