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MartinStenhagenMartinStenhagen
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Feature/13 implement config file (#22)
* Added basic YAML config-file. * Added class ConfigLoader with static classes for encapsulation * Added static metod loadOnce and step one of static method load * Added static method createMapperFor that checks for YAML or JSON-files before creating an ObjectMapper object. * implement ConfigLoader refs #13 * Added AppConfig.java record for config after coderabbit feedback * Updated ConfigLoader to use AppConfig record and jackson 3 * Added tests for ConfigLoader and reset cached method in ConfigLoader to ensure test isolation with static cache * Removed unused dependency. Minor readability tweaks in AppConfig. * Added check for illegal port numbers to withDefaultsApplied-method. * Added test for illegal port numbers.
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‎src/main/java/org/example/config/AppConfig.java‎

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package org.example.config;
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import com.fasterxml.jackson.annotation.JsonIgnoreProperties;
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import com.fasterxml.jackson.annotation.JsonProperty;
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@JsonIgnoreProperties(ignoreUnknown = true)
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public record AppConfig(
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@JsonProperty("server") ServerConfig server,
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@JsonProperty("logging") LoggingConfig logging
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) {
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public static AppConfig defaults() {
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return new AppConfig(ServerConfig.defaults(), LoggingConfig.defaults());
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}
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public AppConfig withDefaultsApplied() {
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ServerConfig serverConfig = (server == null ? ServerConfig.defaults() : server.withDefaultsApplied());
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LoggingConfig loggingConfig = (logging == null ? LoggingConfig.defaults() : logging.withDefaultsApplied());
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return new AppConfig(serverConfig, loggingConfig);
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}
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@JsonIgnoreProperties(ignoreUnknown = true)
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public record ServerConfig(
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@JsonProperty("port") Integer port,
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@JsonProperty("rootDir") String rootDir
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) {
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public static ServerConfig defaults() {
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return new ServerConfig(8080, "./www");
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}
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public ServerConfig withDefaultsApplied() {
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int p = (port == null ? 8080 : port);
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if (p < 1 || p > 65535) {
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throw new IllegalArgumentException("Invalid port number: " + p + ". Port must be between 1 and 65535");
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}
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String rd = (rootDir == null || rootDir.isBlank()) ? "./www" : rootDir;
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return new ServerConfig(p, rd);
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}
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}
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@JsonIgnoreProperties(ignoreUnknown = true)
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public record LoggingConfig(
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@JsonProperty("level") String level
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) {
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public static LoggingConfig defaults() {
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return new LoggingConfig("INFO");
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}
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public LoggingConfig withDefaultsApplied() {
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String lvl = (level == null || level.isBlank()) ? "INFO" : level;
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return new LoggingConfig(lvl);
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}
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}
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}

‎src/main/java/org/example/config/ConfigLoader.java‎

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package org.example.config;
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import tools.jackson.databind.ObjectMapper;
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import tools.jackson.databind.json.JsonMapper;
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import tools.jackson.dataformat.yaml.YAMLFactory;
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import tools.jackson.dataformat.yaml.YAMLMapper;
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import java.io.InputStream;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import java.util.Objects;
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public final class ConfigLoader {
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private static volatile AppConfig cached;
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private ConfigLoader() {}
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public static AppConfig loadOnce(Path configPath) {
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if (cached != null) return cached;
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synchronized (ConfigLoader.class) {
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if (cached == null){
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cached = load(configPath).withDefaultsApplied();
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}
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return cached;
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}
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}
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public static AppConfig get(){
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if (cached == null){
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throw new IllegalStateException("Config not loaded. call ConfigLoader.loadOnce(...) at startup.");
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}
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return cached;
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}
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public static AppConfig load(Path configPath) {
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Objects.requireNonNull(configPath, "configPath");
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if (!Files.exists(configPath)) {
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return AppConfig.defaults();
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}
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ObjectMapper objectMapper = createMapperFor(configPath);
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try (InputStream stream = Files.newInputStream(configPath)){
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AppConfig config = objectMapper.readValue(stream, AppConfig.class);
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return config == null ? AppConfig.defaults() : config;
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} catch (Exception e){
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throw new IllegalStateException("failed to read config file " + configPath.toAbsolutePath(), e);
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}
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}
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private static ObjectMapper createMapperFor(Path configPath) {
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String name = configPath.getFileName().toString().toLowerCase();
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if (name.endsWith(".yml") || name.endsWith(".yaml")) {
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return YAMLMapper.builder(new YAMLFactory()).build();
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} else if (name.endsWith(".json")) {
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return JsonMapper.builder().build();
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} else {
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return YAMLMapper.builder(new YAMLFactory()).build();
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}
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}
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static void resetForTests() {
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cached = null;
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}
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}

