Summary of Java communication API (2) How to use HttpUrlConnection

1. 1. Introduction

This time I will briefly summarize how to use HttpUrlConnection. HttpURLconnection is to support requests such as get, post, put, delete based on http. Usually the get and post methods are often used. Therefore, this article also explains the get and post methods.

2. How to use the GET method

First, specify getUrl and use getUrl as a parameter to create an instance of the URL class. Tried to make it. Once you get the connection target, start communication, return the response code, and if successful, the input stream Read the data information with.

String getUrl = "https://github.com/Hyman1993";
URL url = new URL(getUrl);
//instance of connection
HttpURLConnection connection = (HttpURLConnection) url.openConnection();
//Specify request method
connection.setRequestMethod("GET");
//Start communication
connection.connect();
//Return response code
int responseCode = connection.getResponseCode();
//Judge the response code, if OK, proceed
if(responseCode == HttpURLConnection.HTTP_OK){
      //Successful communication
      //Get the text
      InputStream in= connection.getInputStream();
      String encoding = con.getContentEncoding();
      if(null == encoding){
          encoding = "UTF-8";
      }
  StringBuffer result = new StringBuffer();
  final InputStreamReader inReader = new InputStreamReader(in, encoding);
  final BufferedReader bufReader = new BufferedReader(inReader);
  String line = null;
  //Read text line by line
  while((line = bufReader.readLine()) != null) {
      result.append(line);
  }
  //Close
  bufReader.close();
  inReader.close();
  in.close();
  //Output
  Log.log("result=============:"+result);
}

Also, when passing parameters, you can define the url as follows.

String getUrl = "https://github.com/Hyman1993?userName=Hyman1993&password=123456";

3. 3. How to use the POST method

Regarding the POST method, the most important thing is to get the output stream from the connection and write the data information to the server. Next, let's explain with an example.

3.1 Upload JSON data

Please refer to the source below.

            String postUrl = "https://github.com/Hyman1993";
            URL url = new URL(postUrl);
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            //Designated for POST
            connection.setRequestMethod("POST");
            //Output possible
            connection.setDoOutput(true);
            //Can be entered
            connection.setDoInput(true);
            //No cache
            connection.setUseCaches(false);
　　　　　　//Specify the data type as json
　　　　　　connection.setRequestProperty("Content-Type", "application/json;charset=utf-8");
            //Connection, communication start
            connection.connect();
            //Write json data to output stream
　　　　　　　String body = "userName=hyman1993&password=123456";
            BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(connection.getOutputStream(), "UTF-8"));
            writer.write(body);
            writer.close();

            int responseCode = connection.getResponseCode();
            if(responseCode == HttpURLConnection.HTTP_OK){
                      //Successful communication
		      //GET method as well
            }

3.2 Upload file

    String postUrl = "https://github.com/Hyman1993";
    URL url = new URL(postUrl);
    HttpURLConnection connection = (HttpURLConnection) url.openConnection();
    connection.setRequestMethod("POST");
    connection.setDoOutput(true);
    connection.setDoInput(true);
    connection.setUseCaches(false);
    connection.setRequestProperty("Content-Type", "file/*");
    connection.connect();

    OutputStream outputStream = connection.getOutputStream();
    FileInputStream fileInputStream = new FileInputStream("file");
    int length = -1;
    byte[] bytes = new byte[1024];
    while ((length = fileInputStream.read(bytes)) != -1){
        outputStream.write(bytes,0,length);
    }
    fileInputStream.close();
    outputStream.close();

    int responseCode = connection.getResponseCode();
    if(responseCode == HttpURLConnection.HTTP_OK){
                 //Successful communication
                 //GET method as well
    }

Finally

Thank you for reading to the end. This time, I plan to summarize how to use SocketChannel.