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 Android教程網 >> Android技術 >> 關於Android編程 >> Android中使用HTTP服務的用法詳解

Android中使用HTTP服務的用法詳解

編輯:關於Android編程

在Android中,除了使用Java.NET包下的API訪問HTTP服務之外,我們還可以換一種途徑去完成工作。Android SDK附帶了Apache的HttpClient API。Apache HttpClient是一個完善的HTTP客戶端,它提供了對HTTP協議的全面支持,可以使用HTTP GET和POST進行訪問。下面我們就結合實例,介紹一下HttpClient的使用方法。

我們新建一個http項目,項目結構如圖:

在這個項目中,我們不需要任何的Activity,所有的操作都在單元測試類HttpTest.java中完成。

因為使用到了單元測試,所以在這裡先介紹一下如何配置Android中的單元測試。所有配置信息均在AndroidManifest.xml中完成:

<?xml version="1.0" encoding="utf-8"?> 
<manifest xmlns:android="http://schemas.android.com/apk/res/android" 
   package="com.scott.http" 
   android:versionCode="1" 
   android:versionName="1.0"> 
  <application android:icon="@drawable/icon" android:label="@string/app_name"> 
    <!-- 配置測試要使用的類庫 --> 
    <uses-library android:name="android.test.runner"/> 
  </application> 
  <!-- 配置測試設備的主類和目標包 --> 
  <instrumentation android:name="android.test.InstrumentationTestRunner" 
           android:targetPackage="com.scott.http"/> 
  <!-- 訪問HTTP服務所需的網絡權限 --> 
  <uses-permission android:name="android.permission.INTERNET"/> 
  <uses-sdk android:minSdkVersion="8" /> 
</manifest>  

然後,我們的單元測試類需要繼承android.test.AndroidTestCase類,這個類本身是繼承junit.framework.TestCase,並提供了getContext()方法,用於獲取Android上下文環境,這個設計非常有用,因為很多Android API都是需要Context才能完成的。

現在讓我們來看一下我們的測試用例,HttpTest.java代碼如下:

package com.scot.http.test; 
 
import java.io.ByteArrayOutputStream; 
import java.io.InputStream; 
import java.util.ArrayList; 
import java.util.List; 
 
import junit.framework.Assert; 
 
import org.apache.http.HttpEntity; 
import org.apache.http.HttpResponse; 
import org.apache.http.HttpStatus; 
import org.apache.http.NameValuePair; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.entity.UrlEncodedFormEntity; 
import org.apache.http.client.methods.HttpGet; 
import org.apache.http.client.methods.HttpPost; 
import org.apache.http.entity.mime.MultipartEntity; 
import org.apache.http.entity.mime.content.InputStreamBody; 
import org.apache.http.entity.mime.content.StringBody; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.apache.http.message.BasicNameValuePair; 
 
import android.test.AndroidTestCase; 
 
public class HttpTest extends AndroidTestCase { 
   
  private static final String PATH = "http://192.168.1.57:8080/web"; 
   
  public void testGet() throws Exception { 
    HttpClient client = new DefaultHttpClient(); 
    HttpGet get = new HttpGet(PATH + "/TestServlet?id=1001&name=john&age=60"); 
    HttpResponse response = client.execute(get); 
    if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { 
      InputStream is = response.getEntity().getContent(); 
      String result = inStream2String(is); 
      Assert.assertEquals(result, "GET_SUCCESS"); 
    } 
  } 
   
  public void testPost() throws Exception { 
    HttpClient client = new DefaultHttpClient(); 
    HttpPost post = new HttpPost(PATH + "/TestServlet"); 
    List<NameValuePair> params = new ArrayList<NameValuePair>(); 
    params.add(new BasicNameValuePair("id", "1001")); 
    params.add(new BasicNameValuePair("name", "john")); 
    params.add(new BasicNameValuePair("age", "60")); 
    HttpEntity formEntity = new UrlEncodedFormEntity(params); 
    post.setEntity(formEntity); 
    HttpResponse response = client.execute(post); 
    if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { 
      InputStream is = response.getEntity().getContent(); 
      String result = inStream2String(is); 
      Assert.assertEquals(result, "POST_SUCCESS"); 
    } 
  } 
   
