org.ops4j.pax.logging.slf4j.Slf4jMDCAdapter Maven / Gradle / Ivy

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The Pax Logging API Library is to allow for the Pax Logging Service to be reloaded without stopping the many dependent bundles. It also contains the OSGi Log Service API and the Knopflerfish Log API.
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/*
 * Copyright 2006 Niclas Hedhman.
 *
 * 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 org.ops4j.pax.logging.slf4j;

import java.util.Collections;
import java.util.Deque;
import java.util.HashMap;
import java.util.Map;

import org.ops4j.pax.logging.PaxContext;
import org.ops4j.pax.logging.PaxLoggingManager;
import org.ops4j.pax.logging.PaxLoggingService;
import org.slf4j.helpers.ThreadLocalMapOfStacks;
import org.slf4j.spi.MDCAdapter;

/**
 * pax-logging specific {@link MDCAdapter} returned from {@link org.slf4j.spi.SLF4JServiceProvider}
 */
public class Slf4jMDCAdapter implements MDCAdapter {

    /** {@link PaxContext} used when {@link org.ops4j.pax.logging.PaxLoggingService} is not available */
    private static final PaxContext m_defaultContext = new PaxContext();
    /** {@link PaxContext} obtained from {@link org.ops4j.pax.logging.PaxLoggingService} */
    private static PaxContext m_context;

    private final ThreadLocalMapOfStacks threadLocalMapOfDeques = new ThreadLocalMapOfStacks();

    /**
     * For all the methods that use the context, default, static, {@link PaxContext} may be used (tied to pax-logging-api
     * bundle) if there's no available {@link PaxLoggingManager} or {@link PaxLoggingService}. If the service is
     * available, it is always used to get service specific {@link PaxContext}.
     *
     * Refering always to {@link PaxLoggingService#getPaxContext()} is cheap operation, as it's
     * only reference to fields.
     *
     * See: PAXLOGGING-247
     *
     * @return m_context if the MDC should use the PaxContext object from the PaxLoggingManager,
     *      or m_defaultContext if the logging manager is not set, or does not have its context available yet.
     */
    private static PaxContext getContext() {
        PaxLoggingManager manager = Slf4jLoggerFactory.m_paxLogging;
        if (manager != null) {
            synchronized (Slf4jMDCAdapter.class) {
                PaxLoggingService service = manager.getPaxLoggingService();
                m_context = service != null ? service.getPaxContext() : null;
            }
        }
        return m_context != null ? m_context : m_defaultContext;
    }

    @Override
    public void put(String key, String val) {
        getContext().put(key, val);
    }

    @Override
    public String get(String key) {
        Object value = getContext().get(key);
        return value != null ? value.toString() : null;
    }

    @Override
    public void remove(String key) {
        getContext().remove(key);
    }

    @Override
    public void clear() {
        getContext().clear();
    }

    @Override
    public Map getCopyOfContextMap() {
        Map copy = getContext().getCopyOfContextMap();
        Map result = new HashMap<>();
        if (copy == null) {
            return Collections.emptyMap();
        }
        copy.forEach((k, v) -> {
            if (v instanceof String) {
                result.put(k, (String) v);
            } else {
                result.put(k, v == null ? null : v.toString());
            }
        });
        return result;
    }

    @Override
    @SuppressWarnings("unchecked")
    public void setContextMap(Map contextMap) {
        getContext().setContextMap(contextMap);
    }

    @Override
    public void pushByKey(String key, String value) {
        threadLocalMapOfDeques.pushByKey(key, value);
    }

    @Override
    public String popByKey(String key) {
        return threadLocalMapOfDeques.popByKey(key);
    }

    @Override
    public Deque getCopyOfDequeByKey(String key) {
        return threadLocalMapOfDeques.getCopyOfDequeByKey(key);
    }

    @Override
    public void clearDequeByKey(String key) {
        threadLocalMapOfDeques.clearDequeByKey(key);
    }

}