Decode Base64 data in Java
我有一个base64编码的图像。在Java中解码的最好方法是什么?希望只使用包含在Sun Java 6中的库。
至于V6,JavaSE与JAXB一起使用。
对于Java 8,有一个支持Base64编码和解码的官方API。随着时间的推移,这可能会成为默认的选择。
API包括类
使用"基本"编码的示例代码:
1 2 3 4 5 | import java.util.Base64; byte[] bytes ="Hello, World!".getBytes("UTF-8"); String encoded = Base64.getEncoder().encodeToString(bytes); byte[] decoded = Base64.getDecoder().decode(encoded); |
无需使用共享空间——Sun用Java向Base64编码器传输。您可以这样导入它:
1 | import sun.misc.BASE64Decoder; |
然后像这样使用:
1 2 | BASE64Decoder decoder = new BASE64Decoder(); byte[] decodedBytes = decoder.decodeBuffer(encodedBytes); |
其中,
编辑:谁知道这将是我发表过的最具争议的答案?我知道sun.*软件包不受支持,也不保证能继续存在,我知道commons并一直使用它。然而,海报要求一个班,这是"包括在Sun Java 6",这就是我试图回答。我同意一般来说,公地是最好的方式。
编辑2:正如下面的AMIR75指出的,Java 6 +用JAXB来承载,它包含支持的代码来编译/解码BASE64。请看下面杰里米·罗斯的回答。
特别是在通用编解码器中:类
现在,guava内置了base64解码。
使用baseEncoding.base64().decode())
关于处理输入使用中可能出现的空白
有关详细信息,请参阅此讨论
我的解决方案是最快和最简单的。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 | public class MyBase64 { private final static char[] ALPHABET ="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/".toCharArray(); private static int[] toInt = new int[128]; static { for(int i=0; i< ALPHABET.length; i++){ toInt[ALPHABET[i]]= i; } } /** * Translates the specified byte array into Base64 string. * * @param buf the byte array (not null) * @return the translated Base64 string (not null) */ public static String encode(byte[] buf){ int size = buf.length; char[] ar = new char[((size + 2) / 3) * 4]; int a = 0; int i=0; while(i < size){ byte b0 = buf[i++]; byte b1 = (i < size) ? buf[i++] : 0; byte b2 = (i < size) ? buf[i++] : 0; int mask = 0x3F; ar[a++] = ALPHABET[(b0 >> 2) & mask]; ar[a++] = ALPHABET[((b0 << 4) | ((b1 & 0xFF) >> 4)) & mask]; ar[a++] = ALPHABET[((b1 << 2) | ((b2 & 0xFF) >> 6)) & mask]; ar[a++] = ALPHABET[b2 & mask]; } switch(size % 3){ case 1: ar[--a] = '='; case 2: ar[--a] = '='; } return new String(ar); } /** * Translates the specified Base64 string into a byte array. * * @param s the Base64 string (not null) * @return the byte array (not null) */ public static byte[] decode(String s){ int delta = s.endsWith("==" ) ? 2 : s.endsWith("=" ) ? 1 : 0; byte[] buffer = new byte[s.length()*3/4 - delta]; int mask = 0xFF; int index = 0; for(int i=0; i< s.length(); i+=4){ int c0 = toInt[s.charAt( i )]; int c1 = toInt[s.charAt( i + 1)]; buffer[index++]= (byte)(((c0 << 2) | (c1 >> 4)) & mask); if(index >= buffer.length){ return buffer; } int c2 = toInt[s.charAt( i + 2)]; buffer[index++]= (byte)(((c1 << 4) | (c2 >> 2)) & mask); if(index >= buffer.length){ return buffer; } int c3 = toInt[s.charAt( i + 3 )]; buffer[index++]= (byte)(((c2 << 6) | c3) & mask); } return buffer; } } |
下面是我自己的实现,如果它对某人有用的话:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 | public class Base64Coder { // The line separator string of the operating system. private static final String systemLineSeparator = System.getProperty("line.separator"); // Mapping table from 6-bit nibbles to Base64 characters. private static final char[] map1 = new char[64]; static { int i=0; for (char c='A'; c<='Z'; c++) map1[i++] = c; for (char c='a'; c<='z'; c++) map1[i++] = c; for (char c='0'; c<='9'; c++) map1[i++] = c; map1[i++] = '+'; map1[i++] = '/'; } // Mapping table from Base64 characters to 6-bit nibbles. private static final byte[] map2 = new byte[128]; static { for (int i=0; i<map2.length; i++) map2[i] = -1; for (int i=0; i<64; i++) map2[map1[i]] = (byte)i; } /** * Encodes a string into Base64 format. * No blanks or line breaks are inserted. * @param s A String to be encoded. * @return A String containing the Base64 encoded data. */ public static String encodeString (String s) { return new