Java中文件与字节数组转换

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Java文件与字节数组转换

 

/**
	 * 返回一个byte数组
	 * @param file
	 * @return
	 * @throws IOException
	 */
	private  byte[] getBytesFromFile(File file){

		byte[] bytes = null;
		try {
			InputStream is = new FileInputStream(file);

			// 获取文件大小
			long length = file.length();

			if (length > Integer.MAX_VALUE) {

				// 文件太大，无法读取
				throw new IOException("File is to large " + file.getName());

			}

			// 创建一个数据来保存文件数据

			bytes = new byte[(int) length];

			// 读取数据到byte数组中

			int offset = 0;

			int numRead = 0;

			while (offset < bytes.length

			&& (numRead = is.read(bytes, offset, bytes.length - offset)) >= 0) {

				offset += numRead;

			}

			// 确保所有数据均被读取

			if (offset < bytes.length) {

				throw new IOException("Could not completely read file "
						+ file.getName());

			}

			// Close the input stream and return bytes

			is.close();
		} catch (Exception e) {

           e.printStackTrace();
		}

		return bytes;

	}

 

/** 
     * 文件转化为字节数组 
     *  
     * @param file 
     * @return 
     */  
    public static byte[] getBytesFromFile(File file) {  
        byte[] ret = null;  
        try {  
            if (file == null) {  
                // log.error("helper:the file is null!");  
                return null;  
            }  
            FileInputStream in = new FileInputStream(file);  
            ByteArrayOutputStream out = new ByteArrayOutputStream(4096);  
            byte[] b = new byte[4096];  
            int n;  
            while ((n = in.read(b)) != -1) {  
                out.write(b, 0, n);  
            }  
            in.close();  
            out.close();  
            ret = out.toByteArray();  
        } catch (IOException e) {  
            // log.error("helper:get bytes from file process error!");  
            e.printStackTrace();  
        }  
        return ret;  
    }  

 

/** 
     * 把字节数组保存为一个文件 
     *  
     * @param b 
     * @param outputFile 
     * @return 
     */  
    public static File getFileFromBytes(byte[] b, String outputFile) {  
        File ret = null;  
        BufferedOutputStream stream = null;  
        try {  
            ret = new File(outputFile);  
            FileOutputStream fstream = new FileOutputStream(ret);  
            stream = new BufferedOutputStream(fstream);  
            stream.write(b);  
        } catch (Exception e) {  
            // log.error("helper:get file from byte process error!");  
            e.printStackTrace();  
        } finally {  
            if (stream != null) {  
                try {  
                    stream.close();  
                } catch (IOException e) {  
                    // log.error("helper:get file from byte process error!");  
                    e.printStackTrace();  
                }  
            }  
        }  
        return ret;  
    }