ランダムストリームRandomAccess Fileを使ってファイル指定の内容を削除します。

あるサービスのログファイルが指定サイズに達したら、ログファイルの前の何行を削除しますか？後に新しいログを追加します。

/**   
 * @Title: removeFileLine   
 * @Description: TODO(            n )   
 * @param: @param file   
 * @param: @param lineNum       
 * @param: @throws IOException      
 * @return: void      
 * @throws   
 */ 
public void removeFileLine(File file, int lineNum) throws IOException {
    RandomAccessFile raf = null;
    try {
        raf = new RandomAccessFile(file, "rw");
        // Initial write position.
        //         ,       ,              
        long writePosition = raf.getFilePointer();
        for (int i = 0; i < lineNum; i++) {
            String line = raf.readLine();
            if (line == null) {
                break;
            }
        }
        // Shift the next lines upwards.
        //         ,              
        long readPosition = raf.getFilePointer();

        //       ,
        byte[] buff = new byte[1024];
        int n;
        while (-1 != (n = raf.read(buff))) {
            raf.seek(writePosition);
            raf.write(buff, 0, n);
            readPosition += n;
            writePosition += n;
            raf.seek(readPosition);
        }
        raf.setLength(writePosition);
    } catch (IOException e) {
        logger.error("readAndRemoveFirstLines error", e);
        throw e;
    } finally {
        try {
            if (raf != null) {
                raf.close();
            }
        } catch (IOException e) {
            logger.error("close RandomAccessFile error", e);
            throw e;
        }
    }
}

/**   
 * @Title: appendContentToFile   
 * @Description: TODO(         )   
 * @param: @param file
 * @param: @param content
 * @param: @throws IOException      
 * @return: void      
 * @throws   
 */ 
public static void appendContentToFile(File file, String content) throws IOException {
    RandomAccessFile randomFile = null;
    try {
        //            ，     
        randomFile = new RandomAccessFile(file, "rw");
        //     ，   
        long fileLength = randomFile.length();
        //            。
        randomFile.seek(fileLength);
        randomFile.writeBytes(content);
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (randomFile != null) {
            randomFile.close();
            randomFile = null;
        }
    }
}

/**   
 * @Title: checkFileInSize   
 * @Description: TODO(             )   
 * @param: @param file
 * @param: @param limitSize
 * @param: @return      
 * @return: boolean      
 * @throws   
 */ 
private boolean checkFileInSize(File file, Long limitSize) {
    return file.length() <= limitSize;
}

以上が上記の需要の方法です。上記の方法を統合して需要を完成します。

@Component
@SuppressWarnings("restriction")
@PropertySource("classpath:/config/ivg.properties")
public class AppStartupListener implements ApplicationRunner {

    @Value("${log.startup.path}")
    private String logPath;//       
    @Value("${log.startup.output.statement}")
    private String outputStatement;//         
    @Value("${log.startup.limit.size}")
    private Long limitSize;//       ,eg:50M：50*1024*1024 = 52428800
    @Value("${log.startup.remove.line}")
    private int removeLineNum;//              

    private void initLog() {
        logger.info("***          ***");

        //         
        File file = null;
        try {
            file = new File(logPath);
            if (!file.exists() || !file.isFile()) {
                logger.info("file is not exist,creating " + logPath + " now...");
                file.createNewFile();
            }
            StringBuilder sb = new StringBuilder(outputStatement);
            SimpleDateFormat sdf = new SimpleDateFormat(" yyyy-MM-dd HH:mm:ss");
            String date = sdf.format(new Date());
            String outputLog = sb.append(date).append("\r
").toString();

            //       
            while (!checkFileInSize(file, limitSize)) {
                //       
                removeFileLine(file, removeLineNum);
            }
            //       log  
            appendContentToFile(file, outputLog);
        } catch (FileNotFoundException e) {
            logger.error("StartupLog Listener error,{}", e);
        } catch (IOException e) {
            logger.error("StartupLog Listener error,{}", e);
        }
    }
}