Add HTTP, REST & JSON code snippets

12-http-rest/snippets/AsyncSongLyricsRetriever.java

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+import java.net.URI;
+import java.net.URISyntaxException;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class AsyncSongLyricsRetriever {
+
+    public static void getLyricsAsync(String artist, String song) {
+        try (ExecutorService executor = Executors.newCachedThreadPool()) {
+            HttpClient client =
+                HttpClient.newBuilder().executor(executor).build(); // configure custom executor or use the default
+
+            URI uri = new URI("https", "api.lyrics.ovh", "/v1/" + artist + "/" + song, null);
+            System.out.println(uri);
+
+            HttpRequest request = HttpRequest.newBuilder().uri(uri).build();
+            System.out.println("Thread calling sendAsync(): " + Thread.currentThread().getName());
+
+            CompletableFuture<String> future = client.sendAsync(request, BodyHandlers.ofString())
+                .thenApply(x -> {
+                    System.out.println("Thread executing thenApply(): " + Thread.currentThread().getName());
+                    return x.body();
+                });
+            future.thenAcceptAsync(x -> {
+                System.out.println("Thread executing thenAccept(): " + Thread.currentThread().getName());
+                System.out.println(x);
+            }, executor);
+            System.out.println("The HTTP call is fired. Performing some other work...");
+
+            // wait for the async HTTP call
+            future.join();
+
+            // ExecutorService is AutoCloseable since Java 19, so its shutdown() method will be automatically invoked.
+        } catch (URISyntaxException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    public static void main(String... args) throws Exception {
+        AsyncSongLyricsRetriever.getLyricsAsync("Adele", "Hello");
+    }
+
+}

12-http-rest/snippets/CollectionsMain.java

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+import java.lang.reflect.Type;
+import java.util.List;
+import java.util.Map;
+
+import com.google.gson.Gson;
+import com.google.gson.reflect.TypeToken;
+
+public class CollectionsMain {
+
+    public static void main(String[] args) {
+        // Lists example
+        List<Developer> devs = List.of(
+            new Developer("Kelsey", 28, "Google, Inc"),
+            new Developer("Wesley", 20, "Google, Inc"));
+
+        Gson gson = new Gson();
+        String json = gson.toJson(devs);
+
+        System.out.println(json);
+
+        Type type = new TypeToken<List<Developer>>() {
+        }.getType();
+        List<Developer> devsAgain = gson.fromJson(json, type);
+
+        System.out.println(devsAgain.size()); // 2
+
+        // Maps example
+        json = "{\"apple\":1,\"banana\":2,\"cherry\":3}";
+
+        Map<String, Integer> map = gson.fromJson(json, new TypeToken<Map<String, Integer>>() {
+        }.getType());
+
+        System.out.println(map);  // {apple=1, banana=2, cherry=3}
+    }
+}

12-http-rest/snippets/DevManager.java

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+import com.google.gson.annotations.SerializedName;
+
+public record DevManager(String name, @SerializedName("unit") String department, int level) {
+    // Gson's @SerializedName annotation is also supported for record components
+}

12-http-rest/snippets/Developer.java

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+import com.google.gson.annotations.SerializedName;
+
+public class Developer {
+
+    private String name;
+    private int age;
+    @SerializedName("employer") // this sets custom name to the serialized field
+    private transient String company; // remove transient keyword to serialize
+
+    public Developer(String name, int age, String company) {
+        this.name = name;
+        this.age = age;
+        this.company = company;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public String getCompany() {
+        return company;
+    }
+
+    public void setCompany(String company) {
+        this.company = company;
+    }
+
+}

12-http-rest/snippets/FileDownload.java

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+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse;
+import java.nio.file.Path;
+
+public class FileDownload {
+
+    public static void main(String... args) throws Exception {
+        var url = "https://www.7-zip.org/a/7z1806-x64.exe";
+
+        var client = HttpClient.newBuilder().build();
+        var request = HttpRequest.newBuilder().uri(URI.create(url)).build();
+
+        Path localFile = Path.of("7z.exe");
+
+        HttpResponse<Path> response = client.send(request, HttpResponse.BodyHandlers.ofFile(localFile));
+    }
+
+}

12-http-rest/snippets/FromJsonMain.java

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+import com.google.gson.Gson;
+
+public class FromJsonMain {
+
+    public static void main(String[] args) {
+        String json = "{\"name\": \"Wesley\", \"age\": 20 }";
+
+        Gson gson = new Gson();
+        Developer dev = gson.fromJson(json, Developer.class);
+
+        System.out.printf("%s, %d years old, %s%n", dev.getName(), dev.getAge(), dev.getCompany());
+    }
+
+}

12-http-rest/snippets/JsonReaderMain.java

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+import com.google.gson.Gson;
+
+import java.io.FileReader;
+import java.io.IOException;
+import java.util.List;
+
+public class JsonReaderMain {
+
+    public static void main(String[] args) throws IOException {
+        Gson gson = new Gson();
+
+        FileReader reader = new FileReader("src/devs.json");
+        List<Developer> devs = gson.fromJson(reader, List.class);
+        System.out.println(devs);
+    }
+
+}

