1.概念
HTTP 协议可能是现在 Internet 上使用得最多、最重要的协议了，越来越多的 Java 应用程序需要直接通过 HTTP 协议来访问网络资源。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。
除此之外，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。
2.区别
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。
URLConnection |
HTTPClient |
|
|---|---|---|
Proxies and SOCKS |
Full support in Netscape browser, appletviewer, and applications (SOCKS: Version 4 only); no additional limitations from security policies. |
Full support (SOCKS: Version 4 and 5); limited in applets however by security policies; in Netscape can't pick up the settings from the browser. |
Authorization |
Full support for Basic Authorization in Netscape (can use info given by the user for normal accesses outside of the applet); no support in appletviewer or applications. |
Full support everywhere; however cannot access previously given info from Netscape, thereby possibly requesting the user to enter info (s)he has already given for a previous access. Also, you can add/implement additional authentication mechanisms yourself. |
Methods |
Only has GET and POST. |
Has HEAD, GET, POST, PUT, DELETE, TRACE and OPTIONS, plus any arbitrary method. |
Headers |
Currently you can only set any request headers if you are doing a POST under Netscape; for GETs and the JDK you can't set any headers. |
Allows any arbitrary headers to be sent and received. |
Automatic Redirection Handling |
Yes. |
Yes (as allowed by the HTTP/1.1 spec). |
Persistent Connections |
No support currently in JDK; under Netscape uses HTTP/1.0 Keep-Alive's. |
Supports HTTP/1.0 Keep-Alive's and HTTP/1.1 persistence. |
Pipelining of Requests |
No. |
Yes. |
Can handle protocols other than HTTP |
Theoretically; however only http is currently implemented. |
No. |
Can do HTTP over SSL (https) |
Under Netscape, yes. Using Appletviewer or in an application, no. |
No (not yet). |
Source code available |
No. |
Yes. |
3.案例
URLConnection
String urlAddress = "http://192.168.1.102:8080/AndroidServer/login.do";
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();
return null;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
//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();
return null;
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
HTTPClient
String urlAddress = "http://192.168.1.102:8080/qualityserver/login.do";
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");
//hp.
//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);
System.out.println("========="+response);
return response;
}else{
return "error";
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return "exception";
} catch (IOException e) {
// TODO Auto-generated catch block
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) {
// TODO Auto-generated catch block
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);
System.out.println("=========&&"+response);
return response;
}else{
return "error";
}
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return "exception";
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
return "exception";
}
}
servlet端json转化：
resp.setContentType("text/json");
resp.setCharacterEncoding("UTF-8");
toDo = new ToDo();
List<UserBean> list = new ArrayList<UserBean>();
list = toDo.queryUsers(mySession);
String body;
//设定JSON
JSONArray array = new JSONArray();
for(UserBean bean : list)
{
JSONObject obj = new JSONObject();
try
{
obj.put("username", bean.getUserName());
obj.put("password", bean.getPassWord());
}catch(Exception e){}
array.add(obj);
}
pw.write(array.toString());
System.out.println(array.toString());
android端接收：
String urlAddress = "http://192.168.1.102:8080/qualityserver/result.do";
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) {
// TODO Auto-generated catch block
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"},
new int[]{android.R.id.text1,android.R.id.text2});
listResult.setAdapter(simple);
listResult.setOnItemClickListener(new OnItemClickListener() {
@Override
public void onItemClick(AdapterView<?> parent, View view,
int position, long id) {
int positionId = (int) (id+1);
Toast.makeText(MainActivity.this, "ID："+positionId, Toast.LENGTH_LONG).show();
}
});
}
private void 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();
}
转载自：http://www.cnblogs.com/devinzhang/archive/2012/01/17/2325092.html