为什么 volley 的响应字符串使用的编码与响应标头中的编码不同？

Question

当使用 OkHttp 堆栈执行 volley 请求（StringRequest 或 JsonObjectRequest）时，响应字符串的编码设置为 ISO-8995-1，这是默认编码。响应有一个标题：content-type=text/html; charset=utf-8，应该检测到它。为什么不呢？

Answer 1

这两种请求类型都调用HttpHeaderParser.parseCharset，它能够从标头中确定字符集。但是，它要求标头为Content-Type，而不是content-type：它区分大小写。 （如果使用默认的 HurlStack，我不确定行为，这可能是与 OkHttp 堆栈的实现细节差异。）

解决方案1：复制原始请求类型，但手动覆盖字符集

解决方案2：复制原始请求类型，但强制预期的标头存在

import com.android.volley.NetworkResponse;
import com.android.volley.ParseError;
import com.android.volley.Response;
import com.android.volley.Response.ErrorListener;
import com.android.volley.Response.Listener;
import com.android.volley.toolbox.HttpHeaderParser;
import com.android.volley.toolbox.JsonRequest;

import org.json.JSONException;
import org.json.JSONObject;

import java.io.UnsupportedEncodingException;

public class JsonUTF8Request extends JsonRequest<JSONObject> {
    public JsonUTF8Request(int method, String url, JSONObject jsonRequest,
                           Listener<JSONObject> listener, ErrorListener errorListener) {
        super(method, url, (jsonRequest == null) ? null : jsonRequest.toString(), listener,
                errorListener);
    }

    @Override
    protected Response<JSONObject> parseNetworkResponse(NetworkResponse response) {
        try {
            // solution 1:
            String jsonString = new String(response.data, "UTF-8");
            // solution 2:
            response.headers.put(HTTP.CONTENT_TYPE,
                response.headers.get("content-type"));
            String jsonString = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
            //
            return Response.success(new JSONObject(jsonString),
                    HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));
        } catch (JSONException je) {
            return Response.error(new ParseError(je));
        }
    }
}

Answer 2

首先非常感谢@mjibson 为您在此处发布的 2 个解决方案，我遇到了类似的问题，在我的情况下，内容类型总是丢失，因此以下问题也出现了：

    protected static final String TYPE_UTF8_CHARSET = "charset=UTF-8";

    @Override
    protected Response<String> parseNetworkResponse(
            NetworkResponse response) {
        try {
            String type = response.headers.get(HTTP.CONTENT_TYPE);
            if (type == null) {
                Log.d(LOG_TAG, "content type was null");
                type = TYPE_UTF8_CHARSET;
                response.headers.put(HTTP.CONTENT_TYPE, type);
            } else if (!type.contains("UTF-8")) {
                Log.d(LOG_TAG, "content type had UTF-8 missing");
                type += ";" + TYPE_UTF8_CHARSET;
                response.headers.put(HTTP.CONTENT_TYPE, type);
            }
        } catch (Exception e) {
            //print stacktrace e.g.
        }
        return super.parseNetworkResponse(response);
    }

我只是想分享这个让其他人遇到类似的问题。阅读https://android.googlesource.com/platform/frameworks/volley/+/master/src/com/android/volley/toolbox/HttpHeaderParser.java 中的 parseCharset 方法以了解其工作原理也很重要

Answer 3

覆盖Request<T> 类的方法parseNetworkResponse。
你可以这样做：

/**
 * A canned request for retrieving the response body at a given URL as a String.
 */
public class StringRequest extends Request<String> {
    private final Listener<String> mListener;


    /**
     * the parse charset.
     */
    private String charset = null;

    /**
     * Creates a new request with the given method.
     *
     * @param method the request {@link Method} to use
     * @param url URL to fetch the string at
     * @param listener Listener to receive the String response
     * @param errorListener Error listener, or null to ignore errors
     */
    public StringRequest(int method, String url, Listener<String> listener,
            ErrorListener errorListener) {
        super(method, url, errorListener);
        mListener = listener;
    }

    /**
     * Creates a new GET request.
     *
     * @param url URL to fetch the string at
     * @param listener Listener to receive the String response
     * @param errorListener Error listener, or null to ignore errors
     */
    public StringRequest(String url, Listener<String> listener, ErrorListener errorListener) {
        this(Method.GET, url, listener, errorListener);
    }

    /**
     * Creates a new GET request with the given Charset.
     *
     * @param url URL to fetch the string at
     * @param listener Listener to receive the String response
     * @param errorListener Error listener, or null to ignore errors
     */
    public StringRequest(String url, String charset, Listener<String> listener, ErrorListener errorListener) {
        this(Method.GET, url, listener, errorListener);
        this.charset = charset;
    }

    @Override
    protected void deliverResponse(String response) {
        mListener.onResponse(response);
    }

    @Override
    protected Response<String> parseNetworkResponse(NetworkResponse response) {
        String parsed;
        try {
            if(charset != null) {
                parsed = new String(response.data, charset);
            } else {
                parsed = new String(response.data, HttpHeaderParser.parseCharset(response.headers));
            }
        } catch (UnsupportedEncodingException e) {
            parsed = new String(response.data);
        }
        return Response.success(parsed, HttpHeaderParser.parseCacheHeaders(response));
    }

    /**
     * @return the Parse Charset Encoding
     */
    public String getCharset() {
        return charset;
    }

    /**
     * set the Parse Charset Encoding
     * @param charset
     */
    public void setCharset(String charset) {
        this.charset = charset;
    }

}

Answer 4

将方法从 GET 更改为 POST 以支持 UTF-8

JsonObjectRequest jsonReq = new JsonObjectRequest(Method.POST,
            URL_FEED, null, new Response.Listener<JSONObject>() {
                @Override
                public void onResponse(JSONObject response) {
                    VolleyLog.d(TAG, "Response: " + response.toString());
                    Log.d("SHY", "Response: " + response.toString());
                    if (response != null) {
                        parseJsonFeed(response);
                    }
                }
            }, new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError error) {
                    VolleyLog.d(TAG, "Error: " + error.getMessage());
                }
            });

。 . . .

Answer 5

谢谢@Simon Heinen。根据你的回复，我写了一个函数。

private void addEncodeing2Request(NetworkResponse response) {
    try {
        String type = response.headers.get(HTTP.CONTENT_TYPE);
        if (type == null) {
            //Content-Type:
            Log.d("RVA", "content type was null");
            type = TYPE_UTF8_CHARSET;
            response.headers.put(HTTP.CONTENT_TYPE, type);
        } else if (!type.contains("charset")) {
            //Content-Type: text/plain;
            Log.d("RVA", "charset was null, added encode utf-8");
            type += ";" + TYPE_UTF8_CHARSET;
            response.headers.put(HTTP.CONTENT_TYPE, type);
        } else {
            //nice! Content-Type: text/plain; charset=utf-8'
            Log.d("RVA", "charset is " + type);
        }

    } catch (Exception e) {
        e.printStackTrace();
    }
}

用法：

protected Response<String> parseNetworkResponse(NetworkResponse response) {
          addEncodeing2Request(response);
          return super.parseNetworkResponse(response);
      }

此外，覆盖 getParamsEncoding() 也可以工作。

protected String getParamsEncoding() {
            return "utf-8";
        }