我正在尝试将字符串从base64解码为UTF-8以进行分配。
暂时没有编程Java我可能没有使用最有效的方法，但是我设法实现了99％正确工作的函数。
解码以Base64的例子字符串：的 VGhpcyBpcyBhbiBBcnhhbiBzYW1wbGUgc3RyaW5nIHRoYXQgc2hvdWxkIGJlIGVhc2lseSBkZWNvZGVkIGZyb20gYmFzZTY0LiAgSXQgaW5jbHVkZXMgYSBudW1iZXIgb2YgVVRGOCBjaGFyYWN0ZXJzIHN1Y2ggYXMgdGhlIPEsIOksIOgsIOcgYW5kICYjOTYwOyBjaGFyYWN0ZXJzLg ==
结果： 这是一个Arxan示例字符串，应该可以从base64轻松解码。它包含许多UTF8字符，例如ñ，é，è，ç和＆＃960字符。
然而，在＆amp;＃960的位置应该是输出的π符号。
请注意我删除了;在这里看到＃960后，Stackoverflow似乎自动将其修正为π
我尝试过很多东西，例如创建一个字节数组并打印它，但仍然没有工作。
我正在使用Eclipse，可能只是那里的输出显示不正确吗？
有人建议让这个工作吗？
谢谢， 文森特
这是我的代码：
package base64;
import java.nio.ByteBuffer;
import java.nio.charset.Charset;
public class Base64 {
public static void main(String[] args) {
//Input strings
String base64 = "VGhpcyBpcyBhbiBBcnhhbiBzYW1wbGUgc3RyaW5nIHRoYXQgc2hvdWxkIGJlIGVhc2lseSBkZWNvZGVkIGZyb20gYmFzZTY0LiAgSXQgaW5jbHVkZXMgYSBudW1iZXIgb2YgVVRGOCBjaGFyYWN0ZXJzIHN1Y2ggYXMgdGhlIPEsIOksIOgsIOcgYW5kICYjOTYwOyBjaGFyYWN0ZXJzLg==";
//String base64 = "YW55IGNhcm5hbCBwbGVhc3U=";
String utf8 = "any carnal pleas";
//Base64 to UTF8
System.out.println("Base64 conversion to UTF8");
System.out.println("-------------------------");
System.out.println("Input base64-string: " + base64);
System.out.println("Output UTF8-string: " + stringFromBase64(base64));
System.out.println();
//UTF8 to Base64
System.out.println("UTF8 conversion to base64");
System.out.println("-------------------------");
System.out.println("Input UTF8-string: " + utf8);
System.out.println("Output base64-string: " + stringToBase64(utf8));
System.out.println();
System.out.println("Pi is π");
}
public static String stringFromBase64(String base64) {
StringBuilder binary = new StringBuilder();
int countPadding = countPadding(base64); //count number of padding symbols in source string
//System.out.println("No of *=* in the input is : " + countPadding);
//System.out.println(base64);
for(int i=0; i<(base64.length()-countPadding); i++)
{
int base64Value = fromBase64(String.valueOf(base64.charAt(i))); //convert Base64 character to Int
String base64Binary = Integer.toBinaryString(base64Value); //convert Int to Binary string
StringBuilder base64BinaryCopy = new StringBuilder(); //debugging
if (base64Binary.length()<6) //adds required zeros to make 6 bit string
{
for (int j=base64Binary.length();j<6;j++){
binary.append("0");
base64BinaryCopy.append("0"); //debugging
}
base64BinaryCopy.append(base64Binary); // debugging
} else // debugging
{
base64BinaryCopy.append(base64Binary); //debugging
} // debugging
//System.out.println(base64.charAt(i) + " = " + base64Value + " = " + base64BinaryCopy); //debugging
binary.append(base64Binary);
}
//System.out.println(binary);
//System.out.println(binary.length());
StringBuilder utf8String = new StringBuilder();
for (int bytenum=0;bytenum<(binary.length()/8);bytenum++) //parse string Byte-by-Byte
{
StringBuilder utf8Bit = new StringBuilder();
for (int bitnum=0;bitnum<8;bitnum++){
utf8Bit.append(binary.charAt(bitnum+(bytenum*8)));
}
char utf8Char = (char) Integer.parseInt(utf8Bit.toString(), 2); //Byte to utf8 char
utf8String.append(String.valueOf(utf8Char)); //utf8 char to string and append to final utf8-string
//System.out.println(utf8Bit + " = " + Integer.parseInt(utf8Bit.toString(), 2) + " = " + utf8Char + " = " + utf8String); //debugging
