Android——发送Http请求

一、作用

Android 发送 Http 请求一般有两种方式：HttpURLConnection、HttpClient，由于 HttpClient API 数量过多、扩展困难等问题，Android 官方推荐 HttpURLConnection。

二、概念

三、使用

1. 简单使用

（1） 获取 HttpURLConnection 实例

（2）设置请求方法

（3）自由定制

（4）向服务端携带参数

（5）读取服务端传过来的数据

URL url = null;

HttpURLConnection connection = null;

try {
    url = new URL(address);
    // 1，得到HttpURLConnection 实例
    connection = (HttpURLConnection) url.openConnection();
    // 2，设置请求方法
    connection.setRequestMethod("GET");
    // 3，自由定制:连接超时、读取超时等
    connection.setConnectTimeout(8000);
    connection.setReadTimeout(8000);
    connection.setDoInput(true);
    connection.setDoOutput(true);
    // 4,向服务器发送数据
    //            connection.setRequestMethod("POST");
    //            DataOutputStream out = new DataOutputStream(connection.getOutputStream());
    //            out.writeBytes("username=hh&pwd=12345");
    // 5,得到服务器返回数据
    InputStream inputStream = connection.getInputStream();
    InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
    BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
    StringBuilder response = new StringBuilder();
    String line;
    while ((line = bufferedReader.readLine()) != null) {
        response.append(line);
    }
    return response.toString();
} catch (Exception e) {
    e.printStackTrace();
    return e.getMessage();
} finally {
    if (connection != null) {
        connection.disconnect();
    }
}

2.功能封装

在String sendHttpRequestGet1(String address)中，如果我们直接在该方法中开启线程进行 Http 请求，那么服务端的响应数据是无法返回的，所有耗时逻辑都在子线程中执行，该方法会在服务器还没来得及响应的时候就执行结束了，自然也无法返回响应的数据。

public static String sendHttpRequestGet1(String address) {
    URL url = null;
    HttpURLConnection connection = null;

    try {
        url = new URL(address);
        connection = (HttpURLConnection) url.openConnection();
        connection.setRequestMethod("GET");
        connection.setConnectTimeout(8000);
        connection.setReadTimeout(8000);
        connection.setDoInput(true);
        connection.setDoOutput(true);
        // 得到服务器返回数据
        InputStream inputStream = connection.getInputStream();
        InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
        BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
        StringBuilder response = new StringBuilder();
        String line;
        while ((line = bufferedReader.readLine()) != null) {
            response.append(line);
        }
        return response.toString();
    } catch (Exception e) {
        e.printStackTrace();
        return e.getMessage();
    } finally {
        if (connection != null) {
            connection.disconnect();
        }
    }
}

此时借助 Java 的回调机制，将服务器响应的数据传入onFinish()中，异常时将异常原因传入到onError()中。

public static void sendHttpRequestGet2(final String address, final HttpCallbackListener listener) {
    new Thread(new Runnable() {
        @Override
        public void run() {
            URL url = null;
            HttpURLConnection connection = null;

            try {
                url = new URL(address);
                connection = (HttpURLConnection) url.openConnection();
                connection.setRequestMethod("GET");
                connection.setConnectTimeout(8000);
                connection.setReadTimeout(8000);
                connection.setDoInput(true);
                connection.setDoOutput(true);
                // 得到服务器返回数据
                InputStream inputStream = connection.getInputStream();
                InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
                BufferedReader bufferedReader = new BufferedReader(inputStreamReader);
                StringBuilder response = new StringBuilder();
                String line;
                while ((line = bufferedReader.readLine()) != null) {
                    response.append(line);
                }
                if (listener != null) {
                    listener.onFinish(response.toString());
                }
            } catch (Exception e) {
                e.printStackTrace();
                if (listener != null) {
                    listener.onError(e);
                }
            } finally {
                if (connection != null) {
                    connection.disconnect();
                }
            }
        }
    });

}

public interface HttpCallbackListener {
    void onFinish(String response);

    void onError(Exception e);
}