HTTP 协议再解

HTTP 协议头解析

Request

由四部分组成，包括：请求行、请求头(header) 、空行和请求数据。

Get 请求例子，如下：

GET /api/channelInfo?platformType=androidPhone&adapterNo=7.4.7&pid=&recommendNo=3,2&positionId=&pageSize=20&protocol=1.0.2 HTTP/1.1
User-Agent: Dalvik/2.1.0 (Linux; U; Android 7.0; SM-G9200 Build/NRD90M)
Host: vcis.ifeng.com
Connection: Keep-Alive
Accept-Encoding: gzip

第一部分： 请求行，用来说明请求类型,要访问的资源以及所使用的HTTP版本.

第二部分：请求头部，紧接着请求行（即第一行）之后的部分，用来说明服务器要使用的附加信息

第三部分：空行，请求头部后面的空行是必须的

第四部分：请求数据也叫主体，可以添加任意的其他数据。

Post 请求列子， 如下：

POST /appsta.js HTTP/1.1
Content-Type: application/x-www-form-urlencoded; charset=UTF-8
User-Agent: Dalvik/2.1.0 (Linux; U; Android 7.0; SM-G9200 Build/NRD90M)
Host: stadig0.ifeng.com
Connection: Keep-Alive
Accept-Encoding: gzip
Content-Length: 456
  
// 请求数据
publishid=30007&session=2017-12-28%2B17%3A07%3A43%23adinfo%23ainfo%3D10019143%3Aiis_feather_19143_568332_1514450844546_kmfoh1%3A20%24first%3Dno&pid=358108062984272&datatype=videoapp&mos=android_7.0&sp=cucc&re=2560*1440&sver=V1&net=wifi&userid=&openudid=358108062984272&isupdate=1&logintime=1514436698&ua=sm-g9200%2Csamsung&uid=15144366981231380&userkey=f0663a966d82c57e7eb8976597e195f0&softversion=7.4.7&sig=3fc8rfc43rfcinfc4ac8e2thos0733d43wtc02gh3f076wr&

Response

由 状态行、消息报头、空行和响应政文组成。

//状态行
HTTP/1.1 200 OK
消息报头
Server: nginx/1.8.0
Date: Thu, 28 Dec 2017 08:47:24 GMT
Content-Length: 172
Pragma: No-cache
Cache-Control: no-cache
Expires: Thu, 01 Jan 1970 00:00:00 GMT
Proxy-Connection: Keep-alive
//--空行--
//响应正文
{"result":{"timestamp":1514450844361,"requesthost":"api.exc.mob.com","requestport":80,"enable":1,"filter":[],"upconf":{"crash":"1","sdkerr":"0","apperr":"0"}},"status":200}

Get 和 Post 的区别：

• GET提交的数据会放在URL之后，以?分割URL和传输数据，参数之间以&相连，如stadig.ifeng.com?datatype=videoapp&mos=android_7.0. POST方法是把提交的数据放在HTTP包的Body中.
• GET提交的数据大小有限制（因为浏览器对URL的长度有限制），而POST方法提交的数据没有限制.
• GET方式需要使用Request.QueryString来取得变量的值，而POST方式通过Request.Form来获取变量的值。

Volley Post 请求实现

通过重写 getParams() 方法实现，如下：

private static void postRequest(String url, final Map<String, String> params, final String session, final Map<String, String> sigMap, Response.Listener listener, Response.ErrorListener errorListener) {
    StatisticPostRequest requestString = new StatisticPostRequest(Request.Method.POST, url, null, listener, errorListener) {
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            Map<String, String> map = params;
            map.put("session", session);
            map.put("sver", sigMap.get("sver").trim());
            map.put("sig", sigMap.get("sig").trim());
            return map;
        }
    };
    VolleyHelper.getRequestQueue().add(requestString);
}

StatisticPostRequest 重写 getBody() 方法来对 params 进行 encode, 代码如下：

/**
 * post参数urlencode需要外部传入时自己拼
 */
public class StatisticPostRequest<T> extends BaseRequest<T> {

    private final Class<T> mClazz;

    public StatisticPostRequest(int method,
                                String url,
                                Class<T> clazz,
                                Response.Listener<T> listener,
                                Response.ErrorListener errorListener) {
        super(method, url, listener, errorListener);
        mClazz = clazz;
    }

    @Override
    public byte[] getBody() throws AuthFailureError {
        Map<String, String> params = getParams();
        if (params != null && params.size() > 0) {
            return getParameters(params);
        }
        return null;
    }

    /**
     * Converts <code>params</code> into an application/x-www-form-urlencoded encoded string.
     */
    private byte[] getParameters(Map<String, String> params) {
        StringBuilder encodedParams = new StringBuilder();
        try {
            for (Map.Entry<String, String> entry : params.entrySet()) {
                encodedParams.append(entry.getKey());
                encodedParams.append('=');
                encodedParams.append(entry.getValue());
                encodedParams.append('&');
            }
            return encodedParams.toString().getBytes();
        } catch (Exception uee) {
            throw new RuntimeException("Encoding not supported: ", uee);
        }
    }


