OkHttp –如何发送HTTP请求

r囧r小猫 2023-02-15 05:14 13阅读 0赞

![OkHttp徽标][OkHttp]![OkHttp徽标][OkHttp]

本文向您展示如何使用[OkHttp][OkHttp 1]库发送HTTP GET / POST请求以及一些常用示例。

*PS已通过OkHttp 4.2.2测试*

pom.xml

<dependency>
    	  <groupId>com.squareup.okhttp3</groupId>
    	  <artifactId>okhttp</artifactId>
    	  <version>4.2.2</version>
    	</dependency>

## 1.同步获取请求 ##

OkHttpExample1.java

package com.mkyong.http;
    
    import okhttp3.Headers;
    import okhttp3.OkHttpClient;
    import okhttp3.Request;
    import okhttp3.Response;
    
    import java.io.IOException;
    
    public class OkHttpExample1 {
    
        // only one client, singleton, better puts it in a factory, 
    	// multiple instances will create more memory.
        private final OkHttpClient httpClient = new OkHttpClient();
    
        public static void main(String[] args) throws IOException {
            OkHttpExample1 obj = new OkHttpExample1();
            obj.sendGETSync();
        }
    
        private void sendGETSync() throws IOException {
    
            Request request = new Request.Builder()
                    .url("https://httpbin.org/get")
                    .addHeader("custom-key", "mkyong")  // add request headers
                    .addHeader("User-Agent", "OkHttp Bot")
                    .build();
    
            try (Response response = httpClient.newCall(request).execute()) {
    
                if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
    
                // Get response headers
                Headers responseHeaders = response.headers();
                for (int i = 0; i < responseHeaders.size(); i++) {
                    System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
                }
    
                // Get response body
                System.out.println(response.body().string());
            }
    
        }
    
    }

## 2.异步获取请求 ##

OkHttpExample2.java

package com.mkyong.okhttp;
    
    import okhttp3.*;
    import java.io.IOException;
    
    public class OkHttpExample2 {
    
        // only one client
        private final OkHttpClient httpClient = new OkHttpClient();
    
        public static void main(String[] args) throws IOException {
            OkHttpExample2 obj = new OkHttpExample2();
            obj.sendGET();
        }
    
        private void sendGET() throws IOException {
    
            Request request = new Request.Builder()
                    .url("https://httpbin.org/get")
                    .addHeader("custom-key", "mkyong")  // add request headers
                    .addHeader("User-Agent", "OkHttp Bot")
                    .build();
    
            httpClient.newCall(request).enqueue(new Callback() {
                @Override
                public void onFailure(Call call, IOException e) {
                    e.printStackTrace();
                }
    
                @Override
                public void onResponse(Call call, Response response) throws IOException {
                    try (ResponseBody responseBody = response.body()) {
                        if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
    
                        // Get response headers
                        Headers responseHeaders = response.headers();
                        for (int i = 0, size = responseHeaders.size(); i < size; i++) {
                            System.out.println(responseHeaders.name(i) + ": " + responseHeaders.value(i));
                        }
    
                        // Get response body
                        System.out.println(responseBody.string());
                    }
                }
            });
    
        }
    
    }

## 3. POST请求–表单参数 ##

3.1从`RequestBody`参数添加

OkHttpExample3.java

package com.mkyong.http;
    
    import okhttp3.*;
    
    import java.io.IOException;
    
    public class OkHttpExample3 {
    
        private final OkHttpClient httpClient = new OkHttpClient();
    
        public static void main(String[] args) throws IOException {
            OkHttpExample3 obj = new OkHttpExample3();
            obj.sendPOST();
        }
    
        private void sendPOST() throws IOException {
    
            // form parameters
            RequestBody formBody = new FormBody.Builder()
                    .add("username", "abc")
                    .add("password", "123")
                    .add("custom", "secret")
                    .build();
    
            Request request = new Request.Builder()
                    .url("https://httpbin.org/post")
                    .addHeader("User-Agent", "OkHttp Bot")
                    .post(formBody)
                    .build();
    
            try (Response response = httpClient.newCall(request).execute()) {
    
                if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
    
                // Get response body
                System.out.println(response.body().string());
            }
    
