Java 以base64字符串形式从http Get响应获取图像

当我对图像的GET请求返回一个编码字符串时，如

‰PNGØØ223; nØíénÐpÒœÜÜÜë…

如何将图像作为base64编码字符串而不是任何编码

    String url = http://i.stack.imgur.com/tKsDb.png;

    try{

    URL obj = new URL(url);
    HttpURLConnection con = (HttpURLConnection) obj.openConnection();

    // optional default is GET
    con.setRequestMethod("GET");

    //add request header
    con.setRequestProperty("User-Agent", "Mozilla/5.0");

    int responseCode = con.getResponseCode();
    System.out.println("\nSending 'GET' request to URL : " + url);
    System.out.println("Response Code : " + responseCode);

    BufferedReader in = new BufferedReader(
            new InputStreamReader(con.getInputStream()));
    String inputLine;
    StringBuffer response = new StringBuffer();

    while ((inputLine = in.readLine()) != null) {
        response.append(inputLine);
    }
    in.close();
    System.out.println(response.toString());
    //print result
    return response.toString();

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使用javax.mail.internet.mime实用程序

import javax.mail.internet.MimeUtility;
import java.io.*;

public class Base64Utils {

  private Base64Utils() {}

  public static byte[] encode(byte[] b) throws Exception {
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    OutputStream b64os = MimeUtility.encode(baos, "base64");
    b64os.write(b);
    b64os.close();
    return baos.toByteArray();
  }

  public static byte[] decode(byte[] b) throws Exception {
    ByteArrayInputStream bais = new ByteArrayInputStream(b);
    InputStream b64is = MimeUtility.decode(bais, "base64");
    byte[] tmp = new byte[b.length];
    int n = b64is.read(tmp);
    byte[] res = new byte[n];
    System.arraycopy(tmp, 0, res, 0, n);
    return res;
  }

使用apachecommons

import org.apache.commons.codec.binary.Base64;

public class Codec {
  public static void main(String[] args) {
    try {
      String clearText = "Hello world";
      String encodedText;

      // Base64
      encodedText = new String(Base64.encodeBase64(clearText.getBytes()));
      System.out.println("Encoded: " + encodedText);
      System.out.println("Decoded:"
          + new String(Base64.decodeBase64(encodedText.getBytes())));
      //
      // output :
      //   Encoded: SGVsbG8gd29ybGQ=
      //   Decoded:Hello world
      //
    }
    catch (Exception e) {
      e.printStackTrace();
    }
  }
}

使用sun.misc.base64编码器

import java.io.IOException;

import sun.misc.BASE64Decoder;
import sun.misc.BASE64Encoder;

// Java Base64 Encoder / Java Base64 Decoder Example

public class Base64Test {

  public static void main(String[] args) {
    BASE64Decoder decoder = new BASE64Decoder();
    BASE64Encoder encoder = new BASE64Encoder();
    try {
      String encodedBytes = encoder.encodeBuffer("JavaTips.net".getBytes());
      System.out.println("encodedBytes " + encodedBytes);
      byte[] decodedBytes = decoder.decodeBuffer(encodedBytes);
      System.out.println("decodedBytes " + new String(decodedBytes));
    } catch (IOException e) {
      e.printStackTrace();
    }
  }
}

参考资料：

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响应不是编码字符串，而是图像的原始字节（即，如果您只是将来自该流的字节存储到文件中，那么您就拥有图像）

如果你需要它BASE64编码，你必须自己做