在java中如何对base64字符串进行解码，请指教！

com.sun.mail.* 下面有解码方法
或者 java mail 里有 encode decode

这是我以前写的一个BASE64方面的编码和解码的类，希望对你有点HELPpublic class BASE64
{
 public BASE64()
 {
 }
 public static void main(String arg[])
 {
 String aa="abc";
 sun.misc.BASE64Encoder encoder = new sun.misc.BASE64Encoder ();
 sun.misc.BASE64Decoder decoder = new sun.misc.BASE64Decoder ();
 String encode222222;
 encode222222=encoder.encode(aa.getBytes());
 System.out.println("将 “"+aa+"” 通过Base64编码后的字符是星号中间的内容****"+encode222222+"****");
 try
 {
 int length=decoder.decodeBuffer(encode222222).length;
 System.out.println(length);
 byte[] xxx=decoder.decodeBuffer(encode222222);
 for (int i=0;i<aa.length();i++)
 System.out.println((int)aa.charAt(i));
 for (int i=0;i<length;i++)
 {
 String dddd=new String(xxx);
 System.out.println(dddd);
 System.out.println(xxx[i]);
 Byte bb=null;
 System.out.println(bb.toString(xxx[i]));
 System.out.println("zuihou"+bb.toString(xxx[length-1]));
 System.out.println(i);
 }
 }
 catch(Exception e)
 { }
 //String aa2=decoder();
 }
}
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以前写的一段代码，希望有用package cong.base64;import sun.misc.*;public class Base64{
 public static void main(String[] args){
 if(args.length==0){
 new Base64Form().show();
 }else if(args.length==2){
 make(args);
 }else{
 usage();
 }
 }
 private static void usage(){
 System.out.println("usage: ");
 System.out.println(" \t java cong.base64.Base64 [<-g|-d> <string>]") ;
 }
 private static void make(String[] args){
 if(args[0].equals("-g")){
 System.out.println("after encode is " + Utils.encode(args[1]));
 }else if(args[0].equals("-d")){
 System.out.println("before encode is " + Utils.decode(args[1]));
 }else{
 usage();
 }
 }
}
class Utils{
 public static String encode(String arg){
 BASE64Encoder en = new BASE64Encoder();
 return en.encode(arg.getBytes());
 }
 public static String decode(String arg){
 BASE64Decoder de = new BASE64Decoder();
 try{
 byte[] b= de.decodeBuffer(arg);
 for(int i=0;i<b.length; i++){
 System.out.print(Integer.toHexString(b[i]));
 }

 return new String(b);
 }catch(Exception e){
 return e.toString();
 }
 }
}

直接使用sun.misc.BASE64Encoder / sun.misc.BASE64Decoder 类即可实现编码与解码。或者用第三方提供的工具。可以参考 http://www.sharetop.com 中《webservice初步体验：图像传输》

