OkHttp3简单使用教程(一)：请求和响应

悠悠 2023-06-12 08:42 61阅读 0赞

## 一，HTTP请求、响应报文格式 ##

要弄明白网络框架，首先需要先掌握Http请求的，响应的报文格式。

HTTP请求报文格式:

HTTP请求报文主要由**请求行、请求头部、请求正文**3部分组成.

![format_png][]

request.png

1.  **请求行**：由**请求方法，URL，协议版本**三部分构成，之间用空格隔开  
    请求方法包括：**POST、GET、HEAD、PUT、POST、TRACE、OPTIONS、DELETE**等  
    协议版本：HTTP/主版本号.次版本号，常用的有HTTP/1.0和HTTP/1.1
    
    ![format_png 1][]
    
    请求方法.png
2.  **请求头部**:  
    请求头部为**请求报文添加了一些附加信息，由“名/值”对组成**，每行一对，名和值之间使用冒号分隔  
    常见请求头如下：  
    Host ----接受请求的服务器地址，可以是IP:端口号，也可以是域名  
    User-Agent ----发送请求的应用程序名称  
    Connection ---- 指定与连接相关的属性，如Connection:Keep-Alive  
    Accept-Charset ---- 通知服务端可以发送的编码格式  
    Accept-Encoding ---- 通知服务端可以发送的数据压缩格式  
    Accept-Language ---- 通知服务端可以发送的语言
3.  **请求正文**  
    可选部分，比如GET请求就没有请求正文
4.  **请求示例**：
    
    ![format_png 2][]
    
    image.png

HTTP响应报文格式:

HTTP响应报文主要由**状态行、响应头部、响应正文**3部分组成

![format_png 3][]

响应报文.png

1.  **状态行**：  
    由3部分组成，分别为：**协议版本，状态码，状态码描述**，之间由空格分隔  
    **状态码**:为3位数字，**200-299的状态码表示成功，300-399的状态码指资源重定向，400-499的状态码指客户端请求出错，500-599的状态码指服务端出错**（HTTP/1.1向协议中引入了信息性状态码，范围为100-199)  
    常见的：  
    **200**：响应成功  
    **302**：重定向跳转，跳转地址通过响应头中的Location属性指定  
    **400**：客户端请求有语法错误，参数错误，不能被服务器识别  
    **403**：服务器接收到请求，但是拒绝提供服务（认证失败）  
    **404**：请求资源不存在  
    **500**：服务器内部错误
    
    ![format_png 4][]
    
    image.png
    
     
2.  **响应头部** :  
    与请求头部类似，为响应报文添加了一些附加信息  
    Server - 服务器应用程序软件的名称和版本  
    Content-Type - 响应正文的类型（是图片还是二进制字符串）  
    Content-Length - 响应正文长度  
    Content-Charset - 响应正文使用的编码  
    Content-Encoding - 响应正文使用的数据压缩格式  
    Content-Language - 响应正文使用的语言

Server: bfe/1.0.8.1 
    Date: Sat, 04 Apr 2015 02:49:41 GMT 
    Content-Type: text/html; charset=utf-8 
    Vary: Accept-Encoding 
    Cache-Control: private 
    cxy_all: baidu+8ee3da625d74d1aa1ac9a7c34a2191dc 
    Expires: Sat, 04 Apr 2015 02:49:38 GMT 
    X-Powered-By: HPHP 
    bdpagetype: 1 
    bdqid: 0xb4eababa0002db6e 
    bduserid: 0 
    Set-Cookie: BDSVRTM=0; path=/ 
    BD_HOME=0; path=/ 
    H_PS_PSSID=13165_12942_1430_13075_12867_13322_12691_13348_12723_12797_13309_13325_13203_13161_13256_8498; path=/; domain=.baidu.com 
    __bsi=18221750326646863206_31_0_I_R_2_0303_C02F_N_I_I; expires=Sat, 04-Apr-15 02:49:46 GMT; domain=www.baidu.com; path=/ 
    Content-Encoding: gzip 
    X-Firefox-Spdy: 3.1

1.  **响应正文**  
    是请求响应的最终结果，都在响应体里。  
    报文可以承载很多类型的数字数据：图片、视频、HTML文档、软件应用程序等
2.  **响应示例**
    
    ![format_png 5][]
    
    image.png

## 二，HTTP请求和响应的基本使用 ##

主要包含：

*  一般的get请求
 *  一般的post请求
 *  基于Http的文件上传
 *  文件下载
 *  加载图片
 *  支持请求回调，直接返回对象、对象集合
 *  支持session的保持

1.  **添加网络访问权限并添加库依赖**

<uses-permission android:name="android.permission.INTERNET" />
    api 'com.squareup.okhttp3:okhttp:3.9.0'

1.  **HTTP的GET请求**

//1,创建okHttpClient对象
    OkHttpClient mOkHttpClient = new OkHttpClient();
    //2,创建一个Request
    final Request request = new Request.Builder()
                    .url("https://www.baidu.com")
                    .build();
    //3,新建一个call对象
    Call call = mOkHttpClient.newCall(request); 
    //4，请求加入调度，这里是异步Get请求回调
    call.enqueue(new Callback()
            {
                @Override
                public void onFailure(Request request, IOException e)
                {
                }
    