        }
    
    }

## 4. POST请求– JSON ##

4.1手动创建JSON `RequestBody` 。

OkHttpExample4.java

package com.mkyong.http;
    
    import okhttp3.*;
    
    import java.io.IOException;
    
    public class OkHttpExample4 {
    
        private final OkHttpClient httpClient = new OkHttpClient();
    
        public static void main(String[] args) throws IOException {
            OkHttpExample4 obj = new OkHttpExample4();
            obj.sendPOST();
        }
    
        private void sendPOST() throws IOException {
    
            // json formatted data
            String json = new StringBuilder()
                    .append("{")
                    .append("\"name\":\"mkyong\",")
                    .append("\"notes\":\"hello\"")
                    .append("}").toString();
    
    		// json request body
            RequestBody body = RequestBody.create(
                    json,
                    MediaType.parse("application/json; charset=utf-8")
            );
    
            Request request = new Request.Builder()
                    .url("https://httpbin.org/post")
                    .addHeader("User-Agent", "OkHttp Bot")
                    .post(body)
                    .build();
    
            try (Response response = httpClient.newCall(request).execute()) {
    
                if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
    
                // Get response body
                System.out.println(response.body().string());
            }
    
        }
    
    }

## 5.认证 ##

启动一个提供HTTP基本身份验证的简单Spring Security WebApp ，并使用OkHttp库对其进行测试。

5.1直接在`Request`标头认证。

Request request = new Request.Builder()
    		.url("http://localhost:8080/books")
    		.addHeader("Authorization", Credentials.basic("user", "password"))
    		.build();

5.2创建一个`Authenticator` ，更灵活地处理身份验证。

private final Authenticator authenticator = new Authenticator() {
            @Override
            public Request authenticate(Route route, Response response) throws IOException {
                if (response.request().header("Authorization") != null) {
                    return null; // Give up, we've already attempted to authenticate.
                }
    
                System.out.println("Authenticating for response: " + response);
                System.out.println("Challenges: " + response.challenges());
                String credential = Credentials.basic("user", "password");
                return response.request().newBuilder()
                        .header("Authorization", credential)
                        .build();
            }
        };
    
        private final OkHttpClient httpClient = new OkHttpClient
    		.Builder()
    		.authenticator(authenticator)
    		.build();

## 6.常见问题 ##

6.1禁用重定向。

HttpClientExample5\_1.java

private final OkHttpClient httpClient = new OkHttpClient.Builder()
                .followRedirects(false)
                .build();

6.2超时，5秒。

private final OkHttpClient httpClient = new OkHttpClient.Builder()
                .connectTimeout(5, TimeUnit.SECONDS)
                .writeTimeout(5, TimeUnit.SECONDS)
                .readTimeout(5, TimeUnit.SECONDS)
                .build();

> **注意**  
> 更多[OkHttp食谱][OkHttp 2]

## 参考文献 ##

*  [OkHttp食谱][OkHttp 2]
 *  [Apache HttpClient示例][Apache HttpClient]
 *  [Apache HttpClient官方网站][Apache HttpClient 1]

标签： [身份验证][Link 1] [http][] [http请求][http 1] [java][] [json][] [okhttp][] [重定向][Link 2] [超时][Link 3]

> 翻译自: [https://mkyong.com/java/okhttp-how-to-send-http-requests/][https_mkyong.com_java_okhttp-how-to-send-http-requests]

[OkHttp]: http://imgconvert.csdnimg.cn/aHR0cHM6Ly9ta3lvbmcuY29tL3dwLWNvbnRlbnQvdXBsb2Fkcy8yMDE5LzEwL09rSHR0cC1sb2dvLnBuZw?x-oss-process=image/format,png
[OkHttp 1]: https://square.github.io/okhttp/
[OkHttp 2]: https://square.github.io/okhttp/recipes/
[Apache HttpClient]: https://www.mkyong.com/java/apache-httpclient-examples/
[Apache HttpClient 1]: https://hc.apache.org/httpcomponents-client-4.5.x/index.html
[Link 1]: https://mkyong.com/tag/authentication/
[http]: https://mkyong.com/tag/http/
[http 1]: https://mkyong.com/tag/http-request/
[java]: https://mkyong.com/tag/java/
[json]: https://mkyong.com/tag/json/
[okhttp]: https://mkyong.com/tag/okhttp/
[Link 2]: https://mkyong.com/tag/redirect/
[Link 3]: https://mkyong.com/tag/timeout/
[https_mkyong.com_java_okhttp-how-to-send-http-requests]: https://mkyong.com/java/okhttp-how-to-send-http-requests/