使用Google Roads API抓取道路信息（java实现）

Google Roads API提供了强大的道路获取接口，用户仅仅需调用对应的API就能够获取对应区域的道路坐标以及道路的限速信息。

详细的调用方法例如以下：

https://roads.googleapis.com/v1/snapToRoads?
path=-35.27801,149.12958|-35.28032,149.12907|-35.28099,149.12929|-35.28144,149.12984|-35.28194,149.13003|-35.28282,149.12956|-35.28302,149.12881|-35.28473,149.12836
        &interpolate=true
        &key=API_KEY

key的值须要替换为用户自己申请的key值。

普通开发人员每天能够运行上述查询2500次。Java调用Roads API的代码例如以下：

StringBuffer document = new StringBuffer();
        try {
            String str_url = "https://roads.googleapis.com/v1/snapToRoads?path=-35.27801,149.12958|-35.28032,149.12907|-35.28099,149.12929|-35.28144,149.12984|-35.28194,149.13003|-35.28282,149.12956|-35.28302,149.12881|-35.28473,149.12836&interpolate=true&key=YourKeyHere";
            URL url = new URL(str_url);//远程url
            URLConnection conn = url.openConnection();
            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String line = null;
            int line_number = 0;
            while ((line = reader.readLine()) != null) {
                line_number += 1;
                if (line.startsWith("        \"latitude\": ")) {
                    line = line.replaceAll("        \"latitude\": ", "");
                    document.append(line + " ");
                    System.out.print(line);
                }
                if (line.startsWith("        \"longitude\": ")) {
                    line = line.replaceAll("        \"longitude\": ", "");
                    document.append(line + " ");
                    System.out.println(line);
                }
            }
            if (line_number < 20) {
                System.out.println("error");
            }
            reader.close();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }