feat: add config injection annotations (#75)

* feat: add config injection annotations

* lic headers

* pr remarks

* Update Configuration.java

Co-authored-by: Jim Marino <[email protected]>

---------

Co-authored-by: Jim Marino <[email protected]>

runtime-metamodel/src/main/java/org/eclipse/edc/runtime/metamodel/annotation/Configuration.java

@@ -0,0 +1,33 @@
+/*
+ *  Copyright (c) 2024 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ *
+ *  This program and the accompanying materials are made available under the
+ *  terms of the Apache License, Version 2.0 which is available at
+ *  https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Contributors:
+ *       Bayerische Motoren Werke Aktiengesellschaft (BMW AG) - initial API and implementation
+ *
+ */
+
+package org.eclipse.edc.runtime.metamodel.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Indicates that a certain field is a "configuration object", i.e. a POJO that contains fields annotated with
+ * {@link Setting}. These fields must be declared inside an extension class. Their respective class declaration must be annotated
+ * with {@link Settings}.
+ * Types annotated with this annotation will get instantiated by the EDC dependency injection mechanism using values from the config.
+ */
+@Target({ ElementType.FIELD })
+@Retention(RetentionPolicy.RUNTIME)
+@Documented
+public @interface Configuration {
+}

runtime-metamodel/src/main/java/org/eclipse/edc/runtime/metamodel/annotation/Setting.java

@@ -22,31 +22,42 @@
 import java.lang.annotation.Target;
 
 /**
- * Denotes a runtime configuration setting.
+ * Denotes a runtime configuration setting. This can be put on config value fields and the dependency injection mechanism will
+ * attempt to automatically resolve them.
  */
-@Target({ ElementType.TYPE, ElementType.FIELD })
+@Target({ ElementType.FIELD })
 @Retention(RetentionPolicy.RUNTIME)
 @Documented
 public @interface Setting {
+    String NULL = "";
 
     /**
      * The setting description.
+     *
+     * @deprecated Please use {@link Setting#description()} to supply description. In future releases this property will hold the Setting's config key!
      */
-    String value() default "";
+    @Deprecated
+    String value() default NULL;
 
     /**
      * The setting context
      */
-    String context() default "";
+    String context() default NULL;
 
+    /**
+     * Type of the config value
+     *
+     * @deprecated this attribute is deprecated because it will be inferred from the field
+     */
+    @Deprecated
     String type() default "string";
 
     /**
      * The setting default value. Empty string if no default value is provided
      *
      * @return the setting's default value
      */
-    String defaultValue() default "";
+    String defaultValue() default NULL;
 
     long min() default Long.MIN_VALUE;
 
@@ -55,6 +66,26 @@
     /**
      * Returns true if the setting is required.
      */
-    boolean required() default false;
+    boolean required() default true;
+
+    /**
+     * The key of the property, e.g. "edc.foo.bar.baz". If this attribute is present, the dependency injection mechanism
+     * will attempt to resolve the config value.
+     */
+    String key() default NULL;
 
+    /**
+     * The Setting's description. This is equivalent to {@link Setting#value()} in the current release, but users should
+     * use this attribute.
+     *
+     * @return The setting's description.
+     */
+    String description() default NULL;
+
+    /**
+     * Specify whether a warning should be issued when an optional config value is missing or when the default value is used.
+     * If set to false, a debug log is issued.
+     * Note that this is ignored on mandatory (non-optional) config values.
+     */
+    boolean warnOnMissingConfig() default false;
 }

runtime-metamodel/src/main/java/org/eclipse/edc/runtime/metamodel/annotation/Settings.java

@@ -0,0 +1,31 @@
+/*
+ *  Copyright (c) 2024 Bayerische Motoren Werke Aktiengesellschaft (BMW AG)
+ *
+ *  This program and the accompanying materials are made available under the
+ *  terms of the Apache License, Version 2.0 which is available at
+ *  https://www.apache.org/licenses/LICENSE-2.0
+ *
+ *  SPDX-License-Identifier: Apache-2.0
+ *
+ *  Contributors:
+ *       Bayerische Motoren Werke Aktiengesellschaft (BMW AG) - initial API and implementation
+ *
+ */
+
+package org.eclipse.edc.runtime.metamodel.annotation;
+
+import java.lang.annotation.Documented;
+import java.lang.annotation.ElementType;
+import java.lang.annotation.Retention;
+import java.lang.annotation.RetentionPolicy;
+import java.lang.annotation.Target;
+
+/**
+ * Denotes that a certain class is a "configuration object", i.e. contains fields annotated with {@link Setting}. Note that
+ * if the configuration object is a record, it may ONLY contain fields annotated with {@link Setting}.
+ */
+@Target({ ElementType.TYPE })
+@Retention(RetentionPolicy.CLASS)
+@Documented
+public @interface Settings {
+}