  public void testUpload() throws Exception { 
    InputStream is = getContext().getAssets().open("books.xml"); 
    HttpClient client = new DefaultHttpClient(); 
    HttpPost post = new HttpPost(PATH + "/UploadServlet"); 
    InputStreamBody isb = new InputStreamBody(is, "books.xml"); 
    MultipartEntity multipartEntity = new MultipartEntity(); 
    multipartEntity.addPart("file", isb); 
    multipartEntity.addPart("desc", new StringBody("this is description.")); 
    post.setEntity(multipartEntity); 
    HttpResponse response = client.execute(post); 
    if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { 
      is = response.getEntity().getContent(); 
      String result = inStream2String(is); 
      Assert.assertEquals(result, "UPLOAD_SUCCESS"); 
    } 
  } 
   
  //將輸入流轉換成字符串 
  private String inStream2String(InputStream is) throws Exception { 
    ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
    byte[] buf = new byte[1024]; 
    int len = -1; 
    while ((len = is.read(buf)) != -1) { 
      baos.write(buf, 0, len); 
    } 
    return new String(baos.toByteArray()); 
  } 
} 

因為此文件包含三個測試用例,所以我將會逐個介紹一下。

首先,需要注意的是,我們定位服務器地址時使用到了IP,因為這裡不能用localhost,服務端是在windows上運行,而本單元測試運行在Android平台,如果使用localhost就意味著在Android內部去訪問服務,可能是訪問不到的,所以必須用IP來定位服務。

我們先來分析一下testGet測試用例。我們使用了HttpGet,請求參數直接附在URL後面,然後由HttpClient執行GET請求,如果響應成功的話,取得響應內如輸入流,並轉換成字符串,最後判斷是否為GET_SUCCESS。

testGet測試對應服務端Servlet代碼如下:

@Override 
  protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    System.out.println("doGet method is called."); 
    String id = request.getParameter("id"); 
    String name = request.getParameter("name"); 
    String age = request.getParameter("age"); 
    System.out.println("id:" + id + ", name:" + name + ", age:" + age); 
    response.getWriter().write("GET_SUCCESS"); 
  } 

然後再說testPost測試用例。我們使用了HttpPost,URL後面並沒有附帶參數信息,參數信息被包裝成一個由NameValuePair類型組成的集合的形式,然後經過UrlEncodedFormEntity處理後調用HttpPost的setEntity方法進行參數設置,最後由HttpClient執行。

testPost測試對應的服務端代碼如下:

@Override 
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    System.out.println("doPost method is called."); 
    String id = request.getParameter("id"); 
    String name = request.getParameter("name"); 
    String age = request.getParameter("age"); 
    System.out.println("id:" + id + ", name:" + name + ", age:" + age); 
    response.getWriter().write("POST_SUCCESS"); 
  } 

上面兩個是最基本的GET請求和POST請求,參數都是文本數據類型,能滿足普通的需求,不過在有的場合例如我們要用到上傳文件的時候,就不能使用基本的GET請求和POST請求了,我們要使用多部件的POST請求。下面介紹一下如何使用多部件POST操作上傳一個文件到服務端。

由於Android附帶的HttpClient版本暫不支持多部件POST請求,所以我們需要用到一個HttpMime開源項目,該組件是專門處理與MIME類型有關的操作。因為HttpMime是包含在HttpComponents 項目中的,所以我們需要去apache官方網站下載HttpComponents,然後把其中的HttpMime.jar包放到項目中去,如圖:

