HttpURLConnection和HttpClient获取Json数据

 Android中提供的HttpURLConnection（JDK自带）和HttpClient（Apache提供）接口可以用来开发HTTP程序。

服务器端有如下json数据

[
{
"image": "http://222.22.254.223:8080/web/a.jpg",
"title": "新闻标题1",
"content": "新闻内容1",
"conut": "跟帖人数1"
},
{
"image": "http://222.22.254.223:8080/web/b.jpg",
"title": "新闻标题2",
"content": "新闻内容2",
"conut": "跟帖人数2"
},
{
"image": "http://222.22.254.223:8080/web/c.jpg",
"title": "新闻标题3",
"content": "新闻内容3",
"conut": "跟帖人数3"
},
{
"image": "http://222.22.254.223:8080/web/d.jpg",
"title": "新闻标题4",
"content": "新闻内容4",
"conut": "跟帖人数4"
},
{
"image": "http://222.22.254.223:8080/web/e.jpg",
"title": "新闻标题5",
"content": "新闻内容5",
"conut": "跟帖人数5"
}
]

1.首先来看HttpURLConnection的Get方法获取json数据：

public List<HeadNews> HttpURLConnection_GET()throws Exception{

		List<HeadNews>list=new ArrayList<HeadNews>();

		String path="http://222.22.254.223:8080/web/HeadNewsJson";
		//参数直接加载url后面
		path+="?username="+URLEncoder.encode("我是大帅哥HttpClientGET","utf-8");
		URL url=new URL(path);
		HttpURLConnection conn=(HttpURLConnection) url.openConnection();
		conn.setRequestMethod("GET");
		conn.setConnectTimeout(5000);
		if(conn.getResponseCode()==200){				//200表示请求成功
			InputStream is=conn.getInputStream();		//以输入流的形式返回
			//将输入流转换成字符串
			ByteArrayOutputStream baos=new ByteArrayOutputStream();
			byte [] buffer=new byte[1024];
			int len=0;
			while((len=is.read(buffer))!=-1){
				baos.write(buffer, 0, len);
			}
			String jsonString=baos.toString();
			baos.close();
			is.close();
			//转换成json数据处理
			JSONArray jsonArray=new JSONArray(jsonString);
			for(int i=0;i<jsonArray.length();i++){		//一个循环代表一个headnews对象
				HeadNews headnews=new HeadNews();
				JSONObject jsonObject = jsonArray.getJSONObject(i);
				headnews.setTitle(jsonObject.getString("title"));
				headnews.setContent(jsonObject.getString("content"));
				headnews.setConut(jsonObject.getString("conut"));
				headnews.setImage(jsonObject.getString("image"));
				list.add(headnews);
			}
			
		}
		return list;
	}

2.HttpURLConnection的POST方法获取json数据：

	public List<HeadNews>HttpURLConnection_POST() throws Exception{
		List<HeadNews>list=new ArrayList<HeadNews>();
		
		String path="http://222.22.254.223:8080/web/HeadNewsJson";
		URL url=new URL(path);
		HttpURLConnection conn=(HttpURLConnection) url.openConnection();

		conn.setDoOutput(true);				//允许向服务器输出数据
		conn.setDoInput(true);				//允许接收服务器数据
		conn.setRequestMethod("POST");
		conn.setUseCaches(false); 			// Post 请求不能使用缓存
		conn.setConnectTimeout(5000);
		// 参数前面不能加？号
		String urlParas="username="+URLEncoder.encode("admin", "UTF-8");
		byte [] entity=urlParas.getBytes();
		//设置请求参数
		conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");	//实体参数类型
		conn.setRequestProperty("Content-Length", entity.length+"");					//实体参数长度
		
