java判断文本文件编码格式

灰太狼 2021-11-11 16:34 346阅读 0赞

上篇文章需要读取当前java或者配置文件的编码格式，这里主要支持UTF-8、GBK、UTF-16、Unicode等

/**
    	 * 判断文件的编码格式
    	 * @param fileName :file
    	 * @return 文件编码格式
    	 * @throws Exception
    	 */
    	public static String codeString(File fileName) throws Exception{
    		BufferedInputStream bin = new BufferedInputStream(
    		new FileInputStream(fileName));
    		int p = (bin.read() << 8) + bin.read();
    		String code = null;
    		
    		switch (p) {
    			case 0xefbb:
    				code = "UTF-8";
    				break;
    			case 0xfffe:
    				code = "Unicode";
    				break;
    			case 0xfeff:
    				code = "UTF-16BE";
    				break;
    			default:
    				code = "GBK";
    		}
    		IOUtils.closeQuietly(bin);
    		return code;
    	}

上面这段代码只能判断带bom的文本，如果非bom文本，还有两种方式  
1、 轮询常用的编码，知道找到匹配的，如下面一段测试代码

/*
     *  Copyright 2010 Georgios Migdos <cyberpython@gmail.com>.
     * 
     *  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.
     *  under the License.
     */
    
    import java.io.BufferedInputStream;
    import java.io.File;
    import java.io.FileInputStream;
    import java.io.FileNotFoundException;
    import java.io.IOException;
    import java.io.InputStreamReader;
    import java.nio.ByteBuffer;
    import java.nio.charset.CharacterCodingException;
    import java.nio.charset.Charset;
    import java.nio.charset.CharsetDecoder;
    
    /**
     *
     * @author Georgios Migdos <cyberpython@gmail.com>
     */
    public class CharsetDetector {
    
        public Charset detectCharset(File f, String[] charsets) {
    
            Charset charset = null;
    
            for (String charsetName : charsets) {
                charset = detectCharset(f, Charset.forName(charsetName));
                if (charset != null) {
                    break;
                }
            }
    
            return charset;
        }
    
        private Charset detectCharset(File f, Charset charset) {
            try {
                BufferedInputStream input = new BufferedInputStream(new FileInputStream(f));
    
                CharsetDecoder decoder = charset.newDecoder();
                decoder.reset();
    
                byte[] buffer = new byte[512];
                boolean identified = false;
                while ((input.read(buffer) != -1) && (!identified)) {
                    identified = identify(buffer, decoder);
                }
    
                input.close();
    
                if (identified) {
                    return charset;
                } else {
                    return null;
                }
    
            } catch (Exception e) {
                return null;
            }
        }
    
        private boolean identify(byte[] bytes, CharsetDecoder decoder) {
            try {
                decoder.decode(ByteBuffer.wrap(bytes));
            } catch (CharacterCodingException e) {
                return false;
            }
            return true;
        }
    
        public static void main(String[] args) {
            File f = new File("example.txt");
    
            String[] charsetsToBeTested = {"UTF-8", "windows-1253", "ISO-8859-7"};
    
            CharsetDetector cd = new CharsetDetector();
            Charset charset = cd.detectCharset(f, charsetsToBeTested);
    
            if (charset != null) {
                try {
                    InputStreamReader reader = new InputStreamReader(new FileInputStream(f), charset);
                    int c = 0;
                    while ((c = reader.read()) != -1) {
                        System.out.print((char)c);
                    }
                    reader.close();
                } catch (FileNotFoundException fnfe) {
                    fnfe.printStackTrace();
                }catch(IOException ioe){
                    ioe.printStackTrace();
                }
    
            }else{
                System.out.println("Unrecognized charset.");
            }
        }
    }

2、 使用谷歌依赖库来进行判断  
https://code.google.com/archive/p/juniversalchardet/