Java - Base64-String in einem und aus einem Text

Question

Ich brauche codierten Text in eine Textdatei String mit Base64 zu schreiben und dann später diese Zeichenfolge zurück aus der Textdatei in ein String-Variable lesen.

Wie kann ich es tun, so dass kein Datenverlust Probleme aufgrund der Codierung ist?

Answer 1

Base64 nur A-Z, a-z, 0-9, + und / . So soll es keine Codierung Problem sein. Solange Sie Ascii sind in der Lage richtig zu kodieren. Base64 erfunden wurde Bytes in darzustellen 7-Bit-Zeichen .

Um zu kodieren und dekodieren Sie commons verwenden können Codec Base64 .

Answer 2

Base64 Encoder:

// 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:

// 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:

// 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

Answer 3

Dies ist ein einfacher Code, der wird Codierung und Decodierung:

Schritte von Encoding

1. Encode Bytes
2. Konvertieren Verschlüsselte Bytes String Hex

Schritte der Decodierung

1. Convert Hex String Encoded Bytes
2. Decode Bytes
3. Konvertieren Decoded Bytes zu Hex String

4. Convert Hex String in ASCII-Zeichenkette (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;
   }
   

Answer 4

Es gibt eine Sonnen Klasse, die es für Sie tun (obwohl es Compiler-Warnungen generieren:

import sun.misc.BASE64Encoder;

BASE64Encoder encoder = new BASE64Encoder();

String toEncode = "encodeMe";

String encoded = encodeBuffer(toEncode.getBytes());

Aus dem Gedächtnis, gibt es auch eine Base64Decoder, aber ich habe nicht verwendet, dass ich einen Weg gehe nur zum Vergleich von Benutzername over-the-wire.