在使用 okhttp 的时候，head 的一些项是中文，导致网络请求失败，错误类似下面的

java.lang.IllegalArgumentException: Unexpected char ...

找了一圈发现是 okhttp 对 head 的编码做了验证

Header values are (technically) required to be ISO-8859-1 but in practice only ASCII really works and OkHttp validates such (the exception has nothing to do with Retrofit). That string is a custom user agent and you'll need to restrict its contents to the ASCII character set when creating it.

具体的代码 ( 在 okhttp3 库里面的 okhttp3.Headers.java ) 如下:

private void checkNameAndValue(String name, String value) { if (name == null) throw new NullPointerException("name == null"); if (name.isEmpty()) throw new IllegalArgumentException("name is empty"); for (int i = 0, length = name.length(); i < length; i++) { char c = name.charAt(i); if (c <= '\u001f' || c >= '\u007f') { throw new IllegalArgumentException(Util.format( "Unexpected char %#04x at %d in header name: %s", (int) c, i, name)); } } if (value == null) throw new NullPointerException("value == null"); for (int i = 0, length = value.length(); i < length; i++) { char c = value.charAt(i); if (c <= '\u001f' || c >= '\u007f') { throw new IllegalArgumentException(Util.format( "Unexpected char %#04x at %d in %s value: %s", (int) c, i, name, value)); } }}

看源码，解决的方法很简单，保证所有的 head 都是符合编码要求。

但是我的情况是，其中的某一些字符不合要求，这部分服务器不关心，而本地却又不知道具体哪些是不和要求的。我的解决思路很简单，挑出不合要求的字符，把这些字符单独转码。

private static String encodeHeadInfo( String headInfo ) { StringBuffer stringBuffer = new StringBuffer(); for (int i = 0, length = headInfo.length(); i < length; i++) { char c = headInfo.charAt(i); if (c <= '\u001f' || c >= '\u007f') { stringBuffer.append( String.format ("\\u%04x", (int)c) ); } else { stringBuffer.append(c); } } return stringBuffer.toString();}

这样