Java传输文件使用Base64编码，优化传输速率。

问题：使用http进行文件传输时，将文件的byte[]转为json占用的内存空间会增加三倍左右。
解决：将byte[]数组通过Base64转成String类型，上传String类型，服务端接收到String之后再通过Base64解密成byte[]，最后存储为文件。

//客户端 String base64Str = Base64.getEncoder().encodeToString(byteArray); //服务端 byte [] byteArray = Base64.getDecoder().decode(base64Str); 

如果客户端是android应用，太低的android系统版本不支持自带的Base64。可以使用以下代码。所有版本都适配。

package com.eryuan.util; import android.text.TextUtils; import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; public class Base64 { private static final char last2byte = (char) Integer .parseInt("00000011", 2); private static final char last4byte = (char) Integer .parseInt("00001111", 2); private static final char last6byte = (char) Integer .parseInt("00111111", 2); private static final char lead6byte = (char) Integer .parseInt("11111100", 2); private static final char lead4byte = (char) Integer .parseInt("11110000", 2); private static final char lead2byte = (char) Integer .parseInt("11000000", 2); private static final char[] encodeTable = new char[]{'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', '+', '/'}; /**
     * base64加密
     *
     * @param from
     * @return
     */ public static String encode(byte[] from) { StringBuffer to = new StringBuffer((int) (from.length * 1.34) + 3); int num = 0; char currentByte = 0; for (int i = 0; i < from.length; i++) { num = num % 8; while (num < 8) { switch (num) { case 0: currentByte = (char) (from[i] & lead6byte); currentByte = (char) (currentByte >>> 2); break; case 2: currentByte = (char) (from[i] & last6byte); break; case 4: currentByte = (char) (from[i] & last4byte); currentByte = (char) (currentByte << 2); if ((i + 1) < from.length) { currentByte |= (from[i + 1] & lead2byte) >>> 6; } break; case 6: currentByte = (char) (from[i] & last2byte); currentByte = (char) (currentByte << 4); if ((i + 1) < from.length) { currentByte |= (from[i + 1] & lead4byte) >>> 4; } break; } to.append(encodeTable[currentByte]); num += 6; } } if (to.length() % 4 != 0) { for (int i = 4 - to.length() % 4; i > 0; i--) { to.append("="); } } return to.toString(); } /**
     * md5加密
     *
     * @param string
     * @return
     */ public static String md5(String string) { if (TextUtils.isEmpty(string)) { return ""; } MessageDigest md5 = null; try { md5 = MessageDigest.getInstance("MD5"); byte[] bytes = md5.digest(string.getBytes()); String result = ""; for (byte b : bytes) { String temp = Integer.toHexString(b & 0xff); if (temp.length() == 1) { temp = "0" + temp; } result += temp; } return result; } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } return ""; } } 

本文地址：https://blog.csdn.net/qq_41458550/article/details/108976833