HTTPClient和URLConnection核心区别分析

首先：在 JDK 的 java.net 包中已经提供了访问 HTTP 协议的基本功能：HttpURLConnection。但是对于大部分应用程序来说，JDK 库本身提供的功能还不够丰富和灵活。
在Android中，androidSDK中集成了Apache的HttpClient模块，用来提供高效的、最新的、功能丰富的支持 HTTP 协议工具包，并且它支持 HTTP 协议最新的版本和建议。使用HttpClient可以快速开发出功能强大的Http程序。
其次：HttpClient是个很不错的开源框架，封装了访问http的请求头，参数，内容体，响应等等，

HttpURLConnection是java的标准类，什么都没封装，用起来太原始，不方便，比如重访问的自定义，以及一些高级功能等。

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。

使用HttpClient发送请求、接收响应很简单，只要如下几步即可：
1.创建HttpClient对象。
2.如果需要发送GET请求，创建HttpGet对象；如果需要发送POST请求，创建HttpPost对象。
3.如果需要发送请求参数，可调用HttpGet、HttpPost共同的setParams(HetpParams params)方法来添加请求参数；对于HttpPost对象而言，也可调用setEntity(HttpEntity entity)方法来设置请求参数。
4.调用HttpClient对象的execute(HttpUriRequest request)发送请求，执行该方法返回一个HttpResponse。
5.调用HttpResponse的getAllHeaders()、getHeaders(String name)等方法可获取服务器的响应头；调用HttpResponse的getEntity()方法可获取HttpEntity对象，该对象包装了服务器的响应内容。程序可通过该对象获取服务器的响应内容。

具体对比如下：HTTPClient

String url = "http://192.168.1.100:8080"; 
public HttpClientServer(){ } 
public String doGet(String username,String password){ 
   String getUrl = urlAddress + "?username="+username+"&password="+password; 
   HttpGet httpGet = new HttpGet(getUrl); 
   HttpParams hp = httpGet.getParams(); 
   hp.getParameter("true"); 
  //httpGet.setp 
  HttpClient hc = new DefaultHttpClient(); 
     try { 
     HttpResponse ht = hc.execute(httpGet); 
     if(ht.getStatusLine().getStatusCode() == HttpStatus.SC_OK){ 
      HttpEntity he = ht.getEntity(); 
      InputStream is = he.getContent(); 
      BufferedReader br = new BufferedReader(new InputStreamReader(is)); 
      String response = ""; 
      String readLine = null; 
      while((readLine =br.readLine()) != null){ 
       //response = br.readLine(); 
      response = response + readLine; 
   } 
   is.close(); 
   br.close(); 
//String str = EntityUtils.toString(he); 
    return response; 
}else{ 
    return "error"; 
  } 
} catch (ClientProtocolException e) { 
   e.printStackTrace(); 
   return "exception"; 
} catch (IOException e) { 
   e.printStackTrace(); 
  return "exception"; 
  } 
} 
 public String doPost(String username,String password){ 
     //String getUrl = urlAddress + "?username="+username+"&password="+password; 
     HttpPost httpPost = new HttpPost(urlAddress); 
     List params = new ArrayList(); 
     NameValuePair pair1 = new BasicNameValuePair("username", username); 
     NameValuePair pair2 = new BasicNameValuePair("password", password); 
     params.add(pair1); 
     params.add(pair2); 
     HttpEntity he; 
     try { 
         he = new UrlEncodedFormEntity(params, "gbk"); 
         httpPost.setEntity(he); 
      } catch (UnsupportedEncodingException e1) { 
        e1.printStackTrace(); 
  } 

  HttpClient hc = new DefaultHttpClient(); 
      try { 
        HttpResponse ht = hc.execute(httpPost); 
       //连接成功 
       if(ht.getStatusLine().getStatusCode() == HttpStatus.SC_OK){ 
       HttpEntity het = ht.getEntity(); 
       InputStream is = het.getContent(); 
       BufferedReader br = new BufferedReader(new InputStreamReader(is)); 
       String response = ""; 
       String readLine = null; 
       while((readLine =br.readLine()) != null){ 
       //response = br.readLine(); 
      response = response + readLine; 
    } 
    is.close(); 
    br.close(); 
  //String str = EntityUtils.toString(he); 
     return response; 
  }else{ 
     return "error"; 
  } 
  } catch (ClientProtocolException e) { 
    e.printStackTrace(); 
    return "exception"; 
  } catch (IOException e) { 
    e.printStackTrace(); 
    return "exception"; 
   } 
}
HttpURLConnection:
String url = "http://192.168.1.100:8080"; 
URL url; 
HttpURLConnection uRLConnection; 
public UrlConnectionToServer(){ }
//向服务器发送get请求
public String doGet(String username,String password){ 
String getUrl = urlAddress + "?username="+username+"&password="+password; 
try { 
url = new URL(getUrl); 
uRLConnection = (HttpURLConnection)url.openConnection(); 
InputStream is = uRLConnection.getInputStream(); 
BufferedReader br = new BufferedReader(new InputStreamReader(is)); 
String response = ""; 
String readLine = null; 
while((readLine =br.readLine()) != null){ 
//response = br.readLine(); 
response = response + readLine; 
} 
is.close(); 
br.close(); 
uRLConnection.disconnect(); 
return response; 
} catch (MalformedURLException e) { 
e.printStackTrace(); 
returnnull; 
} catch (IOException e) { 
e.printStackTrace(); 
returnnull; 
} 
} 

