1 files changed, 100 insertions, 0 deletions
diff --git a/chain/src/main/java/com/yahoo/component/chain/ChainedComponent.java b/chain/src/main/java/com/yahoo/component/chain/ChainedComponent.java
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+++ b/chain/src/main/java/com/yahoo/component/chain/ChainedComponent.java
@@ -0,0 +1,100 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.component.chain;
+
+import com.yahoo.component.AbstractComponent;
+import com.yahoo.component.ComponentId;
+import com.yahoo.component.chain.dependencies.After;
+import com.yahoo.component.chain.dependencies.Before;
+import com.yahoo.component.chain.dependencies.Dependencies;
+import com.yahoo.component.chain.dependencies.Provides;
+
+import java.lang.annotation.Annotation;
+import java.lang.reflect.InvocationTargetException;
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.Collection;
+import java.util.Collections;
+import java.util.List;
+
+/**
+ * Component with dependencies.
+ *
+ * @author tonytv
+ */
+public abstract class ChainedComponent extends AbstractComponent {
+
+    /** The immutable set of dependencies of this. NOTE: the default is only for unit testing. */
+    private Dependencies dependencies = getDefaultAnnotatedDependencies();
+
+    public ChainedComponent(ComponentId id) {
+        super(id);
+    }
+
+    protected ChainedComponent() {}
+
+    /**
+     * Called by the container to assign the full set of dependencies to this class (configured and declared).
+     * This is called once before this is started.
+     * @param  dependencies The configured dependencies, that this method will merge with annotated dependencies.
+     */
+    public void initDependencies(Dependencies dependencies) {
+        this.dependencies = dependencies.union(getDefaultAnnotatedDependencies());
+    }
+
+    /** Returns the configured and declared dependencies of this chainedcomponent */
+    public Dependencies getDependencies() { return dependencies; }
+
+    /** This method is here only for legacy reasons, do not override. */
+    protected Dependencies getDefaultAnnotatedDependencies() {
+        Dependencies dependencies = getAnnotatedDependencies(com.yahoo.yolean.chain.Provides.class, com.yahoo.yolean.chain.Before.class, com.yahoo.yolean.chain.After.class);
+        Dependencies legacyDependencies = getAnnotatedDependencies(Provides.class, Before.class, After.class);
+
+        return dependencies.union(legacyDependencies);
+    }
+
+    /**
+     * @param providesClass  The annotation class representing 'provides'.
+     * @param beforeClass    The annotation class representing 'before'.
+     * @param afterClass     The annotation class representing 'after'.
+     * @return a new {@link Dependencies} created from the annotations given in this component's class.
+     */
+    protected Dependencies getAnnotatedDependencies(Class<? extends Annotation> providesClass,
+                                                    Class<? extends Annotation> beforeClass,
+                                                    Class<? extends Annotation> afterClass) {
+        return new Dependencies(
+                allOf(getSymbols(this, providesClass), this.getClass().getSimpleName(), this.getClass().getName()),
+                getSymbols(this, beforeClass),
+                getSymbols(this, afterClass));
+    }
+
+    // TODO: move to vespajlib.
+    private static List<String> allOf(List<String> symbols, String... otherSymbols) {
+        List<String> result = new ArrayList<>(symbols);
+        result.addAll(Arrays.asList(otherSymbols));
+        return result;
+    }
+
+
+    private static List<String> getSymbols(ChainedComponent component, Class<? extends Annotation> annotationClass) {
+        List<String> result = new ArrayList<>();
+
+        result.addAll(annotationSymbols(component, annotationClass));
+        return result;
+    }
+
+    private static Collection<String> annotationSymbols(ChainedComponent component, Class<? extends Annotation> annotationClass) {
+
+        try {
+            Annotation annotation = component.getClass().getAnnotation(annotationClass);
+            if (annotation != null) {
+                Object values = annotationClass.getMethod("value").invoke(annotation);
+                return Arrays.asList((String[])values);
+            }
+            return Collections.emptyList();
+
+        } catch (IllegalAccessException | NoSuchMethodException | InvocationTargetException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+}