Base64Utils

import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.io.OutputStream;

public class Base64Utils {

    /**
     * 文件讀取緩沖區大小
     */
    private static final int CACHE_SIZE = 1024;
    
    /**
     * <p>
     * BASE64字符串解碼為二進制數據
     * </p>
     * 
     * @param base64
     * @return
     * @throws Exception
     */
    public static byte[] decode(String base64) throws Exception {
        return Base64.decode(base64.getBytes());
    }
    
    /**
     * <p>
     * 二進制數據編碼為BASE64字符串
     * </p>
     * 
     * @param bytes
     * @return
     * @throws Exception
     */
    public static String encode(byte[] bytes) throws Exception {
        return new String(Base64.encode(bytes));
    }
    
    /**
     * <p>
     * 將文件編碼為BASE64字符串
     * </p>
     * <p>
     * 大文件慎用，可能會導致內存溢出
     * </p>
     * 
     * @param filePath 文件絕對路徑
     * @return
     * @throws Exception
     */
    public static String encodeFile(String filePath) throws Exception {
        byte[] bytes = fileToByte(filePath);
        return encode(bytes);
    }
    
    /**
     * <p>
     * BASE64字符串轉回文件
     * </p>
     * 
     * @param filePath 文件絕對路徑
     * @param base64 編碼字符串
     * @throws Exception
     */
    public static void decodeToFile(String filePath, String base64) throws Exception {
        byte[] bytes = decode(base64);
        byteArrayToFile(bytes, filePath);
    }
    
    /**
     * <p>
     * 文件轉換為二進制數組
     * </p>
     * 
     * @param filePath 文件路徑
     * @return
     * @throws Exception
     */
    public static byte[] fileToByte(String filePath) throws Exception {
        byte[] data = new byte[0];
        File file = new File(filePath);
        if (file.exists()) {
            FileInputStream in = new FileInputStream(file);
            ByteArrayOutputStream out = new ByteArrayOutputStream(2048);
            byte[] cache = new byte[CACHE_SIZE];
            int nRead = 0;
            while ((nRead = in.read(cache)) != -1) {
                out.write(cache, 0, nRead);
                out.flush();
            }
            out.close();
            in.close();
            data = out.toByteArray();
         }
        return data;
    }
    
    /**
     * <p>
     * 二進制數據寫文件
     * </p>
     * 
     * @param bytes 二進制數據
     * @param filePath 文件生成目錄
     */
    public static void byteArrayToFile(byte[] bytes, String filePath) throws Exception {
        InputStream in = new ByteArrayInputStream(bytes);   
        File destFile = new File(filePath);
        if (!destFile.getParentFile().exists()) {
            destFile.getParentFile().mkdirs();
        }
        destFile.createNewFile();
        OutputStream out = new FileOutputStream(destFile);
        byte[] cache = new byte[CACHE_SIZE];
        int nRead = 0;
        while ((nRead = in.read(cache)) != -1) {   
            out.write(cache, 0, nRead);
            out.flush();
        }
        out.close();
        in.close();
    }
    
    /**
     * 使用Base64加密算法加密字符串 
     * 
     * @param plainText 
     */ 
    public static String encodeStr(String plainText){  
        byte[] b=plainText.getBytes();  
        org.apache.commons.codec.binary.Base64  base64 = new org.apache.commons.codec.binary.Base64();
        b=base64.encode(b);  
        String s=new String(b);  
        return s;  
    }
    
    /**
     * 使用Base64加密算法解密字符串 
     * 
     * @param encodeStr 
     */ 
    public static String decodeStr(String encodeStr){  
        byte[] b=encodeStr.getBytes();  
        org.apache.commons.codec.binary.Base64  base64 = new org.apache.commons.codec.binary.Base64();
        b=base64.decode(b);
        String s=new String(b);  
        return s;  
    }
    
}