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介绍

本文将介绍 OkHttp 客户端的基本用法。
主要介绍 OkHttp 3.x 版本中发送Post请求的几种方式。

pom依赖

        <dependency><groupId>com.squareup.okhttp3</groupId><artifactId>okhttp</artifactId><version>4.8.0</version></dependency>

基本的POST请求

使用 FormBody.Builder 构造基本的 RequestBody ， 包含两个参数：用户名、密码，发送 POST请求。

    public static void main(String[] args) {String BASE_URL = "http://localhost:8080/okhttp3/test";RequestBody formBody = new FormBody.Builder().add("username", "zhangsan").add("password", "123456").build();Request request = new Request.Builder().url(BASE_URL + "/users").post(formBody).build();Call call = new OkHttpClient().newCall(request);Response response = null;try {response = call.execute();} catch (IOException e) {System.out.println("execute failed, message:" + e.getMessage());}assert response != null;if (!response.isSuccessful()) {System.out.println("request failed");}}

带授权的POST请求

如果要对请求进行身份验证，可以使用 Credentials.basic 构建器向请求头中添加凭据。
下面代码给出发送一个 String 字符串作为请求体带授权的例子:

    public static void main(String[] args) {String BASE_URL = "http://localhost:8080/okhttp3/test";// 带授权的POST请求String postBody = "content";Request request = new Request.Builder().url(BASE_URL + "/users").addHeader("Authorization", Credentials.basic("username", "password")).post(RequestBody.create(MediaType.parse("text/x-markdown"), postBody)).build();Call call = new OkHttpClient().newCall(request);Response response = null;try {response = call.execute();} catch (IOException e) {System.out.println("execute failed, message:" + e.getMessage());}assert response != null;if (!response.isSuccessful()) {System.out.println("request failed");}}

POST方式发送JSON数据

为了在请求体中发送 JSON，我们必须设置它的媒体类型 application/json。 我们可以使用 RequestBody.create构建器来构造：

    public static void main(String[] args) {String BASE_URL = "http://localhost:8080/okhttp3/test";// POST方式发送JSON数据String json = "{\"username\":zhangsan,\"password\":\"123456\"}";RequestBody body = RequestBody.create(MediaType.parse("application/json"), json);Request request = new Request.Builder().url(BASE_URL + "/users").post(body).build();Call call = new OkHttpClient().newCall(request);Response response = null;try {response = call.execute();} catch (IOException e) {System.out.println("execute failed, message:" + e.getMessage());}assert response != null;if (!response.isSuccessful()) {System.out.println("request failed");}}

Multipart POST 请求

我们需要将 RequestBody 构建为一个 MultipartBody 来发布文件、用户名和密码的 POST 请求：

    public static void main(String[] args) {String BASE_URL = "http://localhost:8080/okhttp3/test";// Multipart POST请求RequestBody requestBody = new MultipartBody.Builder().setType(MultipartBody.FORM).addFormDataPart("username", "zhangsan").addFormDataPart("password", "123456").addFormDataPart("file", "file.txt",RequestBody.create(MediaType.parse("application/octet-stream"), new File("src/test/resources/test.txt"))).build();Request request = new Request.Builder().url(BASE_URL + "/users/multipart").post(requestBody).build();Call call = new OkHttpClient().newCall(request);Response response = null;try {response = call.execute();} catch (IOException e) {System.out.println("execute failed, message:" + e.getMessage());}assert response != null;if (!response.isSuccessful()) {System.out.println("request failed");}}