为什么我收到HTTP 400错误请求

Question

我正在使用HTTP客户端（从http://www.mkyong.com/java/apache-httpclient-examples/复制的代码）发送帖子请求。 我一直在尝试将它与http://postcodes.io一起使用，以查找大量邮政编码，但失败了。 根据http://postcodes.io，我应该以以下JSON格式向http://api.postcodes.io/postcodes发送发布请求： {"postcodes" : ["OX49 5NU", "M32 0JG", "NE30 1DP"]}但我总是得到HTTP响应代码400。我在下面包括了我的代码。 请告诉我我做错了什么？ 谢谢

private void sendPost() throws Exception {

    String url = "http://api.postcodes.io/postcodes";
    HttpClient client = HttpClientBuilder.create().build();
    HttpPost post = new HttpPost(url);

    List<NameValuePair> urlParameters = new ArrayList<NameValuePair>();
    urlParameters.add(new BasicNameValuePair("postcodes", "[\"OX49 5NU\", \"M32 0JG\", \"NE30 1DP\"]"));
    post.setEntity(new UrlEncodedFormEntity(urlParameters));
    HttpResponse response = client.execute(post);

    System.out.println("Response Code : " 
                + response.getStatusLine().getStatusCode());
    System.out.println("Reason : " 
            + response.getStatusLine().getReasonPhrase());
    BufferedReader br = new BufferedReader(
            new InputStreamReader(response.getEntity().getContent()));
    StringBuffer result = new StringBuffer();
    String line = "";
    while ((line = br.readLine()) != null) {
        result.append(line);
    }
    br.close();
    System.out.println(result.toString());
}

Answer 1

这有效，不建议使用HTTP.UTF_8：

String url = "http://api.postcodes.io/postcodes";
HttpClient client = HttpClientBuilder.create().build();
HttpPost post = new HttpPost(url);

StringEntity params =new StringEntity("{\"postcodes\" : [\"OX49 5NU\", \"M32 0JG\", \"NE30 1DP\"]}");
post.addHeader("Content-Type", "application/json");
post.setEntity(params);

Answer 2

Jon Skeet是正确的（通常，我可能会补充说），您基本上是在发送表单，并且默认情况下为form-url-encoding。 您可以尝试这样的方法：

String jsonString = "{\"postcodes\" : [\"OX49 5NU\", \"M32 0JG\", \"NE30 1DP\"]}";
StringEntity entity = new StringEntity(jsonObj.toString(), HTTP.UTF_8);
entity.setContentType("application/json");
post.setEntity(entity);