//向服务器发送post请求

public String doPost(String username,String password){ 
try { 
url = new URL(urlAddress); 
uRLConnection = (HttpURLConnection)url.openConnection(); 
uRLConnection.setDoInput(true); 
uRLConnection.setDoOutput(true); 
uRLConnection.setRequestMethod("POST"); 
uRLConnection.setUseCaches(false); 
uRLConnection.setInstanceFollowRedirects(false); 
uRLConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded"); 
uRLConnection.connect(); 
DataOutputStream out = new DataOutputStream(uRLConnection.getOutputStream()); 
String content = "username="+username+"&password="+password; 
out.writeBytes(content); 
out.flush(); 
out.close(); 
InputStream is = uRLConnection.getInputStream(); 
BufferedReader br = new BufferedReader(new InputStreamReader(is)); 
String response = ""; 
String readLine = null; 
while((readLine =br.readLine()) != null){ 
//response = br.readLine(); 
response = response + readLine; 
} 
is.close(); 
br.close(); 
uRLConnection.disconnect(); 
return response; 
} catch (MalformedURLException e) { 
e.printStackTrace(); 
returnnull; 
} catch (IOException e) { 
  e.printStackTrace(); 
  returnnull; 
 } 
}
客户端操作：
String url = "http://192.168.1.102:8080"; 
String body = 
getContent(urlAddress); 
JSONArray array = new JSONArray(body); 
for(int i=0;i<array.length();i++) 
{ 
obj = array.getJSONObject(i); 
sb.append("用户名:").append(obj.getString("username")).append("\t"); 
sb.append("密码:").append(obj.getString("password")).append("\n"); 

HashMap<String, Object> map = new HashMap<String, Object>(); 
try { 
userName = obj.getString("username"); 
passWord = obj.getString("password"); 
} catch (JSONException e) { 
e.printStackTrace(); 
} 
map.put("username", userName); 
map.put("password", passWord); 
listItem.add(map); 
} 
} catch (Exception e) { 
e.printStackTrace(); 
} 
if(sb!=null) 
{ 
showResult.setText("用户名和密码信息："); 
showResult.setTextSize(20); 
} else
extracted(); 
//设置adapter 
SimpleAdapter simple = new SimpleAdapter(this,listItem, 
android.R.layout.simple_list_item_2, 
new String[]{"username","password"}, 
newint[]{android.R.id.text1,android.R.id.text2}); 
listResult.setAdapter(simple); 

listResult.setOnItemClickListener(new OnItemClickListener() { 
@Override 
publicvoid onItemClick(AdapterView<?> parent, View view, 
int position, long id) { 
int positionId = (int) (id+1); 
Toast.makeText(MainActivity.this, "ID："+positionId, Toast.LENGTH_LONG).show(); 
} 
}); 
} 
privatevoid extracted() { 
showResult.setText("没有有效的数据！"); 
} 
//和服务器连接 
private String getContent(String url)throws Exception{ 
StringBuilder sb = new StringBuilder(); 
HttpClient client =new DefaultHttpClient(); 
HttpParams httpParams =client.getParams(); 
HttpConnectionParams.setConnectionTimeout(httpParams, 3000); 
HttpConnectionParams.setSoTimeout(httpParams, 5000); 
HttpResponse response = client.execute(new HttpGet(url)); 
HttpEntity entity =response.getEntity(); 
if(entity !=null){ 
BufferedReader reader = new BufferedReader(new InputStreamReader 
(entity.getContent(),"UTF-8"),8192); 
String line =null; 
while ((line= reader.readLine())!=null){ 
sb.append(line +"\n"); 
} 
reader.close(); 
} 
return sb.toString(); 
}