首先，我們來看一個例子：

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

這種情況下，b和b1字節(jié)數(shù)組是相同的。

那下面這種情況呢？

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

打印出來的ss是一堆我們看不懂的東西！而且我們發(fā)現(xiàn)b和b1字節(jié)數(shù)組長度都不同啦？為什么？

我們知道ascii編碼的范圍為0~127，那么-2，-9該如何編碼呢？?

b1和b的字節(jié)表示在傳遞過程中，數(shù)據(jù)失真了，那如何解決失真問題呢？

我們可以使用base64對-128~127的值進行改造（具體請自行g(shù)oogle之）。

通過使base64編碼解碼則可以防止傳輸過程中出錯。base64可使用commons-codec的，如下所示：

Method Summary

Methods?Modifier and TypeMethod 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，當(dāng)url傳輸過程中，為了保證不傳輸錯誤（例如缺少“+”等),請盡量使用urlSafe方法。

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

我們看一下編碼后的s是什么樣子的？

47, 118, 99, 114

編碼后全部變?yōu)?~127的ascii編碼，解碼后b1的值為：

-2, -9, 43

b和b1相同，沒有數(shù)據(jù)失真。

另外，也可以是使用bouncy castle支持。具體可以google之。

一些小細(xì)節(jié)：

1. 跨平臺傳輸時可能傳輸?shù)氖鞘M制字符串，要轉(zhuǎn)換為byte數(shù)組再進行編碼，轉(zhuǎn)換方法為：從高位開始，兩個十六進制字符為一組轉(zhuǎn)為byte。實例如下：

String hex="1a2bcc";

先拆分，把“1a”，“2b” “cc”分別解析為byte數(shù)組 26，43,208?

2. 跨平臺要考慮編碼格式，如utf-8 或者gbk 或者iso-8895-1等。

轉(zhuǎn)載于:https://www.cnblogs.com/davidwang456/p/3935601.html

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