你这个问题我今天遇到，排查了一上午，最后发现图片url请求返回的数据是gzip格式，在base64编码前要gzip解码，再进行base64编码。

浏览器上看到的返回头信息

Age:2829

Connection:keep-alive

Content-Encoding:gzip

Content-Type:image/jpeg

Date:Fri, 28 Sep 2018 02:29:54 GMT

EagleId:790b009515381046232548971e

ETag:"5aefed0a-3a1e"

Last-Modified:Mon, 07 May 2018 06:07:06 GMT

Server:Tengine

Timing-Allow-Origin:*

Via:cache20.l2st3-2[0,304-0,H], cache29.l2st3-2[15,0], kunlun8.cn2372[0,304-0,H], kunlun1.cn2372[1,0]

X-Cache:HIT TCP_IMS_HIT dirn:10:228113073

第三行Content-Encoding:gzip

正确的代码

/**

* 在线图片转换成base64字符串

*

* @param imgURL 图片线上路径

* @return

*/

public static String ImageToBase64ByOnline(String imgURL) {

if (StringUtils.isBlank(imgURL)) {

return null;

}

HttpURLConnection conn = null;

InputStream is = null;

try {

ByteArrayOutputStream out = new ByteArrayOutputStream();

// 创建URL

URL url = new URL(imgURL);

// 创建链接

conn = (HttpURLConnection) url.openConnection();

conn.setRequestMethod("GET");

conn.setConnectTimeout(5000);

is = conn.getInputStream();

// 将内容读取内存中

int len = -1;

byte[] by = new byte[1024];

while ((len = is.read(by)) != -1) {

out.write(by, 0, len);

}

byte[] dataByte = out.toByteArray();

//如果 图片经过nginx就会被压缩，返回头中包含 Content-Encoding:gzip 则需要对图片数据解压缩

String contentEncoding = conn.getContentEncoding();

if("gzip".equalsIgnoreCase(contentEncoding)){

dataByte = GZIPUtils.uncompress(dataByte);

}

// 对字节数组Base64编码

BASE64Encoder encoder = new BASE64Encoder();

return encoder.encode(dataByte);

} catch (IOException e) {

e.printStackTrace();

} finally {

if (is != null) {

// 关闭流

try {

is.close();

} catch (IOException e) {

e.printStackTrace();

} finally {

is = null;

}

}

if (conn != null) {

conn.disconnect();

}

}

return null;

}

gzip解码工具

/**

* GZIP解压缩

*

* @param bytes 压缩内容

* @return

*/

public static byte[] uncompress(byte[] bytes) throws IOException {

if (bytes == null || bytes.length == 0) {

return null;

}

ByteArrayOutputStream out = new ByteArrayOutputStream();

GZIPInputStream ungzip = null;

try {

ByteArrayInputStream in = new ByteArrayInputStream(bytes);

ungzip = new GZIPInputStream(in);

byte[] buffer = new byte[1024];

int n = 0;

while ((n = ungzip.read(buffer)) >= 0) {

out.write(buffer, 0, n);

}

ungzip.close(); //这个会写入一些数据，所以要在out使用前调用

return out.toByteArray();

} finally {

out.close();

}

}