Android使用OKHttp包處理HTTP相關(guān)操作的基本用法講解

更新時(shí)間：2016年07月13日 10:11:27 作者：chenzujie

這篇文章主要介紹了Android使用OKHttp包處理HTTP相關(guān)操作的基本用法講解,包括操作如何利用OKHttp操作HTTP請求與處理緩存等內(nèi)容,需要的朋友可以參考下

OKHttp是一款高效的HTTP客戶端，支持連接同一地址的鏈接共享同一個(gè)socket，通過連接池來減小響應(yīng)延遲，還有透明的GZIP壓縮，請求緩存等優(yōu)勢。（GitHub頁：https://github.com/square/okhttp）

Android為我們提供了兩種HTTP交互的方式：HttpURLConnection 和 Apache HTTP Client，雖然兩者都支持HTTPS，流的上傳和下載，配置超時(shí)，IPv6和連接池，已足夠滿足我們各種HTTP請求的需求。但更高效的使用HTTP 可以讓您的應(yīng)用運(yùn)行更快、更節(jié)省流量。而OkHttp庫就是為此而生。
OkHttp是一個(gè)高效的HTTP庫:

支持 SPDY ，共享同一個(gè)Socket來處理同一個(gè)服務(wù)器的所有請求
如果SPDY不可用，則通過連接池來減少請求延時(shí)
無縫的支持GZIP來減少數(shù)據(jù)流量
緩存響應(yīng)數(shù)據(jù)來減少重復(fù)的網(wǎng)絡(luò)請求
會從很多常用的連接問題中自動恢復(fù)。

如果您的服務(wù)器配置了多個(gè)IP地址，當(dāng)?shù)谝粋€(gè)IP連接失敗的時(shí)候，OkHttp會自動嘗試下一個(gè)IP。OkHttp還處理了代理服務(wù)器問題和SSL握手失敗問題。
使用 OkHttp 無需重寫您程序中的網(wǎng)絡(luò)代碼。OkHttp實(shí)現(xiàn)了幾乎和java.net.HttpURLConnection一樣的API。如果您用了 Apache HttpClient，則OkHttp也提供了一個(gè)對應(yīng)的okhttp-apache 模塊。

引入
可以通過下載jar包直接導(dǎo)入工程地址
或者通過構(gòu)建的方式導(dǎo)入
MAVEN：

<dependency>
 <groupId>com.squareup.okhttp</groupId>
 <artifactId>okhttp</artifactId>
 <version>2.4.0</version>
</dependency>

GRADLE：

compile 'com.squareup.okhttp:okhttp:2.4.0'

用法
在向網(wǎng)絡(luò)發(fā)起請求的時(shí)候，我們最常用的就是GET和POST，下面就來看看如何使用
1. GET
在OKHttp，每次網(wǎng)絡(luò)請求就是一個(gè)Request，我們在Request里填寫我們需要的url，header等其他參數(shù)，再通過Request構(gòu)造出Call，Call內(nèi)部去請求參數(shù)，得到回復(fù)，并將結(jié)果告訴調(diào)用者。

package com.jackchan.test.okhttptest;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import com.squareup.okhttp.Cache;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import java.io.File;
import java.io.IOException;
public class TestActivity extends ActionBarActivity {
  private final static String TAG = "TestActivity";
  private final OkHttpClient client = new OkHttpClient();
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test);
    new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          execute();
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    }).start();
  }
  public void execute() throws Exception {
    Request request = new Request.Builder()
        .url("http://publicobject.com/helloworld.txt")
        .build();
    Response response = client.newCall(request).execute();
    if(response.isSuccessful()){
      System.out.println(response.code());
      System.out.println(response.body().string());
    }
  }
}

我們通過Request.Builder傳入url，然后直接execute執(zhí)行得到Response，通過Response可以得到code,message等信息。
這個(gè)是通過同步的方式去操作網(wǎng)絡(luò)請求，而android本身是不允許在UI線程做網(wǎng)絡(luò)請求操作的，因此我們需要自己開啟一個(gè)線程。
當(dāng)然，OKHttp也支持異步線程并且有回調(diào)返回，有了上面同步的基礎(chǔ)，異步只要稍加改動即可

private void enqueue(){
    Request request = new Request.Builder()
        .url("http://publicobject.com/helloworld.txt")
        .build();
    client.newCall(request).enqueue(new Callback() {
      @Override
      public void onFailure(Request request, IOException e) {
      }
      @Override
      public void onResponse(Response response) throws IOException {
        //NOT UI Thread
        if(response.isSuccessful()){
          System.out.println(response.code());
          System.out.println(response.body().string());
        }
      }
    });
  }

