Http请求-okhttp3基本用法

ゝ一世哀愁。 2022-11-30 15:48 192阅读 0赞

# 简介 #

HTTP是现代应用常用的一种交换数据和媒体的网络方式，高效地使用HTTP能让资源加载更快，节省带宽。OkHttp是一个高效的HTTP客户端，它有以下默认特性：

*  支持HTTP/2，允许所有同一个主机地址的请求共享同一个socket连接
 *  连接池减少请求延时
 *  透明的GZIP压缩减少响应数据的大小
 *  缓存响应内容，避免一些完全重复的请求

源码：[https://github.com/square/okhttp][https_github.com_square_okhttp]  
说明：OkHttp支持Android 2.3及以上版本Android平台,对于Java, JDK1.7及以上。  
当网络出现问题的时候OkHttp依然坚守自己的职责，它会自动恢复一般的连接问题，如果你的服务有多个IP地址，当第一个IP请求失败时，OkHttp会交替尝试你配置的其他IP，OkHttp使用现代TLS技术(SNI, ALPN)初始化新的连接，当握手失败时会回退到TLS 1.0。

# 简单使用 #

引入maven依赖

<dependency>
       <groupId>com.squareup.okhttp3</groupId>
       <artifactId>okhttp</artifactId>
       <version>4.0.0-RC1</version>
    </dependency>

## 请求方法 ##

### 同步请求 ###

> 就是执行请求的操作是阻塞式，直到 HTTP 响应返回。它对应 OKHTTP 中的 execute 方法。

#### GET请求 ####

/** * 同步get方式请求 * * @param url * @return * @throws IOException */
        public static String doGet(String url) throws IOException { 
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url(url)
                    .build();
            try (Response response = client.newCall(request).execute()) { 
                if (response.isSuccessful()) { 
                    return response.body().string();
                } else { 
                    throw new IOException("Unexpected code " + response);
                }
            }
        }

#### POST请求 ####

#### Json提交参数 ####

/** * 同步post方式请求-json提交参数 * * @param url * @param json * @return * @throws IOException */
        public static String doPost(String url, final String json) throws IOException { 
            OkHttpClient client = new OkHttpClient();
            RequestBody body = RequestBody.create(JSON, json);
            Request request = new Request.Builder()
                    .url(url)
                    .post(body)
                    .build();
            try (Response response = client.newCall(request).execute()) { 
                if (response.isSuccessful()) { 
                    return response.body().string();
                } else { 
                    throw new IOException("Unexpected code " + response);
                }
            }
    
        }

#### form表单提交参数 ####

/** * 同步post方式请求-form表单提交参数 * * @param url * @param paramsMap * @return * @throws IOException */
        public static String doPost(String url, Map<String, String> paramsMap) throws IOException { 
            OkHttpClient client = new OkHttpClient();
            FormBody.Builder builder = new FormBody.Builder();
            for (String key : paramsMap.keySet()) { 
                builder.add(key, paramsMap.get(key));
            }
            RequestBody formBody = builder.build();
            Request request = new Request.Builder()
                    .url(url)
                    .post(formBody)
                    .build();
            try (Response response = client.newCall(request).execute()) { 
                if (response.isSuccessful()) { 
                    return response.body().string();
                } else { 
                    throw new IOException("Unexpected code " + response);
                }
            }
    
        }

### 异步请求 ###

> 就是类似于非阻塞式的请求，它的执行结果一般都是通过接口回调的方式告知调用者。它对应 OKHTTP 中的 enqueue 方法。

这是异步请求，所以调用enqueue则无需再开启子线程，enqueue方法会自动将网络请求部分放入子线程中执行。enqueue回调方法onResponse与onFailure都执行在子线程中。  
注意事项：

*  1.  回调接口的onFailure方法和onResponse执行在子线程。
 *  1.  Response.code是http响应行中的code，如果访问成功则返回200.这个不是服务器设置的，而是http协议中自带的。res中的code才是服务器设置的。注意二者的区别。
 *  1.  response.body().string()本质是输入流的读操作，所以它还是网络请求的一部分，所以这行代码必须放在子线程。
 *  1.  response.body().string()只能调用一次，在第一次时有返回值，第二次再调用时将会返回null。原因是：response.body().string()的本质是输入流的读操作，必须有服务器的输出流的写操作时客户端的读操作才能得到数据。而服务器的写操作只执行一次，所以客户端的读操作也只能执行一次，第二次将返回null。
 *  1.  再次强调，response.body().string()方法必须放在子线程中。当执行这行代码得到结果后，再跳转到UI线程修改UI。

异步请求自定义回调函数

/** * okhttp 异步调用回调函数 */
        static class OkHttpCallback implements Callback { 
            @Override
            public void onFailure(@NotNull Call call, @NotNull IOException e) { 
                log.error(e);
            }
    
            @Override
            public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException { 
                if (response.isSuccessful()) { 
                    log.info("Successful data acquisition . . . ");
                    log.info("response.code()==" + response.code());
                    log.info("response.body().string()==" + response.body().string());
                }
            }
        }

#### GET请求 ####

/** * 异步get方式请求 * * @param url * @return * @throws IOException */
        public static void doSyncGet(String url) { 
            OkHttpClient okHttpClient = new OkHttpClient();
            final Request request = new Request.Builder()
                    .url(url)
                    .get()
                    .build();
            Call call = okHttpClient.newCall(request);
            call.enqueue(new OkHttpCallback());
        }

#### POST请求 ####

#### Json提交参数 ####

/** * 异步post方式请求-json提交参数 * * @param url * @param json * @return * @throws IOException */
        public static void doSyncPost(String url, final String json) { 
            OkHttpClient client = new OkHttpClient();
            RequestBody body = RequestBody.create(JSON, json);
            Request request = new Request.Builder()
                    .url(url)
                    .post(body)
                    .build();
            client.newCall(request).enqueue(new OkHttpCallback());
    