                @Override
                public void onResponse(final Response response) throws IOException
                {
                        //String htmlStr =  response.body().string();
                }
            });

对以上的简单请求的构成：

*  发送一个GET请求的步骤，**首先构造一个Request对象，参数最起码有个URL，当然也可以通过Request.Builder设置更多的参数比如：header、method等**。

//URL带的参数
    HashMap<String,String> params = new HashMap<>();
    //GET 请求带的Header
    HashMap<String,String> headers= new HashMap<>();
    //HttpUrl.Builder构造带参数url
     HttpUrl.Builder urlBuilder = HttpUrl.parse(url).newBuilder();
            if (params != null) {
    
                for (String key : params.keySet()) {
                    urlBuilder.setQueryParameter(key, params.get(key));
                }
            }
            Request request = new Request.Builder()
                    .url(urlBuilder.build())
                    .headers(headers == null ? new Headers.Builder().build() : Headers.of(headers))
                    .get()
                    .build();

*  **通过Request的对象去构造得到一个Call对象**，类似于将你的请求封装成了任务，既然是任务，就会有execute(),enqueue()和cancel()等方法。  
    **execute()**:同步GET请求

//同步
    Response response = call.execute()
    if(response.isSuccessful()){
         //响应成功
    }

**enqueue()**:异步GET请求，将call加入调度队列，然后等待任务执行完成，我们在Callback中即可得到结果。  
**cancel()**:Call请求的取消，okHttp支持请求取消功能，当调用请求的cancel()时，请求就会被取消，抛出异常。又是需要监控许多Http请求的执行情况，可以把这些请求的Call搜集起来，执行完毕自动剔除，如果在请求执行过程中(如下载)，想取消执行，可使用call.cancel()取消。

*  **请求的响应Response**  
    对于同步GET请求，Response对象是直接返回的。异步GET请求，通过onResponse回调方法传参数，**需要注意的是这个onResponse回调方法不是在主线程回调，可以使用runInUIThread(new Runnable()\{\})**。  
    我们希望获得返回的字符串，可以通过`response.body().string()`获取；  
    如果希望获得返回的二进制字节数组，则调用`response.body().bytes()`；  
    如果你想拿到返回的inputStream，则调用`response.body().byteStream()`

**3. HTTP的POST请求**  
看来上面的简单的get请求，基本上整个的用法也就掌握了，比如post携带参数，也仅仅是Request的构造的不同。

//POST参数构造MultipartBody.Builder，表单提交
       HashMap<String,String> params = new HashMap<>();
         MultipartBody.Builder urlBuilder = new MultipartBody.Builder()
                                .setType(MultipartBody.FORM);
                        if (params != null) {
                            for (String key : params.keySet()) {
                                if (params.get(key)!=null){
                                    urlBuilder.addFormDataPart(key, params.get(key));
                                }
                                //urlBuilder.addFormDataPart(key, params.get(key));
    
                            }
                        }
    // 构造Request->call->执行
     Request request = new Request.Builder()
                                .headers(extraHeaders == null ? new Headers.Builder().build() : Headers.of(extraHeaders))//extraHeaders 是用户添加头
                                .url(url)
                                .post(urlBuilder.build())//参数放在body体里
                                .build();
    Call call = httpClient.newCall(request);
     try (Response response = call.execute()) {
                if (response.isSuccessful()){
                 //响应成功
                 }
      }

**Post的时候，参数是包含在请求体中的，所以我们通过MultipartBody.Builder 添加多个String键值对，然后去构造RequestBody，最后完成我们Request的构造。**  
**4. OKHTTP的上传文件**  
上传文件本身也是一个**POST请求**。在上面的POST请求中可以知道，POST请求的所有参数都是在BODY体中的，我们看看请求体的源码RequestBody:**请求体=contentType + BufferedSink**  
**RequestBody**

//抽象类请求体，**请求体=contentType + BufferedSink**
    public abstract class RequestBody {
      /** Returns the Content-Type header for this body. */
     //返回Body体的内容类型
      public abstract @Nullable MediaType contentType();
    
      /**
       * Returns the number of bytes that will be written to {@code sink} in a call to {@link #writeTo},
       * or -1 if that count is unknown.
       */
      //返回写入sink的字节长度
      public long contentLength() throws IOException {
        return -1;
      }
    
      /** Writes the content of this request to {@code sink}. */
      //写入缓存sink
      public abstract void writeTo(BufferedSink sink) throws IOException;
    
      /**
       * Returns a new request body that transmits {@code content}. If {@code contentType} is non-null
       * and lacks a charset, this will use UTF-8.
       */
       //创建一个请求体，如果contentType不等于null且缺少字符集，将使用UTF-8
      public static RequestBody create(@Nullable MediaType contentType, String content) {
        Charset charset = Util.UTF_8;
        if (contentType != null) {
          //contentType里面的字符集
          charset = contentType.charset();
          if (charset == null) {
            charset = Util.UTF_8;
            //contentType 里面加入字符集
            contentType = MediaType.parse(contentType + "; charset=utf-8");
          }
        }
        //按字符集变成字节
        byte[] bytes = content.getBytes(charset);
        return create(contentType, bytes);
      }
    
