http協議從客戶端提交數據給服務器並返回數據

老羅視頻學習。

本例從客戶端提交數據給服務器，服務器接收到數據之後，看是否匹配，匹配返回字符串“login is success!”，失敗返回“login is error!”

一.客戶端。

初始化url地址

private static String path = "http://192.168.10.102:8080/myhttp/servlet/LoginActivity";
	private static URL url;
	
	static{
		
		try {
			url = new URL(path);
		} catch (MalformedURLException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}

setPostMessage函數

getOutputStream是向服務器傳遞數據用的。

getInputStream是從服務器獲取數據用的。

向服務器輸入數據傳遞圖片之類的，要用HttpUrlConnection類

doInput默認值是true，doOutput默認值是false。

private static String sendPostMessage(Map<String, String> params,String encode) {
		//請求體封裝在StringBuffer中
		StringBuffer buffer = new StringBuffer();
		//buffer.append("?");
		try {
			
			
			//判斷是否爲空
			if(params!=null && !params.isEmpty()){
				//迭代for循環
				
				for(Map.Entry<String, String> entry : params.entrySet()){
					//append，追加字符串
					buffer.append(entry.getKey())
					.append("=")
					.append(URLEncoder.encode(entry.getValue(),encode))
					.append("&");
				}
				
			}
			//刪掉最後多餘的那個“&”
			buffer.deleteCharAt(buffer.length()-1);
			System.out.print(buffer.toString());
			
			
			//接下來是http協議內容
			//打開鏈接
			HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
			//設置服務器斷開重連時間
			urlConnection.setConnectTimeout(3000);
			//設置提交方式
			urlConnection.setRequestMethod("POST");
			//設置從服務器讀取數據
			urlConnection.setDoInput(true);
			//設置向服務器寫數據
			urlConnection.setDoOutput(true);
			//接下來需要把url的請求的內容，封裝到一個請求體中
			//獲得上傳信息的字節大小
			byte[] data = buffer.toString().getBytes();
			//設置請求體的類型
			//設置請求體類型爲文本類型，暫時不涉及圖片及二進制數據
			urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
			//設置請求體的長度
			urlConnection.setRequestProperty("Content-Length", String.valueOf(data.length));
			
			//獲得輸出流，向服務器輸出數據
			OutputStream outputStream = urlConnection.getOutputStream();
			outputStream.write(data,0,data.length);
			outputStream.close();
			//獲得服務器響應的結果和狀態碼
			int responseCode = urlConnection.getResponseCode();
			if (responseCode == 200) {
				//把inputStream改爲String傳遞出來
				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 path;
		
	}

changeInputStream函數如下：

把InputStream以encode格式轉換爲String

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 resultString = "";
		if(inputStream!=null) {
			try {
				//數據循環存儲在outputStream中
				while ((len=inputStream.read(data))!=-1) {
					outputStream.write(data,0,len);
				}
				//首先轉換爲字節數組，然後以encode編碼格式轉換爲字符串
				resultString = new String(outputStream.toByteArray(),encode);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return resultString;
	}

測試main函數如下：

	public static void main(String[] args) {
		
		Map<String, String> params = new HashMap<String, String>();
		params.put("username", "admin");
		params.put("password", "123");
		
		String encode = "utf-8";
	
		String resString = HttpUrils.sendPostMessage(params, encode);
		System.out.print("------>"+resString);
	}

二.服務器端，還用get方式例子裏用到的服務器。

LoginActivity繼承自HttpServlet

@Override
	protected void doGet(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		super.doPost(req, resp);
	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		// TODO Auto-generated method stub
		//設置編碼格式
		resp.setContentType("text/html;charset=utf-8");
		req.setCharacterEncoding("utf-8");
		resp.setCharacterEncoding("utf-8");
		
		//獲取用戶名username，密碼password
		PrintWriter out = resp.getWriter();
		String usernameString = req.getParameter("username");
		String pswdString = req.getParameter("password");
		System.out.print(usernameString);
		System.out.print(pswdString);
		//匹配成功
		if(usernameString.equals("admin")&&pswdString.equals("123")){
			out.print("login is success!");
		}//匹配不成功
		else {
			out.print("login is error!");
		}
		out.flush();
		out.close();