String(encode(s.getBytes())); } /** * Encodes a byte array into Base 64 format and breaks the output into lines of 76 characters. * This method is compatible with <wyn>sun.misc.BASE64Encoder.encodeBuffer(byte[])</wyn>. * @param in An array containing the data bytes to be encoded. * @return A String containing the Base64 encoded data, broken into lines. */ public static String encodeLines (byte[] in) { return encodeLines(in, 0, in.length, 76, systemLineSeparator); } /** * Encodes a byte array into Base 64 format and breaks the output into lines. * @param in An array containing the data bytes to be encoded. * @param iOff Offset of the first byte in <wyn>in</wyn> to be processed. * @param iLen Number of bytes to be processed in <wyn>in</wyn>, starting at <wyn>iOff</wyn>. * @param lineLen Line length for the output data. Should be a multiple of 4. * @param lineSeparator The line separator to be used to separate the output lines. * @return A String containing the Base64 encoded data, broken into lines. */ public static String encodeLines (byte[] in, int iOff, int iLen, int lineLen, String lineSeparator) { int blockLen = (lineLen*3) / 4; if (blockLen <= 0) throw new IllegalArgumentException(); int lines = (iLen+blockLen-1) / blockLen; int bufLen = ((iLen+2)/3)*4 + lines*lineSeparator.length(); StringBuilder buf = new StringBuilder(bufLen); int ip = 0; while (ip < iLen) { int l = Math.min(iLen-ip, blockLen); buf.append (encode(in, iOff+ip, l)); buf.append (lineSeparator); ip += l; } return buf.toString(); } /** * Encodes a byte array into Base64 format. * No blanks or line breaks are inserted in the output. * @param in An array containing the data bytes to be encoded. * @return A character array containing the Base64 encoded data. */ public static char[] encode (byte[] in) { return encode(in, 0, in.length); } /** * Encodes a byte array into Base64 format. * No blanks or line breaks are inserted in the output. * @param in An array containing the data bytes to be encoded. * @param iLen Number of bytes to process in <wyn>in</wyn>. * @return A character array containing the Base64 encoded data. */ public static char[] encode (byte[] in, int iLen) { return encode(in, 0, iLen); } /** * Encodes a byte array into Base64 format. * No blanks or line breaks are inserted in the output. * @param in An array containing the data bytes to be encoded. * @param iOff Offset of the first byte in <wyn>in</wyn> to be processed. * @param iLen Number of bytes to process in <wyn>in</wyn>, starting at <wyn>iOff</wyn>. * @return A character array containing the Base64 encoded data. */ public static char[] encode (byte[] in, int iOff, int iLen) { int oDataLen = (iLen*4+2)/3; // output length without padding int oLen = ((iLen+2)/3)*4; // output length including padding char[] out = new char[oLen]; int ip = iOff; int iEnd = iOff + iLen; int op = 0; while (ip < iEnd) { int i0 = in[ip++] & 0xff; int i1 = ip < iEnd ? in[ip++] & 0xff : 0; int i2 = ip < iEnd ? in[ip++] & 0xff : 0; int o0 = i0 >>> 2; int o1 = ((i0 & 3) << 4) | (i1 >>> 4); int o2 = ((i1 & 0xf) << 2) | (i2 >>> 6); int o3 = i2 & 0x3F; out[op++] = map1[o0]; out[op++] = map1[o1]; out[op] = op < oDataLen ? map1[o2] : '='; op++; out[op] = op < oDataLen ? map1[o3] : '='; op++; } return out; } /** * Decodes a string from Base64 format. * No blanks or line breaks are allowed within the Base64 encoded input data. * @param s A Base64 String to be decoded. * @return A String containing the decoded data. * @throws IllegalArgumentException If the input is not valid Base64 encoded data. */ public static String decodeString (String s) { return new String(decode(s)); } /** * Decodes a byte array from Base64 format and ignores line separators, tabs and blanks. * CR, LF, Tab and Space characters are ignored in the input data. * This method is compatible with <wyn>sun.misc.BASE64Decoder.decodeBuffer(String)</wyn>. * @param s A Base64 String to be decoded. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException If the input is not valid Base64 encoded data. */ public static byte[] decodeLines (String s) { char[] buf = new char[s.length()]; int p = 0; for (int ip = 0; ip < s.length(); ip++) { char c = s.charAt(ip); if (c != ' ' && c != ' ' && c != ' ' && c != '\t') buf[p++] = c; } return decode(buf, 0, p); } /** * Decodes a byte array from Base64 format. * No blanks or line breaks are allowed within the Base64 encoded input data. * @param s A Base64 String to be decoded. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException If the input is not valid Base64 encoded data. */ public static byte[] decode (String s) { return decode(s.toCharArray()); } /** * Decodes a byte array from Base64 format. * No blanks or line breaks are allowed within the Base64 encoded input data. * @param in A character array containing the Base64 encoded data. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException If the input is not valid Base64 encoded data. */ public static byte[] decode (char[] in) { return decode(in, 0, in.length); } /** * Decodes a byte array from Base64 format. * No blanks or line breaks are allowed within the Base64 encoded input data. * @param in A character array containing the Base64 encoded data. * @param iOff Offset of the first character in <wyn>in</wyn> to be processed. * @param iLen Number of characters to process in <wyn>in</wyn>, starting at <wyn>iOff</wyn>. * @return An array containing the decoded data bytes. * @throws IllegalArgumentException If the input is not valid Base64 encoded data. */ public static byte[] decode (char[] in, int iOff, int iLen) { if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4."); while (iLen > 0 && in[iOff+iLen-1] == '=') iLen--; int oLen = (iLen*3) / 4; byte[] out = new byte[oLen]; int ip = iOff; int iEnd = iOff + iLen; int op = 0; while (ip < iEnd) { int i0 = in[ip++]; int i1 = in[ip++]; int i2 = ip < iEnd ? in[ip++] : 'A'; int i3 = ip < iEnd ? in[ip++] : 'A'; if (i0 > 127 || i1 > 127 || i2 > 127 || i3 > 127) throw new IllegalArgumentException ("Illegal character in Base64 encoded data."); int b0 = map2[i0]; int b1 = map2[i1]; int b2 = map2[i2]; int b3 = map2[i3]; if (b0 < 0 || b1 < 0 || b2 < 0 || b3 < 0) throw new IllegalArgumentException ("Illegal character in Base64 encoded data."); int o0 = ( b0 <<2) | (b1>>>4); int o1 = ((b1 & 0xf)<<4) | (b2>>>2); int o2 = ((b2 & 3)<<6) | b3; out[op++] = (byte)o0; if (op<oLen) out[op++] = (byte)o1; if (op<oLen) out[op++] = (byte)o2; } return out; } // Dummy constructor. private Base64Coder() {} } |
作为
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | public static byte[] encode(byte[] b) throws Exception { ByteArrayOutputStream baos = new ByteArrayOutputStream(); OutputStream b64os = MimeUtility.encode(baos,"base64"); b64os.write(b); b64os.close(); return baos.toByteArray(); } public static byte[] decode(byte[] b) throws Exception { ByteArrayInputStream bais = new ByteArrayInputStream(b); InputStream b64is = MimeUtility.decode(bais,"base64"); byte[] tmp = new byte[b.length]; int n = b64is.read(tmp); byte[] res = new byte[n]; System.arraycopy(tmp, 0, res, 0, n); return res; } |
带完整代码的链接:对base64进行编码/解码
另一个迟来的答案,但我的基准测试表明,Jetty实现base64编码器的速度相当快。没有migbase64快,但比iharder base64快。
1 2 3 |
我还做了一些基准测试:
