pobieranie danych: URL i HttpClient

.gitignore

@@ -3,3 +3,4 @@
 /.project
 /.classpath
 /.settings/
+/waluty.json

src/main/java/pobieranie/Pobieranie1_URL.java

+package pobieranie;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URL;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+
+public class Pobieranie1_URL {
+
+	public static void main(String[] args) {
+		final String adres = "http://api.nbp.pl/api/exchangerates/tables/A/?format=json";
+
+		try {
+			URL url = new URL(adres);
+			// Od Java 21 bardziej zalecane jest:
+			// URI uri = new URI(adres);
+			// URL url = uri.toURL();
+			try(InputStream input = url.openStream()) {
+				// z input stream dane można czytać porcjami jako ciągi bajtów
+				// byte[] tablica_bajtow = new byte[1024];
+				// int ile = input.read(tablica_bajtow);
+				// System.out.println(new String(tablica_bajtow, 0, ile));
+				// ale tutaj całość pobrnaych danych zapiszemy do pliku
+				Files.copy(input, Path.of("waluty.json"), StandardCopyOption.REPLACE_EXISTING);
+				System.out.println("Gotowe");
+			}
+		} catch (IOException e) {
+			e.printStackTrace();
+		}
+	}
+
+}

src/main/java/pobieranie/Pobieranie2_HttpClient_DoPliku.java

+package pobieranie;
+
+import java.io.IOException;
+import java.io.InputStream;
+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.nio.file.StandardCopyOption;
+
+public class Pobieranie2_HttpClient_DoPliku {
+
+	public static void main(String[] args) {
+		final String adres = "http://api.nbp.pl/api/exchangerates/tables/A/?format=json";
+
+		try {
+			URI uri = new URI(adres);
+			HttpClient client = HttpClient.newHttpClient();
+			HttpRequest request = HttpRequest.newBuilder(uri).build();
+			HttpResponse<InputStream> response = client.send(request, BodyHandlers.ofInputStream());
+			System.out.println("response: " + response);
+			System.out.println("status: " + response.statusCode());
+			System.out.println("Content-Type: " + response.headers().firstValue("content-type").orElse("--"));
+			if(response.statusCode() != 200) {
+				return;
+			}
+			// body jest takiego typu, jaki wynika z użytego BodyHandler
+			try(InputStream input = response.body()) {
+				Files.copy(input, Path.of("waluty.json"), StandardCopyOption.REPLACE_EXISTING);
+				System.out.println("Gotowe");
+			}
+		} catch (IOException | URISyntaxException | InterruptedException e) {
+			e.printStackTrace();
+		}
+	}
+
+}