Java - Base64 字符串进出文本
声明：本页面是StackOverFlow热门问题的中英对照翻译，遵循CC BY-SA 4.0协议，如果您需要使用它，必须同样遵循CC BY-SA许可，注明原文地址和作者信息，同时你必须将它归于原作者（不是我）：StackOverFlow
原文地址: http://stackoverflow.com/questions/1802553/
Warning: these are provided under cc-by-sa 4.0 license. You are free to use/share it, But you must attribute it to the original authors (not me):
StackOverFlow
提示：将鼠标放在中文语句上可以显示对应的英文。显示中英文
时间：2020-08-12 22:48:11 来源:igfitidea点击:
Java - Base64 string in and out of a text
提问by rover12
I need to write string containing base64 encoded text to a text file and then later read that string back from the text file to a string variable.
我需要将包含 base64 编码文本的字符串写入文本文件，然后将该字符串从文本文件读回字符串变量。
How can i do it so that there is no data loss due to encoding issues?
我该怎么做才能不因编码问题而丢失数据？
采纳答案by Thomas Jung
Base64is only A–Z, a–z, 0–9, + and /. So there should be no encoding problem. As long as you're able to encode Ascii properly. Base64 was invented to represent bytes in 7-bit characters.
Base64只是 A–Z、a–z、0–9、+ 和 /。所以应该没有编码问题。只要您能够正确编码 Ascii。Base64 被发明来用7 位字符来表示字节。
To encode and decode you can use commons codec Base64.
要编码和解码，您可以使用公共编解码器 Base64。
回答by Sajad Bahmani
Base64 Encoder :
Base64 编码器：
// Sample program to encode a binary file into a Base64 text file.
// Author: Christian d'Heureuse (www.source-code.biz)
import java.io.BufferedInputStream;
import java.io.BufferedWriter;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.InputStream;
import java.io.IOException;
public class Base64FileEncoder {
public static void main (String args[]) throws IOException {
if (args.length != 2) {
System.out.println ("Command line parameters: inputFileName outputFileName");
System.exit (9);
}
encodeFile (args[0], args[1]);
}
private static void encodeFile (String inputFileName, String outputFileName) throws IOException {
BufferedInputStream in = null;
BufferedWriter out = null;
try {
in = new BufferedInputStream(new FileInputStream(inputFileName));
out = new BufferedWriter(new FileWriter(outputFileName));
encodeStream (in, out);
out.flush();
} finally {
if (in != null) in.close();
if (out != null) out.close();
}
}
private static void encodeStream (InputStream in, BufferedWriter out) throws IOException {
int lineLength = 72;
byte[] buf = new byte[lineLength/4*3];
while (true) {
int len = in.read(buf);
if (len <= 0) break;
out.write (Base64Coder.encode(buf, len));
out.newLine();
}
}
} // end class Base64FileEncoder
Base64 Decoder :
Base64 解码器：
// Sample program to decode a Base64 text file into a binary file.
// Author: Christian d'Heureuse (www.source-code.biz)
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileOutputStream;
import java.io.FileReader;
import java.io.IOException;
import java.io.OutputStream;
public class Base64FileDecoder {
public static void main (String args[]) throws IOException {
if (args.length != 2) {
System.out.println ("Command line parameters: inputFileName outputFileName");
System.exit (9);
}
decodeFile (args[0], args[1]);
}
private static void decodeFile (String inputFileName, String outputFileName) throws IOException {
BufferedReader in = null;
BufferedOutputStream out = null;
try {
in = new BufferedReader(new FileReader(inputFileName));
out = new BufferedOutputStream(new FileOutputStream(outputFileName));
decodeStream (in, out);
out.flush();
} finally {
if (in != null) in.close();
if (out != null) out.close();
}
}
private static void decodeStream (BufferedReader in, OutputStream out) throws IOException {
while (true) {
String s = in.readLine();
if (s == null) break;
byte[] buf = Base64Coder.decode(s);
out.write (buf);
}
}
} // end class Base64FileDecoder
Test Base64 Coder :
测试 Base64 编码器：
// Test program for the Base64Coder class.
public class TestBase64Coder {
public static void main (String args[]) throws Exception {
System.out.println ("TestBase64Coder started");
test1();
test2();
System.out.println ("TestBase64Coder completed");
}
// Test Base64Coder with constant strings.
private static void test1() {
System.out.println ("test1 started");
check ("Aladdin:open sesame", "QWxhZGRpbjpvcGVuIHNlc2FtZQ=="); // example from RFC 2617
check ("", "");
check ("1", "MQ==");
check ("22", "MjI=");
check ("333", "MzMz");
check ("4444", "NDQ0NA==");
check ("55555", "NTU1NTU=");
check ("abc:def", "YWJjOmRlZg==");
System.out.println ("test1 completed");
}
private static void check (String plainText, String base64Text) {
String s1 = Base64Coder.encodeString(plainText);
String s2 = Base64Coder.decodeString(base64Text);
if (!s1.equals(base64Text) || !s2.equals(plainText))
System.out.println ("check failed for \""+plainText+"\" / \""+base64Text+"\".");
}
// Test Base64Coder against sun.misc.BASE64Encoder/Decoder with
// random strings.
