用Java解码Base64网址

Question

How can I decode Base64 url in Java?

I tried found smt into javadoc but couldn't find solution.
Do I need install any external -jars for this aim?

Snippet of code:

public static void main(String []args){
    String url = "aHR0cDovL05jLmtwaS51YS9hdXR1bW4yMDEz";

    String decodedUrl = Base64.decode(url);     

    System.out.println( decodedUrl );
    return;
}

How to decode this url?

Answer 1

不需要外部jar，请使用Java SE javax.xml.bind.DatatypeConverter.parseBase64Binary(String lexicalXSDBase64Binary)

Answer 2

You do not need any third party library see the below class I have written to encode and decode in Base64. Your URL is http://Nc.kpi.ua/autumn2013

public class Decode {
 private static 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 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 with the Base64 encoded data.
     */
    public static String encodeString(String s) {
        return new String(encode(s.getBytes()));
    }

    /**
     * Encodes a byte array into Base64 format. No blanks or line breaks are
     * inserted.
     *
     * @param in an array containing the data bytes to be encoded.
     * @return A character array with the Base64 encoded data.
     */
    public static char[] encode(byte[] in) {
        return encode(in, in.length);
    }

    /**
     * Encodes a byte array into Base64 format. No blanks or line breaks are
     * inserted.
     *
     * @param in an array containing the data bytes to be encoded.
     * @param iLen number of bytes to process in <code>in</code>.
     * @return A character array with the Base64 encoded data.
     */
    public static char[] encode(byte[] in, 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 = 0;
        int op = 0;
        while (ip < iLen) {
            int i0 = in[ip++] & 0xff;
            int i1 = ip < iLen ? in[ip++] & 0xff : 0;
            int i2 = ip < iLen ? 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.
     *
     * @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.
     *
     * @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 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) {
        int iLen = in.length;
        if (iLen % 4 != 0) {
            throw new IllegalArgumentException("Length of Base64 encoded input string is not a multiple of 4.");
        }
        while (iLen > 0 && in[iLen - 1] == '=') {
            iLen--;
        }
        int oLen = (iLen * 3) / 4;
        byte[] out = new byte[oLen];
        int ip = 0;
        int op = 0;
        while (ip < iLen) {
            int i0 = in[ip++];
            int i1 = in[ip++];
            int i2 = ip < iLen ? in[ip++] : 'A';
            int i3 = ip < iLen ? 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.
    public Decode() {
    }
    /**
     * @param args the command line arguments
     */
    public static void main(String[] args) {
        String test = "aHR0cDovL05jLmtwaS51YS9hdXR1bW4yMDEz";
      System.out.println(Decode.decodeString(test));
    }
}

You can use this both to Encode and decode. Hope this Helps.

Answer 3

Java-8 provides java.util.Base64 class for Base64 encodings. It supports URL encoding/decoding by its static getUrlEncoder() and getUrlDecoder() methods.

Answer 4

You can use org.apache.commons.codec.binary.Base64 package available in Java for the same.

Sample code(not tested though) :

Base64 decoder = new Base64();
String url = "aHR0cDovL05jLmtwaS51YS9hdXR1bW4yMDEz";
byte[] decoded = Base64.decodeBase64(url);
System.out.println(new String(decoded, "UTF-8") + "\n");

Answer 5

Apache Commons-Codec has a base64 decoder

http://commons.apache.org/proper/commons-codec/apidocs/org/apache/commons/codec/binary/Base64.html

Answer 6

I use org.apache.ws.commons.util.Base64 and simply do:

String encoded = Base64.encode( "whatever" );
byte[] decoded = Base64.decode( encoded );