      /** Returns a new request body that transmits {@code content}. */
     //创建新的请求体，传输字节
      public static RequestBody create(
          final @Nullable MediaType contentType, final ByteString content) {
        return new RequestBody() {
          @Override public @Nullable MediaType contentType() {
            //请求体需要的内容类型
            return contentType;
          }
    
          @Override public long contentLength() throws IOException {
           //写入BufferedSink 的长度
            return content.size();
          }
    
          @Override public void writeTo(BufferedSink sink) throws IOException {
           //将需要传输的字节，写入缓存BufferedSink 中
            sink.write(content);
          }
        };
      }
    
      /** Returns a new request body that transmits {@code content}. */
      public static RequestBody create(final @Nullable MediaType contentType, final byte[] content) {
        return create(contentType, content, 0, content.length);
      }
    
      /** Returns a new request body that transmits {@code content}. */
      public static RequestBody create(final @Nullable MediaType contentType, final byte[] content,
          final int offset, final int byteCount) {
        if (content == null) throw new NullPointerException("content == null");
        Util.checkOffsetAndCount(content.length, offset, byteCount);
        return new RequestBody() {
          @Override public @Nullable MediaType contentType() {
            return contentType;
          }
    
          @Override public long contentLength() {
            return byteCount;
          }
    
          @Override public void writeTo(BufferedSink sink) throws IOException {
            sink.write(content, offset, byteCount);
          }
        };
      }
    
      /** Returns a new request body that transmits the content of {@code file}. */
      //创建一个请求体，传输文件file内容，其实就是file写入bufferedSink
      public static RequestBody create(final @Nullable MediaType contentType, final File file) {
        if (file == null) throw new NullPointerException("content == null");
    
        return new RequestBody() {
          @Override public @Nullable MediaType contentType() {
            return contentType;
          }
    
          @Override public long contentLength() {
            return file.length();
          }
    
          @Override public void writeTo(BufferedSink sink) throws IOException {
            Source source = null;
            try {
             //文件写入BufferedSink 
              source = Okio.source(file);
              sink.writeAll(source);
            } finally {
              Util.closeQuietly(source);
            }
          }
        };
      }
    }

**Http请求中Content-Type**  
客户端在进行http请求服务器的时候，需要告诉服务器请求的类型，服务器在返回给客户端的数据的时候，也需要告诉客户端返回数据的类型  
默认的ContentType为 text/html 也就是网页格式. 常用的内容类型

*  text/plain ：纯文本格式 .txt
 *  text/xml ： XML格式 .xml
 *  image/gif ：gif图片格式 .gif
 *  image/jpeg ：jpg图片格式 .jpg
 *  image/png：png图片格式 .png
 *  audio/mp3 : 音频mp3格式 .mp3
 *  audio/rn-mpeg :音频mpga格式 .mpga
 *  video/mpeg4 : 视频mp4格式 .mp4
 *  video/x-mpg : 视频mpa格式 .mpg
 *  video/x-mpeg :视频mpeg格式 .mpeg
 *  video/mpg : 视频mpg格式 .mpg  
    以application开头的媒体格式类型：
 *  application/xhtml+xml ：XHTML格式
 *  application/xml ： XML数据格式
 *  application/atom+xml ：Atom XML聚合格式
 *  application/json ： JSON数据格式
 *  application/pdf ：pdf格式
 *  application/msword ： Word文档格式
 *  application/octet-stream ： 二进制流数据（如常见的文件下载）  
    **MultipartBody.Builder 添加多个String键值对**

//MultipartBody源码，MultipartBody其实也是RequestBody ，需要在此RequestBody 体内，添加多个Part
    /** An <a href="http://www.ietf.org/rfc/rfc2387.txt">RFC 2387</a>-compliant request body. */
    public final class MultipartBody extends RequestBody {
      /**
       * The "mixed" subtype of "multipart" is intended for use when the body parts are independent and
       * need to be bundled in a particular order. Any "multipart" subtypes that an implementation does
       * not recognize must be treated as being of subtype "mixed".
       */
      //混合的内容类型
      public static final MediaType MIXED = MediaType.parse("multipart/mixed");
    
      /**
       * The "multipart/alternative" type is syntactically identical to "multipart/mixed", but the
       * semantics are different. In particular, each of the body parts is an "alternative" version of
       * the same information.
       */
      public static final MediaType ALTERNATIVE = MediaType.parse("multipart/alternative");
    
      /**
       * This type is syntactically identical to "multipart/mixed", but the semantics are different. In
       * particular, in a digest, the default {@code Content-Type} value for a body part is changed from
       * "text/plain" to "message/rfc822".
       */
      public static final MediaType DIGEST = MediaType.parse("multipart/digest");
    
