如何在java中將Base64編碼二進制字符串轉換為二進制？

Question

如何將以下Base64編碼二進制字符串轉換為java中的二進制文件。 我已經看到人們使用以下代碼在php中做同樣的事情。 如何在java中實現這一點？

在PHP中：

$byteArr = "AAAAAEAA";
$maparray = array();
$map = "";
foreach(str_split($byteArr) as $c)
    $maparray [] = sprintf("%08b", ord($c));
$map = implode("", $maparray );

Output is $map -> "000000000000000000000000000000000100000000000000";

但是當我在java中嘗試這個時：

String input = "AAAAAEAA";
String mapArray = "";
for(int b=0;b<input.length();b++){
   int asciValueOfChar =(int)toByte.charAt(b);
   String binaryInt = Integer.toBinaryString(asciValueOfChar);
   String paddedBinaryInt = String.format("%8s", binaryInt);
   paddedBinaryInt = paddedBinaryInt.replace(' ', '0');
   System.out.println("ASCII Code::"+asciValueOfChar);
   System.out.println("Binary of Char::"+binaryInt);
   System.out.println("Binary of Padded Char::"+binaryInt);
   mapArray = mapArray + paddedBinaryInt ;
}
System.out.println("Binary Array::"+mapArray);

Output is mapArray -> "0100000101000001010000010100000101000001010001010100000101000001"

輸出變化。

我怎樣才能實現相同的輸出？

謝謝，

Answer 1

要解碼base64，最簡單的方法是使用Apache commons Decoder 。

import org.apache.commons.codec.binary.Base64;

byte[] decodedBytes = Base64.decodeBase64(input);

你真的需要二進制作為由“0”和“1”字符組成的字符串嗎？

Answer 2

我希望人們推薦apache commons，但我不知道它是否可移植......

你可以用這個：

public class Base64Coder
{

// 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;
}
// The line separator string of the operating system.
private static final String systemLineSeparator = System.getProperty("line.separator");


/**
 * 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 <code>in</code> to be
 *            processed.
 * @param iLen
 *            Number of characters to process in <code>in</code>, starting
 *            at <code>iOff</code>.
 * @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;
}

/**
 * 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 and ignores line separators, tabs
 * and blanks. CR, LF, Tab and Space characters are ignored in the input
 * data. This method is compatible with
 * <code>sun.misc.BASE64Decoder.decodeBuffer(String)</code>.
 * 
 * @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 != '\r' && c != '\n' && c != '\t') buf[p++] = c;
    }
    return decode(buf, 0, p);
}

/**
 * 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));
}

/**
 * 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 <code>in</code>.
 * @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 <code>in</code> to be processed.
 * @param iLen
 *            Number of bytes to process in <code>in</code>, starting at
 *            <code>iOff</code>.
 * @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;
}

/**
 * Encodes a byte array into Base 64 format and breaks the output into lines
 * of 76 characters. This method is compatible with
 * <code>sun.misc.BASE64Encoder.encodeBuffer(byte[])</code>.
 * 
 * @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 <code>in</code> to be processed.
 * @param iLen
 *            Number of bytes to be processed in <code>in</code>, starting
 *            at <code>iOff</code>.
 * @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 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()));
}

// Dummy constructor.
private Base64Coder()
{
}
}

用法：

String message = "blahblah";
byte[] encoded = Base64Coder.encode(message.getBytes("UTF-8"));
byte[] decoded = Base64Coder.decode(encoded);
String msg2 = new String(decoded, "UTF-8");
if(message.equals(msg2)) System.out.println("yaay");

它也與Sun的代碼兼容......

Answer 3

首先，我不相信PHP會給你上面提到的字符串（ 000000000000000000000000000000000100000000000000 ）作為輸出！

您的問題中的代碼枚舉輸入字符串（ AAAAAEAA ）中的每個字符，檢索每個字符的ASCII值並將其發布到輸出中。 如果你執行你提到的PHP代碼，你將給出與你提到的運行JAVA代碼完全相同的輸出（ 0100000101000001010000010100000101000001010001010100000101000001 ）。

例如，

ord("A") = 65

65依次具有01000001二進制表示。

其次，糾正您的問題以獲得正確的答案。 看來，伙計們，先前回答，根本不理解你的問題。

第三，如果要獲取給定字符串的二進制表示，請使用getBytes（）方法檢索整個字符串的字節表示。 使用或調整此代碼段以獲取給定字節數組的二進制表示。

Answer 4

Android包含自己的Base64編碼器和解碼器。 解碼Base64字符串所需的全部內容如下：

byte[] decoded = Base64.decode( string, Base64.DEFAULT );

第二個參數是一個標志。 見這里： Base64