解码base64字符串Java 5

是否有直接使用JAVA 1.5 LIBRARIES解码base64字符串的方法？

由于Windows和Mac OS X之间的跨平台兼容性问题，我必须使用Java 1.5（只有Mac 10.5支持Java 1.6，低于10.5的所有内容都默认使用Java 1.5）。

对象“sun.misc.Base64Decoder”存在于Java 6中，但不存在于Java 5中。

Answer 1

不，基于仅使用JDK 5.0是不可能的。

您需要推出自己的实现（并不难），或者最好使用其中一个开源实现。 有许多包括Commons Codec，它提供Base64 http://commons.apache.org/codec/api-release/org/apache/commons/codec/binary/Base64.html

JavaMail还通过MimeUtility提供Base64编码/解码，它也引用了可打印的编码等…

http://java.sun.com/products/javamail/javadocs/javax/mail/internet/MimeUtility.html

Answer 2

Apache Commons Codec

仅供参考，你应该在Java 6中使用它。 不要在阳光下使用类。*

Answer 3

只需使用http://iharder.sourceforge.net/current/java/base64/即可 。 它属于公共领域。 因此，您可以将代码放入项目中，而无需担心许可证问题或包括其他jar子。 您要查找的类不在JDK 1.5中。

Answer 4

这是我的版本 – 它应该是完全独立的：

public class Base64 { // ***************************************************************************** // INSTANCE PROPERTIES // ***************************************************************************** private String lineSeparator; private int lineLength; // ***************************************************************************** // INSTANCE CONSTRUCTION/INITIALIZATON/FINALIZATION, OPEN/CLOSE // ***************************************************************************** public Base64() { lineSeparator=System.getProperty("line.separator"); lineLength=0; } // ***************************************************************************** // INSTANCE METHODS // ***************************************************************************** public String encode(byte[] bin) { return encode(bin,0,bin.length); } /** * Encode an array of bytes as Base64. * It will be broken into lines if the line length is not 0. If broken into lines, * the last line is not terminated with a line separator. * * param ba The byte array to encode. */ public String encode(byte[] bin, int str, int len) { int ol; // output length StringBuffer sb; // string buffer for output(must be local for recursion to work). int lp; // line position(must be local for recursion to work). int el; // even multiple of 3 length int ll; // leftover length // CREATE OUTPUT BUFFER ol=(((len+2)/3)*4); if(lineLength!=0) { int lines=(((ol+lineLength-1)/lineLength)-1); if(lines>0) { ol+=(lines*lineSeparator.length()); } } sb=new StringBuffer(ol); lp=0; // EVEN MULTIPLES OF 3 el=(len/3)*3; ll=(len-el); for(int xa=0; xalineLength) { sb.append(lineSeparator); lp=4; } } // get next three bytes in unsigned form lined up, in big-endian order cv =(bin[xa+str+0]&0xFF); cv<<=8; cv|=(bin[xa+str+1]&0xFF); cv<<=8; cv|=(bin[xa+str+2]&0xFF); // break those 24 bits into a 4 groups of 6 bits, working LSB to MSB. c3=cv&0x3F; cv >>>=6; c2=cv&0x3F; cv >>>=6; c1=cv&0x3F; cv >>>=6; c0=cv&0x3F; // Translate into the equivalent alpha character emitting them in big-endian order. sb.append(ENCODE[c0]); sb.append(ENCODE[c1]); sb.append(ENCODE[c2]); sb.append(ENCODE[c3]); } // LEFTOVERS if(lineLength!=0 && ll>0) { lp+=4; if(lp>lineLength) { sb.append(lineSeparator); lp=4; } } if(ll==1) { sb.append(encode(new byte[] { bin[el+str], 0, 0 }).substring(0,2)).append("=="); // Use recursion so escaping logic is not repeated, replacing last 2 chars with "==". } else if(ll==2) { sb.append(encode(new byte[] { bin[el+str], bin[el+str+1], 0 }).substring(0,3)).append("="); // Use recursion so escaping logic is not repeated, replacing last char and "=". } if(ol!=sb.length()) { throw new RuntimeException("Error in Base64 encoding method: Calculated output length of "+ol+" did not match actual length of "+sb.length()); } return sb.toString(); } public byte[] decode(String b64) { return decode(b64,0,b64.length()); } /** * Decode a Base64 string to an array of bytes. * The string must have a length evenly divisible by 4 (not counting line separators and other * ignorable characters, like whitespace). */ public byte[] decode(String b64, int str, int len) { byte[] ba; // target byte array int dc; // decode cycle (within sequence of 4 input chars). int rv; // reconstituted value int ol; // output length int pc; // padding count ba=new byte[(len/4)*3]; // create array to largest possible size. dc=0; rv=0; ol=0; pc=0; for(int xa=0; xa>>=8; ba[ol+1]=(byte)rv; rv>>>=8; ba[ol]=(byte)rv; ol+=3; dc=0; } break; } } } if(dc!=0) { throw new ArrayIndexOutOfBoundsException("Base64 data given as input was not an even multiple of 4 characters (should be padded with '=' characters)."); } ol-=pc; if(ba.length!=ol) { byte[] b2=new byte[ol]; System.arraycopy(ba, 0, b2, 0, ol); ba=b2; } return ba; } /** * Set maximum line length for encoded lines. * Ignored by decode. * @param len Length of each line. 0 means no newlines inserted. Must be a multiple of 4. */ public void setLineLength(int len) { this.lineLength=(len/4)*4; } /** * Set the line separator sequence for encoded lines. * Ignored by decode. * Usually contains only a combination of chars \n and \r, but could be any chars except 'A'-'Z', 'a'-'z', '0'-'9', '+' and '/'. * @param linsep Line separator - may be "" but not null. */ public void setLineSeparator(String linsep) { this.lineSeparator=linsep; } // ***************************************************************************** // STATIC PROPERTIES // ***************************************************************************** static private final char[] ENCODE=new char[64]; // translation array for encoding static private final int[] DECODE=new int[256]; // translation array for decoding static private final int IGNORE=-1; // flag for values to ignore when decoding static private final int PAD=-2; // flag value for padding value when decoding static private final Base64 BASE64=new Base64(); // default converter // ***************************************************************************** // STATIC INIT & MAIN // ***************************************************************************** static { for(int xa=0; xa<=25; xa++) { ENCODE[xa]=(char)('A'+xa); } // 0..25 -> 'A'..'Z' for(int xa=0; xa<=25; xa++) { ENCODE[xa+26]=(char)('a'+xa); } // 26..51 -> 'a'..'z' for(int xa=0; xa<= 9; xa++) { ENCODE[xa+52]=(char)('0'+xa); } // 52..61 -> '0'..'9' ENCODE[62]='+'; ENCODE[63]='/'; for(int xa=0; xa<256; xa++) { DECODE[xa]=IGNORE; } // set all chars to IGNORE, first for(int xa=0; xa< 64; xa++) { DECODE[ENCODE[xa]]=xa; } // set the Base 64 chars to their integer byte values DECODE['=']=PAD; } // ***************************************************************************** // STATIC METHODS // ***************************************************************************** static public String toString(byte[] dta) { return BASE64.encode(dta); } static public String toString(byte[] dta, int str, int len) { return BASE64.encode(dta,str,len); } static public byte[] toBytes(String b64) { return BASE64.decode(b64); } static public byte[] toBytes(String b64, int str, int len) { return BASE64.decode(b64,str,len); } } // END PUBLIC CLASS 

Answer 5

此页面上还有各种实现： http ： //www.rgagnon.com/javadetails/java-0598.html