OkHttp3.x Post方法快速教程

1. 介绍

在这篇相对较短的教程中，我们将会着重介绍OkHttp3.x版本的不同的POST请求方式。

2. 基础的POST

我们可以使用FormBody.Builder 构建一个基础的RequestBody , 通过POST请求传递两个参数– username 和 password :

@Test
public void whenSendPostRequest_thenCorrect() 
  throws IOException {
    RequestBody formBody = new FormBody.Builder()
      .add("username", "test")
      .add("password", "test")
      .build();

    Request request = new Request.Builder()
      .url(BASE_URL + "/users")
      .post(formBody)
      .build();

    Call call = client.newCall(request);
    Response response = call.execute();
    
    assertThat(response.code(), equalTo(200));
}

3. POST 验证

如果我们想要验证请求，我们可以使用Credentials.basic构造器将凭证添加到header中

在这个简单实例中，我们将会发送一个String作为request的body:

@Test
public void whenSendPostRequestWithAuthorization_thenCorrect() 
  throws IOException {
    String postBody = "test post";
    
    Request request = new Request.Builder()
      .url(URL_SECURED_BY_BASIC_AUTHENTICATION)
      .addHeader("Authorization", Credentials.basic("username", "password"))
      .post(RequestBody.create(
        MediaType.parse("text/x-markdown), postBody))
      .build();

    Call call = client.newCall(request);
    Response response = call.execute();

    assertThat(response.code(), equalTo(200));
}

4. POST 与 JSON

为了在请求正文中发送 JSON，我们需要设置媒体类型为application/json。我们可以使用RequestBody.create builder来完成：

@Test
public void whenPostJson_thenCorrect() throws IOException {
    String json = "{"id":1,"name":"John"}";

    RequestBody body = RequestBody.create(
      MediaType.parse("application/json"), json);

    Request request = new Request.Builder()
      .url(BASE_URL + "/users/detail")
      .post(body)
      .build();
 
    Call call = client.newCall(request);
    Response response = call.execute();

    assertThat(response.code(), equalTo(200));
}

5. Multipart POST 请求

我们看到的最后一个示例是 POST Multipart 请求。我们需要将RequestBody构建为MultipartBody用于post 例子中的file、username和password：

@Test
public void whenSendMultipartRequest_thenCorrect() 
  throws IOException {	
    RequestBody requestBody = new MultipartBody.Builder()
      .setType(MultipartBody.FORM)
      .addFormDataPart("username", "test")
      .addFormDataPart("password", "test")
      .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 = client.newCall(request);
    Response response = call.execute();

    assertThat(response.code(), equalTo(200));
}

6. POST with Non-Default Character Encoding

OkHttp 默认的字符编码是 UTF-8：

@Test
public void whenPostJsonWithoutCharset_thenCharsetIsUtf8() throws IOException {
    final String json = "{"id":1,"name":"John"}";

    final RequestBody body = RequestBody.create(
        MediaType.parse("application/json"), json);

    String charset = body.contentType().charset().displayName();

    assertThat(charset, equalTo("UTF-8"));
}

如果我们想使用不同的字符编码，我们可以将它作为MediaType.parse()的第二个参数传递：

@Test
public void whenPostJsonWithUtf16Charset_thenCharsetIsUtf16() throws IOException {
    final String json = "{"id":1,"name":"John"}";

    final RequestBody body = RequestBody.create(
        MediaType.parse("application/json; charset=utf-16"), json);

    String charset = body.contentType().charset().displayName();

    assertThat(charset, equalTo("UTF-16"));
}

7. 总结

在这篇短文中，我们通过OkHttp client提供多种POST请求方法。