然後,我們觀察testUpload測試用例,我們用HttpMime提供的InputStreamBody處理文件流參數,用StringBody處理普通文本參數,最後把所有類型參數都加入到一個MultipartEntity的實例中,並將這個multipartEntity設置為此次POST請求的參數實體,然後執行POST請求。服務端Servlet代碼如下:

package com.scott.web.servlet; 
 
import java.io.FileOutputStream; 
import java.io.IOException; 
import java.util.Iterator; 
import java.util.List; 
 
import javax.servlet.ServletException; 
import javax.servlet.http.HttpServlet; 
import javax.servlet.http.HttpServletRequest; 
import javax.servlet.http.HttpServletResponse; 
 
import org.apache.commons.fileupload.FileItem; 
import org.apache.commons.fileupload.FileItemFactory; 
import org.apache.commons.fileupload.FileUploadException; 
import org.apache.commons.fileupload.disk.DiskFileItemFactory; 
import org.apache.commons.fileupload.servlet.ServletFileUpload; 
 
@SuppressWarnings("serial") 
public class UploadServlet extends HttpServlet { 
   
  @Override 
  @SuppressWarnings("rawtypes") 
  protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { 
    boolean isMultipart = ServletFileUpload.isMultipartContent(request); 
    if (isMultipart) { 
      FileItemFactory factory = new DiskFileItemFactory(); 
      ServletFileUpload upload = new ServletFileUpload(factory); 
      try { 
        List items = upload.parseRequest(request); 
        Iterator iter = items.iterator(); 
        while (iter.hasNext()) { 
          FileItem item = (FileItem) iter.next(); 
          if (item.isFormField()) { 
            //普通文本信息處理 
            String paramName = item.getFieldName(); 
            String paramValue = item.getString(); 
            System.out.println(paramName + ":" + paramValue); 
          } else { 
            //上傳文件信息處理 
            String fileName = item.getName(); 
            byte[] data = item.get(); 
            String filePath = getServletContext().getRealPath("/files") + "/" + fileName; 
            FileOutputStream fos = new FileOutputStream(filePath); 
            fos.write(data); 
            fos.close(); 
          } 
        } 
      } catch (FileUploadException e) { 
        e.printStackTrace(); 
      } 
    } 
    response.getWriter().write("UPLOAD_SUCCESS"); 
  } 
} 

服務端使用apache開源項目FileUpload進行處理,所以我們需要commons-fileupload和commons-io這兩個項目的jar包,對服務端開發不太熟悉的朋友可以到網上查找一下相關資料。

介紹完上面的三種不同的情況之後,我們需要考慮一個問題,在實際應用中,我們不能每次都新建HttpClient,而是應該只為整個應用創建一個HttpClient,並將其用於所有HTTP通信。此外,還應該注意在通過一個HttpClient同時發出多個請求時可能發生的多線程問題。針對這兩個問題,我們需要改進一下我們的項目:

1.擴展系統默認的Application,並應用在項目中。

2.使用HttpClient類庫提供的ThreadSafeClientManager來創建和管理HttpClient。

改進後的項目結構如圖:

其中MyApplication擴展了系統的Application,代碼如下:

package com.scott.http; 
 
import org.apache.http.HttpVersion; 
import org.apache.http.client.HttpClient; 
import org.apache.http.conn.ClientConnectionManager; 
import org.apache.http.conn.scheme.PlainSocketFactory; 
import org.apache.http.conn.scheme.Scheme; 
import org.apache.http.conn.scheme.SchemeRegistry; 
import org.apache.http.conn.ssl.SSLSocketFactory; 
import org.apache.http.impl.client.DefaultHttpClient; 
import org.apache.http.impl.conn.tsccm.ThreadSafeClientConnManager; 
import org.apache.http.params.BasicHttpParams; 
import org.apache.http.params.HttpParams; 
import org.apache.http.params.HttpProtocolParams; 
import org.apache.http.protocol.HTTP; 
 
import android.app.Application; 
 
public class MyApplication extends Application { 
 
  private HttpClient httpClient; 
   
  @Override 
  public void onCreate() { 
    super.onCreate(); 
    httpClient = this.createHttpClient(); 
  } 
   
  @Override 
  public void onLowMemory() { 
    super.onLowMemory(); 
    this.shutdownHttpClient(); 
  } 
   
  @Override 
  public void onTerminate() { 
    super.onTerminate(); 
    this.shutdownHttpClient(); 
  } 
   
