content: package org.apache.solr.update.processor;
  /**
   * 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.
   */
  
  import java.io.UnsupportedEncodingException;
  import java.security.MessageDigest;
  import java.security.NoSuchAlgorithmException;
  
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  
  public class MD5Signature extends Signature {
    protected final static Logger log = LoggerFactory.getLogger(MD5Signature.class);
    private static ThreadLocal<MessageDigest> DIGESTER_FACTORY = new ThreadLocal<MessageDigest>() {
      @Override
      protected MessageDigest initialValue() {
        try {
          return MessageDigest.getInstance("MD5");
        } catch (NoSuchAlgorithmException e) {
          throw new RuntimeException(e);
        }
      }
    };
    private MessageDigest digester;
  
    public MD5Signature() {
      digester = DIGESTER_FACTORY.get();
      digester.reset();
    }
  
    @Override
    public void add(String content) {
      try {
        digester.update(content.getBytes("UTF-8"));
      } catch (UnsupportedEncodingException e) {
        // won't happen
        log.error("UTF-8 not supported", e);
        throw new RuntimeException(e);
      }
    }
  
    @Override
    public byte[] getSignature() {
      return digester.digest();
    }
  }
  