渡课学习日记 20158/02/9/03 java 第十一课

今天学习了jsp 和 数据库的交互 讲了 get 和 post 的两者不同

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操作一样，只是用来查询一下数据，不会修改、增加数据，不会影响资源的内容，即该请求不会产生副作用。无论进行多少次操作，结果都是一样的。

---

post请求：POST是向服务器端发送数据的，但是该请求会改变数据的种类等资源，就像数据库的insert操作一样，会创建新的内容。几乎目前所有的提交操作都是用POST请求的。

/**
     * 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之间的连接
            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);
            // 建立实际的连接
            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);// 创建连接
            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
    }