  //創建HttpClient實例 
  private HttpClient createHttpClient() { 
    HttpParams params = new BasicHttpParams(); 
    HttpProtocolParams.setVersion(params, HttpVersion.HTTP_1_1); 
    HttpProtocolParams.setContentCharset(params, HTTP.DEFAULT_CONTENT_CHARSET); 
    HttpProtocolParams.setUseExpectContinue(params, true); 
     
    SchemeRegistry schReg = new SchemeRegistry(); 
    schReg.register(new Scheme("http", PlainSocketFactory.getSocketFactory(), 80)); 
    schReg.register(new Scheme("https", SSLSocketFactory.getSocketFactory(), 443)); 
     
    ClientConnectionManager connMgr = new ThreadSafeClientConnManager(params, schReg); 
     
    return new DefaultHttpClient(connMgr, params); 
  } 
   
  //關閉連接管理器並釋放資源 
  private void shutdownHttpClient() { 
    if (httpClient != null && httpClient.getConnectionManager() != null) { 
      httpClient.getConnectionManager().shutdown(); 
    } 
  } 
   
  //對外提供HttpClient實例 
  public HttpClient getHttpClient() { 
    return httpClient; 
  } 
} 

我們重寫了onCreate()方法,在系統啟動時就創建一個HttpClient;重寫了onLowMemory()和onTerminate()方法,在內存不足和應用結束時關閉連接,釋放資源。需要注意的是,當實例化DefaultHttpClient時,傳入一個由ThreadSafeClientConnManager創建的一個ClientConnectionManager實例,負責管理HttpClient的HTTP連接。

然後,想要讓我們這個加強版的“Application”生效,需要在AndroidManifest.xml中做如下配置:

<application android:name=".MyApplication" ...> 
... 
</application> 

如果我們沒有配置,系統默認會使用android.app.Application,我們添加了配置,系統就會使用我們的com.scott.http.MyApplication,然後就可以在context中調用getApplication()來獲取MyApplication實例。

有了上面的配置,我們就可以在活動中應用了,HttpActivity.java代碼如下:

package com.scott.http; 
 
import java.io.ByteArrayOutputStream; 
import java.io.InputStream; 
 
import org.apache.http.HttpResponse; 
import org.apache.http.HttpStatus; 
import org.apache.http.client.HttpClient; 
import org.apache.http.client.methods.HttpGet; 
 
import android.app.Activity; 
import android.os.Bundle; 
import android.view.View; 
import android.widget.Button; 
import android.widget.Toast; 
 
public class HttpActivity extends Activity { 
  @Override 
  protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.main); 
    Button btn = (Button) findViewById(R.id.btn); 
    btn.setOnClickListener(new View.OnClickListener() { 
      @Override 
      public void onClick(View v) { 
        execute(); 
      } 
    }); 
     
  } 
   
  private void execute() { 
    try { 
      MyApplication app = (MyApplication) this.getApplication(); //獲取MyApplication實例 
      HttpClient client = app.getHttpClient();  //獲取HttpClient實例 
      HttpGet get = new HttpGet("http://192.168.1.57:8080/web/TestServlet?id=1001&name=john&age=60"); 
      HttpResponse response = client.execute(get); 
      if (response.getStatusLine().getStatusCode() == HttpStatus.SC_OK) { 
        InputStream is = response.getEntity().getContent(); 
        String result = inStream2String(is); 
        Toast.makeText(this, result, Toast.LENGTH_LONG).show(); 
      } 
    } catch (Exception e) { 
      e.printStackTrace(); 
    } 
  } 
   
  //將輸入流轉換成字符串 
  private String inStream2String(InputStream is) throws Exception { 
    ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
    byte[] buf = new byte[1024]; 
    int len = -1; 
    while ((len = is.read(buf)) != -1) { 
      baos.write(buf, 0, len); 
    } 
    return new String(baos.toByteArray()); 
  } 
} 

點擊“execute”按鈕,執行結果如下:

以上就是本文的全部內容,希望對大家的學習有所幫助,也希望大家多多支持本站。

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