        }

#### form表单提交参数 ####

/** * 异步post方式请求-form表单提交参数 * * @param url * @param paramsMap * @return * @throws IOException */
        public static void doSyncPost(String url, Map<String, String> paramsMap) { 
            OkHttpClient client = new OkHttpClient();
            FormBody.Builder builder = new FormBody.Builder();
            for (String key : paramsMap.keySet()) { 
                builder.add(key, paramsMap.get(key));
            }
            RequestBody formBody = builder.build();
            Request request = new Request.Builder()
                    .url(url)
                    .post(formBody)
                    .build();
            client.newCall(request).enqueue(new OkHttpCallback());
    
        }

## 参考 ##

*  https://www.jianshu.com/p/da4a806e599b
 *  https://blog.csdn.net/m0\_38143863/article/details/80220247

# 示例代码 #

package com.ohaotian.feifz.style.study.utils;
    
    import lombok.extern.log4j.Log4j2;
    import okhttp3.Call;
    import okhttp3.Callback;
    import okhttp3.FormBody;
    import okhttp3.MediaType;
    import okhttp3.OkHttpClient;
    import okhttp3.Request;
    import okhttp3.RequestBody;
    import okhttp3.Response;
    import org.jetbrains.annotations.NotNull;
    
    import java.io.IOException;
    import java.util.Map;
    
    /** * @author feifz * @version 1.0.0 * @Description http工具类，基于okhttp3 * @createTime 2019年06月06日 09:30:00 */
    @Log4j2
    public class HttpUtil { 
    
        public static final MediaType JSON = MediaType.get("application/json; charset=utf-8");
    
    
        /** * 同步get方式请求 * * @param url * @return * @throws IOException */
        public static String doGet(String url) throws IOException { 
            OkHttpClient client = new OkHttpClient();
            Request request = new Request.Builder()
                    .url(url)
                    .build();
            try (Response response = client.newCall(request).execute()) { 
                if (response.isSuccessful()) { 
                    return response.body().string();
                } else { 
                    throw new IOException("Unexpected code " + response);
                }
            }
        }
    
        /** * 异步get方式请求 * * @param url * @return * @throws IOException */
        public static void doSyncGet(String url) { 
            OkHttpClient okHttpClient = new OkHttpClient();
            final Request request = new Request.Builder()
                    .url(url)
                    .get()
                    .build();
            Call call = okHttpClient.newCall(request);
            call.enqueue(new OkHttpCallback());
        }
    
        /** * 同步post方式请求-json提交参数 * * @param url * @param json * @return * @throws IOException */
        public static String doPost(String url, final String json) throws IOException { 
            OkHttpClient client = new OkHttpClient();
            RequestBody body = RequestBody.create(JSON, json);
            Request request = new Request.Builder()
                    .url(url)
                    .post(body)
                    .build();
            try (Response response = client.newCall(request).execute()) { 
                if (response.isSuccessful()) { 
                    return response.body().string();
                } else { 
                    throw new IOException("Unexpected code " + response);
                }
            }
    
        }
    
        /** * 异步post方式请求-json提交参数 * * @param url * @param json * @return * @throws IOException */
        public static void doSyncPost(String url, final String json) { 
            OkHttpClient client = new OkHttpClient();
            RequestBody body = RequestBody.create(JSON, json);
            Request request = new Request.Builder()
                    .url(url)
                    .post(body)
                    .build();
            client.newCall(request).enqueue(new OkHttpCallback());
    
        }
    
        /** * 同步post方式请求-form表单提交参数 * * @param url * @param paramsMap * @return * @throws IOException */
        public static String doPost(String url, Map<String, String> paramsMap) throws IOException { 
            OkHttpClient client = new OkHttpClient();
            FormBody.Builder builder = new FormBody.Builder();
            for (String key : paramsMap.keySet()) { 
                builder.add(key, paramsMap.get(key));
            }
            RequestBody formBody = builder.build();
            Request request = new Request.Builder()
                    .url(url)
                    .post(formBody)
                    .build();
            try (Response response = client.newCall(request).execute()) { 
                if (response.isSuccessful()) { 
                    return response.body().string();
                } else { 
                    throw new IOException("Unexpected code " + response);
                }
            }
    
        }
    
        /** * 异步post方式请求-form表单提交参数 * * @param url * @param paramsMap * @return * @throws IOException */
        public static void doSyncPost(String url, Map<String, String> paramsMap) { 
            OkHttpClient client = new OkHttpClient();
            FormBody.Builder builder = new FormBody.Builder();
            for (String key : paramsMap.keySet()) { 
                builder.add(key, paramsMap.get(key));
            }
            RequestBody formBody = builder.build();
            Request request = new Request.Builder()
                    .url(url)
                    .post(formBody)
                    .build();
            client.newCall(request).enqueue(new OkHttpCallback());
    
        }
    
        /** * okhttp 异步调用回调函数 */
        static class OkHttpCallback implements Callback { 
            @Override
            public void onFailure(@NotNull Call call, @NotNull IOException e) { 
                log.error(e);
            }
    
            @Override
            public void onResponse(@NotNull Call call, @NotNull Response response) throws IOException { 
                if (response.isSuccessful()) { 
                    log.info("Successful data acquisition . . . ");
                    log.info("response.code()==" + response.code());
                    log.info("response.body().string()==" + response.body().string());
                }
            }
        }
    
    
    }

## 结语 ##

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![format_png][]

[https_github.com_square_okhttp]: https://github.com/square/okhttp
[format_png]: /images/20221123/a4d6551e08a7474c98ff5b0ab102ada1.png