Java 8實現BASE64編解碼

Java一直缺少BASE64編碼 API，以至于通常在項目開發中會選用第三方的API實現。但是，Java 8實現了BASE64編解碼API，它包含到java.util包。下面我會對Java 8的BASE64 API做一個介紹。

java.util.Base64工具類提供了一套靜態方法獲取下面三種BASE64編解碼器：

1）Basic編碼
2）URL編碼
3）MIME編碼

Basic編碼是標準的BASE64編碼，用于處理常規的需求：輸出的內容不添加換行符，而且輸出的內容由字母加數字組成。下面是用法：

    // 編碼  
    String asB64 = Base64.getEncoder().encodeToString("some string".getBytes("utf-8"));  
    System.out.println(asB64); // 輸出為: c29tZSBzdHJpbmc=  

    // 解碼  
    byte[] asBytes = Base64.getDecoder().decode("c29tZSBzdHJpbmc=");  
    System.out.println(new String(asBytes, "utf-8")); // 輸出為: some string  

URL編碼也是我們經常會面對的需求，但由于URL對反斜線“/”有特殊的意義，因此URL編碼需要替換掉它，使用下劃線替換。比如下面的例子：

    String basicEncoded = Base64.getEncoder().encodeToString("subjects?abcd".getBytes("utf-8"));  
    System.out.println("Using Basic Alphabet: " + basicEncoded);  

    String urlEncoded = Base64.getUrlEncoder().encodeToString("subjects?abcd".getBytes("utf-8"));  
    System.out.println("Using URL Alphabet: " + urlEncoded);  
    // 輸出為:  
    Using Basic Alphabet: c3ViamVjdHM/YWJjZA==  
    Using URL Alphabet: c3ViamVjdHM_YWJjZA==  

MIME編碼器會使用基本的字母數字產生BASE64輸出，而且對MIME格式友好：每一行輸出不超過76個字符，而且每行以“\r\n”符結束。比如下面的例子：

    StringBuilder sb = new StringBuilder();  
    for (int t = 0; t < 10; ++t) {  
      sb.append(UUID.randomUUID().toString());  
    }  

    byte[] toEncode = sb.toString().getBytes("utf-8");  
    String mimeEncoded = Base64.getMimeEncoder().encodeToString(toEncode);  
    System.out.println(mimeEncoded);  
    // 輸出為:  
    NDU5ZTFkNDEtMDVlNy00MDFiLTk3YjgtMWRlMmRkMWEzMzc5YTJkZmEzY2YtM2Y2My00Y2Q4LTk5  
    ZmYtMTU1NzY0MWM5Zjk4ODA5ZjVjOGUtOGMxNi00ZmVjLTgyZjctNmVjYTU5MTAxZWUyNjQ1MjJj  
    NDMtYzA0MC00MjExLTk0NWMtYmFiZGRlNDk5OTZhMDMxZGE5ZTYtZWVhYS00OGFmLTlhMjgtMDM1  
    ZjAyY2QxNDUyOWZiMjI3NDctNmI3OC00YjgyLThiZGQtM2MyY2E3ZGNjYmIxOTQ1MDVkOGQtMzIz  
    Yi00MDg0LWE0ZmItYzkwMGEzNDUxZTIwOTllZTJiYjctMWI3MS00YmQzLTgyYjUtZGRmYmYxNDA4  
    Mjg3YTMxZjMxZmMtYTdmYy00YzMyLTkyNzktZTc2ZDc5ZWU4N2M5ZDU1NmQ4NWYtMDkwOC00YjIy  
    LWIwYWItMzJiYmZmM2M0OTBm  

public void wrapping() throws IOException {  
  String src = "This is the content of any resource read from somewhere" +  
    " into a stream. This can be text, image, video or any other stream.";  

  // 編碼器封裝OutputStream, 文件/tmp/buff-base64.txt的內容是BASE64編碼的形式  
  try (OutputStream os = Base64.getEncoder().wrap(newFileOutputStream("/tmp/buff-base64.txt"))) {  
    os.write(src.getBytes("utf-8"));  
  }  

  // 解碼器封裝InputStream, 以及以流的方式解碼, 無需緩沖  
  // is being consumed. There is no need to buffer the content of the file just for decoding it.  
  try (InputStream is = Base64.getDecoder().wrap(newFileInputStream("/tmp/buff-base64.txt"))) {  
    int len;  
    byte[] bytes = new byte[100];  
    while ((len = is.read(bytes)) != -1) {  
      System.out.print(new String(bytes, 0, len, "utf-8"));  
    }  
  }  
}  

來自：http://blog.csdn.net/chszs