请问sun.misc.BASE64Decoder这个类包在哪里可以下载到

来自Oreilly
1、Encoder
// Copyright (C) 1999-2001 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved. Use of this class is limited.
// Please see the LICENSE for more information.package com.oreilly.servlet;import java.io.*;/**
* A class to encode Base64 streams and strings.
* See RFC 1521 section 5.2 for details of the Base64 algorithm.
* 
* This class can be used for encoding strings:
* <blockquote><pre>
* String unencoded = "webmaster:try2gueSS";
* String encoded = Base64Encoder.encode(unencoded);
* </pre></blockquote>
* or for encoding streams:
* <blockquote><pre>
* OutputStream out = new Base64Encoder(System.out);
* </pre></blockquote>
*
* @author Jason Hunter, Copyright © 2000
* @version 1.1, 2000/11/17, fixed bug with sign bit for char values
* @version 1.0, 2000/06/11
*/
public class Base64Encoder extends FilterOutputStream { private static final char[] chars = {
 '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', '+', '/'
 }; private int charCount;
 private int carryOver; /**
 * Constructs a new Base64 encoder that writes output to the given
 * OutputStream.
 *
 * @param out the output stream
 */
 public Base64Encoder(OutputStream out) {
 super(out);
 } /**
 * Writes the given byte to the output stream in an encoded form.
 *
 * @exception IOException if an I/O error occurs
 */
 public void write(int b) throws IOException {
 // Take 24-bits from three octets, translate into four encoded chars
 // Break lines at 76 chars
 // If necessary, pad with 0 bits on the right at the end
 // Use = signs as padding at the end to ensure encodedLength % 4 == 0 // Remove the sign bit,
 // thanks to Christian Schweingruber <[email protected]>
 if (b < 0) {
 b += 256;
 } // First byte use first six bits, save last two bits
 if (charCount % 3 == 0) {
 int lookup = b >> 2;
 carryOver = b & 3; // last two bits
 out.write(chars[lookup]);
 }
 // Second byte use previous two bits and first four new bits,
 // save last four bits
 else if (charCount % 3 == 1) {
 int lookup = ((carryOver << 4) + (b >> 4)) & 63;
 carryOver = b & 15; // last four bits
 out.write(chars[lookup]);
 }
 // Third byte use previous four bits and first two new bits,
 // then use last six new bits
 else if (charCount % 3 == 2) {
 int lookup = ((carryOver << 2) + (b >> 6)) & 63;
 out.write(chars[lookup]);
 lookup = b & 63; // last six bits
 out.write(chars[lookup]);
 carryOver = 0;
 }
 charCount++; // Add newline every 76 output chars (that's 57 input chars)
 if (charCount % 57 == 0) {
 out.write('\n');
 }
 } /**
 * Writes the given byte array to the output stream in an
 * encoded form.
 *
 * @param b the data to be written
 * @param off the start offset of the data
 * @param len the length of the data
 * @exception IOException if an I/O error occurs
 */
 public void write(byte[] b, int off, int len) throws IOException {
 // This could of course be optimized
 for (int i = 0; i < len; i++) {
 write(b[off + i]);
 }
 } /**
 * Closes the stream, this MUST be called to ensure proper padding is
 * written to the end of the output stream.
 *
 * @exception IOException if an I/O error occurs
 */
 public void close() throws IOException {
 // Handle leftover bytes
 if (charCount % 3 == 1) { // one leftover
 int lookup = (carryOver << 4) & 63;
 out.write(chars[lookup]);
 out.write('=');
 out.write('=');
 }
 else if (charCount % 3 == 2) { // two leftovers
 int lookup = (carryOver << 2) & 63;
 out.write(chars[lookup]);
 out.write('=');
 }
 super.close();
 } /**
 * Returns the encoded form of the given unencoded string.
 *
 * @param unencoded the string to encode
 * @return the encoded form of the unencoded string
 */
 public static String encode(String unencoded) {
 ByteArrayOutputStream out =
 new ByteArrayOutputStream((int) (unencoded.length() * 1.37));
 Base64Encoder encodedOut = new Base64Encoder(out);

 byte[] bytes = null;
 try {
 bytes = unencoded.getBytes("8859_1");
 }
 catch (UnsupportedEncodingException ignored) { } try {
 encodedOut.write(bytes);
 encodedOut.close(); return out.toString("8859_1");
 }
 catch (IOException ignored) { return null; }
 } public static void main(String[] args) throws Exception {
 if (args.length != 1) {
 System.err.println(
 "Usage: java com.oreilly.servlet.Base64Encoder fileToEncode");
 } Base64Encoder encoder = null;
 BufferedInputStream in = null;
 try {
 encoder = new Base64Encoder(System.out);
 in = new BufferedInputStream(new FileInputStream(args[0])); byte[] buf = new byte[4 * 1024]; // 4K buffer
 int bytesRead;
 while ((bytesRead = in.read(buf)) != -1) {
 encoder.write(buf, 0, bytesRead);
 }
 }
 finally {
 if (in != null) in.close();
 if (encoder != null) encoder.close();
 }
 }
}

