Android Http 服务实例

whlily

贡献于2012-07-31

字数:11055 关键词: Android开发 移动开发

 在Android中,除了使用java.net包下的API访问HTTP服务之外,我们还可以换一种途径去完成工作.Android SDK附带了Apache的HttpClient API.Apache HttpClient是一个完善的HTTP客户端,它提供了对HTTP协议的全面支持,可以使用HTTP GET和POST进行访问.下面我们就结合实例,介绍一下HttpClient的使用方法: java代码: 然后,我们的单元测试类需要继承android.test.AndroidTestCase类,这个类本身是继承junit.framework.TestCase,并提供了getContext()方法,用于获取Android上下文环境,这个设计非常有用,因为很多Android API都是需要Context才能完成的.   现在让我们来看一下我们的测试用例,HttpTest.java代码如下: java代码: 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 params = new ArrayList(); 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"); } } //将输入流转换成字符串 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()); } } 因为此文件包含三个测试用例,所以我将会逐个介绍一下.   首先,需要注意的是,我们定位服务器地址时使用到了IP,因为这里不能用localhost,服务端是在windows上运行,而本单元测试运行在Android平台,如果使用localhost就意味着在Android内部去访问服务,可能是访问不到的,所以必须用IP来定位服务.   我们先来分析一下testGet测试用例.我们使用了HttpGet,请求参数直接附在URL后面,然后由HttpClient执行GET请求,如果响应成功的话,取得响应内如输入流,并转换成字符串,最后判断是否为GET_SUCCESS.   testGet测试对应服务端Servlet代码如下: java代码: @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"); } 然后再说testPost测试用例。我们使用了HttpPost,URL后面并没有附带参数信息,参数信息被包装成一个由NameValuePair类型组成的集合的形式,然后经过UrlEncodedFormEntity处理后调用HttpPost的setEntity方法进行参数设置,最后由HttpClient执行。   testPost测试对应的服务端代码如下: java代码: @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"); } 上面两个是最基本的GET请求和POST请求,参数都是文本数据类型,能满足普通的需求,不过在有的场合例如我们要用到上传文件的时候,就不能使用基本的GET请求和POST请求了,我们要使用多部件的POST请求。下面介绍一下如何使用多部件POST操作上传一个文件到服务端。   由于Android附带的HttpClient版本暂不支持多部件POST请求,所以我们需要用到一个HttpMime开源项目,该组件是专门处理与MIME类型有关的操作。因为HttpMime是包含在HttpComponents 项目中的,所以我们需要去apache官方网站下载HttpComponents,然后把其中的HttpMime.jar包放到项目中去。 然后,我们观察testUpload测试用例,我们用HttpMime提供的InputStreamBody处理文件流参数,用StringBody处理普通文本参数,最后把所有类型参数都加入到一个MultipartEntity的实例中,并将这个multipartEntity设置为此次POST请求的参数实体,然后执行POST请求。服务端Servlet代码如下: java代码: 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()) { //普通文本信息处理 String paramName = item.getFieldName(); String paramValue = item.getString(); System.out.println(paramName + ":" + paramValue); } else { //上传文件信息处理 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"); } } 服务端使用apache开源项目FileUpload进行处理,所以我们需要commons-fileupload和commons-io这两个项目的jar包。   介绍完上面的三种不同的情况之后,我们需要考虑一个问题,在实际应用中,我们不能每次都新建HttpClient,而是应该只为整个应用创建一个HttpClient,并将其用于所有HTTP通信.此外,还应该注意在通过一个HttpClient同时发出多个请求时可能发生的多线程问题.针对这两个问题,我们需要改进一下我们的项目:   1.扩展系统默认的Application,并应用在项目中。   2.使用HttpClient类库提供的ThreadSafeClientManager来创建和管理HttpClient。   其中MyApplication扩展了系统的Application,代码如下: java代码: 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(); } //创建HttpClient实例 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); } //关闭连接管理器并释放资源 private void shutdownHttpClient() { if (httpClient != null && httpClient.getConnectionManager() != null) { httpClient.getConnectionManager().shutdown(); } } //对外提供HttpClient实例 public HttpClient getHttpClient() { return httpClient; } } 我们重写了onCreate()方法,在系统启动时就创建一个HttpClient;重写了onLowMemory()和onTerminate()方法,在内存不足和应用结束时关闭连接,释放资源.需要注意的是,当实例化DefaultHttpClient时,传入一个由ThreadSafeClientConnManager创建的一个ClientConnectionManager实例,负责管理HttpClient的HTTP连接.   然后,想要让我们这个加强版的“Application”生效,需要在AndroidManifest.xml中做如下配置: java代码: .... 如果我们没有配置,系统默认会使用android.app.Application,我们添加了配置,系统就会使用我们的com.scott.http.MyApplication,然后就可以在context中调用getApplication()来获取MyApplication实例.   有了上面的配置,我们就可以在活动中应用了,HttpActivity.java代码如下: java代码: 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(); //获取MyApplication实例 HttpClient client = app.getHttpClient(); //获取HttpClient实例 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(); } } //将输入流转换成字符串 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()); } }

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