		// 连接，从postUrl.openConnection()至此的配置必须要在connect之前完成，
        // 要注意的是connection.getOutputStream会隐含的进行connect。
		conn.connect();
		//将要上传的参数写入流中
		conn.getOutputStream().write(entity);
		
		if(conn.getResponseCode()==200){
			InputStream is=conn.getInputStream();
			//将输入流转换成字符串
			ByteArrayOutputStream baos=new ByteArrayOutputStream();
			byte [] buffer=new byte[1024];
			int len=0;
			while((len=is.read(buffer))!=-1){
				baos.write(buffer, 0, len);
			}
			String json=baos.toString();
			baos.close();
			is.close();
			//json处理
			JSONArray jsonArray=new JSONArray(json);
			for(int i=0;i<jsonArray.length();i++){
				HeadNews headnews=new HeadNews();
				JSONObject jsonObject = jsonArray.getJSONObject(i);
				headnews.setTitle(jsonObject.getString("title"));
				headnews.setContent(jsonObject.getString("content"));
				headnews.setConut(jsonObject.getString("conut"));
				headnews.setImage(jsonObject.getString("image"));
				list.add(headnews);
			}
		}
		return list;
	}

3.使用HttpClient的get方法获取Json：

	public List<HeadNews>HttpClient_GET() throws Exception{

		List<HeadNews>list=new LinkedList<HeadNews>();

		String path="http://222.22.254.223:8080/web/HeadNewsJson";
		//get方法设置参数要？号
		StringBuilder sb=new StringBuilder(path);
		sb.append("?");
		sb.append("username=").append(URLEncoder.encode("我是大帅哥HttpClientGET","utf-8"));
		
		//1.得到浏览器
		HttpClient httpClient=new DefaultHttpClient();//浏览器 
		//2指定请求方式
		HttpGet httpGet=new HttpGet(sb.toString());
		//3.执行请求
		HttpResponse httpResponse=httpClient.execute(httpGet);
		//4 判断请求是否成功
		int status=httpResponse.getStatusLine().getStatusCode();
		
		if(status==200){
			//读取响应内容
			String result=EntityUtils.toString(httpResponse.getEntity(), "UTF-8");
			//json处理
			JSONArray jsonArray=new JSONArray(result);
			for(int i=0;i<jsonArray.length();i++){
				HeadNews headnews=new HeadNews();
				JSONObject jsonObject = jsonArray.getJSONObject(i);
				headnews.setTitle(jsonObject.getString("title"));
				headnews.setContent(jsonObject.getString("content"));
				headnews.setConut(jsonObject.getString("conut"));
				headnews.setImage(jsonObject.getString("image"));
				list.add(headnews);
			}
		}
		return list;
	}

.4.使用HttpClient的post方法获取Json：

	public List<HeadNews>HttpClient_POST() throws Exception{
		List<HeadNews>list=new ArrayList<HeadNews>();
		String path="http://222.22.254.223:8080/web/HeadNewsJson";

		//1.得到浏览器
		HttpClient httpClient=new DefaultHttpClient();

		//2指定请求方式
		HttpPost httpPost=new HttpPost(path);

		//3.构建请求实体的数据
		List<NameValuePair> paras=new ArrayList<NameValuePair>();
		paras.add(new BasicNameValuePair("username", "我是帅哥httpclientPost"));

		//4.构建实体
		UrlEncodedFormEntity entity=new UrlEncodedFormEntity(paras,"utf-8");

		//5。。把实体放入请求对象
		httpPost.setEntity(entity);

		//6.执行请求
		HttpResponse httpResponse=httpClient.execute(httpPost);
		
		int status=httpResponse.getStatusLine().getStatusCode();
		
		if(status==200){
			//读取响应内容
			String result=EntityUtils.toString(httpResponse.getEntity(), "UTF-8");
			//
			JSONArray jsonArray=new JSONArray(result);
			for(int i=0;i<jsonArray.length();i++){
				HeadNews headnews=new HeadNews();
				JSONObject jsonObject = jsonArray.getJSONObject(i);
				headnews.setTitle(jsonObject.getString("title"));
				headnews.setContent(jsonObject.getString("content"));
				headnews.setConut(jsonObject.getString("conut"));
				headnews.setImage(jsonObject.getString("image"));
				list.add(headnews);
			}
		}
		return list;
	}

另外提一点：

Get方式提交不论是HttpURLConnection还是HttpClient，传递中文参数会产生乱码，(传递方法看上面代码)

虽然已经用URLEncoder.encode("中文参数","utf-8")转成utf-8格式，在servlet端也使用spring过滤中文乱码，

但是仍然要这样子接收，不然会中文乱码（不知为何）：

new String(request.getParameter("username").getBytes("ISO-8859-1"),"UTF-8")

Post方式接收中文参数则没有这个问题，直接：

request.getParameter("username")