如何将以下Base64编码二进制字符串转换为java中的二进制文件。我已经看到人们使用以下代码在php中做同样的事情。如何在java中实现这一点？
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";
但是当我在java中尝试这个时：
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"
输出变化。
如何实现相同的输出？
谢谢，
答案 0 :(得分：1)
要解码base64，最简单的方法是使用Apache commons Decoder。
import org.apache.commons.codec.binary.Base64;
byte[] decodedBytes = Base64.decodeBase64(input);
你真的需要二进制作为由“0”和“1”字符组成的字符串吗？
答案 1 :(得分：0)
我希望人们推荐apache commons，但我不知道它是否便携......
你可以使用这个：
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");
它也与Sun的代码兼容......
答案 2 :(得分：0)
首先，我不相信PHP会将上面提到的字符串（000000000000000000000000000000000100000000000000）作为输出！
您问题中的代码枚举输入字符串（AAAAAEAA）中的每个字符，检索每个字符的ASCII value并将其发布到输出中。如果你执行你提到的PHP代码，你将提供与你提到的运行JAVA代码完全相同的输出（0100000101000001010000010100000101000001010001010100000101000001）。
例如，
ord("A") = 65
65又有01000001二进制表示。
其次，更正您的问题以获得正确答案。看来，伙计们，先前回答，根本不理解你的问题。
第三，如果要获取给定字符串的二进制表示，请使用getBytes()方法检索整个字符串的字节表示。使用或调整this code snippet来获取给定字节数组的二进制表示。
答案 3 :(得分：0)
Android包含自己的Base64编码器和解码器。解码Base64字符串所需的只是：
byte[] decoded = Base64.decode( string, Base64.DEFAULT );
第二个参数是一个标志。见这里：Base64