前言

過了一個漫長的中秋+國慶假期，大家伙的鴻蒙內功修煉的怎么樣了？難道像小蒙一樣，都在吃吃喝喝中度過么，哎，罪過罪過，對不起那些雞鴨魚肉啊，趕緊回來寫篇文章收收心，讓我們一起看看，在鴻蒙中如何發送網路請求吧，

本文會從Java原生訪問入手，進而再使用Retrofit訪問網路，可以滿足絕大部分開發者對于鴻蒙網路訪問方面的代碼需求，開始之前需要先做一下基礎配置，

鴻蒙系統網路訪問基礎配置

1、跟Android類似，要訪問網路，我們首先要配置網路訪問權限，在config.json的"module"節點最后，添加上網路權限代碼

"reqPermissions": [
      {
        "reason": "",
        "name": "ohos.permission.INTERNET"
      }
    ]

2、配置網路明文訪問白名單

"deviceConfig": {
    "default": {
      "network": {
        "usesCleartext": true,
        "securityConfig": {
          "domainSettings": {
            "cleartextPermitted": true,
            "domains": [
              {
                "subDomains": true,
                "name": "www.baidu.com"
              }
            ]
          }
        }
      }
    }
  }

其中的name即為可以直接http訪問的域名，如果全是https鏈接則可以做該不配置，切記域名是不帶http://的，切記域名是不帶http://的，切記域名是不帶http://的，重要的事說三遍，

Java原生訪問網路

由于鴻蒙系統支持Java開發，所以我們可以直接使用Java原生的Api來進行網路訪問
該方式使用了java的url.openConnection() Api來獲取網路資料

HttpDemo.java

package com.example.demo.classone;

import javax.net.ssl.*;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.security.SecureRandom;

public class HttpDemo {
    /**
     *訪問url，獲取內容
     * @param urlStr
     * @return
     */
    public static String httpGet(String urlStr){
        StringBuilder sb = new StringBuilder();
        try{
            //添加https信任
            SSLContext sslcontext = SSLContext.getInstance("SSL");//第一個引數為協議,第二個引數為提供者(可以預設)
            TrustManager[] tm = {new HttpX509TrustManager()};
            sslcontext.init(null, tm, new SecureRandom());
            HostnameVerifier ignoreHostnameVerifier = new HostnameVerifier() {
                public boolean verify(String s, SSLSession sslsession) {
                    System.out.println("WARNING: Hostname is not matched for cert.");
                    return true;
                }
            };
            HttpsURLConnection.setDefaultHostnameVerifier(ignoreHostnameVerifier);
            HttpsURLConnection.setDefaultSSLSocketFactory(sslcontext.getSocketFactory());
            URL url = new URL(urlStr);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            connection.setRequestMethod("GET");
            connection.setReadTimeout(10000);
            connection.setConnectTimeout(10000);
            connection.connect();
            int code = connection.getResponseCode();
            if (code == HttpURLConnection.HTTP_OK) {
                BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
                String temp;
                while ((temp = reader.readLine()) != null) {
                    sb.append(temp);
                }
                reader.close();
            }
            connection.disconnect();
        } catch (Exception e) {
            e.printStackTrace();
            return e.getMessage();
        }
        return sb.toString();
    }
}

HttpX509TrustManager.java

package com.example.demo.classone;
import javax.net.ssl.X509TrustManager;
import java.security.cert.CertificateException;
import java.security.cert.X509Certificate;

public class HttpX509TrustManager implements X509TrustManager {
    @Override
    public void checkClientTrusted(X509Certificate[] chain, String authType) throws CertificateException {
    }

    @Override
    public void checkServerTrusted(X509Certificate[] chain, String authType) throws CertificateException {
    }

    @Override
    public X509Certificate[] getAcceptedIssuers() {
        return null;
    }
}