      /**
       * This type is syntactically identical to "multipart/mixed", but the semantics are different. In
       * particular, in a parallel entity, the order of body parts is not significant.
       */
      public static final MediaType PARALLEL = MediaType.parse("multipart/parallel");
    
      /**
       * The media-type multipart/form-data follows the rules of all multipart MIME data streams as
       * outlined in RFC 2046. In forms, there are a series of fields to be supplied by the user who
       * fills out the form. Each field has a name. Within a given form, the names are unique.
       */
      public static final MediaType FORM = MediaType.parse("multipart/form-data");
    
      private static final byte[] COLONSPACE = {':', ' '};
      private static final byte[] CRLF = {'\r', '\n'};
      private static final byte[] DASHDASH = {'-', '-'};
    
      private final ByteString boundary;
      private final MediaType originalType;
    
     //请求体的内容类型
      private final MediaType contentType;
      //MultiPartBody需要添加多个Part对象，一起请求
      private final List<Part> parts;
      private long contentLength = -1L;
      //构造函数
      MultipartBody(ByteString boundary, MediaType type, List<Part> parts) {
        this.boundary = boundary;
        this.originalType = type;
        this.contentType = MediaType.parse(type + "; boundary=" + boundary.utf8());
        this.parts = Util.immutableList(parts);
      }
    
      public MediaType type() {
        return originalType;
      }
    
      public String boundary() {
        return boundary.utf8();
      }
    
      /** The number of parts in this multipart body. */
      //multipart 的数量
      public int size() {
        return parts.size();
      }
     //多个parts
      public List<Part> parts() {
        return parts;
      }
     
      public Part part(int index) {
        return parts.get(index);
      }
    
      /** A combination of {@link #type()} and {@link #boundary()}. */
      //MultiPart的内容类型
      @Override public MediaType contentType() {
        return contentType;
      }
    
      @Override public long contentLength() throws IOException {
        long result = contentLength;
        if (result != -1L) return result;
        return contentLength = writeOrCountBytes(null, true);
      }
      //将每个part写入BufferedSink中，传输
      @Override public void writeTo(BufferedSink sink) throws IOException {
        writeOrCountBytes(sink, false);
      }
    
      /**
       * Either writes this request to {@code sink} or measures its content length. We have one method
       * do double-duty to make sure the counting and content are consistent, particularly when it comes
       * to awkward operations like measuring the encoded length of header strings, or the
       * length-in-digits of an encoded integer.
       */
      //将每个Part的内容都写入，MultiPartBody的BufferedSink 中
      private long writeOrCountBytes(@Nullable BufferedSink sink, boolean countBytes) throws IOException {
        long byteCount = 0L;
    
        Buffer byteCountBuffer = null;
        if (countBytes) {
          sink = byteCountBuffer = new Buffer();
        }
       //写每个part
        for (int p = 0, partCount = parts.size(); p < partCount; p++) {
          Part part = parts.get(p);
         //Part的Headers和RequestBody 
          Headers headers = part.headers;
          RequestBody body = part.body;
    
          sink.write(DASHDASH);
          sink.write(boundary);
          sink.write(CRLF);
    
          //Part的Headers写入sink
          if (headers != null) {
         
            for (int h = 0, headerCount = headers.size(); h < headerCount; h++) {
              sink.writeUtf8(headers.name(h))
                  .write(COLONSPACE)
                  .writeUtf8(headers.value(h))
                  .write(CRLF);
            }
          }
          //Part的RequestBody写入Part
         //1,写contentType 
          MediaType contentType = body.contentType();
          if (contentType != null) {
            sink.writeUtf8("Content-Type: ")
                .writeUtf8(contentType.toString())
                .write(CRLF);
          }
         //2,写contentLength 
          long contentLength = body.contentLength();
          if (contentLength != -1) {
            sink.writeUtf8("Content-Length: ")
                .writeDecimalLong(contentLength)
                .write(CRLF);
          } else if (countBytes) {
            // We can't measure the body's size without the sizes of its components.
            byteCountBuffer.clear();
            return -1L;
          }
    
          sink.write(CRLF);
          //3，写body体
          if (countBytes) {
            byteCount += contentLength;
          } else {
            body.writeTo(sink);
          }
    
          sink.write(CRLF);
        }
    
        sink.write(DASHDASH);
        sink.write(boundary);
        sink.write(DASHDASH);
        sink.write(CRLF);
    
        if (countBytes) {
          byteCount += byteCountBuffer.size();
          byteCountBuffer.clear();
        }
    
