【Android每周专题】网络编程

本系列文章均为A2BGeek原创,转载务必在明显处注明：
转载自A2BGeek的【Android每周专题】系列，原文链接：http://blog.csdn.net/a2bgeek/article/details/11580395

本期专题将讲解网络编程。

很多APP或多或少会有一些访问网络的功能，比如用户的登录，文件的上传和下载，更新等功能，本期专题将注重实践，会有大量的代码，读者可以直接拷贝使用。

概述

       HTTP 协议可能是现在 Internet 上使用得最多、最重要的协议了，在 JDK 的 java.net 包中已经提供了访问 HTTP 协议的基本功能：HttpURLConnection。HttpURLConnection是java的标准类，HttpURLConnection继承自URLConnection，可用于向指定网站发送GET请求、POST请求。

       在一般情况下，如果只是需要Web站点的某个简单页面提交请求并获取服务器响应，HttpURLConnection完全可以胜任。但在绝大部分情况下，Web站点的网页可能没这么简单，这些页面并不是通过一个简单的URL就可访问的，可能需要用户登录而且具有相应的权限才可访问该页面。在这种情况下，就需要涉及Session、Cookie的处理了，如果打算使用HttpURLConnection来处理这些细节，当然也是可能实现的，只是处理起来难度就大了。

       为了更好地处理向Web站点请求，包括处理Session、Cookie等细节问题，Apache开源组织提供了一个HttpClient项目，看它的名称就知道，它是一个简单的HTTP客户端（并不是浏览器），可以用于发送HTTP请求，接收HTTP响应。但不会缓存服务器的响应，不能执行HTML页面中嵌入的Javascript代码，也不会对页面内容进行任何解析、处理。

       简单来说，HttpClient就是一个增强版的HttpURLConnection，HttpURLConnection可以做的事情HttpClient全部可以做；HttpURLConnection没有提供的有些功能，HttpClient也提供了，但它只是关注于如何发送请求、接收响应，以及管理HTTP连接。

简单登录功能

这里说的用户登录仅仅是向服务器发送用户名和密码，服务器验证一下，返回一个标志（比如1代表用户名和密码正确登录成功），真正的登录功能是没有这么简单的，还需要维护Session。在本小节我将通过四种方式编写登录代码，分别是HttpURLConnection的GET方式和POST方式以及HttpClient的GET方式和POST方式，目的是熟悉Android的网络编程。服务器端我选用了Facebook的开源框架Tornado，服务器端大家可以根据自己的喜好选择，比如LAMP的经典组合。接下来就直接上代码了。

HttpURLConnection GET

public static String HttpURLConnectionGet(String username, String passwd) {

String response = "HttpURLConnectionGet ";
try {
String urlStr = "http://XXX.XXX.XXX.XXX:8888/normalrequest?username="
+ username + "&password=" + passwd;
URL url = new URL(urlStr);
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
InputStream is = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String readLine = null;
while ((readLine = br.readLine()) != null) {
response += readLine;
}
is.close();
br.close();
urlConnection.disconnect();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "MalformedURLException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "IOException--->" + e.getMessage());
}
return response;
}

我电脑的IP地址就不写啦，用XXX代替了。

HttpURLConnection POST

public static String HttpURLConnectionPost(String username, String passwd) {
String response = "HttpURLConnectionPost ";
try {
String urlStr = "http://XXX.XXX.XXX.XXX:8888/normalrequest";
URL url = new URL(urlStr);
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);
urlConnection.setRequestMethod("POST");
urlConnection.setUseCaches(false);
urlConnection.connect();
DataOutputStream out = new DataOutputStream(
urlConnection.getOutputStream());
String content = "username=" + username + "&password=" + passwd;
out.writeBytes(content);
out.flush();
out.close();

InputStream is = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String readLine = null;
while ((readLine = br.readLine()) != null) {
response += readLine;
}
is.close();
br.close();
urlConnection.disconnect();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "MalformedURLException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "IOException--->" + e.getMessage());
}
return response;
}

HttpGet

public static String HttpClientGet(String username, String passwd) {

String response = "HttpClientGet ";
try {
String urlStr = "http://XXX.XXX.XXX.XXX:8888/normalrequest?username="
+ username + "&password=" + passwd;
HttpGet httpGet = new HttpGet(urlStr);
HttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = httpClient.execute(httpGet);
if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
response += EntityUtils.toString(httpResponse.getEntity());
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "ClientProtocolException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "IOException--->" + e.getMessage());
}
return response;

}

HttpPost

public static String HttpClientPost(String username, String passwd) {

String response = "HttpClientPost ";
try {
String urlStr = "http://XXX.XXX.XXX.XXX:8888/normalrequest";
HttpPost httpPost = new HttpPost(urlStr);
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("username", username));
params.add(new BasicNameValuePair("password", passwd));
HttpEntity httpEntity = new UrlEncodedFormEntity(params);
httpPost.setEntity(httpEntity);
HttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = httpClient.execute(httpPost);
if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
response += EntityUtils.toString(httpResponse.getEntity());
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek",
"UnsupportedEncodingException--->" + e.getMessage());
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "ClientProtocolException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "IOException--->" + e.getMessage());
}
return response;
}

服务器端代码

服务器端是使用tornado框架编写的，不了解的读者请谷歌一下。

server.py

import tornado.ioloop
import tornado.web
from request import NormalRequestHandler
application = tornado.web.Application([
(r"/normalrequest", NormalRequestHandler),
])

if __name__ == "__main__":
application.listen(8888)
tornado.ioloop.IOLoop.instance().start()

request.py

import tornado.web
class NormalRequestHandler(tornado.web.RequestHandler):
def get(self):
username = self.get_argument('username')
password = self.get_argument('password')
if username=='a2bgeek' and password=='123456':
self.write('login success')
else:
self.write('login fail')
def post(self):
username = self.get_argument('username')
password = self.get_argument('password')
if username=='a2bgeek' and password=='123456':
self.write('login success')
else:
self.write('login fail')