最后是測驗是否能夠正確訪問的代碼，注意網路訪問是耗時操作要放執行緒里面執行

new Thread(new Runnable() {
        @Override
        public void run() {
            String result = HttpDemo.httpGet("http://www.baidu.com");
            HiLog.warn(new HiLogLabel(HiLog.LOG_APP, 0, "===demo==="), "網頁回傳結果："+result);
        }
    }).start();

采用Retrofit訪問網路

在模塊的build.gradle里添加Retrofit庫的參考，我這邊采用的是retrofit2的2.5.0版本做示例

implementation 'com.squareup.retrofit2:retrofit:2.5.0'
    implementation 'com.squareup.retrofit2:converter-gson:2.5.0'
    implementation 'io.reactivex.rxjava3:rxjava:3.0.4'

新建ApiManager類用來管理獲取OkHttpClient，SSLSocketClient用來提供https支持，ApiResponseConverterFactory是Retrofit的轉換器，將請求結果轉成String輸出

ApiManager.java

package com.example.demo.classone;

import com.example.demo.DemoAbilityPackage;
import ohos.app.Environment;
import okhttp3.*;
import retrofit2.Retrofit;

import java.io.File;
import java.util.concurrent.TimeUnit;

/**
 * 提供獲取Retrofit物件的方法
 */
public class ApiManager {
    private static final String BUSINESS_BASE_HTTP_URL = "http://www.baidu.com";

    private static Retrofit instance;
    private static OkHttpClient mOkHttpClient;

    private ApiManager(){}

    public static Retrofit get(){
        if (instance == null){
            synchronized (ApiManager.class){
                if (instance == null){
                    setClient();
                    instance = new Retrofit.Builder().baseUrl(BUSINESS_BASE_HTTP_URL).
                            addConverterFactory(ApiResponseConverterFactory.create()).client(mOkHttpClient).build();
                }
            }
        }
        return instance;
    }

    private static void setClient(){
        if (mOkHttpClient != null){
            return;
        }
        Cache cache = new Cache(new File(getRootPath(Environment.DIRECTORY_DOCUMENTS),"HttpCache"),1024*1024*100);
        OkHttpClient.Builder builder = new OkHttpClient.Builder()
//                .followRedirects(false)//關閉重定向
//                .addInterceptor(new AppendUrlParamIntercepter())
                .cache(cache)
                .retryOnConnectionFailure(false)
                .sslSocketFactory(SSLSocketClient.getSSLSocketFactory())
                .hostnameVerifier(SSLSocketClient.getHostnameVerifier())
                .readTimeout(8,TimeUnit.SECONDS)
                .writeTimeout(8,TimeUnit.SECONDS)
                .connectTimeout(8, TimeUnit.SECONDS);
//                .protocols(Collections.singletonList(Protocol.HTTP_1_1));
        mOkHttpClient = builder.build();
        mOkHttpClient.dispatcher().setMaxRequests(100);
    }

    private static String getRootPath(String dirs) {
        String path = DemoAbilityPackage.getInstance().getCacheDir() + "/" + dirs;
        File file = new File(path);
        if (!file.exists()) {
            file.mkdirs();
        }
        return path;
    }
}

SSLSocketClient.java

package com.example.demo.classone;
import javax.net.ssl.*;
import java.security.SecureRandom;
import java.security.cert.X509Certificate;

public class SSLSocketClient {

    //獲取這個SSLSocketFactory
    public static SSLSocketFactory getSSLSocketFactory() {
        try {
            SSLContext sslContext = SSLContext.getInstance("SSL");
            sslContext.init(null, getTrustManager(), new SecureRandom());
            return sslContext.getSocketFactory();
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }

    //獲取TrustManager
    private static TrustManager[] getTrustManager() {
        TrustManager[] trustAllCerts = new TrustManager[]{
                new X509TrustManager() {
                    @Override
                    public void checkClientTrusted(X509Certificate[] chain, String authType) {
                    }

