content: /*
   * Copyright 1999-2018 Alibaba Group Holding Ltd.
   *
   * 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 com.alibaba.druid.filter.encoding;
  
  import java.io.UnsupportedEncodingException;
  
  /**
   * 字符编码转换器
   *
   * @author xianmao.hexm 2007-3-5 09:51:33
   */
  public class CharsetConvert {
      private final String clientEncoding;
  
      private final String serverEncoding;
  
      private final boolean enable;
  
      public CharsetConvert(String clientEncoding, String serverEncoding) {
          this.clientEncoding = clientEncoding;
          this.serverEncoding = serverEncoding;
          this.enable = clientEncoding != null && serverEncoding != null && !clientEncoding.equalsIgnoreCase(serverEncoding);
      }
  
      /**
       * Encodes the specified string using the specified client and server encodings, if enabled.
       * If encoding is not enabled or the input string is empty, the original string is returned unchanged.
       *
       * @param s the string to be encoded
       * @return the encoded string, or the original string if encoding is not enabled or the input string is empty
       * @throws UnsupportedEncodingException if the specified encoding is not supported
       */
      public String encode(String s) throws UnsupportedEncodingException {
          if (enable && !isEmpty(s)) {
              s = new String(s.getBytes(clientEncoding), serverEncoding);
          }
          return s;
      }
  
      /**
       * Decodes the specified string using the specified server and client encodings, if enabled.
       * If decoding is not enabled or the input string is empty, the original string is returned unchanged.
       *
       * @param s the string to be decoded
       * @return the decoded string, or the original string if decoding is not enabled or the input string is empty
       * @throws UnsupportedEncodingException if the specified encoding is not supported
       */
      public String decode(String s) throws UnsupportedEncodingException {
          if (enable && !isEmpty(s)) {
              s = new String(s.getBytes(serverEncoding), clientEncoding);
          }
          return s;
      }
  
      /**
       * Determines whether the specified string is null or empty.
       *
       * @param s the string to be checked
       * @return true if the specified string is null or empty, false otherwise
       */
      public boolean isEmpty(String s) {
          return s == null || s.isEmpty();
      }
  
  }
  