JAVA 发送 POST、GET请求

GET请求：GET请求会向服务器发索取数据的请求，从而来获取信息，该请求就像数据库的select操做同样，只是用来查询一下数据，不会修改、增长数据，不会影响资源的内容，即该请求不会产生反作用。不管进行多少次操做，结果都是同样的。

post请求：POST是向服务器端发送数据的，可是该请求会改变数据的种类等资源，就像数据库的insert操做同样，会建立新的内容。几乎目前全部的提交操做都是用POST请求的。

javaCode:

/**
	 * 向指定URL发送GET方法的请求
	 * 
	 */
	public static String get(String url) {
		BufferedReader in = null;
		try {
			URL realUrl = new URL(url);
			// 打开和URL之间的链接
			URLConnection connection = realUrl.openConnection();
			// 设置通用的请求属性
			connection.setRequestProperty("accept", "*/*");
			connection.setRequestProperty("connection", "Keep-Alive");
			connection.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1;SV1)");
			connection.setConnectTimeout(5000);
			connection.setReadTimeout(5000);
			// 创建实际的链接
			connection.connect();
			// 定义 BufferedReader输入流来读取URL的响应
			in = new BufferedReader(new InputStreamReader(connection.getInputStream()));
			StringBuffer sb = new StringBuffer();
			String line;
			while ((line = in.readLine()) != null) {
				sb.append(line);
			}
			return sb.toString();
		} catch (Exception e) {
			LOG.error("Exception occur when send http get request!", e);
		}
		// 使用finally块来关闭输入流
		finally {
			try {
				if (in != null) {
					in.close();
				}
			} catch (Exception e2) {
				e2.printStackTrace();
			}
		}
		return null;
	}

/**
	 * 发送HttpPost请求
	 * 
	 * @param strURL
	 *            服务地址
	 * @param params
	 * 
	 * @return 成功:返回json字符串<br/>
	 */
	public static String jsonPost(String strURL, Map<String, String> params) {
		try {
			URL url = new URL(strURL);// 建立链接
			HttpURLConnection connection = (HttpURLConnection) url.openConnection();
			connection.setDoOutput(true);
			connection.setDoInput(true);
			connection.setUseCaches(false);
			connection.setInstanceFollowRedirects(true);
			connection.setRequestMethod("POST"); // 设置请求方式
			connection.setRequestProperty("Accept", "application/json"); // 设置接收数据的格式
			connection.setRequestProperty("Content-Type", "application/json"); // 设置发送数据的格式
			connection.connect();
			OutputStreamWriter out = new OutputStreamWriter(connection.getOutputStream(), "UTF-8"); // utf-8编码
			out.append(JSONUtil.object2JsonString(params));
			out.flush();
			out.close();

			int code = connection.getResponseCode();
			InputStream is = null;
			if (code == 200) {
				is = connection.getInputStream();
			} else {
				is = connection.getErrorStream();
			}

			// 读取响应
			int length = (int) connection.getContentLength();// 获取长度
			if (length != -1) {
				byte[] data = new byte[length];
				byte[] temp = new byte[512];
				int readLen = 0;
				int destPos = 0;
				while ((readLen = is.read(temp)) > 0) {
					System.arraycopy(temp, 0, data, destPos, readLen);
					destPos += readLen;
				}
				String result = new String(data, "UTF-8"); // utf-8编码
				return result;
			}

		} catch (IOException e) {
			LOG.error("Exception occur when send http post request!", e);
		}
		return "error"; // 自定义错误信息
	}