                    @Override
                    public void checkServerTrusted(X509Certificate[] chain, String authType) {
                    }

                    @Override
                    public X509Certificate[] getAcceptedIssuers() {
                        return new X509Certificate[]{};
                    }
                }
        };
        return trustAllCerts;
    }


    //獲取HostnameVerifier
    public static HostnameVerifier getHostnameVerifier() {
        HostnameVerifier hostnameVerifier = new HostnameVerifier() {
            @Override
            public boolean verify(String s, SSLSession sslSession) {
                return true;
            }
        };
        return hostnameVerifier;
    }
}

ApiResponseConverterFactory.java

package com.example.demo.classone;

import okhttp3.RequestBody;
import okhttp3.ResponseBody;
import retrofit2.Converter;
import retrofit2.Retrofit;

import java.io.IOException;
import java.lang.annotation.Annotation;
import java.lang.reflect.Type;

/**
 * BaseResponse的轉換器
 */
public class ApiResponseConverterFactory extends Converter.Factory {

    public static Converter.Factory create(){
        return new ApiResponseConverterFactory();
    }

    @Override
    public Converter<ResponseBody, String> responseBodyConverter(Type type, Annotation[] annotations, Retrofit retrofit) {
        return new StringResponseBodyConverter();
    }

    @Override
    public Converter<?, RequestBody> requestBodyConverter(Type type, Annotation[] parameterAnnotations, Annotation[] methodAnnotations, Retrofit retrofit) {
        return null;
    }

    class StringResponseBodyConverter implements Converter<ResponseBody, String> {
        @Override
        public String convert(ResponseBody value) throws IOException {
            String s = value.string();
            return s;
        }
    }
}

開始使用Retrofit書寫業務邏輯

BusinessApiManager.java

package com.example.demo.classone;

/**
 * 服務端訪問介面管理
 */
public class BusinessApiManager {

    private static BusinessApiService instance;
    public static BusinessApiService get(){
        if (instance == null){
            synchronized (BusinessApiManager.class){
                if (instance == null){
                    instance = ApiManager.get().create(BusinessApiService.class);
                }
            }
        }
        return instance;
    }
}

BusinessApiService.java

package com.example.demo.classone;

import retrofit2.Call;
import retrofit2.http.*;

/**
 * 服務端訪問介面
 */
public interface BusinessApiService {
    /**
     * 獲取網頁資訊
     * @param url
     * @return
     */
    @GET()
    Call<String> getHtmlContent(@Url String url);
}

測驗Retrofit是否能夠正常使用

BusinessApiManager.get().getHtmlContent("https://www.baidu.com").enqueue(new Callback<String>() {
    @Override
    public void onResponse(Call<String> call, Response<String> response) {
        if (!response.isSuccessful() || response.body() == null){
            onFailure(null,null);
            return;
        }
        String result = response.body();
        HiLog.warn(new HiLogLabel(HiLog.LOG_APP, 0, "===demo==="), "網頁回傳結果："+result);
    }

    @Override
    public void onFailure(Call<String> call, Throwable throwable) {
        HiLog.warn(new HiLogLabel(HiLog.LOG_APP, 0, "===demo==="), "網頁訪問例外");
    }
});

總結

鴻蒙是基于Java開發的，所有Java原生api都是可以直接在鴻蒙系統上使用的，另外只要和java相關的庫都是可以直接參考的，例如在參考retrofit的時候也帶入了RxJava，
更多retrofit的使用方式，可以參考retrofit在android系統中的實作，鴻蒙系統基本兼容，

所有相關代碼已上傳至github：https://github.com/maolinnan/HarmonyosClass

這是本系列的第三篇，后面還會為大家帶來更多的鴻蒙干貨，敬請期待…，

如果文章對您有一點啟發的話，希望您能點個贊，

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鴻蒙開發實戰系列之三：網路請求(原生+ Retrofit)

前言