详解Retrofit Interceptor(拦截器) 拦截请求并做相关处理

/*** Observes, modifies, and potentially short-circuits requests going out and the corresponding* responses coming back in. Typically interceptors add, remove, or transform headers on the request* or response.*/public interface Interceptor {  Response intercept(Chain chain) throws IOException;  interface Chain {    Request request();    Response proceed(Request request) throws IOException;    /**     * Returns the connection the request will be executed on. This is only available in the chains     * of network interceptors; for application interceptors this is always null.     */    @Nullable Connection connection();  }}

public class CommonInterceptor implements Interceptor {  private static Map<String, String> commonParams;  public synchronized static void setCommonParam(Map<String, String> commonParams) {    if (commonParams != null) {      if (CommonInterceptor.commonParams != null) {        CommonInterceptor.commonParams.clear();      } else {        CommonInterceptor.commonParams = new HashMap<>();      }      for (String paramKey : commonParams.keySet()) {        CommonInterceptor.commonParams.put(paramKey, commonParams.get(paramKey));      }    }  }  public synchronized static void updateOrInsertCommonParam(@NonNull String paramKey, @NonNull String paramValue) {    if (commonParams == null) {      commonParams = new HashMap<>();    }    commonParams.put(paramKey, paramValue);  }  @Override  public synchronized Response intercept(Chain chain) throws IOException {    Request request = rebuildRequest(chain.request());    Response response = chain.proceed(request);    // 输出返回结果    try {      Charset charset;      charset = Charset.forName("UTF-8");      ResponseBody responseBody = response.peekBody(Long.MAX_VALUE);      Reader jsonReader = new InputStreamReader(responseBody.byteStream(), charset);      BufferedReader reader = new BufferedReader(jsonReader);      StringBuilder sbJson = new StringBuilder();      String line = reader.readLine();      do {        sbJson.append(line);        line = reader.readLine();      } while (line != null);      LogUtil.e("response: " + sbJson.toString());    } catch (Exception e) {      e.printStackTrace();      LogUtil.e(e.getMessage(), e);    }//    saveCookies(response, request.url().toString());    return response;  }  public static byte[] toByteArray(RequestBody body) throws IOException {    Buffer buffer = new Buffer();    body.writeTo(buffer);    InputStream inputStream = buffer.inputStream();    ByteArrayOutputStream output = new ByteArrayOutputStream();    byte[] bufferWrite = new byte[4096];    int n;    while (-1 != (n = inputStream.read(bufferWrite))) {      output.write(bufferWrite, 0, n);    }    return output.toByteArray();  }  private Request rebuildRequest(Request request) throws IOException {    Request newRequest;    if ("POST".equals(request.method())) {      newRequest = rebuildPostRequest(request);    } else if ("GET".equals(request.method())) {      newRequest = rebuildGetRequest(request);    } else {      newRequest = request;    }    LogUtil.e("requestUrl: " + newRequest.url().toString());    return newRequest;  }  /**   * 对post请求添加统一参数   */  private Request rebuildPostRequest(Request request) {//    if (commonParams == null || commonParams.size() == 0) {//      return request;//    }    Map<String, String> signParams = new HashMap<>(); // 假设你的项目需要对参数进行签名    RequestBody originalRequestBody = request.body();    assert originalRequestBody != null;    RequestBody newRequestBody;    if (originalRequestBody instanceof FormBody) { // 传统表单      FormBody.Builder builder = new FormBody.Builder();      FormBody requestBody = (FormBody) request.body();      int fieldSize = requestBody == null ? 0 : requestBody.size();      for (int i = 0; i < fieldSize; i++) {        builder.add(requestBody.name(i), requestBody.value(i));        signParams.put(requestBody.name(i), requestBody.value(i));      }      if (commonParams != null && commonParams.size() > 0) {        signParams.putAll(commonParams);        for (String paramKey : commonParams.keySet()) {          builder.add(paramKey, commonParams.get(paramKey));        }      }      // ToDo 此处可对参数做签名处理 signParams      /**       * String sign = SignUtil.sign(signParams);       * builder.add("sign", sign);       */      newRequestBody = builder.build();    } else if (originalRequestBody instanceof MultipartBody) { // 文件      MultipartBody requestBody = (MultipartBody) request.body();      MultipartBody.Builder multipartBodybuilder = new MultipartBody.Builder();      if (requestBody != null) {        for (int i = 0; i < requestBody.size(); i++) {          MultipartBody.Part part = requestBody.part(i);          multipartBodybuilder.addPart(part);          /*           上传文件时，请求方法接收的参数类型为RequestBody或MultipartBody.Part参见ApiService文件中uploadFile方法           RequestBody作为普通参数载体，封装了普通参数的value; MultipartBody.Part即可作为普通参数载体也可作为文件参数载体           当RequestBody作为参数传入时，框架内部仍然会做相关处理，进一步封装成MultipartBody.Part，因此在拦截器内部，           拦截的参数都是MultipartBody.Part类型           */          /*           1.