1 2 3 4 5 6 | library | encode | decode ------------------+--------------+------------- 'MiGBase64' | 10146001.00 | 6426446.00 'Jetty B64Code' | 8846191.00 | 3101361.75 'iHarder Base64' | 3259590.50 | 2505280.00 'Commons-Codec' | 241318.04 | 255179.96 |
这些是每秒运行次数,所以越高越好。
给出了一个javax.xml.bind.datatypeconverter的测试编码/解码示例,使用parsebase64binary()和printbase64binary()方法引用@jeremy ross和@nightfirecat answer。
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | @Test public void EncodeDecode() { //ENCODE String hello ="Hello World"; byte[] helloBytes = hello.getBytes(StandardCharsets.UTF_8); String encodedHello = DatatypeConverter.printBase64Binary(helloBytes); LOGGER.info(hello +" encoded=>" + encodedHello); //DECODE byte[] encodedHelloBytes = DatatypeConverter.parseBase64Binary(encodedHello); String helloAgain = new String(encodedHelloBytes, StandardCharsets.UTF_8) ; LOGGER.info(encodedHello +" decoded=>" + helloAgain); Assert.assertEquals(hello, helloAgain); } |
结果:
1 2 | INFO - Hello World encoded=> SGVsbG8gV29ybGQ= INFO - SGVsbG8gV29ybGQ= decoded=> Hello World |
如果您喜欢基于性能的解决方案,则可以使用"migbase64"
http://migbase64.sourceforge.net/
1 2 3 4 5 6 7 8 | public class Base64Test { public static void main(String[] args) { String encodeToString = Base64.encodeToString("JavaTips.net".getBytes(), true); System.out.println("encodeToString" + encodeToString); byte[] decodedBytes = Base64.decode(encodeToString.getBytes()); System.out.println("decodedBytes" + new String(decodedBytes)); } } |
希望这对您有所帮助:
1 2 3 |
或:
1 2 3 4 5 6 |
但它不在JRE类白名单中
不在GAE/J白名单中未列出的可用类中
真遗憾!
另外,在Android中,这很容易,因为从AndroidAPI第8级开始,
这是一个迟来的回答,但约书亚·布洛克(Joshua Bloch)在他为Sun,Ahem,Oracle工作的时候)在
例如。
1 2 |
您可以从编码的base64字符串写入或下载文件:
1 2 3 4 5 6 7 8 9 10 11 | Base64 base64 = new Base64(); String encodedFile="JVBERi0xLjUKJeLjz9MKMSAwIG9iago8PCAKICAgL1R5cGUgL0NhdGFsb2cKICAgL1BhZ2VzIDIgMCBSCiAgIC9QYWdlTGF5b3V0IC9TaW5"; byte[] dd=encodedFile.getBytes(); byte[] bytes = Base64.decodeBase64(dd); response.setHeader("Content-disposition","attachment; filename=""+filename+"""); response.setHeader("Cache-Control","no-cache"); response.setHeader("Expires","-1"); // actually send result bytes response.getOutputStream().write(bytes); |
为我工作,希望也为你工作…
EDCOX1(18)的Java 8实现不依赖于其他Java 8特定的类。
我不确定这是否适用于Java 6项目,但是可以将EDOCX1的21文档文件复制和粘贴到Java 7项目中,除了导入JavaU.L.Stand和EDCX1(22)之外,没有修改就可以编译它。
注意,base64.java文件由gnu gpl2覆盖。
如果您已经为Java添加了AWS SDK,可以使用COM.AxaNavaS.UTI.Base64。
我用的
用途:
1 | byte[] decodedKey = Base64.decode(encodedPublicKey, Base64.DEFAULT); |
软件包COM.TEST;
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 | import java.io.UnsupportedEncodingException; /** * Utilities for encoding and decoding the Base64 representation of * binary data. See RFCs <a * href="http://www.ietf.org/rfc/rfc2045.txt">2045 and <a * href="http://www.ietf.org/rfc/rfc3548.txt">3548. */ public class Base64 { public static final int DEFAULT = 0; public static final int NO_PADDING = 1; public static final int NO_WRAP = 2; public static final int CRLF = 4; public static final int URL_SAFE = 8; public static final int NO_CLOSE = 16; // -------------------------------------------------------- // shared code // -------------------------------------------------------- /* package */ static abstract class Coder { public byte[] output; public int op; public abstract boolean process(byte[] input, int offset, int len, boolean finish); public abstract int maxOutputSize(int len); } // -------------------------------------------------------- // decoding // -------------------------------------------------------- public static byte[] decode(String str, int flags) { return decode(str.getBytes(), flags); } public static byte[] decode(byte[] input, int flags) { return decode(input, 0, input.length, flags); } public