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1 files changed, 120 insertions, 0 deletions

diff --git a/config-lib/src/main/java/com/yahoo/config/LeafNode.java b/config-lib/src/main/java/com/yahoo/config/LeafNode.java
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+++ b/config-lib/src/main/java/com/yahoo/config/LeafNode.java
@@ -0,0 +1,120 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.config;
+
+import edu.umd.cs.findbugs.annotations.NonNull;
+
+/**
+ * Superclass for all leaf nodes in a {@link ConfigInstance}.
+ * <p>
+ * Subclasses represents leaf nodes with different types. These
+ * implementations should implement method value() with return-value
+ * corresponding to the actual type.
+ *
+ */
+public abstract class LeafNode<T> extends Node implements Cloneable {
+
+    protected boolean initialized;
+    protected T value;
+
+    /**
+     * Creates a new, uninitialized LeafNode
+     */
+    protected LeafNode() {
+        initialized = false;
+    }
+
+    /**
+     * Creates a new LeafNode.
+     *
+     * @param initialized true if this node is initialized.
+     */
+    protected LeafNode(boolean initialized) {
+        this.initialized = initialized;
+    }
+
+    public T value() {
+        return value;
+    }
+
+    /**
+     * Try to initialize this node with the given value. Returns true
+     * on success, false otherwise.
+     *
+     * @param value     the string represention of the desired node value.
+     * @return true on success, false otherwise.
+     */
+    final boolean initialize(String value) {
+        boolean success = setValue(value);
+        initialized |= success;
+        return success;
+    }
+
+    /**
+     * Subclasses must implement this, in compliance with the rules given in the return tag.
+     *
+     * @return the String representation of the node value, or the string "(null)" if the value is null.
+     */
+    public abstract String toString();
+
+    /**
+     * Subclasses must implement this, in compliance with the rules given in the return tag.
+     *
+     * @return the String representation of the node value, or the 'null' object if the node value is null.
+     */
+    public abstract String getValue();
+
+    /**
+     * Sets the value based on a string representation. Returns false if the value could
+     * not be set from the given string.
+     * TODO: return void (see doSetValue)
+     *
+     * @param value the value to set
+     * @return true on success, false otherwise
+     * @throws IllegalArgumentException when value is null
+     */
+    protected final boolean setValue(String value) {
+        if (value == null)
+            throw new IllegalArgumentException("Null value is not allowed");
+        return doSetValue(value);
+    }
+
+    // TODO: should throw exception instead of return false.
+    protected abstract boolean doSetValue(@NonNull String value);
+
+    /**
+     * This method is meant for internal use in the configuration
+     * system. Overrides Object.clone().
+     *
+     * @return a new instance similar to this object.
+     */
+    @Override
+    protected Object clone() {
+        try {
+            return super.clone();
+        } catch (CloneNotSupportedException e) {
+            throw new ConfigurationRuntimeException(e);
+        }
+    }
+
+    @Override
+    public boolean equals(Object o) {
+        if (! (o instanceof LeafNode))
+            return false;
+
+        LeafNode<?> other = (LeafNode)o;
+        return value == null ? other.value == null :  value().equals(other.value);
+    }
+
+    @Override
+    public int hashCode() {
+        return (value == null) ? 0 : value.hashCode();
+    }
+
+    void serialize(String name, Serializer serializer) {
+        serializer.serialize(name, getValue());
+    }
+
+    void serialize(Serializer serializer) {
+        serializer.serialize(getValue());
+    }
+}