就是在同步的基礎(chǔ)上講execute改成enqueue，并且傳入回調(diào)接口，但接口回調(diào)回來的代碼是在非UI線程的，因此如果有更新UI的操作記得用Handler或者其他方式。
2、POST
說完GET該介紹些如何使用POST，POST情況下我們一般需要傳入?yún)?shù)，甚至一些header，傳入?yún)?shù)或者h(yuǎn)eader
比如傳入header

Request request = new Request.Builder() 
.url("https://api.github.com/repos/square/okhttp/issues") 
.header("User-Agent", "OkHttp Headers.java") 
.addHeader("Accept", "application/json; q=0.5") 
.addHeader("Accept", "application/vnd.github.v3+json") 
.build();

傳入POST參數(shù)

RequestBody formBody = new FormEncodingBuilder()
  .add("platform", "android")
  .add("name", "bug")
  .add("subject", "XXXXXXXXXXXXXXX")
  .build();
  Request request = new Request.Builder()
   .url(url)
   .post(body)
   .build();

可以看出來，傳入header或者post參數(shù)都是傳到Request里面，因此最后的調(diào)用方式也和GET方式一樣

Response response = client.newCall(request).execute();
  if (response.isSuccessful()) {
    return response.body().string();
  } else {
    throw new IOException("Unexpected code " + response);
  }

這個(gè)代碼是同步網(wǎng)絡(luò)請求，異步就改成enqueue就行了。

請求緩存
在網(wǎng)絡(luò)請求中，緩存技術(shù)是一項(xiàng)應(yīng)用比較廣泛的技術(shù)，需要對請求過的網(wǎng)絡(luò)資源進(jìn)行緩存，而okhttp也支持這一技術(shù)，也使用十分方便，前文漲經(jīng)常出現(xiàn)的OkHttpclient這個(gè)時(shí)候就要派送用場了?？聪旅娲a

package com.jackchan.test.okhttptest;
import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.util.Log;
import com.squareup.okhttp.Cache;
import com.squareup.okhttp.CacheControl;
import com.squareup.okhttp.Call;
import com.squareup.okhttp.Callback;
import com.squareup.okhttp.OkHttpClient;
import com.squareup.okhttp.Request;
import com.squareup.okhttp.Response;
import java.io.File;
import java.io.IOException;
public class TestActivity extends ActionBarActivity {
  private final static String TAG = "TestActivity";
  private final OkHttpClient client = new OkHttpClient();
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test);
    File sdcache = getExternalCacheDir();
    int cacheSize = 10 * 1024 * 1024; // 10 MiB
    client.setCache(new Cache(sdcache.getAbsoluteFile(), cacheSize));
    new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          execute();
        } catch (Exception e) {
          e.printStackTrace();
        }
      }
    }).start();
  }
  public void execute() throws Exception {
    Request request = new Request.Builder()
        .url("http://publicobject.com/helloworld.txt")
        .build();
    Response response1 = client.newCall(request).execute();
    if (!response1.isSuccessful()) throw new IOException("Unexpected code " + response1);
    String response1Body = response1.body().string();
    System.out.println("Response 1 response:     " + response1);
    System.out.println("Response 1 cache response:  " + response1.cacheResponse());
    System.out.println("Response 1 network response: " + response1.networkResponse());
    Response response2 = client.newCall(request).execute();
    if (!response2.isSuccessful()) throw new IOException("Unexpected code " + response2);
    String response2Body = response2.body().string();
    System.out.println("Response 2 response:     " + response2);
    System.out.println("Response 2 cache response:  " + response2.cacheResponse());
    System.out.println("Response 2 network response: " + response2.networkResponse());
    System.out.println("Response 2 equals Response 1? " + response1Body.equals(response2Body));
  }
}

okhttpclient有點(diǎn)像Application的概念，統(tǒng)籌著整個(gè)okhttp的大功能，通過它設(shè)置緩存目錄，我們執(zhí)行上面的代碼，得到的結(jié)果如下

response1 的結(jié)果在networkresponse，代表是從網(wǎng)絡(luò)請求加載過來的，而response2的networkresponse 就為null，而cacheresponse有數(shù)據(jù)，因?yàn)槲以O(shè)置了緩存因此第二次請求時(shí)發(fā)現(xiàn)緩存里有就不再去走網(wǎng)絡(luò)請求了。
但有時(shí)候即使在有緩存的情況下我們依然需要去后臺請求最新的資源（比如資源更新了）這個(gè)時(shí)候可以使用強(qiáng)制走網(wǎng)絡(luò)來要求必須請求網(wǎng)絡(luò)數(shù)據(jù)

