Java学习笔记16：Java中发送网络请求的各种方式

[QiYongchuan]

1.使用 Java 原生的 HttpURLConnection

private JSONObject sendHttpRequest(String requestURI, JSONObject jsonBody) throws IOException, BusinessException, JSONException {
    String access_token = nc.bs.einvoice.util.BillEffectUtils.ensureToken();
    HttpURLConnection debtorsRequest = (HttpURLConnection) new URL(requestURI).openConnection();
    debtorsRequest.setRequestMethod("POST");
    debtorsRequest.setRequestProperty("Authorization", "Bearer " + access_token);
    debtorsRequest.setRequestProperty("Content-Type", "application/json");
    debtorsRequest.setRequestProperty("Accept", "*/*");
    debtorsRequest.setDoOutput(true);

    try (OutputStream os = debtorsRequest.getOutputStream()) {
        byte[] input = jsonBody.toString().getBytes("utf-8");
        os.write(input, 0, input.length);
    }

    int responseCode = debtorsRequest.getResponseCode();
    if (responseCode == HttpURLConnection.HTTP_OK || responseCode == HttpURLConnection.HTTP_CREATED) {
        BufferedReader reader = new BufferedReader(new InputStreamReader(debtorsRequest.getInputStream()));
        StringBuilder response = new StringBuilder();
        String line;
        while ((line = reader.readLine()) != null) {
            response.append(line);
        }
        return new JSONObject(response.toString());
    } else {
        handleError(debtorsRequest);
        return null; 
    }
}

private void handleError(HttpURLConnection debtorsRequest) throws IOException, JSONException, BusinessException {
    BufferedReader errorResponseReader = new BufferedReader(new InputStreamReader(debtorsRequest.getErrorStream()));
    StringBuilder errorResponseText = new StringBuilder();
    String errorLine;
    while ((errorLine = errorResponseReader.readLine()) != null) {
        errorResponseText.append(errorLine);
    }
    JSONObject errorResponse = new JSONObject(errorResponseText.toString());
    String errorMessage = errorResponse.optString("message", "Unknown error");
    JSONObject errors = errorResponse.optJSONObject("errors");
    throw new BusinessException("Error from API: " + errorMessage + "  \\nDetails: " + errors);
}

[QiYongchuan]

2. 使用 Apache HttpClient

public static JSONObject doPost(String url, Map<String, Object> payload, Map<String, String> headers) throws BusinessException {  
    HttpPost httpPost = new HttpPost(url);    
    JSONObject jsonObject = new JSONObject(payload); // 直接将Map转换为JSONObject  
    StringEntity entity = new StringEntity(jsonObject.toString(), "UTF-8");  
    httpPost.setEntity(entity);  
    httpPost.setHeader("Content-Type", "application/json");  
    if (headers != null) {  
        headers.forEach(httpPost::addHeader);  
    }  

    try (CloseableHttpResponse response = httpClient.execute(httpPost)) {  
        JSONObject jsonObjectRes = handleResponse(response);  
        return jsonObjectRes;  
    } catch (IOException | BusinessException | JSONException e) {  
        throw new BusinessException("执行POST请求失败", e);  
    }  
}

private static JSONObject handleResponse(CloseableHttpResponse response) throws BusinessException, JSONException {  
    int statusCode;
    String jsonResponse;
    try {
        statusCode = response.getStatusLine().getStatusCode();
        jsonResponse = EntityUtils.toString(response.getEntity());
    } catch (IOException e) {
        throw new BusinessException("网络请求失败: " + e.getMessage(), e);
    }

    if (statusCode >= 200 && statusCode <= 300) {
        if (statusCode == HttpStatus.SC_NO_CONTENT) {
            return new JSONObject(); // 或者返回null，具体取决于业务逻辑
        }

        if (jsonResponse.trim().startsWith("[")) {
            JSONArray jsonArray = new JSONArray(jsonResponse);
            if (jsonArray.length() == 0) {
                JSONObject fixedJson = new JSONObject();
                fixedJson.put("message", "old_invoice");
                return fixedJson;
            }
            JSONObject lastElement = jsonArray.getJSONObject(jsonArray.length() - 1);
            return lastElement;
        } else {
            return new JSONObject(jsonResponse);
        }
    } else if (statusCode == 400 || statusCode == 401 || statusCode == 404) {
        JSONObject errorResponse = new JSONObject(jsonResponse);
        String errorMessage = errorResponse.getString("message");
        String status = errorResponse.getString("status");
        JSONObject errors = errorResponse.getJSONObject("errors");
        throw new BusinessException("Status: " + status + "\nError from API: " + errorMessage + "  \nDetails: " + errors);
    } else {
        throw new BusinessException("HTTP请求失败: 状态码 " + statusCode);
    }
}

[QiYongchuan]

[QiYongchuan]

3.Java 11 引入的 HttpClient

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class HttpClientExample {
    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClient.newHttpClient();
        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("https://jsonplaceholder.typicode.com/posts"))
                .header("Content-Type", "application/json")
                .POST(HttpRequest.BodyPublishers.ofString("{\"title\":\"foo\",\"body\":\"bar\",\"userId\":1}"))
                .build();

        HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
        System.out.println(response.body());
    }
}

[QiYongchuan]

4. Spring's RestTemplate

import org.springframework.web.client.RestTemplate;
import org.springframework.http.ResponseEntity;

public class RestTemplateExample {
    public static void main(String[] args) {
        RestTemplate restTemplate = new RestTemplate();
        String url = "https://jsonplaceholder.typicode.com/posts";
        String requestJson = "{\"title\":\"foo\",\"body\":\"bar\",\"userId\":1}";
        ResponseEntity<String> response = restTemplate.postForEntity(url, requestJson, String.class);
        System.out.println(response.getBody());
    }
}

[QiYongchuan]

[QiYongchuan]

[QiYongchuan]

import retrofit2.Call;
import retrofit2.Retrofit;
import retrofit2.converter.gson.GsonConverterFactory;
import retrofit2.http.Body;
import retrofit2.http.POST;

import java.io.IOException;

public class RetrofitExample {
    public static void main(String[] args) throws IOException {
        Retrofit retrofit = new Retrofit.Builder()
                .baseUrl("https://jsonplaceholder.typicode.com/")
                .addConverterFactory(GsonConverterFactory.create())
                .build();

        PostService service = retrofit.create(PostService.class);
        Call<Post> call = service.createPost(new Post("foo", "bar", 1));
        Post post = call.execute().body();
        System.out.println(post);
    }

    interface PostService {
        @POST("posts")
        Call<Post> createPost(@Body Post post);
    }

    class Post {
        String title;
        String body;
        int userId;

        Post(String title, String body, int userId) {
            this.title = title;
            this.body = body;
            this.userId = userId;
        }

        @Override
        public String toString() {
            return "Post{" +
                    "title='" + title + '\'' +
                    ", body='" + body + '\'' +
                    ", userId=" + userId +
                    '}';
        }
    }
}

[QiYongchuan]