Android常用的访问web的数据操作

1、利用HttpURLConnection对象,从网络中获取网页数据.

 

 

URL url = new URL("http://localhost:8080/mytest");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6* 1000);//设置连接超时
if (conn.getResponseCode() != 200) throw new RuntimeException("请求url失败");
InputStream is = conn.getInputStream();//得到网络返回的输入流
String result = readData(is, "GBK");
conn.disconnect();
System.out.println(result);
//第一个参数为输入流,第二个参数为字符集编码
public static String readData(InputStream inSream, String charsetName) throws Exception{
	ByteArrayOutputStream outStream = new ByteArrayOutputStream();
	byte[] buffer = new byte[1024];
	int len = -1;
	while( (len = inSream.read(buffer)) != -1 ){
		outStream.write(buffer, 0, len);
	}
	byte[] data = outStream.toByteArray();
	outStream.close();
	inSream.close();
	return new String(data, charsetName);
}

 

 2、利用HttpURLConnection对象,从网络中获取文件数据

 

 

URL url = new URL("http://localhost:8080/mytest/Img269812337.jpg");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6* 1000);
if (conn.getResponseCode() != 200) throw new RuntimeException("请求url失败");
InputStream is = conn.getInputStream();
readAsFile(is, "Img269812337.jpg"); 

public static void readAsFile(InputStream inSream, File file) throws Exception{
	FileOutputStream outStream = new FileOutputStream(file);
	byte[] buffer = new byte[1024];
	int len = -1;
	while( (len = inSream.read(buffer)) != -1 ){
		outStream.write(buffer, 0, len);
	}
 	outStream.close();
	inSream.close();
}

 

3、向Internet发送POST请求参数

 

 

String requestUrl = "http://localhost:8080/mytest/contanctmanage.do";
Map<String, String> requestParams = new HashMap<String, String>();
requestParams.put("age", "12");
requestParams.put("name", "中国");
 StringBuilder params = new StringBuilder();
for(Map.Entry<String, String> entry : requestParams.entrySet()){
	params.append(entry.getKey());
	params.append("=");
	params.append(URLEncoder.encode(entry.getValue(), "UTF-8"));
	params.append("&");
}
if (params.length() > 0) params.deleteCharAt(params.length() - 1);
byte[] data = params.toString().getBytes();
URL realUrl = new URL(requestUrl);
HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();

conn.setDoOutput(true);//发送POST请求必须设置允许输出
conn.setUseCaches(false);//不使用Cache
conn.setRequestMethod("POST");	        
conn.setRequestProperty("Connection", "Keep-Alive");//维持长连接
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Content-Length", String.valueOf(data.length));
conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
DataOutputStream outStream = new DataOutputStream(conn.getOutputStream());
outStream.write(data);
outStream.flush();
if( conn.getResponseCode() == 200 ){
        String result = readAsString(conn.getInputStream(), "UTF-8");
        outStream.close();
        System.out.println(result);
}

 

4、利用HttpURLConnection对象,我们可以向网络发送xml数据

 

 

StringBuilder xml =  new StringBuilder();
xml.append("<?xml version=\"1.0\" encoding=\"utf-8\" ?>");
xml.append("<M1 V=10000>");
xml.append("<U I=1 D=\"N73\">中国</U>");
xml.append("</M1>");
byte[] xmlbyte = xml.toString().getBytes("UTF-8");
URL url = new URL("http://localhost:8080/mytest/contanctmanage.do?method=readxml");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(6* 1000);
conn.setDoOutput(true);//允许输出
conn.setUseCaches(false);//不使用Cache
conn.setRequestMethod("POST");	        
conn.setRequestProperty("Connection", "Keep-Alive");//维持长连接
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Content-Length", String.valueOf(xmlbyte.length));
conn.setRequestProperty("Content-Type", "text/xml; charset=UTF-8");
DataOutputStream outStream = new DataOutputStream(conn.getOutputStream());
outStream.write(xmlbyte);//发送xml数据
outStream.flush();
if (conn.getResponseCode() != 200) throw new RuntimeException("请求url失败");
InputStream is = conn.getInputStream();//获取返回数据
String result = readAsString(is, "UTF-8");
outStream.close();	

 

5、HTTP多线程断点下载应用程序

 

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• 如何才能从文件的指定位置处开始下载文件？（比如从50MB开始）这一点我们可以通过HTTP请求信息头来设置，可以使用HTTP请求信息头的“Range”属性。 

   例如：只要在请求头中加入以下代码就可以只请求部分数据： Content-Range: bytes 20000-40000/47000 ,
即从第20000字节请求到第40000个字节,(文件长度是47000字节) 

• •如何支持断点下载。就是将下载的进度保存到文件中，但在Android中却不能这么做。在Android平台中，我们需要向文件中写出下载的文件数据，我们通过数据库的方式保存下载进度 。