* 每个HTTP-GET和HTTP-POST都由一系列HTTP请求头组成，这些请求头定义了客户端从服务器请求了什么，而响应则是由一系列HTTP请求数据和响应数据组成，如果请求成功则返回响应的数据。
* HTTP-GET以使用MIME类型application/x-www-form-urlencoded的urlencoded文本的格式传递参数。Urlencoding是一种字符编码，保证被传送的参数由遵循规范的文本组成，例如一个空格的编码是"%20"。附加参数还能被认为是一个查询字符串。
* 与HTTP-GET类似，HTTP-POST参数也是被URL编码的。然而，变量名/变量值不作为URL的一部分被传送，而是放在实际的HTTP请求消息内部被传送。
* GET和POST之间的主要区别
1、GET是从服务器上获取数据，POST是向服务器传送数据。
2、在客户端， GET方式在通过URL提交数据，数据在URL中可以看到；POST方式，数据放置在HTML HEADER内提交
3、对于GET方式，服务器端用Request.QueryString获取变量的值，对于POST方式，服务器端用Request.Form获取提交的数据。
4、GET方式提交的数据最多只能有1024字节，而POST则没有此限制
5、安全性问题。正如在（2）中提到，使用 GET 的时候，参数会显示在地址栏上，而 POST 不会。所以，如果这些数据是中文数据而且是非敏感数据，那么使用 GET ；如果用户输入的数据不是中文字符而且包含敏感数据，那么还是使用 POST为好
* URL的定义和组成
Uniform Resource Locator 统一资源定位符
URL的组成部分：http://www.mbalib.com/china/index.htm
http://：代表超文本传输协议
www：代表一个万维网服务器
mbalib.com/：服务器的域名，或服务器名称
China/：子目录，类似于我们的文件夹
Index.htm:是文件夹中的一个文件
/china/index.htm统称为URL路径
服务器端
public class LoginAction extends HttpServlet {
/**
* Constructor of the object.
*/
public LoginAction() {
super();
}
/**
* Destruction of the servlet. <br>
*/
public void destroy() {
super.destroy(); // Just puts "destroy" string in log
// Put your code here
}
/**
* The doGet method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to get.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
this.doPost(request, response);
}
/**
* The doPost method of the servlet. <br>
*
* This method is called when a form has its tag value method equals to post.
*
* @param request the request send by the client to the server
* @param response the response send by the server to the client
* @throws ServletException if an error occurred
* @throws IOException if an error occurred
*/
public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html;charset=utf-8");
request.setCharacterEncoding("utf-8");
response.setCharacterEncoding("utf-8");
PrintWriter out = response.getWriter();
String username = request.getParameter("username");
System.out.println("-username->>"+username);
String pswd = request.getParameter("password");
System.out.println("-password->>"+pswd);
if(username.equals("admin")&&pswd.equals("123")){
//表示服务器端返回的结果
out.print("login is success!!!!");
}else{
out.print("login is fail!!!");
}
out.flush();
out.close();
}
/**
* Initialization of the servlet. <br>
*
* @throws ServletException if an error occurs
*/
public void init() throws ServletException {
// Put your code here
}
}
HTTP-GET方式
public class HttpUtils {
private static String URL_PATH = "http://192.168.0.102:8080/myhttp/pro1.png";
public HttpUtils() {
// TODO Auto-generated constructor stub
}
public static void saveImageToDisk() {
InputStream inputStream = getInputStream();
byte[] data = new byte[1024];
int len = 0;
FileOutputStream fileOutputStream = null;
try {
fileOutputStream = new FileOutputStream("C:\test.png");
while ((len = inputStream.read(data)) != -1) {
fileOutputStream.write(data, 0, len);
}
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (inputStream != null) {
try {
inputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
if (fileOutputStream != null) {
try {
fileOutputStream.close();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
}
/**
* 获得服务器端的数据,以InputStream形式返回
* @return
*/
public static InputStream getInputStream() {
InputStream inputStream = null;
HttpURLConnection httpURLConnection = null;
try {
URL url = new URL(URL_PATH);
if (url != null) {
httpURLConnection = (HttpURLConnection) url.openConnection();
// 设置连接网络的超时时间
httpURLConnection.setConnectTimeout(3000);
httpURLConnection.setDoInput(true);
// 表示设置本次http请求使用GET方式请求
httpURLConnection.setRequestMethod("GET");
int responseCode = httpURLConnection.getResponseCode();
if (responseCode == 200) {
// 从服务器获得一个输入流
inputStream = httpURLConnection.getInputStream();
}
}
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return inputStream;
}
public static void main(String[] args) {
// 从服务器获得图片保存到本地
saveImageToDisk();
}
}
HTTP-POST(Java接口)方式
public class HttpUtils {
// 请求服务器端的url
private static String PATH = "http://192.168.0.102:8080/myhttp/servlet/LoginAction";
private static URL url;
public HttpUtils() {
// TODO Auto-generated constructor stub
}
static {
try {
url = new URL(PATH);
} catch (MalformedURLException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
