Core/src/main/java/fr/altarik/toolbox/core/config/ConfigI.java

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+package fr.altarik.toolbox.core.config;
+
+import com.google.gson.*;
+
+import java.io.FileReader;
+import java.io.IOException;
+import java.lang.reflect.InvocationTargetException;
+import java.lang.reflect.Modifier;
+import java.nio.file.Files;
+import java.nio.file.Path;
+
+/**
+ * Code "inspired" from <a href="https://github.com/CaffeineMC/sodium-fabric/blob/dev/src/main/java/me/jellysquid/mods/sodium/client/gui/SodiumGameOptions.java">
+ *     https://github.com/CaffeineMC/sodium-fabric/blob/dev/src/main/java/me/jellysquid/mods/sodium/client/gui/SodiumGameOptions.java
+ *     </a>
+ */
+public class ConfigI {
+
+    protected static final Gson GSON = new GsonBuilder().setFieldNamingPolicy(FieldNamingPolicy.LOWER_CASE_WITH_UNDERSCORES).setPrettyPrinting().excludeFieldsWithModifiers(Modifier.PROTECTED, Modifier.PRIVATE).create();
+
+    protected Path configPath;
+
+    protected static Path getConfigPath(Path configPath, String name) {
+        return configPath.resolve(name);
+    }
+
+    public static ConfigI load(Path configPath, String name, Class<? extends ConfigI> clazz) throws IOException, JsonSyntaxException, JsonIOException {
+        Path path = getConfigPath(configPath, name);
+
+        ConfigI file;
+
+        if(Files.exists(path)) {
+            FileReader reader = new FileReader(path.toFile());
+            file = GSON.fromJson(reader, clazz);
+        } else {
+            try {
+                file = clazz.getConstructor().newInstance();
+            } catch (InstantiationException | InvocationTargetException | IllegalAccessException | NoSuchMethodException e) {
+                throw new IOException(e);
+            }
+        }
+
+        file.configPath = path;
+
+        file.writeChanges();
+        return file;
+    }
+
+    public void writeChanges() throws IOException {
+        Path dir = this.configPath.getParent();
+        if(!Files.exists(dir)) {
+            Files.createDirectories(dir);
+        } else if (!Files.isDirectory(dir)) {
+            throw new IOException("Not a directory: " + dir);
+        }
+        // Use a temporary location next to the config's final destination to replace it atomically
+//        Path tempPath = this.configPath.resolveSibling(this.configPath.getFileName() + ".tmp");
+        Files.writeString(this.configPath, GSON.toJson(this));
+//        Files.copy(tempPath, this.configPath, StandardCopyOption.REPLACE_EXISTING);
+//        Files.delete(tempPath);
+    }
+
+}

Core/src/test/java/ConfigITest.java

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+import fr.altarik.toolbox.core.config.ConfigI;
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
+import java.io.IOException;
+import java.nio.file.Path;
+
+public class ConfigITest {
+
+    public static class ConfigClazz extends ConfigI {
+
+        public int par1 = 5;
+        public String par2 = "bad";
+        public double para3 = 3.14;
+
+        public static ConfigClazz load() throws IOException {
+            return (ConfigClazz) load(Path.of("."), "test.json", ConfigClazz.class);
+        }
+
+    }
+
+    @Test
+    public void testConfig() throws IOException {
+        ConfigClazz config = ConfigClazz.load();
+        Assertions.assertEquals(5, config.par1);
+        Assertions.assertEquals("bad", config.par2);
+        Assertions.assertEquals(3.14, config.para3);
+        config.par1 = 6;
+        config.par2 = "good";
+        config.para3 = 4.2;
+        Assertions.assertEquals(6, config.par1);
+        config.writeChanges();
+        config = ConfigClazz.load();
+        Assertions.assertEquals(6, config.par1);
+        Assertions.assertEquals("good", config.par2);
+        Assertions.assertEquals(4.2, config.para3);
+
+        Path.of(".").resolve("test.json").toFile().delete();
+    }
+}