我有一个Base64编码的图像。Java中最好的解码方法是什么?希望只使用Sun Java 6中包含的库。
当前回答
从Java 8开始,就有了官方支持的用于Base64编码和解码的API。 随着时间的推移,这可能会成为默认的选择。
该API包括java.util类。Base64及其嵌套类。它支持三种不同的风格:基本的、URL安全的和MIME。
使用“基本”编码的示例代码:
import java.util.Base64;
byte[] bytes = "Hello, World!".getBytes("UTF-8");
String encoded = Base64.getEncoder().encodeToString(bytes);
byte[] decoded = Base64.getDecoder().decode(encoded);
String decodedStr = new String(decoded, StandardCharsets.UTF_8);
java.util的文档。Base64还包括一些配置编码器和解码器的方法,以及使用不同的类作为输入和输出(字节数组,字符串,ByteBuffers, java。io流)。
其他回答
不需要使用commons——Sun在Java中附带了base64编码器。你可以这样导入它:
import sun.misc.BASE64Decoder;
然后像这样使用它:
BASE64Decoder decoder = new BASE64Decoder();
byte[] decodedBytes = decoder.decodeBuffer(encodedBytes);
其中encodedBytes是java.lang.String或java.io.InputStream。只是要当心太阳。*类不是Sun的“官方支持”。
编辑:谁能想到这将是我发表过的最具争议的答案呢?我知道太阳。*不支持或保证软件包继续存在,我确实了解Commons并一直在使用它。然而,发帖者要求一个“包含在Sun Java 6中”的类,这就是我试图回答的问题。总的来说,我同意Commons是最好的方式。
编辑2:正如amir75在下面指出的那样,Java 6+附带了JAXB,其中包含支持的编码/解码Base64的代码。请看下面Jeremy Ross的回答。
这是我自己的实现,如果它对某人有用的话:
public class Base64Coder {
// The line separator string of the operating system.
private static final String systemLineSeparator = System.getProperty("line.separator");
// 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; }
/**
* 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())); }
/**
* 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 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; }
/**
* 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)); }
/**
* 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 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.
* 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; }
// Dummy constructor.
private Base64Coder() {}
}
如果你喜欢基于性能的解决方案,那么你可以使用“MiGBase64”
http://migbase64.sourceforge.net/
public class Base64Test {
public static void main(String[] args) {
String encodeToString = Base64.encodeToString("JavaTips.net".getBytes(), true);
System.out.println("encodeToString " + encodeToString);
byte[] decodedBytes = Base64.decode(encodeToString.getBytes());
System.out.println("decodedBytes " + new String(decodedBytes));
}
}
使用java8 -
public static String encodeString(String plainString) {
return Base64.getEncoder().encodeToString(plainString.getBytes());
}
public static String decodeString(String encodedString) {
byte[] bytes = Base64.getDecoder().decode(encodedString);
return new String(bytes);
}
作为sun.misc的替代品。BASE64Decoder或非核心库,请查看javax.mail.internet.MimeUtility.decode()。
public static byte[] encode(byte[] b) throws Exception {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
OutputStream b64os = MimeUtility.encode(baos, "base64");
b64os.write(b);
b64os.close();
return baos.toByteArray();
}
public static byte[] decode(byte[] b) throws Exception {
ByteArrayInputStream bais = new ByteArrayInputStream(b);
InputStream b64is = MimeUtility.decode(bais, "base64");
byte[] tmp = new byte[b.length];
int n = b64is.read(tmp);
byte[] res = new byte[n];
System.arraycopy(tmp, 0, res, 0, n);
return res;
}
链接与完整的代码:编码/解码到/从Base64
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