        return byteCount;
      }
    
      /**
       * Appends a quoted-string to a StringBuilder.
       *
       * <p>RFC 2388 is rather vague about how one should escape special characters in form-data
       * parameters, and as it turns out Firefox and Chrome actually do rather different things, and
       * both say in their comments that they're not really sure what the right approach is. We go with
       * Chrome's behavior (which also experimentally seems to match what IE does), but if you actually
       * want to have a good chance of things working, please avoid double-quotes, newlines, percent
       * signs, and the like in your field names.
       */
        //装换换行符，tab符号，引号
      static StringBuilder appendQuotedString(StringBuilder target, String key) {
        target.append('"');
        for (int i = 0, len = key.length(); i < len; i++) {
          char ch = key.charAt(i);
          switch (ch) {
            case '\n':
              target.append("%0A");
              break;
            case '\r':
              target.append("%0D");
              break;
            case '"':
              target.append("%22");
              break;
            default:
              target.append(ch);
              break;
          }
        }
        target.append('"');
        return target;
      }
     //Part 的定义，Part 是由Headers+RequestBody组成
      public static final class Part {
        public static Part create(RequestBody body) {
          return create(null, body);
        }
    
        public static Part create(@Nullable Headers headers, RequestBody body) {
          if (body == null) {
            throw new NullPointerException("body == null");
          }
          //Part的headers不能存在Content-Type和Content-Length字段
          if (headers != null && headers.get("Content-Type") != null) {
            throw new IllegalArgumentException("Unexpected header: Content-Type");
          }
          if (headers != null && headers.get("Content-Length") != null) {
            throw new IllegalArgumentException("Unexpected header: Content-Length");
          }
          return new Part(headers, body);
        }
        //创建key-value的Part，name其实就是key
        public static Part createFormData(String name, String value) {
          return createFormData(name, null, RequestBody.create(null, value));
        }
        //创建key-value的Part
        public static Part createFormData(String name, @Nullable String filename, RequestBody body) {
          if (name == null) {
            throw new NullPointerException("name == null");
          }
          StringBuilder disposition = new StringBuilder("form-data; name=");
          // disposition =  form-data; name=name;
          appendQuotedString(disposition, name);//对name中的特殊符号转换
    
          if (filename != null) {
            disposition.append("; filename=");
            // disposition =  form-data; name=name; filename=filename;
            appendQuotedString(disposition, filename);//对filename中的特殊符号转换
          }
         //创建Part 体，Headers（Content-Disposition- form-data; name=name; filename=filename）+body
          return create(Headers.of("Content-Disposition", disposition.toString()), body);
        }
        //headers
        final @Nullable Headers headers;
        //body
        final RequestBody body;
    
        private Part(@Nullable Headers headers, RequestBody body) {
          this.headers = headers;
          this.body = body;
        }
       //Part的headers
        public @Nullable Headers headers() {
          return headers;
        }
        //Part的body体
        public RequestBody body() {
          return body;
        }
      }
    
      public static final class Builder {
        private final ByteString boundary;
        private MediaType type = MIXED;
        private final List<Part> parts = new ArrayList<>();
    
        public Builder() {
          this(UUID.randomUUID().toString());
        }
    
        public Builder(String boundary) {
          this.boundary = ByteString.encodeUtf8(boundary);
        }
    
        /**
         * Set the MIME type. Expected values for {@code type} are {@link #MIXED} (the default), {@link
         * #ALTERNATIVE}, {@link #DIGEST}, {@link #PARALLEL} and {@link #FORM}.
         */
        public Builder setType(MediaType type) {
          if (type == null) {
            throw new NullPointerException("type == null");
          }
          if (!type.type().equals("multipart")) {
            throw new IllegalArgumentException("multipart != " + type);
          }
          this.type = type;
          return this;
        }
    
        /** Add a part to the body. */
       //添加Part
        public Builder addPart(RequestBody body) {
          return addPart(Part.create(body));
        }
    
        /** Add a part to the body. */
        //添加Part
        public Builder addPart(@Nullable Headers headers, RequestBody body) {
          return addPart(Part.create(headers, body));
        }
    
        /** Add a form data part to the body. */
       //添加表单数据Part
        public Builder addFormDataPart(String name, String value) {
          return addPart(Part.createFormData(name, value));
        }
    
        /** Add a form data part to the body. */
        //添加表单数据Part
        public Builder addFormDataPart(String name, @Nullable String filename, RequestBody body) {
          return addPart(Part.createFormData(name, filename, body));
        }
    
        /** Add a part to the body. */
        public Builder addPart(Part part) {
          if (part == null) throw new NullPointerException("part == null");
          parts.add(part);
          return this;
        }
    
        /** Assemble the specified parts into a request body. */
        public MultipartBody build() {
          if (parts.isEmpty()) {
            throw new IllegalStateException("Multipart body must have at least one part.");
          }
         //构建MultipartBody对象
          return new MultipartBody(boundary, type, parts);
        }
      }
    }

总结一下MultipartBody：

1.  MultipartBody本质一个是一个RequestBody，具有自己的contentType+BufferedSink，是POST请求的最外层封装，需要添加多个Part
2.  Part对象组成：Headers+RequestBody。是MultipartBody的成员变量，需要写入MultipartBody的BufferedSink中。

**HTTP真正的上传文件**

1.  最基本的上传文件：

**重点：RequestBody create(MediaType contentType, final File file)构造文件请求体RequestBody ,并且添加到MultiPartBody中**

OkHttpClient client = new OkHttpClient();
            // form 表单形式上传,MultipartBody的内容类型是表单格式，multipart/form-data
            MultipartBody.Builder urlBuilder= new MultipartBody.Builder().setType(MultipartBody.FORM);
          