static byte[] decode(byte[] input, int offset, int len, int flags) { // Allocate space for the most data the input could represent. // (It could contain less if it contains whitespace, etc.) Decoder decoder = new Decoder(flags, new byte[len*3/4]); if (!decoder.process(input, offset, len, true)) { throw new IllegalArgumentException("bad base-64"); } // Maybe we got lucky and allocated exactly enough output space. if (decoder.op == decoder.output.length) { return decoder.output; } // Need to shorten the array, so allocate a new one of the // right size and copy. byte[] temp = new byte[decoder.op]; System.arraycopy(decoder.output, 0, temp, 0, decoder.op); return temp; } static class Decoder extends Coder { private static final int DECODE[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, }; /** * Decode lookup table for the"web safe" variant (RFC 3548 * sec. 4) where - and _ replace + and /. */ private static final int DECODE_WEBSAFE[] = { -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -2, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, 63, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, }; /** Non-data values in the DECODE arrays. */ private static final int SKIP = -1; private static final int EQUALS = -2; private int state; // state number (0 to 6) private int value; final private int[] alphabet; public Decoder(int flags, byte[] output) { this.output = output; alphabet = ((flags & URL_SAFE) == 0) ? DECODE : DECODE_WEBSAFE; state = 0; value = 0; } public int maxOutputSize(int len) { return len * 3/4 + 10; } /** * Decode another block of input data. * * @return true if the state machine is still healthy. false if * bad base-64 data has been detected in the input stream. */ public boolean process(byte[] input, int offset, int len, boolean finish) { if (this.state == 6) return false; int p = offset; len += offset; int state = this.state; int value = this.value; int op = 0; final byte[] output = this.output; final int[] alphabet = this.alphabet; while (p < len) { if (state == 0) { while (p+4 <= len && (value = ((alphabet[input[p] & 0xff] << 18) | (alphabet[input[p+1] & 0xff] << 12) | (alphabet[input[p+2] & 0xff] << 6) | (alphabet[input[p+3] & 0xff]))) >= 0) { output[op+2] = (byte) value; output[op+1] = (byte) (value >> 8); output[op] = (byte) (value >> 16); op += 3; p += 4; } if (p >= len) break; } int d = alphabet[input[p++] & 0xff]; switch (state) { case 0: if (d >= 0) { value = d; ++state; } else if (d != SKIP) { this.state = 6; return false; } break; case 1: if (d >= 0) { value = (value << 6) | d; ++state; } else if (d != SKIP) { this.state = 6; return false; } break; case 2: if (d >= 0) { value = (value << 6) | d; ++state; } else if (d == EQUALS) { // Emit the last (partial) output tuple; // expect exactly one more padding character. output[op++] = (byte) (value >> 4); state = 4; } else if (d != SKIP) { this.state = 6; return false; } break; case 3: if (d >= 0) { // Emit the output triple and return to state 0. value = (value << 6) | d; output[op+2] = (byte) value; output[op+1] = (byte) (value >> 8); output[op] = (byte) (value >> 16); op += 3; state = 0; } else if (d == EQUALS) { // Emit the last (partial) output tuple; // expect no further data or padding characters. output[op+1] = (byte) (value >> 2); output[op] = (byte) (value >> 10); op += 2; state = 5; } else if (d != SKIP) { this.state = 6; return false; } break; case 4: if (d == EQUALS) { ++state; } else if (d != SKIP) { this.state = 6; return false; } break; case 5: if (d != SKIP) { this.state = 6; return false; } break; } } if (!finish) { // We're out of input, but a future call could provide // more. this.state = state; this.value = value; this.op = op; return true; } switch (state) { case 0: break; case 1: this.state = 6; return false; case 2: output[op++] = (byte) (value >> 4); break; case 3: output[op++] = (byte) (value >> 10); output[op++] = (byte) (value >> 2); break; case 4: this.state = 6; return false; case 5: break; } this.state = state; this.op = op; return true; } } // -------------------------------------------------------- // encoding // -------------------------------------------------------- public static String encodeToString(byte[] input, int flags) { try { return new String(encode(input, flags),"US-ASCII"); } catch (UnsupportedEncodingException e) { // US-ASCII is guaranteed to be available. throw new AssertionError(e); } } public static String encodeToString(byte[] input, int offset, int len, int flags) { try { return new String(encode(input, offset, len, flags),"US-ASCII"); } catch (UnsupportedEncodingException e) { // US-ASCII is guaranteed to be available. throw new AssertionError(e); } } public static byte[] encode(byte[] input, int flags) { return encode(input, 0, input.length, flags); } public static byte[] encode(byte[] input, int offset, int len, int flags) { Encoder encoder = new Encoder(flags, null); // Compute the exact length of the array we will produce. int output_len = len / 3 * 4; // Account for the tail of the data and the padding bytes, if any. if (encoder.do_padding) { if (len % 3 > 0) { output_len += 4; } } else { switch (len % 3) { case 0: break; case 1: output_len += 2; break; case 2: output_len += 3; break; } } // Account for the newlines, if any. if (encoder.do_newline && len > 0) { output_len += (((len-1) / (3 * Encoder.LINE_GROUPS)) + 1) * (encoder.do_cr ? 2 : 1); } encoder.output = new byte[output_len]; encoder.process(input, offset, len, true); assert encoder.op == output_len; return encoder.output; } /* package */ static class Encoder extends Coder { /** * Emit a new line every this many output tuples. Corresponds to * a 76-character line length (the maximum allowable according to * RFC 2045). */ public static final int LINE_GROUPS = 19; /** * Lookup table for turning Base64 alphabet positions (6 bits) * into output bytes. */ private static final byte ENCODE[] = { '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', '+', '/', }; /** * Lookup table for turning Base64 alphabet positions (6 bits) * into output bytes. */ private static final byte ENCODE_WEBSAFE[] = { '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', '-', '_', }; final private byte[] tail; /* package */ int tailLen; private int count; final public boolean do_padding; final public boolean do_newline; final public boolean do_cr; final private byte[] alphabet; public Encoder(int flags, byte[] output) { this.output = output; do_padding = (flags & NO_PADDING) == 0; do_newline = (flags & NO_WRAP) == 0; do_cr = (flags & CRLF) != 0; alphabet = ((flags & URL_SAFE) == 0) ? ENCODE : ENCODE_WEBSAFE; tail = new byte[2]; tailLen = 0; count = do_newline ? LINE_GROUPS : -1; } /** * @return an overestimate for the number of bytes {@code * len} bytes could encode to. */ public int maxOutputSize(int len) { return len * 8/5 + 10; } public boolean process(byte[] input, int offset, int len, boolean finish) { // Using local variables makes the encoder about 9% faster. final byte[] alphabet = this.alphabet; final byte[] output = this.output; int op = 0; int count = this.count; int p = offset; len += offset; int v = -1; // First we need to concatenate the tail of the previous call // with any input bytes available now and see if we can empty // the tail. switch (tailLen) { case 0: // There was no