Get和Post

Android应用通过HTTP协议向WEB应用传递数据,常用Get和Post两种方式
Get方式传递的数据的小余2K(此大小也因浏览器不同而相异),而使用Post方式向WEB应用传递数据时没有数据大小的限制.
在执行复杂的操作可以选用,如要操作https和cookie以及重定向时可选用Android的提供的开源项目HttpClient来处理(见下)

第一部分:Get方式
注意:
1 Get方式中被传送的数据就跟在URl后面
2 conn.setRequestMethod("GET")中的GET一定要大写
3 sb.append(URLEncoder.encode(entry.getValue(), encoding))对URL进行编码防止中文时乱码.Tomcat默认采用的ISO8859-1
代码如下:
public static boolean save(String title, String timelength) throws Exception{
		Map<String,String> params = new HashMap<String, String>();
		params.put("title", title);
		params.put("timelength", timelength);
		params.put("method", "save");//传给WEB应用中的save()方法
		String path = "http://192.168.1.100:8080/videoweb/video/manage.do";
		return sendHttpClientGETRequest(path, params, "UTF-8");
}
 
private static boolean sendGETRequest(String path, Map<String, String> params, String encoding) throws Exception{
		//http://192.168.1.100:8080/videoweb/video/manage.do?method=save&title=xxxx&timelength=45
		StringBuilder sb = new StringBuilder(path);
		sb.append('?');
		if(params!=null && !params.isEmpty()){
			for(Map.Entry<String, String> entry : params.entrySet()){
				sb.append(entry.getKey()).append('=');
				sb.append(URLEncoder.encode(entry.getValue(), encoding));//URL编码
				sb.append('&');
			}
		}
		sb.deleteCharAt(sb.length() - 1);
		HttpURLConnection conn = (HttpURLConnection) new URL(sb.toString()).openConnection();
		conn.setConnectTimeout(5000);
		conn.setRequestMethod("GET");//必须大写GET
		if(conn.getResponseCode() == 200){
			return true;
		}		
		return false;
}

第二部分:Post方式
注意:
1 Post方式中数据是作为协议的实体数据发送给WEB应用的,而不是跟在uri的后面
  在发送实体数据时,用到了输出流OutputStream outStream = conn.getOutputStream();outStream.write(entity);
  其中entity为实体数据,类型为字节数组
2 各个数据用&连接如:name=liming&age=16
3 在设置协议的HTTP协议的头字段(即HttpURLConnection)时content-type和content-length绝不能省略
4 可用工具HttpWatch professional进行观测
代码如下:
public static boolean save(String title, String timelength) throws Exception{
		Map<String,String> params = new HashMap<String, String>();
		params.put("title", title);
		params.put("timelength", timelength);
		params.put("method", "save");
		String path = "http://192.168.1.100:8080/videoweb/video/manage.do";
		return sendPOSTRequest(path, params, "UTF-8");
	}

private static boolean sendPOSTRequest(String path, Map<String, String> params, String encoding) throws Exception{		
		StringBuilder sb = new StringBuilder();
		if(params!=null && !params.isEmpty()){//完成实体数据
			for(Map.Entry<String, String> entry : params.entrySet()){
				sb.append(entry.getKey()).append('=');
				sb.append(URLEncoder.encode(entry.getValue(), encoding));
				sb.append('&');
			}
			sb.deleteCharAt(sb.length() - 1);
		}
		byte[] entity = sb.toString().getBytes();//得到实体数据,类型为字节数组
		HttpURLConnection conn = (HttpURLConnection) new URL(path).openConnection();
		conn.setConnectTimeout(5000);
		conn.setRequestMethod("POST");
		conn.setDoOutput(true);//允许对外输出数据
		// Content-Type: application/x-www-form-urlencoded
		conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
		conn.setRequestProperty("Content-Length", String.valueOf(entity.length));
		OutputStream outStream = conn.getOutputStream();
		outStream.write(entity);
		if(conn.getResponseCode() == 200){
			return true;
		}
		return false;
	}



第三部分:使用Android的开源项目来实现GET和POST请求
但是方式的性能不如前面讲的直接使用GET和POST,因为里面封装了许多东西
在进行简单操作的时候没必要使用它.在执行复杂的操作可以选用,如要操作https和cookie以及重定向时可选用

public static boolean save(String title, String timelength) throws Exception{
	Map<String,String> params = new HashMap<String, String>();
	params.put("title", title);
	params.put("timelength", timelength);
	params.put("method", "save");
	String path = "http://192.168.1.100:8080/videoweb/video/manage.do";
	return sendHttpClientPOSTRequest(path, params, "UTF-8");
}
	
private static boolean sendHttpClientPOSTRequest(String path, Map<String, String> params, String encoding) throws Exception{
	List<NameValuePair> pairs = new ArrayList<NameValuePair>();
	if(params!=null && !params.isEmpty()){
		for(Map.Entry<String, String> entry : params.entrySet()){
			pairs.add(new BasicNameValuePair(entry.getKey(), entry.getValue()));
		}
	}
	//完成实体数据
	UrlEncodedFormEntity entity = new UrlEncodedFormEntity(pairs, encoding);
	HttpPost post = new HttpPost(path);
	post.setEntity(entity);
	DefaultHttpClient client = new DefaultHttpClient();//可将DefaultHttpClient看作浏览器
	HttpResponse response = client.execute(post);//client.execute(post)发送消息,返回值为服务器返回给浏览器的响应
	if( response.getStatusLine().getStatusCode() == 200){
		return true;
	}
	return false;
}