          //参数
           HashMap<String,String> params = new HashMap<>();
           if (params != null) {
                    for (String key : params.keySet()) {
                        if (params.get(key)!=null){
                            urlBuilder.addFormDataPart(key, params.get(key));
                        }
                   }
                }
            //需要上传的文件，需要携带上传的文件（小型文件 不建议超过500K）
             HashMap<String,String> files= new HashMap<>();
             if (files != null) {
                 for (String key : files.keySet()) {
                    //重点：RequestBody create(MediaType contentType, final File file)构造文件请求体RequestBody 
                     urlBuilder.addFormDataPart(key, files.get(key).getName(), RequestBody.create(MediaType.parse("multipart/form-data"), files.get(key)));
                   }
                 }
               //构造请求request 
                Request request = new Request.Builder()
                                .headers(extraHeaders == null ? new Headers.Builder().build() : Headers.of(extraHeaders))
                                .url(url)
                                .post(urlBuilder.build())
                                .build();
             //异步执行请求
              newCall(request).enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {
                    Log.i("lfq" ,"onFailure");
                }
    
                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    //非主线程
                    if (response.isSuccessful()) {
                        String str = response.body().string();
                        Log.i("tk", response.message() + " , body " + str);
    
                    } else {
                        Log.i("tk" ,response.message() + " error : body " + response.body().string());
                    }
                }
            });

**2. 大文件分块异步上传**  
我们知道Post上传文件，**简单的说就是将文件file封装成RequestBody体，然后添加到MultiPartBody的addPart中构造MultiPartBody所需要的Part对象(Headers+body)**,RequestBody是个抽象类，里面的所有create方法如下：

![format_png 6][]

image.png

![format_png 7][]

filebody.png

可以看出，基本都是重写了抽象类的RequestBody的三种方法，所以我们也可以继承实现自己的Body体：

![format_png 8][]

image.png

EG：已上传相机图片（5M）为例，**分块多线程异步同时上传**，但是这种方法需要服务端接口才行。

//文件路径
    String path = "xxx.jpg";

1,文件块对象

public static final int FILE_BLOCK_SIZE = 500 * 1024;//500k
     /*文件块描述*/
        public static class FileBlock {
            public long start;//起始字节位置
            public long end;//结束字节位置
            public int index;//文件分块索引
        }

2,文件切块

//计算切块,存储在数组
     final SparseArray<FileBlock> blockArray = splitFile(path, FILE_BLOCK_SIZE);
     /**
         * 文件分块
         *
         * @param filePath  文件路径
         * @param blockSize 块大小
         *
         * @return 分块描述集合 文件不存在时返回空
         */
        public static SparseArray<FileBlock> splitFile(String filePath, long blockSize) {
            File file = new File(filePath);
            if (!file.exists()) {
                return null;
            }
            SparseArray<FileBlock> blockArray = new SparseArray<>();
            int i = 0;
            int start = 0;
            while (start < file.length()) {
                i++;
                FileBlock fileBlock = new FileBlock();
                fileBlock.index = i;
                fileBlock.start = start;
                start += blockSize;
                fileBlock.end = start;
                blockArray.put(i, fileBlock);
            }
            blockArray.get(i).end = file.length();
            return blockArray;
        }

3,对文件块分块多线程异步上传  
服务端的接口：

url：domain/sync/img/upload
    method: POST
    //请求参数
    data = {
            'img_md5': 'dddddsds',
            'total': 10, #总的分片数
            'index': 5, #该分片所在的位置, start by 1
        }
    请求返回值json:
     {
            'status': 206/205/400/409/500,
            'msg': '分片上传成功/上传图片成功/参数错误/上传数据重复/上传失败'
            'data': {  # 205时有此字段
                'img_url': 'https://foo.jpg',
            }
        }

只需要图片的md5,总的分片数，该分片的位置，当一块传输成功时返回206，当全部块传完成是返回206，并返回该图片在服务器的url  
服务端接口返回解析类：

/**
         * 分片上传部分的接口返回
         *
         * @link {http://10.16.69.11:5000/iSync/iSync%E6%9C%8D%E5%8A%A1%E7%AB%AFv4%E6%96%87%E6%A1%A3/index.html#4_1}
         */
        public static class ChuckUploadData  implements Serializable {
            public ChuckUploadBean data;
            public static class ChuckUploadBean implements Serializable{
                public String img_url;
            }
            /** 此块是否上传成功 */
            public boolean isPicSuccess() {
                return status == 206 || status == 409;
            }
    
            /** 全部原图是否上传成功 */
            public boolean isAllPicSuccess() {
                return status == 205;
            }
    
            public boolean isRepitition(){
                return status == 409;
            }
    