}
return utf8String.toString();
}
public static String stringToBase64(String utf8) {
StringBuilder binary = new StringBuilder();
String paddingString = "";
String paddingSymbols = "";
for(int i=0; i<(utf8.length()); i++)
{
int utf8Value = utf8.charAt(i); //convert utf8 character to Int
String utf8Binary = Integer.toBinaryString(utf8Value); //convert Int to Binary string
StringBuilder utf8BinaryCopy = new StringBuilder(); //debugging
if (utf8Binary.length()<8) //adds required zeros to make 8 bit string
{
for (int j=utf8Binary.length();j<8;j++){
binary.append("0");
utf8BinaryCopy.append("0"); //debugging
}
utf8BinaryCopy.append(utf8Binary); // debugging
} else // debugging
{
utf8BinaryCopy.append(utf8Binary); //debugging
} // debugging
//System.out.println(utf8.charAt(i) + " = " + utf8Value + " = " + utf8BinaryCopy);
binary.append(utf8Binary);
}
if ((binary.length() % 6) == 2) {
paddingString = "0000"; //add 4 padding zeroes
paddingSymbols = "==";
} else if ((binary.length() % 6) == 4) {
paddingString = "00"; //add 2 padding zeroes
paddingSymbols = "=";
}
binary.append(paddingString); //add padding zeroes
//System.out.println(binary);
//System.out.println(binary.length());
StringBuilder base64String = new StringBuilder();
for (int bytenum=0;bytenum<(binary.length()/6);bytenum++) //parse string Byte-by-Byte per 6 bits
{
StringBuilder base64Bit = new StringBuilder();
for (int bitnum=0;bitnum<6;bitnum++){
base64Bit.append(binary.charAt(bitnum+(bytenum*6)));
}
int base64Int = Integer.parseInt(base64Bit.toString(), 2); //Byte to Int
char base64Char = toBase64(base64Int); //Int to Base64 char
base64String.append(String.valueOf(base64Char)); //base64 char to string and append to final Base64-string
//System.out.println(base64Bit + " = " + base64Int + " = " + base64Char + " = " + base64String); //debugging
}
base64String.append(paddingSymbols); //add padding ==
return base64String.toString();
}
public static char toBase64(int a) { //converts integer to corresponding base64 char
String charBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
//charBase64 = new char[]{'A','B','C','D','E','F','G','H','I','J','K','L','M','N'};
return charBase64.charAt(a);
}
public static int fromBase64(String x) { //converts base64 string to corresponding integer
String charBase64 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
return charBase64.indexOf(x);
}
public static int countPadding(String countPadding) { //counts the number of padding symbols in base64 input string
int index = countPadding.indexOf("=");
int count = 0;
while (index != -1) {
count++;
countPadding = countPadding.substring(index + 1);
index = countPadding.indexOf("=");
}
return count;
}
}
答案 0 :(得分：1)
UTF8是一种字符编码，可将给定的char转换为1,2或更多字节。您的代码假定每个字节都应转换为字符。这适用于ASCII字符，例如a，b，c，它们确实被UTF8转换为单个字节，但它不适用于像PI这样转换为多字节序列的字符。
你的算法非常低效，我只是抛弃它并使用现成的ecnoder /解码器。 JDK 8 comes with one。 Guava和commons-codec也可以。您的代码应该像
一样简单String base64EncodedByteArray = "....";
byte[] decodedByteArray = decoder.decode(base64EncodedByteArray);
String asString = new String(decodedByteArray, StandardCharSets.UTF_8);
或者，对于另一个方向：
String someString = "VGhpcyBpcyBhb...";
byte[] asByteArray = someString.getBytes(StandardCharSets.UTF_8);
String base64EncodedByteArray = encoder.encode(asBytArray);