HTTP 请求方式: GET和POST的比较
请求包.png例子.png响应包.png例子.png
请求头描述了客户端向服务器发送请求时使用的http协议类型，所使用的编码，以及发送内容的长度，等等。
相应的响应头用来描述服务器回给你对所返回的content的一些描述，服务器类型，我返回的编码，我返回的内容有多长等等。
原文链接：http://www.jianshu.com/p/42a396430be5
著作权归作者所有，转载请联系作者获得授权，并标注“简书作者”。
- GET请求能够被缓存
- GET请求会保存在浏览器的浏览记录中
- 以GET请求的URL能够保存为浏览器书签
- GET请求有长度限制
- GET请求主要用以获取数据
- POST请求不能被缓存下来
- POST请求不会保存在浏览器浏览记录中
- 以POST请求的URL无法保存为浏览器书签
- POST请求没有长度限制
| GET | POST | |
| 点击返回/刷新按钮 | 没有影响 | 数据会重新发送（浏览器将会提示用户“数据被从新提交”） |
| 添加书签 | 可以 | 不可以 |
| 缓存 | 可以 | 不可以 |
| 编码类型(Encoding type) | application/x-www-form-urlencoded |
application/x-www-form-urlencoded or multipart/form-data. 请为二进制数据使用multipart编码
|
| 历史记录 | 有 | 没有 |
| 长度限制 | 有 | 没有 |
| 数据类型限制 | 只允许ASCII字符类型 | 没有限制。允许二进制数据 |
| 安全性 | 查询字符串会显示在地址栏的URL中，不安全，请不要使用GET请求提交敏感数据 | 因为数据不会显示在地址栏中，也不会缓存下来或保存在浏览记录中，所以看POST求情比GET请求安全，但也不是最安全的方式。如需要传送敏感数据，请使用加密方式传输 |
| 可见性 | 查询字符串显示在地址栏的URL中，可见 | 查询字符串不会显示在地址栏中，不可见 |
其他HTTP请求方式
| 方式 | 描述 |
| HEAD | 与GET请求类似，不同在与服务器只返回HTTP头部信息，没有页面内容 |
| PUT | 上传指定URL的描述 |
| DELETE | 删除指定资源 |
| OPTIONS | 返回服务器支持的HTTP方法 |
| CONNECT | 转换为透明TCP/IP隧道的连接请求 |
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
1.HttpURLConnection连接URL
1)创建一个URL对象
URL url = new URL(http://www.baidu.com);
2)利用HttpURLConnection对象从网络中获取网页数据
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
3)设置连接超时
conn.setConnectTimeout(6*1000);
4)对响应码进行判断
if (conn.getResponseCode() != 200) //从Internet获取网页,发送请求,将网页以流的形式读回来
throw new RuntimeException("请求url失败");
5)得到网络返回的输入流
InputStream is = conn.getInputStream();
6)String result = readData(is, "GBK"); //文件流输入出文件用outStream.write
7)conn.disconnect();
总结:
--记得设置连接超时,如果网络不好,Android系统在超过默认时间会收回资源中断操作.
--返回的响应码200,是成功.
--在Android中对文件流的操作和JAVA SE上面是一样的.
--在对大文件的操作时,要将文件写到SDCard上面,不要直接写到手机内存上.
--操作大文件是,要一遍从网络上读,一遍要往SDCard上面写,减少手机内存的使用.这点很重要,面试经常会被问到.
--对文件流操作完,要记得及时关闭.
2.向Internet发送请求参数
步骤：
1)创建URL对象:URL realUrl = new URL(requestUrl);
2)通过HttpURLConnection对象,向网络地址发送请求
HttpURLConnection conn = (HttpURLConnection) realUrl.openConnection();
3)设置容许输出:conn.setDoOutput(true);
4)设置不使用缓存:conn.setUseCaches(false);
5)设置使用POST的方式发送:conn.setRequestMethod("POST");
6)设置维持长连接:conn.setRequestProperty("Connection", "Keep-Alive");
7)设置文件字符集:conn.setRequestProperty("Charset", "UTF-8");
8)设置文件长度:conn.setRequestProperty("Content-Length", String.valueOf(data.length));
9)设置文件类型:conn.setRequestProperty("Content-Type","application/x-www-form-urlencoded");
10)以流的方式输出.
总结:
--发送POST请求必须设置允许输出
--不要使用缓存,容易出现问题.
--在开始用HttpURLConnection对象的setRequestProperty()设置,就是生成HTML文件头.
3.向Internet发送xml数据
XML格式是通信的标准语言,Android系统也可以通过发送XML文件传输数据.
1)将生成的XML文件写入到byte数组中,并设置为UTF-8:byte[] xmlbyte = xml.toString().getBytes("UTF-8");
2)创建URL对象,并指定地址和参数:URL url = new URL(http://localhost:8080/itcast/contanctmanage.do?method=readxml);
3)获得链接:HttpURLConnection conn = (HttpURLConnection) url.openConnection();
4)设置连接超时:conn.setConnectTimeout(6* 1000);
5)设置允许输出conn.setDoOutput(true);
6)设置不使用缓存:conn.setUseCaches(false);
7)设置以POST方式传输:conn.setRequestMethod("POST");
8)维持长连接:conn.setRequestProperty("Connection", "Keep-Alive");
9)设置字符集:conn.setRequestProperty("Charset", "UTF-8");
10)设置文件的总长度:conn.setRequestProperty("Content-Length", String.valueOf(xmlbyte.length));
11)设置文件类型:conn.setRequestProperty("Content-Type", "text/xml; charset=UTF-8");
12)以文件流的方式发送xml数据:outStream.write(xmlbyte);
总结:
--我们使用的是用HTML的方式传输文件,这个方式只能传输一般在5M一下的文件.
--传输大文件不适合用HTML的方式,传输大文件我们要面向Socket编程.确保程序的稳定性
--将地址和参数存到byte数组中:byte[] data = params.toString().getBytes();
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();
}