OkHttp修仙手册：从HTTP小白到请求大神的终极奥义-优快云博客

本文链接：https://blog.youkuaiyun.com/wang543203/article/details/147026208

各位在代码江湖摸爬滚打的少侠们！今天我们要修炼的是Square派镇派绝学——OkHttp！这货堪称HTTP界的瑞士军刀，能屈能伸，上能砍高性能，下能怼低延迟！准备好让你的网络请求快如御剑飞行了吗？ 🚀

一、筑基篇：初识OkHttp

1.1 法宝祭炼（添加依赖）

// Gradle配置（Android/JVM通用）
implementation 'com.squareup.okhttp3:okhttp:4.12.0' // 2023最新稳定版

<!-- Maven配置 -->
<dependency>
    <groupId>com.squareup.okhttp3</groupId>
    <artifactId>okhttp</artifactId>
    <version>4.12.0</version>
</dependency>

1.2 创建本命法宝（OkHttpClient）

OkHttpClient client = new OkHttpClient.Builder()
    .connectTimeout(10, TimeUnit.SECONDS) // 连接超时
    .readTimeout(30, TimeUnit.SECONDS)    // 读取超时
    .writeTimeout(30, TimeUnit.SECONDS)   // 写入超时
    .build(); // 建议全局单例，功德+10086

二、金丹篇：基础请求术

2.1 GET请求（探查敌情）

Request request = new Request.Builder()
    .url("https://api.example.com/data")
    .header("User-Agent", "OkHttp-Discovery") // 伪装术
    .get() // 可省略，默认GET
    .build();

try (Response response = client.newCall(request).execute()) {
    if (response.isSuccessful()) {
        String body = response.body().string(); // 响应体读取（注意：只能读一次！）
        System.out.println("秘籍到手：" + body);
    } else {
        System.out.println("渡劫失败：" + response.code());
    }
}

2.2 POST请求（传送物资）

// 构建JSON灵力包
MediaType JSON = MediaType.parse("application/json; charset=utf-8");
String json = "{\"name\":\"张无忌\",\"age\":20}";
RequestBody body = RequestBody.create(json, JSON);

Request request = new Request.Builder()
    .url("https://api.example.com/users")
    .post(body)
    .build();

// 发送请求（同上execute流程）

三、元婴篇：高级神通

3.1 异步请求（分身术）

client.newCall(request).enqueue(new Callback() {
    @Override
    public void onResponse(Call call, Response response) throws IOException {
        if (response.isSuccessful()) {
            System.out.println("异步成功：" + response.body().string());
        }
    }

    @Override
    public void onFailure(Call call, IOException e) {
        System.err.println("渡劫失败：" + e.getMessage());
    }
});
// 主线程继续修炼，不阻塞！

3.2 文件上传（乾坤大挪移）

// 构建multipart/form-data
RequestBody requestBody = new MultipartBody.Builder()
    .setType(MultipartBody.FORM)
    .addFormDataPart("name", "赵敏")
    .addFormDataPart("avatar", "photo.jpg",
        RequestBody.create(new File("avatar.jpg"), MediaType.parse("image/jpeg"))
    .build();

Request request = new Request.Builder()
    .url("https://api.example.com/upload")
    .post(requestBody)
    .build();

四、化神篇：拦截器（偷天换日）

4.1 日志拦截器（天眼通）

OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(new HttpLoggingInterceptor()
        .setLevel(HttpLoggingInterceptor.Level.BODY)) // 打印完整请求信息
    .build();

4.2 统一请求头（万法归一）

Interceptor headerInterceptor = chain -> {
    Request original = chain.request();
    Request request = original.newBuilder()
        .header("Authorization", "Bearer your_token")
        .header("App-Version", "1.0.0")
        .method(original.method(), original.body())
        .build();
    return chain.proceed(request);
};

OkHttpClient client = new OkHttpClient.Builder()
    .addInterceptor(headerInterceptor)
    .build();

五、大乘篇：安全渡劫

5.1 HTTPS证书验证（金钟罩）

OkHttpClient client = new OkHttpClient.Builder()
    .sslSocketFactory(sslContext.getSocketFactory(), trustManager) // 自定义证书
    .hostnameVerifier((hostname, session) -> true) // 慎用！仅测试环境
    .build();

5.2 超时重试（不死之身）

client = client.newBuilder()
    .retryOnConnectionFailure(true) // 自动重试
    .addInterceptor(new RetryInterceptor(3)) // 自定义重试策略
    .build();

// 自定义重试拦截器示例
static class RetryInterceptor implements Interceptor {
    private int maxRetry;
    public RetryInterceptor(int maxRetry) { this.maxRetry = maxRetry; }

    @Override
    public Response intercept(Chain chain) throws IOException {
        Request request = chain.request();
        Response response = null;
        IOException exception = null;
        
        for (int i = 0; i <= maxRetry; i++) {
            try {
                response = chain.proceed(request);
                if (response.isSuccessful()) return response;
            } catch (IOException e) {
                exception = e;
            }
        }
        throw exception;
    }
}

六、飞升篇：性能优化

6.1 连接池（灵气循环）

ConnectionPool pool = new ConnectionPool(
    5,  // 最大空闲连接数
    5,  // 保持时间
    TimeUnit.MINUTES);

OkHttpClient client = new OkHttpClient.Builder()
    .connectionPool(pool)
    .build();

6.2 响应缓存（过目不忘）

File cacheDir = new File("okhttp_cache");
int cacheSize = 10 * 1024 * 1024; // 10MB
Cache cache = new Cache(cacheDir, cacheSize);

OkHttpClient client = new OkHttpClient.Builder()
    .cache(cache)
    .build();