Http請求-okhttp3基本用法

簡介

HTTP是現代應用常用的一種交換數據和媒體的網絡方式，高效地使用HTTP能讓資源加載更快，節省帶寬。OkHttp是一個高效的HTTP客戶端，它有以下默認特性：

• 支持HTTP/2，允許所有同一個主機地址的請求共享同一個socket連接
• 連接池減少請求延時
• 透明的GZIP壓縮減少響應數據的大小
• 緩存響應內容，避免一些完全重復的請求

源碼：https://github.com/square/okhttp
說明：OkHttp支持Android 2.3及以上版本Android平台,對於Java, JDK1.7及以上。
當網絡出現問題的時候OkHttp依然堅守自己的職責，它會自動恢復一般的連接問題，如果你的服務有多個IP地址，當第一個IP請求失敗時，OkHttp會交替嘗試你配置的其他IP，OkHttp使用現代TLS技術(SNI, ALPN)初始化新的連接，當握手失敗時會回退到TLS 1.0。

簡單使用

引入maven依賴

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

請求方法

同步請求

就是執行請求的操作是阻塞式，直到 HTTP 響應返回。它對應 OKHTTP 中的 execute 方法。

GET請求

    /**
     * 同步get方式請求
     *
     * @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請求

Json提交參數

/**
     * 同步post方式請求-json提交參數
     *
     * @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表單提交參數

    /**
     * 同步post方式請求-form表單提交參數
     *
     * @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);
            }
        }

    }

異步請求

就是類似於非阻塞式的請求，它的執行結果一般都是通過接口回調的方式告知調用者。它對應 OKHTTP 中的 enqueue 方法。

這是異步請求，所以調用enqueue則無需再開啟子線程，enqueue方法會自動將網絡請求部分放入子線程中執行。enqueue回調方法onResponse與onFailure都執行在子線程中。
注意事項：

• 1. 回調接口的onFailure方法和onResponse執行在子線程。
• 2. Response.code是http響應行中的code，如果訪問成功則返回200.這個不是服務器設置的，而是http協議中自帶的。res中的code才是服務器設置的。注意二者的區別。
• 3. response.body().string()本質是輸入流的讀操作，所以它還是網絡請求的一部分，所以這行代碼必須放在子線程。
• 4. response.body().string()只能調用一次，在第一次時有返回值，第二次再調用時將會返回null。原因是：response.body().string()的本質是輸入流的讀操作，必須有服務器的輸出流的寫操作時客戶端的讀操作才能得到數據。而服務器的寫操作只執行一次，所以客戶端的讀操作也只能執行一次，第二次將返回null。
• 5. 再次強調，response.body().string()方法必須放在子線程中。當執行這行代碼得到結果后，再跳轉到UI線程修改UI。

異步請求自定義回調函數

/**
     * okhttp 異步調用回調函數
     */
    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請求

    /**
     * 異步get方式請求
     *
     * @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請求

Json提交參數

    /**
     * 異步post方式請求-json提交參數
     *
     * @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表單提交參數

 /**
     * 異步post方式請求-form表單提交參數
     *
     * @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());

    }

參考

• https://www.jianshu.com/p/da4a806e599b
• https://blog.csdn.net/m0_38143863/article/details/80220247

示例代碼

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工具類，基於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方式請求
     *
     * @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);
            }
        }
    }

    /**
     * 異步get方式請求
     *
     * @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方式請求-json提交參數
     *
     * @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);
            }
        }

    }

    /**
     * 異步post方式請求-json提交參數
     *
     * @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方式請求-form表單提交參數
     *
     * @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);
            }
        }

    }

    /**
     * 異步post方式請求-form表單提交參數
     *
     * @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 異步調用回調函數
     */
    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());
            }
        }
    }


}

結語

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