Get content via HTTP

** HttpClient class ** (Java 11 or later)
HTTP2 support
Asynchronous processing
WebSocket communication (lightweight)
Module (bundle of packages)
The HttpClient class belongs to the java.net.http module
Describe below under / src to enable access to the module from the current project

`module-info.java`


module selflearn{
  requires java.net.http;
}

** HttpClient object creation **
** Instantiate with newHttpClient method **
** Operation parameter setting with newBuilder method **
Authentication code (authenticator), connection timeout time (connectTimeout), version specification (version), etc.
- var client = HttpClient.newBuilder() .version(HttpClient.Version.HTTP_1_1) .connectTimeout(Duration.parse("PT3S")).build();
Finally, call build () to create an HttpClient object based on each setting
** HTTPRequest object generation **
Call the build method at the end of the newBuilder method
** Send request **
** send method of HttpClient class **
Specify handler method for response operation
String (ofString), Stream (ofLines), File (ofFile), Input Stream (ofInputStream), Byte Array (ofByteArray)
** Get response **
send method returns response as an object
Body (body), response headers (headers), HttpRequest (request), status code (statusCode), URI (uri)

//Access Qiita to get content
import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
  public static void main(String[] args) {
    try {
      //HTTP client generation
      var client = HttpClient.newHttpClient();
      //Request preparation
      var req = HttpRequest.newBuilder()
        .uri(URI.create("https://qiita.com/"))
        .build();
      //Get response
      var res = client.send(req, HttpResponse.BodyHandlers.ofString());
      System.out.println(res.body());
      //<!DOCTYPE html><html><head><meta charset="utf-8" /><title>Qiita</title><meta content="Qiita is a technical information sharing service for programmers. Easily record programming tips, know-how, and notes&amp;amp;You can publish it."(Abbreviation)
    } catch (IOException | InterruptedException e) {
      e.printStackTrace();
    }
  }
}

Asynchronous request transmission

sendAsync method
Subsequent processing can be performed without waiting for a response
Result processing with thenAccept method

//Get response by asynchronous processing
client.send(req, HttpResponse.BodyHandlers.ofString())
.thenAccept(response -> {
  System.out.println(response.body());
});

HTTP POST data communication

Get data by HTTP GET, send data by HTTP POST
** Generate request with method of HttpRequest.BodyPublishers class **
String (ofString), File Length (ofFile), InputStream (ofInputStream), Byte Array (ofByteArray)

import java.io.IOException;
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class Main {
  public static void main(String[] args) throws IOException, InterruptedException {
    var client = HttpClient.newHttpClient();
    //Receive name key and generate String
    var req = HttpRequest.newBuilder()
      .uri(URI.create("https://www.sample/post.php")) //"Hello,!"
      .header("Content-Type","application/json")
      .POST(HttpRequest.BodyPublishers.ofString(
         "{ \"name\" : \"Qiita Neko\" }")) 
      .build();
    var res = client.send(req, HttpResponse.BodyHandlers.ofString());
    System.out.println(res.body()); //Hello, Qiita Neko-san!
  }
}

`post.php`


<?php
$data = json_decode(file_get_contents('php://input'));
print ('Hello,'.$data->name.'San!');

[Java] Content acquisition with HttpCliient

Get content via HTTP

module-info.java

Asynchronous request transmission

HTTP POST data communication

post.php

`module-info.java`

`post.php`