        }
       //上传图片的线程池
       ExcutorService threadPool =  Executors.newCachedThreadPool();
       //上传函数
     /**
         * 上传原图,异步上传
         *
         * @param httpCallback 回调接口
         * @param md5         文件md5
         * @param path         图片路径
         * @param total        总块数
         * @param index        分块索引
         * @param start        分块开始位置
         * @param end          分块结束位置
         */
        public static void uploadBigImage(String userId, final HttpListenerAdapter<ChuckUploadData> httpCallback, String md5, String path, int total, int index, long start, long end) {
            HashMap<String, String> params = new HashMap<String, String>();
            params.put("img_uuid", uuid);//完整文件的md5
            params.put("total", String.valueOf(total));//总的分片数
            params.put("index", String.valueOf(index));//当前分片位置，从1开始
            //全局单例OKHttpClient
            OkHttpClient httpClient = DataProvider.getInstance().inkApi.getLongWaitHttpClient();
    
            Runnable httpUploadRunnable = HttpRunnableFactory.newPostFileBlockRunnable(
                    httpClient,
                    upload_url,//上传url，自定义
                    null,
                    params,//上传参数
                    "image",
                    new File(path),//图片文件
                    start,//index块开始的位置
                    end,//index块结束的位置
                    ChuckUploadData.class,
                    httpCallback);//回调函数
            threadManager.submit httpUploadRunnable );
        }
     /**
         * 异步post请求 表单方式拆块上传大型文件用，构造Runnable 
         *
         * @param httpClient  okhttp客户端
         * @param url         请求地址
         * @param headers     额外添加的header（通用header由中断器统一添加）
         * @param params      请求参数
         * @param fileKey     文件的接收用key
         * @param file        大型文件对象
         * @param seekStart   起始字节
         * @param seekEnd     结束字节
         * @param cls         返回结果需要序列化的类型
         * @param listener    异步回调
         * @param <T>         返回结果需要序列化的类型声明
         *
         * @return 异步post请求用的默认Runnable
         */
        public static <T> Runnable newPostFileBlockRunnable(final OkHttpClient httpClient,  final String url, final Map<String, String> headers, final Map<String, String> params, final String fileKey, final File file, final long seekStart, final long seekEnd, final Class<T> cls, final HttpListenerAdapter<T> listener) {
            return new Runnable () {
                @Override
                public void run() {
                    Log.e("http", "---postfile---");
                    Log.e("http", "url: " + url);
                    Log.e("http", "extraHeaders: " + headers);
                    Log.e("http", "params: " + params);
                    Log.e("http", "filepath: " + file.getPath());
                    Log.e("http", "seekStart: " + seekStart);
                    Log.e("http", "seekEnd: " + seekEnd);
    
                    Call call = null;
                    if (listener != null) {
                        listener.onStart(call);
                    }
                    try {
                        if (TextUtils.isEmpty(url)) {
                            throw new InterruptedException("url is null exception");
                        }
                         //构造path文件的index块的seekStart到seekEnd的请求体requestBody ，添加到MultiPartBody中
                        RequestBody requestBody = new RequestBody() {
                            @Override
                            public MediaType contentType() {
                               //请求体的内容类型
                                return MediaType.parse("multipart/form-data");
                            }
    
                            @Override
                            public void writeTo(BufferedSink sink) throws IOException {
                                //切块上传
                                long nowSeek = seekStart;
                                long seekEndWrite = seekEnd;
                                if (seekEndWrite == 0) {
                                    seekEndWrite = file.length();
                                }
                                //跳到开始位置
                                FileInputStream in = new FileInputStream(file);
                                if (seekStart > 0) {
                                    long amt = in.skip(seekStart);
                                    if (amt == -1) {
                                        nowSeek = 0;
                                    }
                                }
                                //将该块的字节内容写入body的BufferedSink 中
                                int len;
                                byte[] buf = new byte[BUFFER_SIZE_DEFAULT];
                                while ((len = in.read(buf)) >= 0 && nowSeek < seekEndWrite) {
                                    sink.write(buf, 0, len);
                                    nowSeek += len;
                                    if (nowSeek + BUFFER_SIZE_DEFAULT > seekEndWrite) {
                                        buf = new byte[Integer.valueOf((seekEndWrite - nowSeek) + "")];
                                    }
                                }
                                closeStream(in);
                            }
    
                        };
                        //组装其它参数
                        MultipartBody.Builder urlBuilder = new MultipartBody.Builder()
                                .setType(MultipartBody.FORM);
                        if (params != null) {
                            for (String key : params.keySet()) {
                                //urlBuilder.addFormDataPart(key, params.get(key));
                                if (params.get(key)!=null){
                                    urlBuilder.addFormDataPart(key, params.get(key));
                                }
                            }
                        }
                        //把文件块的请求体添加到MultiPartBody中
                        urlBuilder.addFormDataPart(fileKey, file.getName(), requestBody);
                        Request request = new Request.Builder()
                                .headers(headers == null ? new Headers.Builder().build() : Headers.of(headers))
                                .url(url)
                                .post(urlBuilder.build())
                                .build();
    
