【Android每周专题】网络编程

蔚落 2023-01-13 10:07 108阅读 0赞

*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][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。

[http_blog.csdn.net_a2bgeek_article_details_11580395]: http://blog.csdn.net/a2bgeek/article/details/11580395