private static void test2() throws Exception {
System.out.println ("test2 started");
sun.misc.BASE64Encoder enc = new sun.misc.BASE64Encoder();
sun.misc.BASE64Decoder dec = new sun.misc.BASE64Decoder();
java.util.Random rnd = new java.util.Random(0x538afb92);
for (int i = 0; i < 50000; i++) {
int len = rnd.nextInt(55);
byte[] b0 = new byte[len];
rnd.nextBytes(b0);
String e1 = new String(Base64Coder.encode(b0));
String e2 = enc.encode(b0);
if (!e1.equals(e2))
System.out.println ("Error\ne1=" + e1 + " len=" + e1.length() + "\ne2=" + e2 + " len=" + e2.length());
byte[] b1 = Base64Coder.decode(e1);
byte[] b2 = dec.decodeBuffer(e2);
if (!compareByteArrays(b1, b0) || !compareByteArrays(b2, b0))
System.out.println ("Decoded data not equal. len1=" + b1.length + " len2=" + b2.length);
}
System.out.println ("test2 completed");
}
// Compares two byte arrays.
private static boolean compareByteArrays (byte[] a1, byte[] a2) {
if (a1.length != a2.length) return false;
for (int p = 0; p < a1.length; p++)
if (a1[p] != a2[p]) return false;
return true;
}
} // end class TestBase64Coder
回答by James B
There is a sun class that will do it for you (although it will generate compiler warnings:
有一个 sun 类可以为您完成（尽管它会生成编译器警告：
import sun.misc.BASE64Encoder;
BASE64Encoder encoder = new BASE64Encoder();
String toEncode = "encodeMe";
String encoded = encodeBuffer(toEncode.getBytes());
From memory, there's also a BASE64Decoder, but I've not used that, I only go one way for comparison of usernames over-the-wire.
从记忆中，还有一个 BASE64Decoder，但我没有使用过它，我只采用一种方法来在线比较用户名。
回答by Atyab
Here is a Simple Code which will Encode and Decode:
这是一个简单的代码，它将编码和解码：
Steps of Encoding
编码步骤
- Encode Bytes
- Convert Encoded Bytes to Hex String
- 编码字节
- 将编码字节转换为十六进制字符串
Steps of Decoding
解码步骤
- Convert Hex String to Encoded Bytes
- Decode Bytes
- Convert Decoded Bytes to Hex String
Convert Hex String to ASCII Character String (Normal String)
// Encoding Bytes byte[] b64ENC = Base64.encode("Hello World".getBytes("UTF-8")); String ENCStr = getHexString(b64ENC,b64ENC.length); T1.setText(ENCStr); //-- for output // Decoding Bytes byte[] DECBarray = hexStringToByteArray(ENCStr); byte[] b64DEC = Base64.decode(DECBarray); // Displaying Decoded Byte Array by Converting it To String try { String ResDec = new String(b64DEC,"UTF-8"); T2.setText(ResDec); //This Displays Hello World :) } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } // Following are the functions that I used above ! public String getHexString(byte[] b, int length) { // TODO Auto-generated method stub String result = ""; for (int i = 0; i < length; i++) { result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring(1); } return result; } public static String bytesToHex(byte[] data) { StringBuffer buf = new StringBuffer(); for (int i = 0; i < data.length; i++) { buf.append(byteToHex(data[i])); buf.append(" "); } return (buf.toString()); } public static String byteToHex(byte data) { StringBuffer buf = new StringBuffer(); buf.append(toHexChar((data >>> 4) & 0x0F)); buf.append(toHexChar(data & 0x0F)); return buf.toString(); } public static char toHexChar(int i) { if ((0 <= i) && (i <= 9)) { return (char) ('0' + i); } else { return (char) ('a' + (i - 10)); } } public static byte[] hexStringToByteArray(String s) { int len = s.length(); byte[] data = new byte[len / 2]; for (int i = 0; i < len; i += 2) { data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16)); } return data; }
- 将十六进制字符串转换为编码字节
- 解码字节
- 将解码字节转换为十六进制字符串
将十六进制字符串转换为 ASCII 字符串（普通字符串）
// Encoding Bytes byte[] b64ENC = Base64.encode("Hello World".getBytes("UTF-8")); String ENCStr = getHexString(b64ENC,b64ENC.length); T1.setText(ENCStr); //-- for output // Decoding Bytes byte[] DECBarray = hexStringToByteArray(ENCStr); byte[] b64DEC = Base64.decode(DECBarray); // Displaying Decoded Byte Array by Converting it To String try { String ResDec = new String(b64DEC,"UTF-8"); T2.setText(ResDec); //This Displays Hello World :) } catch (UnsupportedEncodingException e) { // TODO Auto-generated catch block e.printStackTrace(); } // Following are the functions that I used above ! public String getHexString(byte[] b, int length) { // TODO Auto-generated method stub String result = ""; for (int i = 0; i < length; i++) { result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring(1); } return result; } public static String bytesToHex(byte[] data) { StringBuffer buf = new StringBuffer(); for (int i = 0; i < data.length; i++) { buf.append(byteToHex(data[i])); buf.append(" "); } return (buf.toString()); } public static String byteToHex(byte data) { StringBuffer buf = new StringBuffer(); buf.append(toHexChar((data >>> 4) & 0x0F)); buf.append(toHexChar(data & 0x0F)); return buf.toString(); } public static char toHexChar(int i) { if ((0 <= i) && (i <= 9)) { return (char) ('0' + i); } else { return (char) ('a' + (i - 10)); } } public static byte[] hexStringToByteArray(String s) { int len = s.length(); byte[] data = new byte[len / 2]; for (int i = 0; i < len; i += 2) { data[i / 2] = (byte) ((Character.digit(s.charAt(i), 16) << 4) + Character.digit(s.charAt(i+1), 16)); } return data; }
