feat: abstract class to load factories (#488)

Co-authored-by: g00563573 <L0kuj;lfyysq>

Author: olenagerasimova

…/artipie/asto/factory/StorageConfig.java …ava/com/artipie/asto/factory/Config.javaasto-core/src/main/java/com/artipie/asto/factory/StorageConfig.java renamed to asto-core/src/main/java/com/artipie/asto/factory/Config.java asto-core/src/main/java/com/artipie/asto/factory/StorageConfig.java renamed to asto-core/src/main/java/com/artipie/asto/factory/Config.java

@@ -12,11 +12,11 @@
 import java.util.stream.Collectors;
 
 /**
- * Storage config.
+ * Factory config.
  *
  * @since 1.13.0
  */
-public interface StorageConfig {
+public interface Config {
 
     /**
      * Gets string value.
@@ -40,26 +40,26 @@ public interface StorageConfig {
      * @param key Key.
      * @return Config.
      */
-    StorageConfig config(String key);
+    Config config(String key);
 
     /**
      * Strict storage config throws {@code NullPointerException} when value is not exist.
      *
      * @since 1.13.0
      */
-    class StrictStorageConfig implements StorageConfig {
+    class StrictStorageConfig implements Config {
 
         /**
          * Original config.
          */
-        private final StorageConfig original;
+        private final Config original;
 
         /**
          * Ctor.
          *
          * @param original Original config.
          */
-        public StrictStorageConfig(final StorageConfig original) {
+        public StrictStorageConfig(final Config original) {
             this.original = original;
         }
 
@@ -80,7 +80,7 @@ public Collection<String> sequence(final String key) {
         }
 
         @Override
-        public StorageConfig config(final String key) {
+        public Config config(final String key) {
             return Objects.requireNonNull(
                 this.original.config(key),
                 String.format("No config found for key %s", key)
@@ -93,7 +93,7 @@ public StorageConfig config(final String key) {
      *
      * @since 1.13.0
      */
-    class YamlStorageConfig implements StorageConfig {
+    class YamlStorageConfig implements Config {
         /**
          * Original {@code YamlMapping}.
          */
@@ -145,8 +145,13 @@ public Collection<String> sequence(final String key) {
         }
 
         @Override
-        public StorageConfig config(final String key) {
+        public Config config(final String key) {
             return new YamlStorageConfig(this.original.yamlMapping(key));
         }
+
+        @Override
+        public String toString() {
+            return this.original.toString();
+        }
     }
 }

asto-core/src/main/java/com/artipie/asto/factory/FactoryLoader.java

@@ -0,0 +1,125 @@
+/*
+ * The MIT License (MIT) Copyright (c) 2020-2022 artipie.com
+ * https://github.com/artipie/asto/LICENSE.txt
+ */
+package com.artipie.asto.factory;
+
+import com.artipie.ArtipieException;
+import com.google.common.base.Strings;
+import com.google.common.collect.Lists;
+import com.jcabi.log.Logger;
+import java.lang.reflect.InvocationTargetException;
+import java.util.Arrays;
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.reflections.Reflections;
+import org.reflections.scanners.Scanners;
+
+/**
+ * Loader for various factories for different objects.
+ * @param <F> Factory class
+ * @param <A> Factory annotation class
+ * @param <C> Config class
+ * @param <O> Object to instantiate class
+ * @since 1.16
+ */
+@SuppressWarnings("unchecked")
+public abstract class FactoryLoader<F, A, C, O> {
+
+    /**
+     * The name of the factory <-> factory.
+     * @checkstyle VisibilityModifierCheck (5 lines)
+     */
+    protected final Map<String, F> factories;
+
+    /**
+     * Annotation class.
+     */
+    private final Class<A> annot;
+
+    /**
+     * Ctor.
+     * @param annot Annotation class
+     * @param env Environment
+     */
+    protected FactoryLoader(final Class<A> annot, final Map<String, String> env) {
+        this.annot = annot;
+        this.factories = this.init(env);
+    }
+
+    /**
+     * Default package name.
+     * @return The name of the default scan package
+     */
+    abstract String defPackage();
+
+    /**
+     * Environment parameter to define packages to find factories.
+     * Package names should be separated by semicolon ';'.
+     * @return Env param name
+     */
+    abstract String scanPackagesEnv();
+
+    /**
+     * Find factory by name and create object.
+     * @param name The factory name
+     * @param config Configuration
+     * @return The object
+     */
+    abstract O newObject(String name, C config);
+
+    /**
+     * Get the name of the factory from provided element. Call {@link Class#getAnnotations()}
+     * method on the element, filter required annotations and get factory implementation name.
+     * @param element Element to get annotations from
+     * @return The name of the factory
+     */
+    abstract String getFactoryName(Class<?> element);
+
+    /**
+     * Finds and initiates annotated classes in default and env packages.
+     *
+     * @param env Environment parameters.
+     * @return Map of StorageFactories.
+     */
+    private Map<String, F> init(final Map<String, String> env) {
+        final List<String> pkgs = Lists.newArrayList(this.defPackage());
+        final String pgs = env.get(this.scanPackagesEnv());
+        if (!Strings.isNullOrEmpty(pgs)) {
+            pkgs.addAll(Arrays.asList(pgs.split(";")));
+        }
+        final Map<String, F> res = new HashMap<>();
+        pkgs.forEach(
+            pkg -> new Reflections(pkg)
+                .get(Scanners.TypesAnnotated.with(this.annot).asClass())
+                .forEach(
+                    element -> {
+                        final String type = this.getFactoryName(element);
+                        final F existed = res.get(type);
+                        if (existed != null) {
+                            throw new ArtipieException(
+                                String.format(
+                                    "Factory with type '%s' already exists [class=%s].",
+                                    type, existed.getClass().getSimpleName()
+                                )
+                            );
+                        }
+                        try {
+                            res.put(type, (F) element.getDeclaredConstructor().newInstance());
+                            Logger.info(
+                                StoragesLoader.class,
+                                "Initiated factory [type=%s, class=%s]",
+                                type, element.getSimpleName()
+                            );
+                        } catch (final InstantiationException | IllegalAccessException
+                            | InvocationTargetException | NoSuchMethodException err) {
+                            throw new ArtipieException(err);
+                        }
+                    }
+                )
+        );
+        return res;
+    }
+
+}

asto-core/src/main/java/com/artipie/asto/factory/StorageFactory.java

@@ -20,7 +20,7 @@ public interface StorageFactory {
      * @param cfg Storage configuration.
      * @return Storage
      */
-    Storage newStorage(StorageConfig cfg);
+    Storage newStorage(Config cfg);
 
     /**
      * Create new storage.
@@ -30,7 +30,7 @@ public interface StorageFactory {
      */
     default Storage newStorage(YamlMapping cfg) {
         return this.newStorage(
-            new StorageConfig.YamlStorageConfig(cfg)
+            new Config.YamlStorageConfig(cfg)
         );
     }
 }