org.slf4j.helpers.Log4jLoggerFactory is not on classpath. Good!

View Javadoc

   /*
    * 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.logging.slf4j;
  
  import java.net.URI;
  
  import org.apache.logging.log4j.spi.LoggerContext;
  import org.apache.logging.log4j.spi.LoggerContextFactory;
  import org.apache.logging.log4j.status.StatusLogger;
  
  /**
   *
   */
  public class SLF4JLoggerContextFactory implements LoggerContextFactory {
      private static final StatusLogger LOGGER = StatusLogger.getLogger();
      private static LoggerContext context = new SLF4JLoggerContext();
  
      public SLF4JLoggerContextFactory() {
          // LOG4J2-230, LOG4J2-204 (improve error reporting when misconfigured)
          boolean misconfigured = false;
          try {
              Class.forName("org.slf4j.helpers.Log4jLoggerFactory");
              misconfigured = true;
          } catch (final ClassNotFoundException classNotFoundIsGood) {
              LOGGER.debug("org.slf4j.helpers.Log4jLoggerFactory is not on classpath. Good!");
          }
          if (misconfigured) {
              throw new IllegalStateException("slf4j-impl jar is mutually exclusive with log4j-to-slf4j jar "
                      + "(the first routes calls from SLF4J to Log4j, the second from Log4j to SLF4J)");
          }
      }
  
      @Override
      public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
                                      final boolean currentContext) {
          return context;
      }
  
      @Override
      public LoggerContext getContext(final String fqcn, final ClassLoader loader, final Object externalContext,
                                      final boolean currentContext, final URI configLocation, final String name) {
          return context;
      }
  
      @Override
      public void removeContext(final LoggerContext context) {
      }
  }