在这里有一点必须要提醒读者，Android4.0以后涉及网络的操作不能放在主线程里面做了，所以需要开一个线程来做。

文件的上传

一般文件的上传使用POST方式，因为GET对字节数有限制只能传很少的数据，而POST理论上是没有限制的。

HttpURLConnection POST

public static String HttpURLConnectionFileUpload(File file) {
String response = "HttpURLConnectionFileUpload ";
String boundary = "a2bgeek";
try {
String urlStr = "http://XXX.XXX.XXX.XXX:8888/fileupload";
URL url = new URL(urlStr);
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
urlConnection.setDoInput(true);
urlConnection.setDoOutput(true);
urlConnection.setRequestMethod("POST");
urlConnection.setUseCaches(false);
urlConnection.setRequestProperty("Content-Type",
"multipart/form-data; boundary=" + boundary);
urlConnection.connect();
DataOutputStream dos = new DataOutputStream(
urlConnection.getOutputStream());
dos.writeBytes("--" + boundary);
dos.writeBytes("\r\n");
dos.writeBytes("Content-Disposition: form-data; name=\"file\"; filename=\""
+ file.getName() + "\"" + "\r\n");
dos.writeBytes("\r\n");
FileInputStream fis = new FileInputStream(file.getPath());
byte[] buffer = new byte[1024 * 1024];
int count = 0;
while ((count = fis.read(buffer)) != -1) {
dos.write(buffer, 0, count);
}
fis.close();
dos.writeBytes("\r\n");
dos.writeBytes("--" + boundary + "--");
dos.flush();
dos.close();

InputStream is = urlConnection.getInputStream();
BufferedReader br = new BufferedReader(new InputStreamReader(is));
String readLine = null;
while ((readLine = br.readLine()) != null) {
response += readLine;
}
is.close();
br.close();
urlConnection.disconnect();
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "MalformedURLException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "IOException--->" + e.getMessage());
}
return response;
}

HttpPost

public static String HttpClientFileUpload(File file) {
String response = "HttpClientFileUpload ";
try {
String urlStr = "http://XXX.XXX.XXX.XXX:8888/fileupload";
HttpPost httpPost = new HttpPost(urlStr);

MultipartEntity multipartEntity = new MultipartEntity();
multipartEntity.addPart("file", new FileBody(file));

httpPost.setEntity(multipartEntity);
HttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = httpClient.execute(httpPost);
if (httpResponse.getStatusLine().getStatusCode() == HttpStatus.SC_OK) {
response += EntityUtils.toString(httpResponse.getEntity());
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek",
"UnsupportedEncodingException--->" + e.getMessage());
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "ClientProtocolException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "IOException--->" + e.getMessage());
}
return response;

}

服务器端代码

import tornado.web
import os

class UploadFileHandler(tornado.web.RequestHandler):
def get(self):
self.write('''
<html>
<head><title>Upload File</title></head>
<body>
<form action='fileupload' enctype="multipart/form-data" method='post'>
<input type='file' name='file'/><br/>
<input type='submit' value='submit'/>
</form>
</body>
</html>
''')

def post(self):
upload_path=os.path.join(os.path.dirname(__file__),'files')
if not os.path.exists(upload_path):
os.makedirs(upload_path)
file_metas=self.request.files['file']
for meta in file_metas:
filename=meta['filename']
filepath=os.path.join(upload_path,filename)
with open(filepath,'w') as up:
up.write(meta['body'])
self.write('upload success')

文件的下载

一般文件的下载使用的是GET方式，其实也可以使用POST方式，这两种是没有本质区别的。只是GET比较方便，POST的话需要在服务器端编写返回文件的代码。

HttpURLConnection GET

public static void HttpURLConnectionFileDownload() {
try {
int BUFFER_SIZE = 1024 * 1024;
String urlStr = "http://XXX.XXX.XXX.XXX:8888/pic/one.png";
URL url = new URL(urlStr);
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
InputStream is = urlConnection.getInputStream();
FileOutputStream fos = new FileOutputStream(new File(Environment
.getExternalStorageDirectory().getPath()
+ "/NetConn/downone.png"));
byte[] buffer = new byte[BUFFER_SIZE];
int count = 0;
while ((count = is.read(buffer)) > 0) {
fos.write(buffer, 0, count);
}
is.close();
fos.close();
Log.v("a2bgeek", "HttpURLConnectionFileDownload success");
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
Log.v("a2bgeek", "MalformedURLException--->" + e.getMessage());
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

HttpGet

public static void HttpClientFileDownload() {
try {
int BUFFER_SIZE = 1024 * 1024;
String urlStr = "http://XXX.XXX.XXX.XXX:8888/pic/two.png";
HttpGet httpGet = new HttpGet(urlStr);
HttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = httpClient.execute(httpGet);
HttpEntity httpEntity = httpResponse.getEntity();
InputStream is = httpEntity.getContent();
FileOutputStream fos = new FileOutputStream(new File(Environment
.getExternalStorageDirectory().getPath()
+ "/NetConn/downtwo.png"));
byte[] buffer = new byte[BUFFER_SIZE];
int count = 0;
while ((count = is.read(buffer)) > 0) {
fos.write(buffer, 0, count);
}
is.close();
fos.close();
Log.v("a2bgeek", "HttpClientFileDownload success");
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}

好了今天就到这里了，代码的大部分已经放在博客里面了，由于个人时间紧张，上传代码又要等很长时间，代码就不贴了，需要的同学可以留言。