    @Override
    protected T parseNetworkResponseDelegate(String jsonString) {
        return (T) jsonString;
    }

}

还有一种方式，可以传入 请求体 requestBody, 代码如下：

/**
 * Post请求，请求体为Json格式
 */
public class JsonPostRequest<T> extends JsonRequest<T> {

    private final Class<T> mClazz;

    public JsonPostRequest(int method, String url, String requestBody,
                           Class<T> clazz,
                           Response.Listener<T> listener,
                           Response.ErrorListener errorListener) {
        super(method, url, requestBody, listener, errorListener);
        mClazz = clazz;
    }

    @Override
    protected Response<T> parseNetworkResponse(NetworkResponse response) {
        try {
            String jsonString = new String(response.data, HttpHeaderParser.parseCharset(response.headers));

            return Response.success(JsonUtils.parseObject(jsonString, mClazz),
                    HttpHeaderParser.parseCacheHeaders(response));
        } catch (UnsupportedEncodingException e) {
            return Response.error(new ParseError(e));
        }
    }
}

父类如下：

/**
 * A request for retrieving a T type response body at a given URL that also
 * optionally sends along a JSON body in the request specified.
 *
 * @param <T> JSON type of response expected
 */
public abstract class JsonRequest<T> extends Request<T> {
    /** Charset for request. */
    private static final String PROTOCOL_CHARSET = "utf-8";

    /** Content type for request. */
    private static final String PROTOCOL_CONTENT_TYPE =
        String.format("application/json; charset=%s", PROTOCOL_CHARSET);

    private final Listener<T> mListener;
    private final String mRequestBody;

    /**
     * Deprecated constructor for a JsonRequest which defaults to GET unless {@link #getPostBody()}
     * or {@link #getPostParams()} is overridden (which defaults to POST).
     *
     * @deprecated Use {@link #JsonRequest(int, String, String, Listener, ErrorListener)}.
     */
    public JsonRequest(String url, String requestBody, Listener<T> listener,
            ErrorListener errorListener) {
        this(Method.DEPRECATED_GET_OR_POST, url, requestBody, listener, errorListener);
    }

    public JsonRequest(int method, String url, String requestBody, Listener<T> listener,
            ErrorListener errorListener) {
        super(method, url, errorListener);
        mListener = listener;
        mRequestBody = requestBody;
    }

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

    @Override
    abstract protected Response<T> parseNetworkResponse(NetworkResponse response);

    /**
     * @deprecated Use {@link #getBodyContentType()}.
     */
    @Override
    public String getPostBodyContentType() {
        return getBodyContentType();
    }

    /**
     * @deprecated Use {@link #getBody()}.
     */
    @Override
    public byte[] getPostBody() {
        return getBody();
    }

    @Override
    public String getBodyContentType() {
        return PROTOCOL_CONTENT_TYPE;
    }

    @Override
    public byte[] getBody() {
        try {
            return mRequestBody == null ? null : mRequestBody.getBytes(PROTOCOL_CHARSET);
        } catch (UnsupportedEncodingException uee) {
            VolleyLog.wtf("Unsupported Encoding while trying to get the bytes of %s using %s",
                    mRequestBody, PROTOCOL_CHARSET);
            return null;
        }
    }
}

如果要对 body 参数进行 UrlEncode ，如下：

    private static final String DEFAULT_PARAMS_ENCODING = "UTF-8";    
/**
     * Returns the raw POST or PUT body to be sent.
     *
     * @throws AuthFailureError in the event of auth failure
     */
    public byte[] getBody() throws AuthFailureError {
        Map<String, String> params = getParams();
        if (params != null && params.size() > 0) {
            return encodeParameters(params, getParamsEncoding());
        }
        return null;
    }

    /**
     * Converts <code>params</code> into an application/x-www-form-urlencoded encoded string.
     */
    private byte[] encodeParameters(Map<String, String> params, String paramsEncoding) {
        StringBuilder encodedParams = new StringBuilder();
        try {
            for (Map.Entry<String, String> entry : params.entrySet()) {
                encodedParams.append(URLEncoder.encode(entry.getKey(), paramsEncoding));
                encodedParams.append('=');
                encodedParams.append(URLEncoder.encode(entry.getValue(), paramsEncoding));
                encodedParams.append('&');
            }
            return encodedParams.toString().getBytes(paramsEncoding);
        } catch (UnsupportedEncodingException uee) {
            throw new RuntimeException("Encoding not supported: " + paramsEncoding, uee);
        }
    }

    protected String getParamsEncoding() {
        return DEFAULT_PARAMS_ENCODING;
    }

---

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