/**
* @param params
* 填写的url的参数
* @param encode
* 字节编码
* @return
*/
public static String sendPostMessage(Map<String, String> params,
String encode) {
// 作为StringBuffer初始化的字符串
StringBuffer buffer = new StringBuffer();
try {
if (params != null && !params.isEmpty()) {
for (Map.Entry<String, String> entry : params.entrySet()) {
// 完成转码操作
buffer.append(entry.getKey()).append("=").append(
URLEncoder.encode(entry.getValue(), encode))
.append("&");
}
buffer.deleteCharAt(buffer.length() - 1);
}
// System.out.println(buffer.toString());
// 删除掉最有一个&
System.out.println("-->>"+buffer.toString());
HttpURLConnection urlConnection = (HttpURLConnection) url
.openConnection();
urlConnection.setConnectTimeout(3000);
urlConnection.setRequestMethod("POST");
urlConnection.setDoInput(true);// 表示从服务器获取数据
urlConnection.setDoOutput(true);// 表示向服务器写数据
// 获得上传信息的字节大小以及长度
byte[] mydata = buffer.toString().getBytes();
// 表示设置请求体的类型是文本类型
urlConnection.setRequestProperty("Content-Type",
"application/x-www-form-urlencoded");
urlConnection.setRequestProperty("Content-Length",
String.valueOf(mydata.length));
// 获得输出流,向服务器输出数据
OutputStream outputStream = urlConnection.getOutputStream();
outputStream.write(mydata,0,mydata.length);
outputStream.close();
// 获得服务器响应的结果和状态码
int responseCode = urlConnection.getResponseCode();
if (responseCode == 200) {
return changeInputStream(urlConnection.getInputStream(), encode);
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return "";
}
/**
* 将一个输入流转换成指定编码的字符串
*
* @param inputStream
* @param encode
* @return
*/
private static String changeInputStream(InputStream inputStream,
String encode) {
// TODO Auto-generated method stub
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
String result = "";
if (inputStream != null) {
try {
while ((len = inputStream.read(data)) != -1) {
outputStream.write(data, 0, len);
}
result = new String(outputStream.toByteArray(), encode);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return result;
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
Map<String, String> params = new HashMap<String, String>();
params.put("username", "admin");
params.put("password", "1234");
String result = HttpUtils.sendPostMessage(params, "utf-8");
System.out.println("--result->>" + result);
}
}
HTTP-POST(Apache接口)方式
public class HttpUtils {
public HttpUtils() {
// TODO Auto-generated constructor stub
}
public static String sendHttpClientPost(String path,
Map<String, String> map, String encode) {
List<NameValuePair> list = new ArrayList<NameValuePair>();
if (map != null && !map.isEmpty()) {
for (Map.Entry<String, String> entry : map.entrySet()) {
list.add(new BasicNameValuePair(entry.getKey(), entry
.getValue()));
}
}
try {
// 实现将请求的参数封装到表单中,请求体重
UrlEncodedFormEntity entity = new UrlEncodedFormEntity(list, encode);
// 使用Post方式提交数据
HttpPost httpPost = new HttpPost(path);
httpPost.setEntity(entity);
// 指定post请求
DefaultHttpClient client = new DefaultHttpClient();
HttpResponse httpResponse = client.execute(httpPost);
if (httpResponse.getStatusLine().getStatusCode() == 200) {
return changeInputStream(httpResponse.getEntity().getContent(),
encode);
}
} catch (UnsupportedEncodingException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (ClientProtocolException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return "";
}
/**
* 将一个输入流转换成指定编码的字符串
*
* @param inputStream
* @param encode
* @return
*/
public static String changeInputStream(InputStream inputStream,
String encode) {
// TODO Auto-generated method stub
ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
byte[] data = new byte[1024];
int len = 0;
String result = "";
if (inputStream != null) {
try {
while ((len = inputStream.read(data)) != -1) {
outputStream.write(data, 0, len);
}
result = new String(outputStream.toByteArray(), encode);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
return result;
}
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
String path = "http://192.168.0.102:8080/myhttp/servlet/LoginAction";
Map<String, String> params = new HashMap<String, String>();
params.put("username", "admin");
params.put("password", "123");
String result = HttpUtils.sendHttpClientPost(path, params, "utf-8");
System.out.println("-->>"+result);
}
}