Android_HTTP服务实例

    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：

package=""

android:versionCode="1"

android:versionName="1.0">

android:targetPackage="com.scott.http"/>

    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());

}

}