                        call = httpClient.newCall(request);
                        //虽说是同步调用call.execute()，但是此Http请求过程是在线程池中的，相当于异步调用
                        try (Response response = call.execute()) {
                            if (!response.isSuccessful()){
                                throw new IOException("Unexpected code " + response.code());
                            }
                             /*打印json串，json样式的*/
                            String json = response.body().string();
                            //解析返回的响应json
                            T result = JsonUtils.getObjFromStr(cls, json);
                            if (listener != null) {
                                //防止回调内的业务逻辑引起二次onFailure回调
                                try {
                                    listener.onResponse(call, result);
                                } catch (Exception e) {
                                    e.printStackTrace();
                                }
                            }
                        } finally {
                           
                        }
                    } catch (Exception e) {
                        if (listener != null) {
                            //中途取消导致的中断
                            if (call != null && call.isCanceled()) {
                                listener.onCancel(call);
                            } else {
                                //其它意义上的请求失败
                                listener.onFailure(call, e);
                            }
                        }
                    } finally {
                        if (listener != null) {
                            listener.onEnd(call);
                        }
                    }
                }
            };
        }

//循环遍历所有的文章块，多线程上传
     for (int i = 0; i < blockArray.size(); i++) {
                 //异步分块上传
                  final FileUtil.FileBlock block = blockArray.get(i + 1);
                  //提交线程池，异步上传单块
                uploadBigImage(userId, new HttpListenerAdapter<ChuckUploadData>() {
                             @Override
                             public void onResponse(Call call, SyncBeans.ChuckUploadData bean) {
                                  try {
                                       //单块上传
                                        if (bean != null ) {
                                              if (bean.isPicSuccess()) {
                                                    //205,单块成功不做处理
                                               } else if (bean.isAllPicSuccess()) {
                                                   //206,全部成功
                                               }
                                          }
                                    }catch(Exception e){}
                                },uuid, mediaBean.imageNativeUrl, blockArray.size(), block.index, block.start, block.end);
         }

**5. OKHttp下载文件，并通知进度**

下载文件的原理其实很简单，下载过程其实就是一个GET过程(上传文件是POST过程相对应)，下载文件需要在异步线程中执行（**方法有二，1，使用okhttp的call.enquene()方法异步执行，2，使用call.excute()同步方法，但是在线程次中执行整个请求过程**），在成功响应之后，获得网络文件输入流InputStream，然后循环读取输入流上的文件，写入文件输出流。

/**
         * @param url 下载连接
         * @param saveDir 储存下载文件的SDCard目录
         * @param params url携带参数
         * @param extraHeaders 请求携带其他的要求的headers
         * @param listener 下载监听
         */
        public void download(final String url, final String saveDir,HashMap<String,String> params, HashMap<String,String> extraHeaders，final OnDownloadListener listener) {
           //构造请求Url
           HttpUrl.Builder urlBuilder = HttpUrl.parse(url).newBuilder();
               if (params != null) {
                   for (String key : params.keySet()) {
                       if (params.get(key)!=null){
                          urlBuilder.setQueryParameter(key, params.get(key));//非必须
                         } 
                  }
                }
            //构造请求request
             Request request = new Request.Builder()
                                .url(urlBuilder.build())
                                .headers(extraHeaders == null ? new Headers.Builder().build() : Headers.of(extraHeaders))//headers非必须
                                .get()
                                .build();
           //异步执行请求
            okHttpClient.newCall(request).enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {
                    // 下载失败
                    listener.onDownloadFailed();
                }
                @Override
                public void onResponse(Call call, Response response) throws IOException {
                   //非主线程
                    InputStream is = null;
                    byte[] buf = new byte[2048];
                    int len = 0;
                    FileOutputStream fos = null;
                    // 储存下载文件的目录
                    String savePath = isExistDir(saveDir);
                    try {
                        //获取响应的字节流
                        is = response.body().byteStream();
                        //文件的总大小
                        long total = response.body().contentLength();
                        File file = new File(savePath);
                        fos = new FileOutputStream(file);
                        long sum = 0;
                       //循环读取输入流
                        while ((len = is.read(buf)) != -1) {
                            fos.write(buf, 0, len);
                            sum += len;
                            int progress = (int) (sum * 1.0f / total * 100);
                            // 下载中
                            if(listener != null){
                                listener.onDownloading(progress);
                             }
                           
                        }
                        fos.flush();
                        // 下载完成
                        if(listener != null){
                              listener.onDownloadSuccess();
                         }
                    
                    } catch (Exception e) {
                         if(listener != null){
                              listener.onDownloadFailed();
                         }
                       
                    } finally {
                        try {
                            if (is != null)
                                is.close();
                        } catch (IOException e) {
                        }
                        try {
                            if (fos != null)
                                fos.close();
                        } catch (IOException e) {
                        }
                    }
                }
            });
        }

**至此，OKHTTP3的基本网络请求访问，发送GET请求，发送POST请求，基本上传文件，切块多线程异步上传文件，下载文件就到这里了，其实下载文件还可以做成断点续传，获取每次的seek点**

作者：木有粗面\_9602  
链接：https://www.jianshu.com/p/f3f228d3598c  
来源：简书  
著作权归作者所有。商业转载请联系作者获得授权，非商业转载请注明出处。

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