2、Decoder
// Copyright (C) 1999-2001 by Jason Hunter <jhunter_AT_acm_DOT_org>.
// All rights reserved. Use of this class is limited.
// Please see the LICENSE for more information.package com.oreilly.servlet;import java.io.*;/**
* A class to decode Base64 streams and strings.
* See RFC 1521 section 5.2 for details of the Base64 algorithm.
* 
* This class can be used for decoding strings:
* <blockquote><pre>
* String encoded = "d2VibWFzdGVyOnRyeTJndWVTUw";
* String decoded = Base64Decoder.decode(encoded);
* </pre></blockquote>
* or for decoding streams:
* <blockquote><pre>
* InputStream in = new Base64Decoder(System.in);
* </pre></blockquote>
*
* @author Jason Hunter, Copyright © 2000
* @version 1.0, 2000/06/11
*/
public class Base64Decoder extends FilterInputStream { private static final char[] chars = {
 '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', '+', '/'
 }; // A mapping between char values and six-bit integers
 private static final int[] ints = new int[128];
 static {
 for (int i = 0; i < 64; i++) {
 ints[chars[i]] = i;
 }
 } private int charCount;
 private int carryOver; /**
 * Constructs a new Base64 decoder that reads input from the given
 * InputStream.
 *
 * @param in the input stream
 */
 public Base64Decoder(InputStream in) {
 super(in);
 } /**
 * Returns the next decoded character from the stream, or -1 if
 * end of stream was reached.
 *
 * @return the decoded character, or -1 if the end of the
 * input stream is reached
 * @exception IOException if an I/O error occurs
 */
 public int read() throws IOException {
 // Read the next non-whitespace character
 int x;
 do {
 x = in.read();
 if (x == -1) {
 return -1;
 }
 } while (Character.isWhitespace((char)x));
 charCount++; // The '=' sign is just padding
 if (x == '=') {
 return -1; // effective end of stream
 } // Convert from raw form to 6-bit form
 x = ints[x]; // Calculate which character we're decoding now
 int mode = (charCount - 1) % 4; // First char save all six bits, go for another
 if (mode == 0) {
 carryOver = x & 63;
 return read();
 }
 // Second char use previous six bits and first two new bits,
 // save last four bits
 else if (mode == 1) {
 int decoded = ((carryOver << 2) + (x >> 4)) & 255;
 carryOver = x & 15;
 return decoded;
 }
 // Third char use previous four bits and first four new bits,
 // save last two bits
 else if (mode == 2) {
 int decoded = ((carryOver << 4) + (x >> 2)) & 255;
 carryOver = x & 3;
 return decoded;
 }
 // Fourth char use previous two bits and all six new bits
 else if (mode == 3) {
 int decoded = ((carryOver << 6) + x) & 255;
 return decoded;
 }
 return -1; // can't actually reach this line
 } /**
 * Reads decoded data into an array of bytes and returns the actual
 * number of bytes read, or -1 if end of stream was reached.
 *
 * @param buf the buffer into which the data is read
 * @param off the start offset of the data
 * @param len the maximum number of bytes to read
 * @return the actual number of bytes read, or -1 if the end of the
 * input stream is reached
 * @exception IOException if an I/O error occurs
 */
 public int read(byte[] b, int off, int len) throws IOException {
 // This could of course be optimized
 int i;
 for (i = 0; i < len; i++) {
 int x = read();
 if (x == -1 && i == 0) { // an immediate -1 returns -1
 return -1;
 }
 else if (x == -1) { // a later -1 returns the chars read so far
 break;
 }
 b[off + i] = (byte) x;
 }
 return i;
 } /**
 * Returns the decoded form of the given encoded string.
 *
 * @param encoded the string to decode
 * @return the decoded form of the encoded string
 */
 public static String decode(String encoded) {
 byte[] bytes = null;
 try {
 bytes = encoded.getBytes("8859_1");
 }
 catch (UnsupportedEncodingException ignored) { } Base64Decoder in = new Base64Decoder(
 new ByteArrayInputStream(bytes));

 ByteArrayOutputStream out =
 new ByteArrayOutputStream((int) (bytes.length * 0.67)); try {
 byte[] buf = new byte[4 * 1024]; // 4K buffer
 int bytesRead;
 while ((bytesRead = in.read(buf)) != -1) {
 out.write(buf, 0, bytesRead);
 }
 out.close(); return out.toString("8859_1");
 }
 catch (IOException ignored) { return null; }
 } public static void main(String[] args) throws Exception {
 if (args.length != 1) {
 System.err.println("Usage: java Base64Decoder fileToDecode");
 } Base64Decoder decoder = null;
 try {
 decoder = new Base64Decoder(
 new BufferedInputStream(
 new FileInputStream(args[0])));
 byte[] buf = new byte[4 * 1024]; // 4K buffer
 int bytesRead;
 while ((bytesRead = decoder.read(buf)) != -1) {
 System.out.write(buf, 0, bytesRead);
 }
 }
 finally {
 if (decoder != null) decoder.close();
 }
 }
}

调试易

在java中如何对base64字符串进行解码，请指教！

解决方案 »