Java，获取文件的Base64字符串，解码Base64字符串还原文件

在jdk1.8以前，获取文件Base64字符串需要用到第三方库，从1.8开始，Java中引入了Base64相关的类

以下是代码示例

获取文件的Base64编码字符串

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Base64;
import java.util.Scanner;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Base64Encoder {

    private static final Logger LOGGER = Logger.getLogger("Base64Encoder");

    public static void main(String[] args) {
        System.out.print("Enter an input filename: ");
        Scanner inputFromConsole = new Scanner(System.in);
        String filename = inputFromConsole.nextLine();
        FileOutputStream outputToFile = null;
        try (FileInputStream inputFromFile = new FileInputStream(filename)) {
            System.out.print("Enter an encoded filename: ");
            filename = inputFromConsole.nextLine();
            outputToFile = new FileOutputStream(filename);
            byte[] src = new byte[inputFromFile.available()];
            inputFromFile.read(src);
            byte[] encodedBytes = Base64.getEncoder().encode(src);
            outputToFile.write(encodedBytes);
        } catch (IOException ex) {
            LOGGER.log(Level.SEVERE, null, ex);
        } finally {
            if (outputToFile != null) {
                try {
                    outputToFile.close();
                } catch (IOException ex) {
                    LOGGER.log(Level.SEVERE, null, ex);
                }
            }
        }
    }
}

解码Base64字符串还原文件

import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import static java.lang.System.out;
import java.util.Base64;
import java.util.logging.Level;
import java.util.logging.Logger;

public class Base64Decoder {

    private static final Logger LOGGER = Logger.getLogger("Base64Decoder");

    public static void main(String[] args) {
        if (args.length == 2) {
            try (FileInputStream encoded = new FileInputStream(args[0]); FileOutputStream decoded = new FileOutputStream(args[1])) {
                byte[] buffer = new byte[encoded.available()];
                encoded.read(buffer);
                Base64.Decoder base64Decoder = Base64.getMimeDecoder();
                decoded.write(base64Decoder.decode(buffer));
            } catch (IOException ex) {
                LOGGER.log(Level.SEVERE, null, ex);
            }
        } else {
            out.println("usage:\n\tjava Base64Decoder <encoded filename> <decoded filename>");
            out.println("for example:\n\tjava Base64Decoder MyPic.jpg.txt MyPic.jpg");
        }
    }
}