跨平台传输中使用base64来保证非ascii码字符串的完整性

时间 2019-12-02

标签跨平台传输使用 base64 base 保证 ascii 码字符串完整性繁體版

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首先，咱们来看一个例子：html

byte[] b=new byte[]{2,9,43};
String ss=new String(b,"utf-8");
byte[] b1=ss.getbytes();

这种状况下，b和b1字节数组是相同的。java

那下面这种状况呢？apache

byte[] b=new byte[]{-2,-9,43};
String ss=new String(b,"utf-8");
byte[] b1=ss.getbytes();

打印出来的ss是一堆咱们看不懂的东西！并且咱们发现b和b1字节数组长度都不一样啦？为何？api

咱们知道ascii编码的范围为0~127，那么-2，-9该如何编码呢？数组

b1和b的字节表示在传递过程当中，数据失真了，那如何解决失真问题呢？oracle

咱们能够使用base64对-128~127的值进行改造（具体请自行google之）。google

经过使base64编码解码则能够防止传输过程当中出错。base64可以使用commons-codec的，以下所示：编码

Method Summary

Methods
Modifier and Type	Method and Description
`static byte[]`	`decodeBase64(byte[] base64Data)` Decodes Base64 data into octets
`static byte[]`	`decodeBase64(String base64String)` Decodes a Base64 String into octets
`static BigInteger`	`decodeInteger(byte[] pArray)` Decodes a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
`static byte[]`	`encodeBase64(byte[] binaryData)` Encodes binary data using the base64 algorithm but does not chunk the output.
`static byte[]`	`encodeBase64(byte[] binaryData, boolean isChunked)` Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
`static byte[]`	`encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe)` Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
`static byte[]`	`encodeBase64(byte[] binaryData, boolean isChunked, boolean urlSafe, int maxResultSize)` Encodes binary data using the base64 algorithm, optionally chunking the output into 76 character blocks.
`static byte[]`	`encodeBase64Chunked(byte[] binaryData)` Encodes binary data using the base64 algorithm and chunks the encoded output into 76 character blocks
`static String`	`encodeBase64String(byte[] binaryData)` Encodes binary data using the base64 algorithm but does not chunk the output.
`static byte[]`	`encodeBase64URLSafe(byte[] binaryData)` Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output.
`static String`	`encodeBase64URLSafeString(byte[] binaryData)` Encodes binary data using a URL-safe variation of the base64 algorithm but does not chunk the output.
`static byte[]`	`encodeInteger(BigInteger bigInt)` Encodes to a byte64-encoded integer according to crypto standards such as W3C's XML-Signature
`static boolean`	`isArrayByteBase64(byte[] arrayOctet)` Deprecated. 1.5 Use `isBase64(byte[])`, will be removed in 2.0.
`static boolean`	`isBase64(byte octet)` Returns whether or not the `octet` is in the base 64 alphabet.
`static boolean`	`isBase64(byte[] arrayOctet)` Tests a given byte array to see if it contains only valid characters within the Base64 alphabet.
`static boolean`	`isBase64(String base64)` Tests a given String to see if it contains only valid characters within the Base64 alphabet.
`protected boolean`	`isInAlphabet(byte octet)` Returns whether or not the `octet` is in the Base64 alphabet.
`boolean`	`isUrlSafe()` Returns our current encode mode.

注意，当url传输过程当中，为了保证不传输错误（例如缺乏“+”等),请尽可能使用urlSafe方法。url

        byte[] b=new byte[]{-2,-9,43};
        byte[] s=Base64.encodeBytesToBytes(b);
        byte[] b1=Base64.decode(s);

咱们看一下编码后的s是什么样子的？spa

47, 118, 99, 114

编码后所有变为0~127的ascii编码，解码后b1的值为：

-2, -9, 43

b和b1相同，没有数据失真。

另外，也能够是使用bouncy castle支持。具体能够google之。

一些小细节：

1. 跨平台传输时可能传输的是十六进制字符串，要转换为byte数组再进行编码，转换方法为：从高位开始，两个十六进制字符为一组转为byte。实例以下：

String hex="1a2bcc";

先拆分，把“1a”，“2b” “cc”分别解析为byte数组 26，43,208

2. 跨平台要考虑编码格式，如utf-8 或者gbk 或者iso-8895-1等。