12-http-rest/snippets/ParallelHttpRequestsSender.java

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+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.CompletableFuture;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class ParallelHttpRequestsSender {
+
+    private static final String WEB_SITE = "http://www.google.com";
+    private static final int PARALLEL_REQUESTS = 100;
+
+    public long executeRequestsSync(HttpClient client, HttpRequest request) throws Exception {
+        // send some synchronous requests and measure time
+        long startTime = System.currentTimeMillis();
+
+        for (int i = 0; i < PARALLEL_REQUESTS; i++) {
+            client.send(request, BodyHandlers.ofString()).body();
+        }
+
+        return System.currentTimeMillis() - startTime;
+    }
+
+    public long executeRequestsAsync(HttpClient client, HttpRequest request) {
+        List<CompletableFuture<String>> futures = new ArrayList<>();
+
+        // send some asynchronous requests and measure time
+        long startTime = System.currentTimeMillis();
+
+        for (int i = 0; i < PARALLEL_REQUESTS; i++) {
+            futures.add(client.sendAsync(request, BodyHandlers.ofString()).thenApply(x -> {
+                System.out.println("thenApply() thread: " + Thread.currentThread().getName());
+                return x.body();
+            }));
+        }
+
+        // uncomment to dump responses to console
+        // futures.stream().map(f -> f.join()).forEach(System.out::println);
+
+        // wait for all futures to complete
+        CompletableFuture.allOf(futures.toArray(CompletableFuture[]::new)).join();
+
+        return System.currentTimeMillis() - startTime;
+    }
+
+    public static void main(String... args) throws Exception {
+        try (ExecutorService executor = Executors.newCachedThreadPool()) {
+            HttpClient client =
+                HttpClient.newBuilder().executor(executor).build(); // configure custom executor or use the default
+
+            // build a request
+            HttpRequest request = HttpRequest.newBuilder().uri(URI.create(WEB_SITE)).build();
+
+            var sender = new ParallelHttpRequestsSender();
+
+            long syncExecutionTime = sender.executeRequestsSync(client, request);
+            long asyncExecutionTime = sender.executeRequestsAsync(client, request);
+
+            System.out.println("Async: " + asyncExecutionTime + " Sync: " + syncExecutionTime);
+
+            // ExecutorService is AutoCloseable since Java 19, so its shutdown() method will be automatically invoked.
+        }
+    }
+
+}

12-http-rest/snippets/SimpleHttpCaller.java

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+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.PrintWriter;
+import java.net.Socket;
+
+public class SimpleHttpCaller {
+
+    private static final String HOST = "google.com";
+    private static final int HTTP_PORT = 80;
+    private static final String HTTP_REQUEST = "GET / HTTP/1.1" + System.lineSeparator();
+
+    public static void main(String[] args) {
+
+        try (Socket socket = new Socket(HOST, HTTP_PORT);
+             PrintWriter writer = new PrintWriter(socket.getOutputStream(), true); // autoflush on
+             BufferedReader reader = new BufferedReader(new InputStreamReader(socket.getInputStream()))) {
+
+            writer.println(HTTP_REQUEST);
+
+            String line;
+            while ((line = reader.readLine()) != null) {
+                System.out.println(line);
+            }
+
+        } catch (IOException e) {
+            throw new RuntimeException("Could not access web site", e);
+        }
+
+    }
+
+}

12-http-rest/snippets/SyncSongLyricsRetriever.java

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+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse.BodyHandlers;
+
+public class SyncSongLyricsRetriever {
+
+    public String getLyricsSync(String artist, String song) throws Exception {
+        HttpClient client = HttpClient.newBuilder().build();
+
+        URI uri = new URI("https", "api.lyrics.ovh", "/v1/" + artist + "/" + song, null);
+        System.out.println(uri);
+
+        HttpRequest request = HttpRequest.newBuilder().uri(uri).build();
+        return client.send(request, BodyHandlers.ofString()).body();
+    }
+
+    public static void main(String... args) throws Exception {
+        System.out.println(new SyncSongLyricsRetriever().getLyricsSync("Adele", "Hello"));
+    }
+
+}

12-http-rest/snippets/TextToSpeech.java

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+import java.net.URI;
+import java.net.http.HttpClient;
+import java.net.http.HttpRequest;
+import java.net.http.HttpResponse.BodyHandlers;
+import java.nio.file.Path;
+
+public class TextToSpeech {
+
+    // signup here to get your API key: https://account.cloudmersive.com/signup
+    private static final String API_KEY = "YOUR_API_KEY_HERE";
+
+    private static final String TEXT =
+            "\"I must admit I was skeptical about the Modern Java Technologies course but in the end I am starting to appreciate it. \"";
+
+    public static void main(String... args) throws Exception {
+        HttpClient client = HttpClient.newHttpClient();
+
+        URI uri = new URI("https", "api.cloudmersive.com", "/speech/speak/text/basicVoice/wav", null);
+        HttpRequest request = HttpRequest.newBuilder()
+                .header("Apikey", API_KEY)
+                .header("Content-Type", "application/json")
+                .POST(HttpRequest.BodyPublishers.ofString(TEXT))
+                .uri(uri)
+                .build();
+
+        client.send(request, BodyHandlers.ofFile(Path.of("speech.wav")));
+    }
+
+}

12-http-rest/snippets/ToJsonMain.java

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+import com.google.gson.Gson;
+import com.google.gson.GsonBuilder;
+
+public class ToJsonMain {
+
+    public static void main(String[] args) {
+        Developer dev = new Developer("Kelsey", 28, "Google, Inc");
+        DevManager devManager = new DevManager("Mike", "Google AI R&D", 7);
+
+        Gson gson = new Gson();
+        //Gson gson = new GsonBuilder().setPrettyPrinting().create();
+        String devJson = gson.toJson(dev);
+        System.out.println(devJson);
+
+        // Gson version 2.10 and later also supports records
+        // Note that the & character in the department value would be replaced by default with its unicode escape, \u0026
+        Gson gsonNonEscaping = new GsonBuilder().disableHtmlEscaping().create();
+        String devManagerJson = gsonNonEscaping.toJson(devManager);
+        System.out.println(devManagerJson);
+    }
+
+}