我应该使用HttpURLConnection还是RestTemplate[duplicate]

Question

我应该在Spring项目中使用HttpURLConnection，还是更好地使用restemplate？换句话说，什么时候使用每种方法更好？

Answer 1

HttpURLConnection和restemplate是不同的类型。它们在不同的抽象级别上运行。

restemplate有助于使用RESTapi，HttpURLConnection与HTTP协议一起工作。

你在问什么更好用。答案取决于你想实现什么：

• 如果您需要使用RESTapi，请坚持使用RestTemboard
• 如果您需要使用超文本传输协议，请使用 <罢工> HttpURLConnection 如果你使用的是Java11，你可以试试它的代码。

此外，RestTemboard使用HttpUrlConnection/OkHttpClient/...来完成它的工作（参见ClientHttpRequest estFactory，SimpleClientHttpRequest estFactory，OkHttp3ClientHttpRequest estFactory

最好显示一些代码：

在下面的示例中，使用了JSONPlaceholder

让我们GET一个帖子：

public static void main(String[] args) {
  URL url;
  try {
    url = new URL("https://jsonplaceholder.typicode.com/posts/1");
  } catch (MalformedURLException e) {
    // Deal with it.
    throw new RuntimeException(e);
  }
  HttpURLConnection connection = null;
  try {
    connection = (HttpURLConnection) url.openConnection();
    try (InputStream inputStream = connection.getInputStream();
         InputStreamReader isr = new InputStreamReader(inputStream);
         BufferedReader bufferedReader = new BufferedReader(isr)) {
      // Wrap, wrap, wrap

      StringBuilder response = new StringBuilder();
      String line;
      while ((line = bufferedReader.readLine()) != null) {
        response.append(line);
      }
      // Here is the response body
      System.out.println(response.toString());
    }

  } catch (IOException e) {
    throw new RuntimeException(e);
  } finally {
    if (connection != null) {
      connection.disconnect();
    }
  }
}

现在让我们POST发布一些内容：

connection = (HttpURLConnection) url.openConnection();
connection.setDoInput(true);
connection.setDoOutput(true);
connection.setRequestMethod("POST");
connection.setRequestProperty("Content-type", "application/json; charset=UTF-8");

try (OutputStream os = connection.getOutputStream();
     OutputStreamWriter osw = new OutputStreamWriter(os);
     BufferedWriter wr = new BufferedWriter(osw)) {
  wr.write("{\"title\":\"foo\", \"body\": \"bar\", \"userId\": 1}");
}

如果需要响应：

try (InputStream inputStream = connection.getInputStream();
     InputStreamReader isr = new InputStreamReader(inputStream);
     BufferedReader bufferedReader = new BufferedReader(isr)) {
  // Wrap, wrap, wrap

  StringBuilder response = new StringBuilder();
  String line;
  while ((line = bufferedReader.readLine()) != null) {
    response.append(line);
  }

  System.out.println(response.toString());
}

正如您所见，HttpURLConnection提供的api是禁欲主义的。

你总是需要处理“低级”InputStream，Reader，OutputStream，Writer，但幸运的是，还有其他选择。

OkHttpClient减少了痛苦：

获取发布帖子：

OkHttpClient okHttpClient = new OkHttpClient();
Request request = new Request.Builder()
    .url("https://jsonplaceholder.typicode.com/posts/1")
    .build();
Call call = okHttpClient.newCall(request);
try (Response response = call.execute();
     ResponseBody body = response.body()) {

  String string = body.string();
  System.out.println(string);
} catch (IOException e) {
  throw new RuntimeException(e);
}

POSTing一篇帖子：

Request request = new Request.Builder()
    .post(RequestBody.create(MediaType.parse("application/json; charset=UTF-8"),
        "{\"title\":\"foo\", \"body\": \"bar\", \"userId\": 1}"))
    .url("https://jsonplaceholder.typicode.com/posts")
    .build();

Call call = okHttpClient.newCall(request);

try (Response response = call.execute();
     ResponseBody body = response.body()) {

  String string = body.string();
  System.out.println(string);
} catch (IOException e) {
  throw new RuntimeException(e);
}

容易多了，对吧？

获取帖子：

HttpClient httpClient = HttpClient.newHttpClient();

HttpResponse<String> response = httpClient.send(HttpRequest.newBuilder()
    .uri(URI.create("https://jsonplaceholder.typicode.com/posts/1"))
    .GET()
    .build(), HttpResponse.BodyHandlers.ofString());

System.out.println(response.body());

POSTing一篇帖子：

HttpResponse<String> response = httpClient.send(HttpRequest.newBuilder()
    .header("Content-Type", "application/json; charset=UTF-8")
    .uri(URI.create("https://jsonplaceholder.typicode.com/posts"))
    .POST(HttpRequest.BodyPublishers.ofString("{\"title\":\"foo\", \"body\": \"barzz\", \"userId\": 2}"))
    .build(), HttpResponse.BodyHandlers.ofString());

根据其javadoc：

同步客户端执行HTTP请求，在底层HTTP客户端库（例如JDK{@code HttpURLConnection}、Apache HttpComponents等）上公开一个简单的模板方法API。

让我们做同样的事

首先，为了方便起见，创建了Post类。（当restemplate读取响应时，它将使用HttpMessageConverter将其转换为Post）

public static class Post {
  public long userId;
  public long id;
  public String title;
  public String body;

  @Override
  public String toString() {
    return new ReflectionToStringBuilder(this)
        .toString();
  }
}

获取一篇帖子。

RestTemplate restTemplate = new RestTemplate();
ResponseEntity<Post> entity = restTemplate.getForEntity("https://jsonplaceholder.typicode.com/posts/1", Post.class);
Post post = entity.getBody();
System.out.println(post);

POSTing一篇帖子：

public static class PostRequest {
  public String body;
  public String title;
  public long userId;
}

public static class CreatedPost {
  public String body;
  public String title;
  public long userId;
  public long id;

  @Override
  public String toString() {
    return new ReflectionToStringBuilder(this)
        .toString();
  }
}

public static void main(String[] args) {

  PostRequest postRequest = new PostRequest();
  postRequest.body = "bar";
  postRequest.title = "foo";
  postRequest.userId = 11;


  RestTemplate restTemplate = new RestTemplate();
  CreatedPost createdPost = restTemplate.postForObject("https://jsonplaceholder.typicode.com/posts/", postRequest, CreatedPost.class);
  System.out.println(createdPost);
}

所以回答你的问题：

什么时候最好各用一种？

• 需要使用RESTapi吗？使用RestTemplate

还值得一提的是：

• 改装