[[oktatas:programozás:java:java_rest_api_kliens|< Java REST API kliens]]

====== Java REST API kliens - HttpURLConnection ======

  * **Szerző:** Sallai András
  * Copyright (c) 2024, Sallai András
  * Szerkesztve: 2024
  * Licenc: [[https://creativecommons.org/licenses/by-sa/4.0/|CC BY-SA 4.0]]
  * Web: https://szit.hu

===== Használatra példa =====

<code java Client.java>
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class Client {
  public static void connect() throws IOException {
    URL url = new URL("https://jsonplaceholder.typicode.com/users/");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    conn.connect();

    InputStream is = conn.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);

    StringBuffer sb = new StringBuffer();
    String line = br.readLine();
    while (line != null) {
      sb.append(line);
      sb.append(System.lineSeparator());
      line = br.readLine();
    }    
    conn.disconnect();
    System.out.println(sb.toString());

  }
}
</code>

<code java App.java>
public class App {
    public static void main(String[] args) throws Exception {
        Client.connect();
    }
}

</code>

===== CRUD műveletek =====

<code java Client.java>
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class Client {
  public static void get() throws IOException {
    URL url = new URL("https://jsonplaceholder.typicode.com/users/");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("GET");
    conn.connect();

    InputStream is = conn.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);

    StringBuffer sb = new StringBuffer();
    String line = br.readLine();
    while (line != null) {
      sb.append(line);
      sb.append(System.lineSeparator());
      line = br.readLine();
    }    
    conn.disconnect();
    System.out.println(sb.toString());

  }

  public static void post() throws IOException {
    URL url = new URL("https://jsonplaceholder.typicode.com/users/");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("POST");
    conn.setRequestProperty("Content-type", "application/json");
    conn.setDoOutput(true);

    String jsonInputString = "{\"name\":\"morpheus\",\"job\":\"leader\"}";
    conn.getOutputStream().write(jsonInputString.getBytes());
    conn.getOutputStream().flush();
    conn.getOutputStream().close();
    conn.connect();

    InputStream is = conn.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);

    StringBuffer sb = new StringBuffer();
    String line = br.readLine();
    while (line != null) {
      sb.append(line);
      sb.append(System.lineSeparator());
      line = br.readLine();
    }    
    conn.disconnect();
    System.out.println(sb.toString());
  
  }

  public static void put() throws IOException {
    URL url = new URL("https://jsonplaceholder.typicode.com/users/1");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("PUT");
    conn.setRequestProperty("Content-type", "application/json");
    conn.setDoOutput(true);

    String jsonInputString = "{\"name\":\"morpheus\",\"job\":\"zion resident\"}";
    conn.getOutputStream().write(jsonInputString.getBytes());
    conn.getOutputStream().flush();
    conn.getOutputStream().close();
    conn.connect();

    InputStream is = conn.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);

    StringBuffer sb = new StringBuffer();
    String line = br.readLine();
    while (line != null) {
      sb.append(line);
      sb.append(System.lineSeparator());
      line = br.readLine();
    }    
    conn.disconnect();
    System.out.println(sb.toString());
  
  }

  public static void delete() throws IOException {
    URL url = new URL("https://jsonplaceholder.typicode.com/users/1");
    HttpURLConnection conn = (HttpURLConnection) url.openConnection();
    conn.setRequestMethod("DELETE");
    conn.connect();

    InputStream is = conn.getInputStream();
    InputStreamReader isr = new InputStreamReader(is);
    BufferedReader br = new BufferedReader(isr);

    StringBuffer sb = new StringBuffer();
    String line = br.readLine();
    while (line != null) {
      sb.append(line);
      sb.append(System.lineSeparator());
      line = br.readLine();
    }    
    conn.disconnect();
    System.out.println(sb.toString());
  }

}
</code>