 public void execute() throws Exception {
    Request request = new Request.Builder()
        .url("http://publicobject.com/helloworld.txt")
        .build();
    Response response1 = client.newCall(request).execute();
    if (!response1.isSuccessful()) throw new IOException("Unexpected code " + response1);
    String response1Body = response1.body().string();
    System.out.println("Response 1 response:     " + response1);
    System.out.println("Response 1 cache response:  " + response1.cacheResponse());
    System.out.println("Response 1 network response: " + response1.networkResponse());
    request = request.newBuilder().cacheControl(CacheControl.FORCE_NETWORK).build();
    Response response2 = client.newCall(request).execute();
    if (!response2.isSuccessful()) throw new IOException("Unexpected code " + response2);
    String response2Body = response2.body().string();
    System.out.println("Response 2 response:     " + response2);
    System.out.println("Response 2 cache response:  " + response2.cacheResponse());
    System.out.println("Response 2 network response: " + response2.networkResponse());
    System.out.println("Response 2 equals Response 1? " + response1Body.equals(response2Body));
  }

上面的代碼中
response2對應(yīng)的request變成

request = request.newBuilder().cacheControl(CacheControl.FORCE_NETWORK).build();

我們看看運(yùn)行結(jié)果

response2的cache response為null，network response依然有數(shù)據(jù)。
同樣的我們可以使用 FORCE_CACHE 強(qiáng)制只要使用緩存的數(shù)據(jù)，但如果請求必須從網(wǎng)絡(luò)獲取才有數(shù)據(jù)，但又使用了FORCE_CACHE 策略就會返回504錯(cuò)誤，代碼如下，我們?nèi)khttpclient的緩存，并設(shè)置request為FORCE_CACHE

protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_test);
    File sdcache = getExternalCacheDir();
    int cacheSize = 10 * 1024 * 1024; // 10 MiB
    //client.setCache(new Cache(sdcache.getAbsoluteFile(), cacheSize));
    new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          execute();
        } catch (Exception e) {
          e.printStackTrace();
          System.out.println(e.getMessage().toString());
        }
      }
    }).start();
  }
  public void execute() throws Exception {
    Request request = new Request.Builder()
        .url("http://publicobject.com/helloworld.txt")
        .build();
    Response response1 = client.newCall(request).execute();
    if (!response1.isSuccessful()) throw new IOException("Unexpected code " + response1);
    String response1Body = response1.body().string();
    System.out.println("Response 1 response:     " + response1);
    System.out.println("Response 1 cache response:  " + response1.cacheResponse());
    System.out.println("Response 1 network response: " + response1.networkResponse());
    request = request.newBuilder().cacheControl(CacheControl.FORCE_CACHE).build();
    Response response2 = client.newCall(request).execute();
    if (!response2.isSuccessful()) throw new IOException("Unexpected code " + response2);
    String response2Body = response2.body().string();
    System.out.println("Response 2 response:     " + response2);
    System.out.println("Response 2 cache response:  " + response2.cacheResponse());
    System.out.println("Response 2 network response: " + response2.networkResponse());
    System.out.println("Response 2 equals Response 1? " + response1Body.equals(response2Body));
  }

取消操作
網(wǎng)絡(luò)操作中，經(jīng)常會使用到對請求的cancel操作，okhttp的也提供了這方面的接口，call的cancel操作。使用Call.cancel()可以立即停止掉一個(gè)正在執(zhí)行的call。如果一個(gè)線程正在寫請求或者讀響應(yīng)，將會引發(fā)IOException，同時(shí)可以通過Request.Builder.tag(Object tag)給請求設(shè)置一個(gè)標(biāo)簽，并使用OkHttpClient.cancel(Object tag)來取消所有帶有這個(gè)tag的call。但如果該請求已經(jīng)在做讀寫操作的時(shí)候，cancel是無法成功的，會拋出IOException異常。

public void canceltest() throws Exception {
    Request request = new Request.Builder()
        .url("http://httpbin.org/delay/2") // This URL is served with a 2 second delay.
        .build();
    final long startNanos = System.nanoTime();
    final Call call = client.newCall(request);
    // Schedule a job to cancel the call in 1 second.
    executor.schedule(new Runnable() {
      @Override
      public void run() {
        System.out.printf("%.2f Canceling call.%n", (System.nanoTime() - startNanos) / 1e9f);
        call.cancel();
        System.out.printf("%.2f Canceled call.%n", (System.nanoTime() - startNanos) / 1e9f);
      }
    }, 1, TimeUnit.SECONDS);
    try {
      System.out.printf("%.2f Executing call.%n", (System.nanoTime() - startNanos) / 1e9f);
      Response response = call.execute();
      System.out.printf("call is cancel:" + call.isCanceled() + "%n");
      System.out.printf("%.2f Call was expected to fail, but completed: %s%n",
          (System.nanoTime() - startNanos) / 1e9f, response);
    } catch (IOException e) {
      System.out.printf("%.2f Call failed as expected: %s%n",
          (System.nanoTime() - startNanos) / 1e9f, e);
    }
  }

成功取消