OkHttp 网络库快速使用

OkHttp 快速使用

Square-OkHttp 是一个基于 Java 的 HTTP 网络操作框架，可以提供比 JDK 的 URLConnection 更加强大的功能，同时在使用上比 Apache-HttpClient 更加简便高效；

OkHttp 支持 HTTP 的 CRUD 方法（POST，GET，PUT，DELETE 等），支持 HTTP/2 、SPDY，同时也提供了对 HTTP 的缓存机制，进一步提供 HTTP 连接效率；

OkHttp 项目主页：http://square.github.io/okhttp/

参考文档： https://www.ibm.com/developerworks/cn/java/j-lo-okhttp/index.html

使用 OkHttp 需要导入的依赖：

com.squareup.okhttp3:okhttp (3.x版本)

以下示例都是基于 OkHttp 3.X 版本，和 2.X 版本部分代码不同；

发送 GET 请求

OkHttpClient httpClient = new OkHttpClient();

//构建 Request 请求对象
Request request = new Request.Builder()
        .url("http://blog.csdn.net/")
        //.header("User-Agent","Chrome/58.0.3029.110")  //添加请求头
        .build();

// 运行httpClient，获取 Response 响应对象
Response response = httpClient.newCall(request).execute();
if(!response.isSuccessful()) {
    throw new IOException("server connection error");
}

//获取所有响应头
Headers headers = response.headers();
for(int i=0; i

发送 POST 请求

提交键表单键值对

OkHttpClient httpClient = new OkHttpClient();

//构建 Request 请求对象
RequestBody formBody = new FormBody.Builder()
        .add("username","assad")
        .add("password","1234")
        .build();
Request request = new Request.Builder()
        .url("http://127.0.0.1:8080/loginCheck")
        .post(formBody)
        .build();

//获取 Response 对象
Response response = httpClient.newCall(request).execute();
if(!response.isSuccessful())
    throw new IOException("server connection error");
//以字符串的形式获取响应正文
System.out.println(response.body().string());

提交文本正文

OkHttpClient httpClient = new OkHttpClient();

//构建 Request 请求对象
RequestBody postBody = RequestBody.create(MediaType.parse("text/plain"),"Hello world!");
Request request = new Request.Builder()
        .url("http://www.baidu.com")
        .post(postBody)
        .build();

//获取 Response 对象
Response response = httpClient.newCall(request).execute();
if(response.isSuccessful())
    throw new IOException("server connection error");
System.out.println(response.body().string());

当正文文本长度比较长时，可以使用输入流添加 reqeustBody 以节约内存，如下：

OkHttpClient httpClient = new OkHttpClient();

//使用输入流的方式构建 RequestBody
RequestBody postBody = new RequestBody() {
    @Override
    public MediaType contentType() {
        return MediaType.parse("text/plain");
    }
    @Override
    public void writeTo(BufferedSink sink) throws IOException {
        sink.writeUtf8("This is a long length text content");
    }
};
//构建 Request 请求对象
Request request = new Request.Builder()
        .url("http://www.baidu.com")
        .post(postBody)
        .build();

//获取 Response 对象
Response response = httpClient.newCall(request).execute();
if(response.isSuccessful())
    throw new IOException("server connection error");
System.out.println(response.body().string());

提交 json 正文

提交 json 正文类似提交文本正文，只需要修改相应的请求头即可；

String jsonStr = "{\"user\":\"assad\",\"id\":2333331010}";

OkHttpClient httpClient = new OkHttpClient();

//构建 Request 请求对象
RequestBody postBody = RequestBody.create(MediaType.parse("application/json;charset=utf-8"),jsonStr);
Request request = new Request.Builder()
        .url("http://127.0.0.1:8080/exchangeJsonTest")
        .post(postBody)
        .build();

//获取 Response 对象
Response response = httpClient.newCall(request).execute();
if(response.isSuccessful())
    throw new IOException("server connection error");
System.out.println(response.body().string());

文件上传

OkHttpClient httpClient = new OkHttpClient();

//构建 Multipart 类型 RequestBody，上传图片（如果需要上传多个文件，只需要添加多个addFormDataPart即可）
RequestBody postBody = new MultipartBody.Builder()
        .setType(MultipartBody.FORM)
        .addFormDataPart("files",null, new MultipartBody.Builder()
                .addPart(Headers.of("Content-Disposition","form-data; uploadfilename=\"testImg.png\""),
                        RequestBody.create(MediaType.parse("image/png"),new File("./testImg.png")))
                .build())
        .build();

//构建 Request 请求对象
Request request = new Request.Builder()
        .url("http://127.0.0.1:8080/getImage")
        .post(postBody)
        .build();

//获取 Response 对象
Response response = httpClient.newCall(request).execute();
if(response.isSuccessful())
    throw new IOException("server connection error");
System.out.println(response.body().string());

文件下载

 OkHttpClient httpClient = new OkHttpClient();

//构建 Request 请求对象
Request request = new Request.Builder()
        .url("http://wx2.sinaimg.cn/mw600/dac9e610ly1fnzld0k3j4j20rs12wjw6.jpg")
        .build();

// 运行httpClient，获取 Response 响应对象
Response response = httpClient.newCall(request).execute();
if(!response.isSuccessful()) {
    throw new IOException("server connection error");
}

//以字节流的形式读取响应二进制正文，并保存为文件
BufferedInputStream input = new BufferedInputStream(response.body().byteStream());
BufferedOutputStream output = new BufferedOutputStream(new FileOutputStream("download.jpg"));
int bytes;
while(( bytes = input.read()) != -1)
    output.write(bytes);
input.close();
output.flush();
output.close();