如何使用 x-www-form-urlencoded 正文發送 post 請求

Question

如何在 java 中發送帶有x-www-form-urlencoded header的請求。 我不明白如何發送帶有鍵值的正文，如上面的屏幕截圖所示。

我試過這段代碼：

String urlParameters =
  cafedra_name+ data_to_send;
URL url;
    HttpURLConnection connection = null;  
    try {
      //Create connection
      url = new URL(targetURL);
      connection = (HttpURLConnection)url.openConnection();
      connection.setRequestMethod("POST");
      connection.setRequestProperty("Content-Type", 
           "application/x-www-form-urlencoded");

      connection.setRequestProperty("Content-Length", "" + 
               Integer.toString(urlParameters.getBytes().length));
      connection.setRequestProperty("Content-Language", "en-US");  

      connection.setUseCaches (false);
      connection.setDoInput(true);
      connection.setDoOutput(true);

      //Send request
      DataOutputStream wr = new DataOutputStream (
                  connection.getOutputStream ());
      wr.writeBytes (urlParameters);
      wr.flush ();
      wr.close ();

但是在響應中，我沒有收到正確的數據。

Answer 1

當您將application/x-www-form-urlencoded為內容類型時，發送的數據必須是這種格式。

String urlParameters  = "param1=data1&param2=data2&param3=data3";

現在發送部分非常簡單。

byte[] postData = urlParameters.getBytes( StandardCharsets.UTF_8 );
int postDataLength = postData.length;
String request = "<Url here>";
URL url = new URL( request );
HttpURLConnection conn= (HttpURLConnection) url.openConnection();           
conn.setDoOutput(true);
conn.setInstanceFollowRedirects(false);
conn.setRequestMethod("POST");
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 
conn.setRequestProperty("charset", "utf-8");
conn.setRequestProperty("Content-Length", Integer.toString(postDataLength ));
conn.setUseCaches(false);
try(DataOutputStream wr = new DataOutputStream(conn.getOutputStream())) {
   wr.write( postData );
}

或者您可以創建一個通用方法來構建application/x-www-form-urlencoded所需的鍵值模式。

private String getDataString(HashMap<String, String> params) throws UnsupportedEncodingException{
    StringBuilder result = new StringBuilder();
    boolean first = true;
    for(Map.Entry<String, String> entry : params.entrySet()){
        if (first)
            first = false;
        else
            result.append("&");    
        result.append(URLEncoder.encode(entry.getKey(), "UTF-8"));
        result.append("=");
        result.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
    }    
    return result.toString();
}

Answer 2

對於HttpEntity ，以下答案有效

HttpHeaders headers = new HttpHeaders();
headers.setContentType(MediaType.APPLICATION_FORM_URLENCODED);

MultiValueMap<String, String> map= new LinkedMultiValueMap<String, String>();
map.add("email", "first.last@example.com");

HttpEntity<MultiValueMap<String, String>> request = new HttpEntity<MultiValueMap<String, String>>(map, headers);

ResponseEntity<String> response = restTemplate.postForEntity( url, request , String.class );

供參考： 如何使用 Spring RestTemplate POST 表單數據？

Answer 3

使用 Java 11 HttpClient

HTTP客戶端是在Java 11中新增的，可以用來通過.network請求HTTP資源。 它支持同步和異步編程模型 HTTP/1.1 和 HTTP/2，將請求和響應主體作為反應流處理，並遵循熟悉的構建器模式。

https://openjdk.java.net/groups.net/httpclient/intro.html

HttpClient client = HttpClient.newHttpClient();;
HttpRequest request = HttpRequest.newBuilder()
        .uri(new URI(targetUrl))
        .POST(urlParameters)
        .headers("Content-Type", "application/x-www-form-urlencoded")
        .build();
HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());

Answer 4

string urlParameters = "param1=value1&param2=value2";
string _endPointName = "your url post api";

var httpWebRequest = (HttpWebRequest)WebRequest.Create(_endPointName);

httpWebRequest.ContentType = "application/x-www-form-urlencoded";
httpWebRequest.Method = "POST";
httpWebRequest.Headers["ContentType"] = "application/x-www-form-urlencoded";

System.Net.ServicePointManager.ServerCertificateValidationCallback +=
                                                  (se, cert, chain, sslerror) =>
                                                  {
                                                      return true;
                                                  };


using (var streamWriter = new StreamWriter(httpWebRequest.GetRequestStream()))
                {
                    streamWriter.Write(urlParameters);
                    streamWriter.Flush();
                    streamWriter.Close();
                }
var httpResponse = (HttpWebResponse)httpWebRequest.GetResponse();

using (var streamReader = new StreamReader(httpResponse.GetResponseStream()))
                {
                    var result = streamReader.ReadToEnd();
                }

Answer 5

基於Navoneel 的回答，我喜歡使用StreamEx 的EntryStream 。

這是重寫的 Naveoneel 方法。

private String getDataString(HashMap<String, String> params)
{
   return EntryStream.
      of(data).
      mapKeys(key -> URLEncoder.encode(key, StandardCharsets.UTF_8)).        // Encode the keys
      mapValues(value -> URLEncoder.encode(value, StandardCharsets.UTF_8)).  // Encode the values
      join("=").                                                             // Create a key=value
      joining("&");                                                          // Assemble into key1=value1&key2=value2...
}

Answer 6

響應有問題！

當我從 Postman 發送媒體類型application/x-www-form-urlencoded的請求時，我遇到了類似的問題，我收到了正確的回復。

但是，在使用代碼發送請求時，我收到的行話有點像：

�-�YO�`:ur���g�
.n��l���u)�i�h3J%Gl�?����k  

---

我嘗試了什么：

出於沮喪，連續幾天嘗試了所有可能的解決方案，從更改字符集到更改 header 值再到代碼更改等等。

---

解決方案在於Postman。

Select Java-OkHttp

復制代碼並將其粘貼到 IDE。

就是這樣。

HttpOk參考： https://www.vogella.com/tutorials/JavaLibrary-OkHttp/article.html