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karpadokarpado
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Rest API in Java (#18428)
* Rest API in Java * Addressing the feedback comments
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‎core-java-modules/core-java-httpclient/src/main/java/com/baeldung/rest/RestApiServer.java

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package com.baeldung.rest;
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import com.sun.net.httpserver.HttpExchange;
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import com.sun.net.httpserver.HttpHandler;
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import com.sun.net.httpserver.HttpServer;
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import java.io.*;
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import java.net.InetSocketAddress;
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import java.nio.charset.StandardCharsets;
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import java.util.ArrayList;
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import java.util.List;
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public class RestApiServer implements HttpHandler {
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private final List<String> users = new ArrayList<>();
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@Override
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public void handle(HttpExchange exchange) throws IOException {
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String method = exchange.getRequestMethod();
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switch (method) {
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case "GET" -> handleGet(exchange);
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case "POST" -> handlePost(exchange);
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case "PUT" -> handlePut(exchange);
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case "DELETE" -> handleDelete(exchange);
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default -> sendResponse(exchange, 405, "Method Not Allowed");
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}
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}
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private void handleGet(HttpExchange exchange) throws IOException {
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sendResponse(exchange, 200, users.toString());
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}
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private void handlePost(HttpExchange exchange) throws IOException {
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String newUser = readRequestBody(exchange);
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if (!newUser.isBlank()) {
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users.add(newUser);
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sendResponse(exchange, 201, "User added: " + newUser);
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} else {
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sendResponse(exchange, 400, "Invalid user data");
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}
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}
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private void handlePut(HttpExchange exchange) throws IOException {
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String body = readRequestBody(exchange);
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String[] parts = body.split(":", 2);
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if (parts.length == 2) {
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int index = Integer.parseInt(parts[0]);
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String newName = parts[1];
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if (index >= 0 && index < users.size()) {
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users.set(index, newName);
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sendResponse(exchange, 200, "User updated: " + newName);
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} else {
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sendResponse(exchange, 404, "User not found");
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}
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} else {
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sendResponse(exchange, 400, "Invalid input format");
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}
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}
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private void handleDelete(HttpExchange exchange) throws IOException {
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String body = readRequestBody(exchange);
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int index;
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try {
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index = Integer.parseInt(body);
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if (index >= 0 && index < users.size()) {
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String removedUser = users.remove(index);
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sendResponse(exchange, 200, "User deleted: " + removedUser);
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} else {
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sendResponse(exchange, 404, "User not found");
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}
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} catch (NumberFormatException e) {
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sendResponse(exchange, 400, "Invalid index");
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}
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}
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private void sendResponse(HttpExchange exchange, int statusCode, String response) throws IOException {
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exchange.sendResponseHeaders(statusCode, response.length());
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OutputStream os = exchange.getResponseBody();
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os.write(response.getBytes(StandardCharsets.UTF_8));
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os.close();
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}
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private String readRequestBody(HttpExchange exchange) throws IOException {
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InputStream is = exchange.getRequestBody();
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return new String(is.readAllBytes(), StandardCharsets.UTF_8);
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}
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// Helper methods for testing
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public List<String> getUsers() {
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return new ArrayList<>(users); // Return a copy to prevent external modification
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}
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public void addUser(String user) {
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users.add(user);
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}
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public void clearUsers() {
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users.clear();
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}
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public static void main(String[] args) throws IOException {
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HttpServer server = HttpServer.create(new InetSocketAddress(8080), 0);
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server.createContext("/users", new RestApiServer());
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server.setExecutor(null);
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System.out.println("Server started at http://localhost:8080/users");
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server.start();
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}
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}

‎core-java-modules/core-java-httpclient/src/test/java/com/baeldung/rest/RestApiServerUnitTest.java

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package com.baeldung.rest;
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import com.sun.net.httpserver.HttpExchange;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.Test;
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import org.mockito.Mockito;
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import java.io.*;
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import java.nio.charset.StandardCharsets;
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import static org.junit.jupiter.api.Assertions.*;
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import static org.mockito.Mockito.*;
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class RestApiServerUnitTest {
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private RestApiServer restApiServer;
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private HttpExchange exchange;
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private ByteArrayOutputStream responseStream;
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@BeforeEach
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void setUp() {
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restApiServer = new RestApiServer();
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exchange = mock(HttpExchange.class);
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responseStream = new ByteArrayOutputStream();
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}
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private void mockRequest(String method, String body) throws IOException {
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InputStream requestBody = new ByteArrayInputStream(body.getBytes(StandardCharsets.UTF_8));
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when(exchange.getRequestMethod()).thenReturn(method);
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when(exchange.getRequestBody()).thenReturn(requestBody);
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when(exchange.getResponseBody()).thenReturn(responseStream);
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when(exchange.getResponseHeaders()).thenReturn(Mockito.mock(com.sun.net.httpserver.Headers.class));
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}
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@Test
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void givenEmptyUserList_whenGetRequest_thenReturnEmptyList() throws IOException {
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mockRequest("GET", "");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertEquals("[]", response.trim());
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}
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@Test
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void givenValidUser_whenPostRequest_thenUserIsAdded() throws IOException {
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mockRequest("POST", "JohnDoe");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertTrue(response.contains("User added: JohnDoe"));
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}
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@Test
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void givenEmptyBody_whenPostRequest_thenReturnInvalidUserDataMessage() throws IOException {
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mockRequest("POST", "");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertTrue(response.contains("Invalid user data"));
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}
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@Test
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void givenValidIndex_whenPutRequest_thenUserIsUpdated() throws IOException {
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mockRequest("POST", "JohnDoe");
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restApiServer.handle(exchange);
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mockRequest("PUT", "0:JaneDoe");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertTrue(response.contains("User updated: JaneDoe"));
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}
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@Test
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void givenInvalidIndex_whenPutRequest_thenReturnUserNotFoundMessage() throws IOException {
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mockRequest("PUT", "10:NewUser");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertTrue(response.contains("User not found"));
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}
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@Test
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void givenValidIndex_whenDeleteRequest_thenUserIsDeleted() throws IOException {
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mockRequest("POST", "JohnDoe");
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restApiServer.handle(exchange);
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mockRequest("DELETE", "0");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertTrue(response.contains("User deleted: JohnDoe"));
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}
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@Test
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void givenInvalidIndex_whenDeleteRequest_thenReturnUserNotFoundMessage() throws IOException {
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mockRequest("DELETE", "5");
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restApiServer.handle(exchange);
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String response = responseStream.toString(StandardCharsets.UTF_8);
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assertTrue(response.contains("User not found"));
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}
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}

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