Base64 可以将二进制转码成可见字符方便进行http传输，但是base64转码时会生成“+”，“/”，“=”这些被URL进行转码的特殊字符，导致两方面数据不一致。
我们可以在发送前将“+”，“/”，“=”替换成URL不会转码的字符，接收到数据后，再将这些字符替换回去，再进行解码。
Base64加密转换原理与代码实现 :http://www.cnblogs.com/jxust-jiege666/p/8590116.html
PHP：
1 /** 2 3 * URL base64解码 4 5 * '-' -> '+' 6 7 * '_' -> '/' 8 9 * 字符串长度%4的余数，补'=' 10 11 * @param unknown $string 12 13 */ 14 15 public static function urlsafe_b64decode($string) { 16 17 $data = str_replace(array('-','_'),array('+','/'),$string); 18 19 $mod4 = strlen($data) % 4; 20 21 if ($mod4) { 22 23 $data .= substr('====', $mod4); 24 25 } 26 27 return base64_decode($data); 28 29 } 30 31 32 33 /** 34 35 * URL base64编码 36 37 * '+' -> '-' 38 39 * '/' -> '_' 40 41 * '=' -> '' 42 43 * @param unknown $string 44 45 */ 46 47 function urlsafe_b64encode($string) { 48 49 $data = base64_encode($string); 50 51 $data = str_replace(array('+','/','='),array('-','_',''),$data); 52 53 return $data; 54 55 }
OC:
1 #pragma - 将saveBase64编码中的"-"，"_"字符串转换成"+"，"/"，字符串长度余4倍的位补"=" 2 3 +(NSData*)safeUrlBase64Decode:(NSString*)safeUrlbase64Str 4 5 { 6 7 // '-' -> '+' 8 9 // '_' -> '/' 10 11 // 不足4倍长度，补'=' 12 13 NSMutableString * base64Str = [[NSMutableString alloc]initWithString:safeUrlbase64Str]; 14 15 base64Str = (NSMutableString * )[base64Str stringByReplacingOccurrencesOfString:@"-" withString:@"+"]; 16 17 base64Str = (NSMutableString * )[base64Str stringByReplacingOccurrencesOfString:@"_" withString:@"/"]; 18 19 NSInteger mod4 = base64Str.length % 4; 20 21 if(mod4 > 0) 22 23 [base64Str appendString:[@"====" substringToIndex:(4-mod4)]]; 24 25 NSLog(@"Base64原文：%@", base64Str); 26 27 return [GTMBase64 decodeData:[base64Str dataUsingEncoding:NSUTF8StringEncoding]]; 28 29 30 31 } 32 33 34 35 #pragma - 因为Base64编码中包含有+,/,=这些不安全的URL字符串，所以要进行换字符 36 37 +(NSString*)safeUrlBase64Encode:(NSData*)data 38 39 { 40 41 // '+' -> '-' 42 43 // '/' -> '_' 44 45 // '=' -> '' 46 47 NSString * base64Str = [GTMBase64 stringByEncodingData:data]; 48 49 NSMutableString * safeBase64Str = [[NSMutableString alloc]initWithString:base64Str]; 50 51 safeBase64Str = (NSMutableString * )[safeBase64Str stringByReplacingOccurrencesOfString:@"+" withString:@"-"]; 52 53 safeBase64Str = (NSMutableString * )[safeBase64Str stringByReplacingOccurrencesOfString:@"/" withString:@"_"]; 54 55 safeBase64Str = (NSMutableString * )[safeBase64Str stringByReplacingOccurrencesOfString:@"=" withString:@""]; 56 57 NSLog(@"safeBase64编码：%@", safeBase64Str); 58 59 return safeBase64Str; 60 61 }
Java：
1 public static String safeUrlBase64Encode(byte[] data){ 2 3 String encodeBase64 = new BASE64Encoder().encode(data); 4 5 String safeBase64Str = encodeBase64.replace('+', '-'); 6 7 safeBase64Str = safeBase64Str.replace('/', '_'); 8 9 safeBase64Str = safeBase64Str.replaceAll("=", ""); 10 11 return safeBase64Str; 12 13 } 14 15 16 17 public static byte[] safeUrlBase64Decode(final String safeBase64Str){ 18 19 String base64Str = safeBase64Str.replace('-', '+'); 20 21 base64Str = base64Str.replace('_', '/'); 22 23 int mod4 = base64Str.length()%4; 24 25 if(mod4 > 0){ 26 27 base64Str = base64Str + "====".substring(mod4); 28 29 } 30 31 return new BASE64Decoder().decodeBuffer(base64Str); 32 33 } 34 35
如果是Android的话，android.utils.Base64自带该功能：
1 Base64.encodeToString(encrypted, Base64.URL_SAFE|Base64.NO_WRAP) 2 Base64.decode(data, Base64.URL_SAFE);