若MultipartBody.Part作为文件参数载体传入，则构造MultipartBody.Part实例时，           需使用MultipartBody.Part.createFormData(String name, @Nullable String filename, RequestBody body)方法，           其中name参数可作为key使用(因为你可能一次上传多个文件，服务端可以此作为区分)且不能为null，           body参数封装了包括MimeType在内的文件信息，其实例创建方法为RequestBody.create(final @Nullable MediaType contentType, final File file)           MediaType获取方式如下：           String fileType = FileUtil.getMimeType(file.getAbsolutePath());           MediaType mediaType = MediaType.parse(fileType);           2.若MultipartBody.Part作为普通参数载体，建议使用MultipartBody.Part.createFormData(String name, String value)方法创建Part实例            name可作为key使用，name不能为null,通过这种方式创建的实例，其RequestBody属性的MediaType为null；当然也可以使用其他方法创建           */          /*           提取非文件参数时,以RequestBody的MediaType为判断依据.           此处提取方式简单暴力。默认part实例的RequestBody成员变量的MediaType为null时，part为非文件参数           前提是:           a.构造RequestBody实例参数时，将MediaType设置为null           b.构造MultipartBody.Part实例参数时,推荐使用MultipartBody.Part.createFormData(String name, String value)方法，或使用以下方法            b1.MultipartBody.Part.create(RequestBody body)            b2.MultipartBody.Part.create(@Nullable Headers headers, RequestBody body)            若使用方法b1或b2，则要求           备注：           您也可根据需求修改RequestBody的MediaType，但尽量保持外部传入参数的MediaType与拦截器内部添加参数的MediaType一致，方便统一处理           */          MediaType mediaType = part.body().contentType();          if (mediaType == null) {            String normalParamKey;            String normalParamValue;            try {              normalParamValue = getParamContent(requestBody.part(i).body());              Headers headers = part.headers();              if (!TextUtils.isEmpty(normalParamValue) && headers != null) {                for (String name : headers.names()) {                  String headerContent = headers.get(name);                  if (!TextUtils.isEmpty(headerContent)) {                    String[] normalParamKeyContainer = headerContent.split("name=/"");                    if (normalParamKeyContainer.length == 2) {                      normalParamKey = normalParamKeyContainer[1].split("/"")[0];                      signParams.put(normalParamKey, normalParamValue);                      break;                    }                  }                }              }            } catch (Exception e) {              e.printStackTrace();            }          }        }      }      if (commonParams != null && commonParams.size() > 0) {        signParams.putAll(commonParams);        for (String paramKey : commonParams.keySet()) {          // 两种方式添加公共参数          // method 1          multipartBodybuilder.addFormDataPart(paramKey, commonParams.get(paramKey));          // method 2//          MultipartBody.Part part = MultipartBody.Part.createFormData(paramKey, commonParams.get(paramKey));//          multipartBodybuilder.addPart(part);        }      }      // ToDo 此处可对参数做签名处理 signParams      /**       * String sign = SignUtil.sign(signParams);       * multipartBodybuilder.addFormDataPart("sign", sign);       */      newRequestBody = multipartBodybuilder.build();    } else {      try {        JSONObject jsonObject;        if (originalRequestBody.contentLength() == 0) {          jsonObject = new JSONObject();        } else {          jsonObject = new JSONObject(getParamContent(originalRequestBody));        }        if (commonParams != null && commonParams.size() > 0) {          for (String commonParamKey : commonParams.keySet()) {            jsonObject.put(commonParamKey, commonParams.get(commonParamKey));          }        }        // ToDo 此处可对参数做签名处理        /**         * String sign = SignUtil.sign(signParams);         * jsonObject.put("sign", sign);         */        newRequestBody = RequestBody.create(originalRequestBody.contentType(), jsonObject.toString());        LogUtil.e(getParamContent(newRequestBody));      } catch (Exception e) {        newRequestBody = originalRequestBody;        e.printStackTrace();      }    }//    可根据需求添加或修改header,此处制作示意//    return request.newBuilder()//        .addHeader("header1", "header1")//        .addHeader("header2", "header2")//        .method(request.method(), newRequestBody)//        .build();    return request.newBuilder().method(request.method(), newRequestBody).build();  }  /**   * 获取常规post请求参数   */  private String getParamContent(RequestBody body) throws IOException {    Buffer buffer = new Buffer();    body.writeTo(buffer);    return buffer.readUtf8();  }  /**   * 对get请求做统一参数处理   */  private Request rebuildGetRequest(Request request) {    if (commonParams == null || commonParams.size() == 0) {      return request;    }    String url = request.url().toString();    int separatorIndex = url.lastIndexOf("?");    StringBuilder sb = new StringBuilder(url);    if (separatorIndex == -1) {      sb.append("?");    }    for (String commonParamKey : commonParams.keySet()) {      sb.append("&").append(commonParamKey).append("=").append(commonParams.get(commonParamKey));    }    Request.Builder requestBuilder = request.newBuilder();    return requestBuilder.url(sb.toString()).build();  }}