Base64编码和解码java版本资源-CSDN下载

共5个文件

xml：2个

class：1个

java：1个

base64

java

需积分: 9 20 浏览量 2008-11-11 10:32:05 上传评论收藏 5KB ZIP 举报

Base64是一种在网络上传输二进制数据时常用的编码方式，它将任意的二进制数据转换成可打印的ASCII字符序列。这种编码方法在处理包含图像、音频、视频等非文本内容的电子邮件时尤为常见，因为传统的ASCII邮件系统无法处理二进制数据。Java作为一种广泛使用的编程语言，提供了对Base64编码和解码的支持。在Java中，Base64编码和解码的功能主要通过`java.util.Base64`这个类来实现，该类在Java 8及以上版本中引入。下面将详细介绍如何使用这个类进行Base64的编码和解码操作。我们来看Base64编码的过程。编码的基本思路是将每三个字节的数据（24位）转换为4个Base64字符（每个字符6位）。如果原始数据不是3的倍数，那么最后可能会剩下1或2个字节，这时会用零填充，并在编码结果的末尾添加1或2个等号（`=`）作为标识。在Java中，你可以使用`Base64.Encoder`接口的`encodeToString()`方法进行编码，如下所示： ```java import java.util.Base64; public class Base64Example { public static void main(String[] args) { String originalString = "Hello, World!"; byte[] originalBytes = originalString.getBytes(); // 创建Base64编码器对象 Base64.Encoder encoder = Base64.getEncoder(); // 对字节数组进行编码 String encodedString = encoder.encodeToString(originalBytes); System.out.println("原始字符串: " + originalString); System.out.println("Base64编码后: " + encodedString); } } ``` 接下来，我们看看Base64解码的过程。解码是编码的逆过程，它将Base64编码的字符串还原为原始的字节数组。同样，`Base64.Decoder`接口的`decode()`方法可以用于解码： ```java import java.util.Base64; public class Base64Example { public static void main(String[] args) { String encodedString = "SGVsbG8sIFdvcmxkIQ=="; Base64.Decoder decoder = Base64.getDecoder(); // 对Base64字符串进行解码 byte[] decodedBytes = decoder.decode(encodedString); String originalString = new String(decodedBytes); System.out.println("Base64编码后: " + encodedString); System.out.println("解码后字符串: " + originalString); } } ``` 在实际开发中，你可能会遇到需要对文件进行Base64编码和解码的情况。在这种情况下，可以读取文件内容到字节数组，然后进行编码或解码。例如，以下代码演示了如何对一个文件进行Base64编码： ```java import java.io.*; import java.util.Base64; public class FileBase64Example { public static void main(String[] args) throws IOException { File inputFile = new File("input.txt"); File outputFile = new File("output.txt"); // 读取文件内容 byte[] fileBytes = Files.readAllBytes(inputFile.toPath()); // 创建Base64编码器 Base64.Encoder encoder = Base64.getEncoder(); // 编码文件内容 String encodedContent = encoder.encodeToString(fileBytes); // 将编码后的内容写入新文件 Files.write(outputFile.toPath(), encodedContent.getBytes()); } } ``` 对于解码，你需要先将编码后的文件内容读取为字符串，然后解码并写入新的文件： ```java import java.io.*; import java.util.Base64; public class FileBase64Example { public static void main(String[] args) throws IOException { File encodedFile = new File("encoded.txt"); File outputFile = new File("decoded.txt"); // 读取编码文件内容 String encodedContent = new String(Files.readAllBytes(encodedFile.toPath())); Base64.Decoder decoder = Base64.getDecoder(); // 对编码内容进行解码 byte[] decodedBytes = decoder.decode(encodedContent); // 将解码后的数据写入新文件 Files.write(outputFile.toPath(), decodedBytes); } } ``` 以上就是关于Java中使用`java.util.Base64`进行Base64编码和解码的基本知识。在实际项目中，你可能还需要处理一些特殊情况，如编码/解码过程中可能出现的异常处理，以及如何在不同的IO流之间进行转换等。希望这些内容能帮助你理解和应用Base64编码技术。

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Base64编码和解码.zip （5个子文件）

srcbase64

WEB-INF

web.xml 292B

lib

classes

netjsp

Base64Coder.java 4KB

Base64Coder.class 2KB

index.jsp 609B

build.xml 1KB

package netjsp; /************************************************************************** * * A Base64 Encoder/Decoder. * * This class is used to encode and decode data in Base64 format * as described in RFC 1521. * * * Copyright 2003: Christian d'Heureuse, Inventec Informatik AG, Switzerland. * License: This is "Open Source" software and released under the <a href="http://www.gnu.org/licenses/lgpl.html" target="_top">GNU/LGPL</a> license. * It is provided "as is" without warranty of any kind. Please contact the author for other licensing arrangements. * Home page: <a href="http://www.source-code.biz" target="_top">www.source-code.biz</a> * * * Version history: * 2003-07-22 Christian d'Heureuse (chdh): Module created. * 2005-08-11 chdh: Lincense changed from GPL to LGPL. * **************************************************************************/ public class Base64Coder { // Mapping table from 6-bit nibbles to Base64 characters. private static 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 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 with the Base64 encoded data. */ public static String encode (String s) { return new String(encode(s.getBytes())); } /** * Encodes a byte array into Base64 format. * No blanks or line breaks are inserted. * @param in an array containing the data bytes to be encoded. * @return A character array with the Base64 encoded data. */ public static char[] encode (byte[] in) { int iLen = in.length; 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 = 0; int op = 0; while (ip < iLen) { int i0 = in[ip++] & 0xff; int i1 = ip < iLen ? in[ip++] & 0xff : 0; int i2 = ip < iLen ? 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 Base64 string. * @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 decode (String s) { return new String(decode(s.toCharArray())); } /** * Decodes Base64 data. * No blanks or line breaks are allowed within the Base64 encoded 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) { int iLen = in.length; if (iLen%4 != 0) throw new IllegalArgumentException ("Length of Base64 encoded input string is not a multiple of 4."); while (iLen > 0 && in[iLen-1] == '=') iLen--; int oLen = (iLen*3) / 4; byte[] out = new byte[oLen]; int ip = 0; int op = 0; while (ip < iLen) { int i0 = in[ip++]; int i1 = in[ip++]; int i2 = ip < iLen ? in[ip++] : 'A'; int i3 = ip < iLen ? 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; } }

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