http协议从客户端提交数据给服务器并返回数据

老罗视频学习。

本例从客户端提交数据给服务器，服务器接收到数据之后，看是否匹配，匹配返回字符串“login is success!”，失败返回“login is error!”

一.客户端。

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函数

getOutputStream是向服务器传递数据用的。

getInputStream是从服务器获取数据用的。

向服务器输入数据传递图片之类的，要用HttpUrlConnection类

doInput默认值是true，doOutput默认值是false。

private static String sendPostMessage(Map<String, String> params,String encode) {
		//请求体封装在StringBuffer中
		StringBuffer buffer = new StringBuffer();
		//buffer.append("?");
		try {
			
			
			//判断是否为空
			if(params!=null && !params.isEmpty()){
				//迭代for循环
				
				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("&");
				}
				
			}
			//删掉最后多余的那个“&”
			buffer.deleteCharAt(buffer.length()-1);
			System.out.print(buffer.toString());
			
			
			//接下来是http协议内容
			//打开链接
			HttpURLConnection urlConnection = (HttpURLConnection)url.openConnection();
			//设置服务器断开重连时间
			urlConnection.setConnectTimeout(3000);
			//设置提交方式
			urlConnection.setRequestMethod("POST");
			//设置从服务器读取数据
			urlConnection.setDoInput(true);
			//设置向服务器写数据
			urlConnection.setDoOutput(true);
			//接下来需要把url的请求的内容，封装到一个请求体中
			//获得上传信息的字节大小
			byte[] data = buffer.toString().getBytes();
			//设置请求体的类型
			//设置请求体类型为文本类型，暂时不涉及图片及二进制数据
			urlConnection.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
			//设置请求体的长度
			urlConnection.setRequestProperty("Content-Length", String.valueOf(data.length));
			
			//获得输出流，向服务器输出数据
			OutputStream outputStream = urlConnection.getOutputStream();
			outputStream.write(data,0,data.length);
			outputStream.close();
			//获得服务器响应的结果和状态码
			int responseCode = urlConnection.getResponseCode();
			if (responseCode == 200) {
				//把inputStream改为String传递出来
				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函数如下：

把InputStream以encode格式转换为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 {
				//数据循环存储在outputStream中
				while ((len=inputStream.read(data))!=-1) {
					outputStream.write(data,0,len);
				}
				//首先转换为字节数组，然后以encode编码格式转换为字符串
				resultString = new String(outputStream.toByteArray(),encode);
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		
		return resultString;
	}

测试main函数如下：

	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.服务器端，还用get方式例子里用到的服务器。

LoginActivity继承自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
		//设置编码格式
		resp.setContentType("text/html;charset=utf-8");
		req.setCharacterEncoding("utf-8");
		resp.setCharacterEncoding("utf-8");
		
		//获取用户名username，密码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();