tail. break; case 1: if (p+2 <= len) { // A 1-byte tail with at least 2 bytes of // input available now. v = ((tail[0] & 0xff) << 16) | ((input[p++] & 0xff) << 8) | (input[p++] & 0xff); tailLen = 0; }; break; case 2: if (p+1 <= len) { // A 2-byte tail with at least 1 byte of input. v = ((tail[0] & 0xff) << 16) | ((tail[1] & 0xff) << 8) | (input[p++] & 0xff); tailLen = 0; } break; } if (v != -1) { output[op++] = alphabet[(v >> 18) & 0x3f]; output[op++] = alphabet[(v >> 12) & 0x3f]; output[op++] = alphabet[(v >> 6) & 0x3f]; output[op++] = alphabet[v & 0x3f]; if (--count == 0) { if (do_cr) output[op++] = ' '; output[op++] = ' '; count = LINE_GROUPS; } } // At this point either there is no tail, or there are fewer // than 3 bytes of input available. // The main loop, turning 3 input bytes into 4 output bytes on // each iteration. while (p+3 <= len) { v = ((input[p] & 0xff) << 16) | ((input[p+1] & 0xff) << 8) | (input[p+2] & 0xff); output[op] = alphabet[(v >> 18) & 0x3f]; output[op+1] = alphabet[(v >> 12) & 0x3f]; output[op+2] = alphabet[(v >> 6) & 0x3f]; output[op+3] = alphabet[v & 0x3f]; p += 3; op += 4; if (--count == 0) { if (do_cr) output[op++] = ' '; output[op++] = ' '; count = LINE_GROUPS; } } if (finish) { if (p-tailLen == len-1) { int t = 0; v = ((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 4; tailLen -= t; output[op++] = alphabet[(v >> 6) & 0x3f]; output[op++] = alphabet[v & 0x3f]; if (do_padding) { output[op++] = '='; output[op++] = '='; } if (do_newline) { if (do_cr) output[op++] = ' '; output[op++] = ' '; } } else if (p-tailLen == len-2) { int t = 0; v = (((tailLen > 1 ? tail[t++] : input[p++]) & 0xff) << 10) | (((tailLen > 0 ? tail[t++] : input[p++]) & 0xff) << 2); tailLen -= t; output[op++] = alphabet[(v >> 12) & 0x3f]; output[op++] = alphabet[(v >> 6) & 0x3f]; output[op++] = alphabet[v & 0x3f]; if (do_padding) { output[op++] = '='; } if (do_newline) { if (do_cr) output[op++] = ' '; output[op++] = ' '; } } else if (do_newline && op > 0 && count != LINE_GROUPS) { if (do_cr) output[op++] = ' '; output[op++] = ' '; } assert tailLen == 0; assert p == len; } else { // Save the leftovers in tail to be consumed on the next // call to encodeInternal. if (p == len-1) { tail[tailLen++] = input[p]; } else if (p == len-2) { tail[tailLen++] = input[p]; tail[tailLen++] = input[p+1]; } } this.op = op; this.count = count; return true; } } private Base64() { } // don't instantiate } |
在用Java 7编译的代码中,但潜在地运行在更高的Java版本中,检测EDOCX1×1类的存在似乎是有用的,并且在这里的其他问题中使用的JVM最好使用该方法。
我用了这个代码:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 | private static final Method JAVA_UTIL_BASE64_GETENCODER; static { Method getEncoderMethod; try { final Class<?> base64Class = Class.forName("java.util.Base64"); getEncoderMethod = base64Class.getMethod("getEncoder"); } catch (ClassNotFoundException | NoSuchMethodException e) { getEncoderMethod = null; } JAVA_UTIL_BASE64_GETENCODER = getEncoderMethod; } static String base64EncodeToString(String s) { final byte[] bytes = s.getBytes(StandardCharsets.ISO_8859_1); if (JAVA_UTIL_BASE64_GETENCODER == null) { // Java 7 and older // TODO: remove this branch after switching to Java 8 return DatatypeConverter.printBase64Binary(bytes); } else { // Java 8 and newer try { final Object encoder = JAVA_UTIL_BASE64_GETENCODER.invoke(null); final Class<?> encoderClass = encoder.getClass(); final Method encodeMethod = encoderClass.getMethod("encode", byte[].class); final byte[] encodedBytes = (byte[]) encodeMethod.invoke(encoder, bytes); return new String(encodedBytes); } catch (NoSuchMethodException | IllegalAccessException | InvocationTargetException e) { throw new IllegalStateException(e); } } } |