Decode base64 String Java 5

Question

¿Existe una manera directa de decodificar una cadena base64 utilizando SOLO LAS BIBLIOTECAS JAVA 1.5?

Tengo que usar Java 1.5 debido a problemas de compatibilidad multiplataforma entre Windows y Mac OS X (solo Mac 10.5 admite Java 1.6, todo menos de 10.5 tiene Java 1.5 por defecto).

El objeto "sun.misc.Base64Decoder" existe en Java 6, pero no en Java 5.

Answer 1

No, no es posible sobre la base de sólo usar JDK 5.0.

Tendrá que implementar su propia implementación (no es tan difícil) o, preferiblemente, utilizar una de las implementaciones de código abierto. Hay un montón incluyendo Commons-Codec que ofrece base 64 http://commons.apache.org/codec/api-release/org/apache/commons/codec/binary/Base64.html

JavaMail también proporciona base 64 de codificación/decodificación a través MimeUtility que tampoco citó codificación imprimible etc ...

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

Answer 2

Sólo tiene que utilizar http://iharder.sourceforge.net/current/java/base64/. Está en el dominio público. De modo que puede simplemente colocar el código en su proyecto sin preocuparse por problemas de licencia ni otros tarros. La clase que estás buscando no está en JDK 1.5.

Answer 3

También hay varias implementaciones de esta página: http://www.rgagnon.com/javadetails/java-0598.html

Answer 4

Apache Commons Codec

su información, usted debe utilizar esto incluso en Java 6. Don't use classes in sun.*

Answer 5

aquí está mi versión - que debe ser completamente independiente:

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; xa<el; xa+=3) { 
     int cv; 
     int c0,c1,c2,c3; 

     if(lineLength!=0) { 
      lp+=4; 
      if(lp>lineLength) { 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<len; xa++) { 
     int ch=b64.charAt(xa+str); 
     int value=(ch<=255 ? DECODE[ch] : IGNORE); 
     if(value!=IGNORE) { 
      if(value==PAD) { 
       value=0; 
       pc++; 
       } 
      switch(dc) { 
       case 0: { 
        rv=value; 
        dc=1; 
        } break; 

       case 1: { 
        rv<<=6; 
        rv|=value; 
        dc=2; 
        } break; 

       case 2: { 
        rv<<=6; 
        rv|=value; 
        dc=3; 
        } break; 

       case 3: { 
        rv<<=6; 
        rv|=value; 

        // Completed a cycle of 4 chars, so recombine the four 6-bit values in big-endian order 
        ba[ol+2]=(byte)rv; rv>>>=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