‎src/main/resources/application.yml‎

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server:
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port: 8080
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rootDir: ./www
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logging:
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level: INFO

‎src/test/java/org/example/config/ConfigLoaderTest.java‎

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package org.example.config;
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import org.junit.jupiter.api.BeforeEach;
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import org.junit.jupiter.api.DisplayName;
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import org.junit.jupiter.api.Test;
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import org.junit.jupiter.api.io.TempDir;
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import java.nio.file.Files;
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import java.nio.file.Path;
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import static org.assertj.core.api.Assertions.*;
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class ConfigLoaderTest {
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@TempDir
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Path tempDir;
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@BeforeEach
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void reset() {
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ConfigLoader.resetForTests();
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}
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@Test
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@DisplayName("Should return default configuration when config file is missing")
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void load_returns_defaults_when_file_missing() {
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Path missing = tempDir.resolve("missing.yml");
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AppConfig appConfig = ConfigLoader.load(missing).withDefaultsApplied();
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assertThat(appConfig.server().port()).isEqualTo(8080);
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assertThat(appConfig.server().rootDir()).isEqualTo("./www");
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assertThat(appConfig.logging().level()).isEqualTo("INFO");
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}
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@Test
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@DisplayName("Should load values from YAML file when file exists")
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void loadOnce_reads_yaml_values() throws Exception {
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Path configFile = tempDir.resolve("application.yml");
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Files.writeString(configFile, """
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server:
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port: 9090
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rootDir: ./public
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logging:
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level: DEBUG
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""");
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AppConfig appConfig = ConfigLoader.loadOnce(configFile);
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assertThat(appConfig.server().port()).isEqualTo(9090);
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assertThat(appConfig.server().rootDir()).isEqualTo("./public");
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assertThat(appConfig.logging().level()).isEqualTo("DEBUG");
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}
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@Test
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@DisplayName("Should apply default values when sections or fields are missing")
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void defaults_applied_when_sections_or_fields_missing() throws Exception {
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Path configFile = tempDir.resolve("application.yml");
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Files.writeString(configFile, """
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server:
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port: 1234
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""");
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AppConfig cfg = ConfigLoader.loadOnce(configFile);
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assertThat(cfg.server().port()).isEqualTo(1234);
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assertThat(cfg.server().rootDir()).isEqualTo("./www"); // default
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assertThat(cfg.logging().level()).isEqualTo("INFO"); // default
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}
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@Test
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@DisplayName("Should ignore unknown fields in configuration file")
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void unknown_fields_are_ignored() throws Exception {
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Path configFile = tempDir.resolve("application.yml");
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Files.writeString(configFile, """
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server:
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port: 8081
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rootDir: ./www
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threads: 8
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logging:
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level: INFO
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json: true
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""");
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AppConfig cfg = ConfigLoader.loadOnce(configFile);
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assertThat(cfg.server().port()).isEqualTo(8081);
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assertThat(cfg.server().rootDir()).isEqualTo("./www");
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assertThat(cfg.logging().level()).isEqualTo("INFO");
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}
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@Test
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@DisplayName("Should return same instance on repeated loadOnce calls")
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void loadOnce_caches_same_instance() throws Exception {
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Path configFile = tempDir.resolve("application.yml");
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Files.writeString(configFile, """
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server:
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port: 8080
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rootDir: ./www
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logging:
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level: INFO
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""");
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AppConfig a = ConfigLoader.loadOnce(configFile);
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AppConfig b = ConfigLoader.loadOnce(configFile);
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assertThat(a).isSameAs(b);
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}
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@Test
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@DisplayName("Should throw exception when get is called before configuration is loaded")
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void get_throws_if_not_loaded() {
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assertThatThrownBy(ConfigLoader::get)
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.isInstanceOf(IllegalStateException.class)
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.hasMessageContaining("not loaded");
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}
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@Test
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@DisplayName("Should fail when configuration file is invalid")
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void invalid_yaml_fails() throws Exception {
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Path configFile = tempDir.resolve("broken.yml");
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Files.writeString(configFile, "server:\n port 8080\n"); // saknar ':' efter port
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assertThatThrownBy(() -> ConfigLoader.load(configFile))
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.isInstanceOf(IllegalStateException.class)
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.hasMessageContaining("failed to read config file");
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}
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@Test
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@DisplayName("Should fail when port is out of range")
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void invalid_port_should_Throw_Exception () throws Exception {
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Path configFile = tempDir.resolve("application.yml");
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Files.writeString(configFile, """
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server:
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port: 70000
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""");
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assertThatThrownBy(() -> ConfigLoader.loadOnce(configFile))
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.isInstanceOf(IllegalArgumentException.class).hasMessageContaining("Invalid port number");
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}
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}

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