JAVA 将文件转换为字节

package com.tacct.tradecontract.web;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;


public class FileUtil {
	private FileUtil(){};
	// 返回一个byte数组
	public static byte[] getBytesFromFile(File file) throws IOException {
		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
		byte[] 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());
		}
		is.close();
		return bytes;
	}
}